Basic checkpoint-restart [C/R]: v8 adds support for "external" checkpoint
and improves documentation. Older announcements below.
The git tree tracking v8 (branch 'ckpt-v8'), and older versions, is at:
git://gorgona.ncl.cs.columbia.edu/pub/git/linux-cr-dev.git
(or for the latest version -
git://gorgona.ncl.cs.columbia.edu/pub/git/linux-cr.git)
We'd like to see these make their way into -mm.
As Dave Hansen put it:
--
Why do we want it? It allows containers to be moved between physical
machines' kernels in the same way that VMWare can move VMs between
physical machines' hypervisors. There are currently at least two
out-of-tree implementations of this in the commercial world (IBM's
Metacluster and Parallels' OpenVZ/Virtuozzo) and several in the academic
world like Zap.
Why do we need it in mainline now? Because we already have plenty of
out-of-tree ones, and want to know what an in-tree one will be like. :)
What *I* want right now is the extra review and scrutiny that comes with
a mainline submission to make sure we're not going in a direction
contrary to the community.
This only supports pretty simple apps. But, I trust Ingo when he says:
>> > > Generally, if something works for simple apps already (in a robust,
>> > > compatible and supportable way) and users find it "very cool", then
>> > > support for more complex apps is not far in the future. but if you
>> > > want to support more complex apps straight away, it takes forever and
>> > > gets ugly.
We're *certainly* going to be changing the ABI (which is the format of
the checkpoint). I'd like to follow the model that we used for
ext4-dev, which is to make it very clear that this is a development-only
feature for now. Perhaps we do that by making the interface only
available through debugfs or something similar for now. Or, reserving
the syscall numbers but require some runtime switch to be thrown before
they can be used. I'm open to suggestions here.
--
Oren.
--
Todo:
- Add support for x86-64 and improve ABI
- Refine or change syscall interface
- Extend to handle (multiple) tasks in a container
- Handle multiple namespaces in a container (e.g. save the filesystem
namespaces state with the file descriptors)
- Security (without CAPS_SYS_ADMIN files restore may fail)
Changelog:
[2008-Oct-29] v8:
- Support "external" checkpoint
- Include Dave Hansen's 'deny-checkpoint' patch
- Split docs in Documentation/checkpoint/..., and improve contents
[2008-Oct-17] v7:
- Fix save/restore state of FPU
- Fix argument given to kunmap_atomic() in memory dump/restore
[2008-Oct-07] v6:
- Balance all calls to cr_hbuf_get() with matching cr_hbuf_put()
(even though it's not really needed)
- Add assumptions and what's-missing to documentation
- Misc fixes and cleanups
[2008-Sep-11] v5:
- Config is now 'def_bool n' by default
- Improve memory dump/restore code (following Dave Hansen's comments)
- Change dump format (and code) to allow chunks of <vaddrs, pages>
instead of one long list of each
- Fix use of follow_page() to avoid faulting in non-present pages
- Memory restore now maps user pages explicitly to copy data into them,
instead of reading directly to user space; got rid of mprotect_fixup()
- Remove preempt_disable() when restoring debug registers
- Rename headers files s/ckpt/checkpoint/
- Fix misc bugs in files dump/restore
- Fixes and cleanups on some error paths
- Fix misc coding style
[2008-Sep-09] v4:
- Various fixes and clean-ups
- Fix calculation of hash table size
- Fix header structure alignment
- Use stand list_... for cr_pgarr
[2008-Aug-29] v3:
- Various fixes and clean-ups
- Use standard hlist_... for hash table
- Better use of standard kmalloc/kfree
[2008-Aug-20] v2:
- Added Dump and restore of open files (regular and directories)
- Added basic handling of shared objects, and improve handling of
'parent tag' concept
- Added documentation
- Improved ABI, 64bit padding for image data
- Improved locking when saving/restoring memory
- Added UTS information to header (release, version, machine)
- Cleanup extraction of filename from a file pointer
- Refactor to allow easier reviewing
- Remove requirement for CAPS_SYS_ADMIN until we come up with a
security policy (this means that file restore may fail)
- Other cleanup and response to comments for v1
[2008-Jul-29] v1:
- Initial version: support a single task with address space of only
private anonymous or file-mapped VMAs; syscalls ignore pid/crid
argument and act on current process.
--
At the containers mini-conference before OLS, the consensus among
all the stakeholders was that doing checkpoint/restart in the kernel
as much as possible was the best approach. With this approach, the
kernel will export a relatively opaque 'blob' of data to userspace
which can then be handed to the new kernel at restore time.
This is different than what had been proposed before, which was
that a userspace application would be responsible for collecting
all of this data. We were also planning on adding lots of new,
little kernel interfaces for all of the things that needed
checkpointing. This unites those into a single, grand interface.
The 'blob' will contain copies of select portions of kernel
structures such as vmas and mm_structs. It will also contain
copies of the actual memory that the process uses. Any changes
in this blob's format between kernel revisions can be handled by
an in-userspace conversion program.
This is a similar approach to virtually all of the commercial
checkpoint/restart products out there, as well as the research
project Zap.
These patches basically serialize internel kernel state and write
it out to a file descriptor. The checkpoint and restore are done
with two new system calls: sys_checkpoint and sys_restart.
In this incarnation, they can only work checkpoint and restore a
single task. The task's address space may consist of only private,
simple vma's - anonymous or file-mapped. The open files may consist
of only simple files and directories.
--
(Following Dave Hansen's refactoring of the original post)
Add logic to save and restore architecture specific state, including
thread-specific state, CPU registers and FPU state.
Currently only x86-32 is supported. Compiling on x86-64 will trigger
an explicit error.
Changelog[v7]:
- Fix save/restore state of FPU
Changelog[v5]:
- Remove preempt_disable() when restoring debug registers
Changelog[v4]:
- Fix header structure alignment
Changelog[v2]:
- Pad header structures to 64 bits to ensure compatibility
Signed-off-by: Oren Laadan <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
---
arch/x86/mm/Makefile | 2 +
arch/x86/mm/checkpoint.c | 200 ++++++++++++++++++++++++++++++++++++++
arch/x86/mm/restart.c | 194 ++++++++++++++++++++++++++++++++++++
checkpoint/checkpoint.c | 13 +++-
checkpoint/checkpoint_arch.h | 7 ++
checkpoint/restart.c | 13 +++-
include/asm-x86/checkpoint_hdr.h | 72 ++++++++++++++
include/linux/checkpoint_hdr.h | 1 +
8 files changed, 500 insertions(+), 2 deletions(-)
create mode 100644 arch/x86/mm/checkpoint.c
create mode 100644 arch/x86/mm/restart.c
create mode 100644 checkpoint/checkpoint_arch.h
create mode 100644 include/asm-x86/checkpoint_hdr.h
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index dfb932d..58fe072 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -22,3 +22,5 @@ endif
obj-$(CONFIG_ACPI_NUMA) += srat_$(BITS).o
obj-$(CONFIG_MEMTEST) += memtest.o
+
+obj-$(CONFIG_CHECKPOINT_RESTART) += checkpoint.o restart.o
diff --git a/arch/x86/mm/checkpoint.c b/arch/x86/mm/checkpoint.c
new file mode 100644
index 0000000..bfa7180
--- /dev/null
+++ b/arch/x86/mm/checkpoint.c
@@ -0,0 +1,200 @@
+/*
+ * Checkpoint/restart - architecture specific support for x86
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <asm/desc.h>
+#include <asm/i387.h>
+
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+/* dump the thread_struct of a given task */
+int cr_write_thread(struct cr_ctx *ctx, struct task_struct *t)
+{
+ struct cr_hdr h;
+ struct cr_hdr_thread *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct thread_struct *thread;
+ struct desc_struct *desc;
+ int ntls = 0;
+ int n, ret;
+
+ h.type = CR_HDR_THREAD;
+ h.len = sizeof(*hh);
+ h.parent = task_pid_vnr(t);
+
+ thread = &t->thread;
+
+ /* calculate no. of TLS entries that follow */
+ desc = thread->tls_array;
+ for (n = GDT_ENTRY_TLS_ENTRIES; n > 0; n--, desc++) {
+ if (desc->a || desc->b)
+ ntls++;
+ }
+
+ hh->gdt_entry_tls_entries = GDT_ENTRY_TLS_ENTRIES;
+ hh->sizeof_tls_array = sizeof(thread->tls_array);
+ hh->ntls = ntls;
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ return ret;
+
+ /* for simplicity dump the entire array, cherry-pick upon restart */
+ ret = cr_kwrite(ctx, thread->tls_array, sizeof(thread->tls_array));
+
+ cr_debug("ntls %d\n", ntls);
+
+ /* IGNORE RESTART BLOCKS FOR NOW ... */
+
+ return ret;
+}
+
+#ifdef CONFIG_X86_64
+
+#error "CONFIG_X86_64 unsupported yet."
+
+#else /* !CONFIG_X86_64 */
+
+void cr_write_cpu_regs(struct cr_hdr_cpu *hh, struct task_struct *t)
+{
+ struct thread_struct *thread = &t->thread;
+ struct pt_regs *regs = task_pt_regs(t);
+
+ hh->bp = regs->bp;
+ hh->bx = regs->bx;
+ hh->ax = regs->ax;
+ hh->cx = regs->cx;
+ hh->dx = regs->dx;
+ hh->si = regs->si;
+ hh->di = regs->di;
+ hh->orig_ax = regs->orig_ax;
+ hh->ip = regs->ip;
+ hh->cs = regs->cs;
+ hh->flags = regs->flags;
+ hh->sp = regs->sp;
+ hh->ss = regs->ss;
+
+ hh->ds = regs->ds;
+ hh->es = regs->es;
+
+ /*
+ * for checkpoint in process context (from within a container)
+ * the GS and FS registers should be saved from the hardware;
+ * otherwise they are already sabed on the thread structure
+ */
+ if (t == current) {
+ savesegment(gs, hh->gs);
+ savesegment(fs, hh->fs);
+ } else {
+ hh->gs = thread->gs;
+ hh->fs = thread->fs;
+ }
+
+ /*
+ * for checkpoint in process context (from within a container),
+ * the actual syscall is taking place at this very moment; so
+ * we (optimistically) subtitute the future return value (0) of
+ * this syscall into the orig_eax, so that upon restart it will
+ * succeed (or it will endlessly retry checkpoint...)
+ */
+ if (t == current) {
+ BUG_ON(hh->orig_ax < 0);
+ hh->ax = 0;
+ }
+}
+
+void cr_write_cpu_debug(struct cr_hdr_cpu *hh, struct task_struct *t)
+{
+ struct thread_struct *thread = &t->thread;
+
+ /* debug regs */
+
+ preempt_disable();
+
+ /*
+ * for checkpoint in process context (from within a container),
+ * get the actual registers; otherwise get the saved values.
+ */
+
+ if (t == current) {
+ get_debugreg(hh->debugreg0, 0);
+ get_debugreg(hh->debugreg1, 1);
+ get_debugreg(hh->debugreg2, 2);
+ get_debugreg(hh->debugreg3, 3);
+ get_debugreg(hh->debugreg6, 6);
+ get_debugreg(hh->debugreg7, 7);
+ } else {
+ hh->debugreg0 = thread->debugreg0;
+ hh->debugreg1 = thread->debugreg1;
+ hh->debugreg2 = thread->debugreg2;
+ hh->debugreg3 = thread->debugreg3;
+ hh->debugreg6 = thread->debugreg6;
+ hh->debugreg7 = thread->debugreg7;
+ }
+
+ hh->debugreg4 = 0;
+ hh->debugreg5 = 0;
+
+ hh->uses_debug = !!(task_thread_info(t)->flags & TIF_DEBUG);
+
+ preempt_enable();
+}
+
+void cr_write_cpu_fpu(struct cr_hdr_cpu *hh, struct task_struct *t)
+{
+ struct thread_struct *thread = &t->thread;
+ struct thread_info *thread_info = task_thread_info(t);
+
+ /* i387 + MMU + SSE logic */
+
+ preempt_disable(); /* needed it (t == current) */
+
+ hh->used_math = tsk_used_math(t) ? 1 : 0;
+ if (hh->used_math) {
+ /*
+ * normally, no need to unlazy_fpu(), since TS_USEDFPU flag
+ * have been cleared when task was conexted-switched out...
+ * except if we are in process context, in which case we do
+ */
+ if (t == current) {
+ if (thread_info->status & TS_USEDFPU)
+ unlazy_fpu(current);
+ }
+
+ hh->has_fxsr = cpu_has_fxsr;
+ memcpy(&hh->xstate, thread->xstate, sizeof(*thread->xstate));
+ }
+
+ preempt_enable(); /* needed it (t == current) */
+}
+
+#endif /* CONFIG_X86_64 */
+
+/* dump the cpu state and registers of a given task */
+int cr_write_cpu(struct cr_ctx *ctx, struct task_struct *t)
+{
+ struct cr_hdr h;
+ struct cr_hdr_cpu *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ int ret;
+
+ h.type = CR_HDR_CPU;
+ h.len = sizeof(*hh);
+ h.parent = task_pid_vnr(t);
+
+ cr_write_cpu_regs(hh, t);
+ cr_write_cpu_debug(hh, t);
+ cr_write_cpu_fpu(hh, t);
+
+ cr_debug("math %d debug %d\n", hh->used_math, hh->uses_debug);
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
diff --git a/arch/x86/mm/restart.c b/arch/x86/mm/restart.c
new file mode 100644
index 0000000..2bff5eb
--- /dev/null
+++ b/arch/x86/mm/restart.c
@@ -0,0 +1,194 @@
+/*
+ * Checkpoint/restart - architecture specific support for x86
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <asm/desc.h>
+#include <asm/i387.h>
+
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+/* read the thread_struct into the current task */
+int cr_read_thread(struct cr_ctx *ctx)
+{
+ struct cr_hdr_thread *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct task_struct *t = current;
+ struct thread_struct *thread = &t->thread;
+ int parent, ret;
+
+ parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_THREAD);
+ if (parent < 0) {
+ ret = parent;
+ goto out;
+ }
+
+ ret = -EINVAL;
+
+#if 0 /* activate when containers are used */
+ if (parent != task_pid_vnr(t))
+ goto out;
+#endif
+ cr_debug("ntls %d\n", hh->ntls);
+
+ if (hh->gdt_entry_tls_entries != GDT_ENTRY_TLS_ENTRIES ||
+ hh->sizeof_tls_array != sizeof(thread->tls_array) ||
+ hh->ntls < 0 || hh->ntls > GDT_ENTRY_TLS_ENTRIES)
+ goto out;
+
+ if (hh->ntls > 0) {
+ struct desc_struct *desc;
+ int size, cpu;
+
+ /*
+ * restore TLS by hand: why convert to struct user_desc if
+ * sys_set_thread_entry() will convert it back ?
+ */
+
+ size = sizeof(*desc) * GDT_ENTRY_TLS_ENTRIES;
+ desc = kmalloc(size, GFP_KERNEL);
+ if (!desc)
+ return -ENOMEM;
+
+ ret = cr_kread(ctx, desc, size);
+ if (ret >= 0) {
+ /*
+ * FIX: add sanity checks (eg. that values makes
+ * sense, that we don't overwrite old values, etc
+ */
+ cpu = get_cpu();
+ memcpy(thread->tls_array, desc, size);
+ load_TLS(thread, cpu);
+ put_cpu();
+ }
+ kfree(desc);
+ }
+
+ ret = 0;
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
+
+#ifdef CONFIG_X86_64
+
+#error "CONFIG_X86_64 unsupported yet."
+
+#else /* !CONFIG_X86_64 */
+
+int cr_read_cpu_regs(struct cr_hdr_cpu *hh, struct task_struct *t)
+{
+ struct thread_struct *thread = &t->thread;
+ struct pt_regs *regs = task_pt_regs(t);
+
+ regs->bx = hh->bx;
+ regs->cx = hh->cx;
+ regs->dx = hh->dx;
+ regs->si = hh->si;
+ regs->di = hh->di;
+ regs->bp = hh->bp;
+ regs->ax = hh->ax;
+ regs->ds = hh->ds;
+ regs->es = hh->es;
+ regs->orig_ax = hh->orig_ax;
+ regs->ip = hh->ip;
+ regs->cs = hh->cs;
+ regs->flags = hh->flags;
+ regs->sp = hh->sp;
+ regs->ss = hh->ss;
+
+ thread->gs = hh->gs;
+ thread->fs = hh->fs;
+ loadsegment(gs, hh->gs);
+ loadsegment(fs, hh->fs);
+
+ return 0;
+}
+
+int cr_read_cpu_debug(struct cr_hdr_cpu *hh, struct task_struct *t)
+{
+ /* debug regs */
+
+ if (hh->uses_debug) {
+ set_debugreg(hh->debugreg0, 0);
+ set_debugreg(hh->debugreg1, 1);
+ /* ignore 4, 5 */
+ set_debugreg(hh->debugreg2, 2);
+ set_debugreg(hh->debugreg3, 3);
+ set_debugreg(hh->debugreg6, 6);
+ set_debugreg(hh->debugreg7, 7);
+ }
+
+ return 0;
+}
+
+int cr_read_cpu_fpu(struct cr_hdr_cpu *hh, struct task_struct *t)
+{
+ struct thread_struct *thread = &t->thread;
+ int ret;
+
+ /* i387 + MMU + SSE */
+
+ preempt_disable();
+
+ __clear_fpu(t); /* in case we used FPU in user mode */
+
+ if (!hh->used_math)
+ clear_used_math();
+ else {
+ if (hh->has_fxsr != cpu_has_fxsr) {
+ force_sig(SIGFPE, t);
+ return -EINVAL;
+ }
+ /* init_fpu() also calls set_used_math() */
+ ret = init_fpu(current);
+ if (ret < 0)
+ return ret;
+ memcpy(thread->xstate, &hh->xstate, sizeof(*thread->xstate));
+ }
+
+ preempt_enable();
+ return 0;
+}
+
+#endif /* CONFIG_X86_64 */
+
+/* read the cpu state and registers for the current task */
+int cr_read_cpu(struct cr_ctx *ctx)
+{
+ struct cr_hdr_cpu *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct task_struct *t = current;
+ int parent, ret;
+
+ parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_CPU);
+ if (parent < 0) {
+ ret = parent;
+ goto out;
+ }
+
+ ret = -EINVAL;
+
+#if 0 /* activate when containers are used */
+ if (parent != task_pid_vnr(t))
+ goto out;
+#endif
+ /* FIX: sanity check for sensitive registers (eg. eflags) */
+
+ ret = cr_read_cpu_regs(hh, t);
+ if (ret < 0)
+ goto out;
+ ret = cr_read_cpu_debug(hh, t);
+ if (ret < 0)
+ goto out;
+ ret = cr_read_cpu_fpu(hh, t);
+
+ cr_debug("math %d debug %d\n", hh->used_math, hh->uses_debug);
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index 317b0e8..ba18e44 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c
@@ -20,6 +20,8 @@
#include <linux/checkpoint.h>
#include <linux/checkpoint_hdr.h>
+#include "checkpoint_arch.h"
+
/**
* cr_write_obj - write a record described by a cr_hdr
* @ctx: checkpoint context
@@ -145,8 +147,17 @@ static int cr_write_task(struct cr_ctx *ctx, struct task_struct *t)
}
ret = cr_write_task_struct(ctx, t);
- cr_debug("ret %d\n", ret);
+ cr_debug("task_struct: ret %d\n", ret);
+ if (ret < 0)
+ goto out;
+ ret = cr_write_thread(ctx, t);
+ cr_debug("thread: ret %d\n", ret);
+ if (ret < 0)
+ goto out;
+ ret = cr_write_cpu(ctx, t);
+ cr_debug("cpu: ret %d\n", ret);
+ out:
return ret;
}
diff --git a/checkpoint/checkpoint_arch.h b/checkpoint/checkpoint_arch.h
new file mode 100644
index 0000000..bf2d21e
--- /dev/null
+++ b/checkpoint/checkpoint_arch.h
@@ -0,0 +1,7 @@
+#include <linux/checkpoint.h>
+
+extern int cr_write_thread(struct cr_ctx *ctx, struct task_struct *t);
+extern int cr_write_cpu(struct cr_ctx *ctx, struct task_struct *t);
+
+extern int cr_read_thread(struct cr_ctx *ctx);
+extern int cr_read_cpu(struct cr_ctx *ctx);
diff --git a/checkpoint/restart.c b/checkpoint/restart.c
index 69befa7..766e381 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -15,6 +15,8 @@
#include <linux/checkpoint.h>
#include <linux/checkpoint_hdr.h>
+#include "checkpoint_arch.h"
+
/**
* cr_read_obj - read a whole record (cr_hdr followed by payload)
* @ctx: checkpoint context
@@ -172,8 +174,17 @@ static int cr_read_task(struct cr_ctx *ctx)
int ret;
ret = cr_read_task_struct(ctx);
- cr_debug("ret %d\n", ret);
+ cr_debug("task_struct: ret %d\n", ret);
+ if (ret < 0)
+ goto out;
+ ret = cr_read_thread(ctx);
+ cr_debug("thread: ret %d\n", ret);
+ if (ret < 0)
+ goto out;
+ ret = cr_read_cpu(ctx);
+ cr_debug("cpu: ret %d\n", ret);
+ out:
return ret;
}
diff --git a/include/asm-x86/checkpoint_hdr.h b/include/asm-x86/checkpoint_hdr.h
new file mode 100644
index 0000000..44a903c
--- /dev/null
+++ b/include/asm-x86/checkpoint_hdr.h
@@ -0,0 +1,72 @@
+#ifndef __ASM_X86_CKPT_HDR_H
+#define __ASM_X86_CKPT_HDR_H
+/*
+ * Checkpoint/restart - architecture specific headers x86
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <asm/processor.h>
+
+struct cr_hdr_thread {
+ /* NEED: restart blocks */
+
+ __s16 gdt_entry_tls_entries;
+ __s16 sizeof_tls_array;
+ __s16 ntls; /* number of TLS entries to follow */
+} __attribute__((aligned(8)));
+
+struct cr_hdr_cpu {
+ /* see struct pt_regs (x86-64) */
+ __u64 r15;
+ __u64 r14;
+ __u64 r13;
+ __u64 r12;
+ __u64 bp;
+ __u64 bx;
+ __u64 r11;
+ __u64 r10;
+ __u64 r9;
+ __u64 r8;
+ __u64 ax;
+ __u64 cx;
+ __u64 dx;
+ __u64 si;
+ __u64 di;
+ __u64 orig_ax;
+ __u64 ip;
+ __u64 cs;
+ __u64 flags;
+ __u64 sp;
+ __u64 ss;
+
+ /* segment registers */
+ __u64 ds;
+ __u64 es;
+ __u64 fs;
+ __u64 gs;
+
+ /* debug registers */
+ __u64 debugreg0;
+ __u64 debugreg1;
+ __u64 debugreg2;
+ __u64 debugreg3;
+ __u64 debugreg4;
+ __u64 debugreg5;
+ __u64 debugreg6;
+ __u64 debugreg7;
+
+ __u16 uses_debug;
+ __u16 used_math;
+ __u16 has_fxsr;
+ __u16 _padding;
+
+ union thread_xstate xstate; /* i387 */
+
+} __attribute__((aligned(8)));
+
+#endif /* __ASM_X86_CKPT_HDR__H */
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 79e4df2..03ec72e 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -12,6 +12,7 @@
#include <linux/types.h>
#include <linux/utsname.h>
+#include <asm/checkpoint_hdr.h>
/*
* To maintain compatibility between 32-bit and 64-bit architecture flavors,
--
1.5.4.3
Add those interfaces, as well as helpers needed to easily manage the
file format. The code is roughly broken out as follows:
checkpoint/sys.c - user/kernel data transfer, as well as setup of the
CR context (a per-checkpoint data structure for housekeeping)
checkpoint/checkpoint.c - output wrappers and basic checkpoint handling
checkpoint/restart.c - input wrappers and basic restart handling
For now, we can only checkpoint the 'current' task ("self" checkpoint),
and the 'pid' argument to to the syscall is ignored.
Patches to add the per-architecture support as well as the actual
work to do the memory checkpoint follow in subsequent patches.
Changelog[v6]:
- Balance all calls to cr_hbuf_get() with matching cr_hbuf_put()
(although it's not really needed)
Changelog[v5]:
- Rename headers files s/ckpt/checkpoint/
Changelog[v2]:
- Added utsname->{release,version,machine} to checkpoint header
- Pad header structures to 64 bits to ensure compatibility
Signed-off-by: Oren Laadan <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
---
Makefile | 2 +-
checkpoint/Makefile | 2 +-
checkpoint/checkpoint.c | 174 +++++++++++++++++++++++++++++++
checkpoint/restart.c | 197 ++++++++++++++++++++++++++++++++++++
checkpoint/sys.c | 219 +++++++++++++++++++++++++++++++++++++++-
include/linux/checkpoint.h | 56 ++++++++++
include/linux/checkpoint_hdr.h | 75 ++++++++++++++
include/linux/magic.h | 3 +
8 files changed, 722 insertions(+), 6 deletions(-)
create mode 100644 checkpoint/checkpoint.c
create mode 100644 checkpoint/restart.c
create mode 100644 include/linux/checkpoint.h
create mode 100644 include/linux/checkpoint_hdr.h
diff --git a/Makefile b/Makefile
index ce9eceb..cb99128 100644
--- a/Makefile
+++ b/Makefile
@@ -619,7 +619,7 @@ export mod_strip_cmd
ifeq ($(KBUILD_EXTMOD),)
-core-y += kernel/ mm/ fs/ ipc/ security/ crypto/ block/
+core-y += kernel/ mm/ fs/ ipc/ security/ crypto/ block/ checkpoint/
vmlinux-dirs := $(patsubst %/,%,$(filter %/, $(init-y) $(init-m) \
$(core-y) $(core-m) $(drivers-y) $(drivers-m) \
diff --git a/checkpoint/Makefile b/checkpoint/Makefile
index 07d018b..d2df68c 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile
@@ -2,4 +2,4 @@
# Makefile for linux checkpoint/restart.
#
-obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o
+obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
new file mode 100644
index 0000000..317b0e8
--- /dev/null
+++ b/checkpoint/checkpoint.c
@@ -0,0 +1,174 @@
+/*
+ * Checkpoint logic and helpers
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/version.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/dcache.h>
+#include <linux/mount.h>
+#include <linux/utsname.h>
+#include <linux/magic.h>
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+/**
+ * cr_write_obj - write a record described by a cr_hdr
+ * @ctx: checkpoint context
+ * @h: record descriptor
+ * @buf: record buffer
+ */
+int cr_write_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf)
+{
+ int ret;
+
+ ret = cr_kwrite(ctx, h, sizeof(*h));
+ if (ret < 0)
+ return ret;
+ return cr_kwrite(ctx, buf, h->len);
+}
+
+/**
+ * cr_write_string - write a string
+ * @ctx: checkpoint context
+ * @str: string pointer
+ * @len: string length
+ */
+int cr_write_string(struct cr_ctx *ctx, char *str, int len)
+{
+ struct cr_hdr h;
+
+ h.type = CR_HDR_STRING;
+ h.len = len;
+ h.parent = 0;
+
+ return cr_write_obj(ctx, &h, str);
+}
+
+/* write the checkpoint header */
+static int cr_write_head(struct cr_ctx *ctx)
+{
+ struct cr_hdr h;
+ struct cr_hdr_head *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct new_utsname *uts;
+ struct timeval ktv;
+ int ret;
+
+ h.type = CR_HDR_HEAD;
+ h.len = sizeof(*hh);
+ h.parent = 0;
+
+ do_gettimeofday(&ktv);
+
+ hh->magic = CHECKPOINT_MAGIC_HEAD;
+ hh->major = (LINUX_VERSION_CODE >> 16) & 0xff;
+ hh->minor = (LINUX_VERSION_CODE >> 8) & 0xff;
+ hh->patch = (LINUX_VERSION_CODE) & 0xff;
+
+ hh->rev = CR_VERSION;
+
+ hh->flags = ctx->flags;
+ hh->time = ktv.tv_sec;
+
+ uts = utsname();
+ memcpy(hh->release, uts->release, __NEW_UTS_LEN);
+ memcpy(hh->version, uts->version, __NEW_UTS_LEN);
+ memcpy(hh->machine, uts->machine, __NEW_UTS_LEN);
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
+
+/* write the checkpoint trailer */
+static int cr_write_tail(struct cr_ctx *ctx)
+{
+ struct cr_hdr h;
+ struct cr_hdr_tail *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ int ret;
+
+ h.type = CR_HDR_TAIL;
+ h.len = sizeof(*hh);
+ h.parent = 0;
+
+ hh->magic = CHECKPOINT_MAGIC_TAIL;
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
+
+/* dump the task_struct of a given task */
+static int cr_write_task_struct(struct cr_ctx *ctx, struct task_struct *t)
+{
+ struct cr_hdr h;
+ struct cr_hdr_task *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ int ret;
+
+ h.type = CR_HDR_TASK;
+ h.len = sizeof(*hh);
+ h.parent = 0;
+
+ hh->state = t->state;
+ hh->exit_state = t->exit_state;
+ hh->exit_code = t->exit_code;
+ hh->exit_signal = t->exit_signal;
+
+ hh->task_comm_len = TASK_COMM_LEN;
+
+ /* FIXME: save remaining relevant task_struct fields */
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ return ret;
+
+ return cr_write_string(ctx, t->comm, TASK_COMM_LEN);
+}
+
+/* dump the entire state of a given task */
+static int cr_write_task(struct cr_ctx *ctx, struct task_struct *t)
+{
+ int ret ;
+
+ if (t->state == TASK_DEAD) {
+ pr_warning("C/R: task may not be in state TASK_DEAD\n");
+ return -EAGAIN;
+ }
+
+ ret = cr_write_task_struct(ctx, t);
+ cr_debug("ret %d\n", ret);
+
+ return ret;
+}
+
+int do_checkpoint(struct cr_ctx *ctx)
+{
+ int ret;
+
+ /* FIX: need to test whether container is checkpointable */
+
+ ret = cr_write_head(ctx);
+ if (ret < 0)
+ goto out;
+ ret = cr_write_task(ctx, current);
+ if (ret < 0)
+ goto out;
+ ret = cr_write_tail(ctx);
+ if (ret < 0)
+ goto out;
+
+ /* on success, return (unique) checkpoint identifier */
+ ret = ctx->crid;
+
+ out:
+ return ret;
+}
diff --git a/checkpoint/restart.c b/checkpoint/restart.c
new file mode 100644
index 0000000..69befa7
--- /dev/null
+++ b/checkpoint/restart.c
@@ -0,0 +1,197 @@
+/*
+ * Restart logic and helpers
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/version.h>
+#include <linux/sched.h>
+#include <linux/file.h>
+#include <linux/magic.h>
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+/**
+ * cr_read_obj - read a whole record (cr_hdr followed by payload)
+ * @ctx: checkpoint context
+ * @h: record descriptor
+ * @buf: record buffer
+ * @n: available buffer size
+ *
+ * Returns size of payload
+ */
+int cr_read_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf, int n)
+{
+ int ret;
+
+ ret = cr_kread(ctx, h, sizeof(*h));
+ if (ret < 0)
+ return ret;
+
+ cr_debug("type %d len %d parent %d\n", h->type, h->len, h->parent);
+
+ if (h->len < 0 || h->len > n)
+ return -EINVAL;
+
+ return cr_kread(ctx, buf, h->len);
+}
+
+/**
+ * cr_read_obj_type - read a whole record of expected type
+ * @ctx: checkpoint context
+ * @buf: record buffer
+ * @n: available buffer size
+ * @type: expected record type
+ *
+ * Returns object reference of the parent object
+ */
+int cr_read_obj_type(struct cr_ctx *ctx, void *buf, int n, int type)
+{
+ struct cr_hdr h;
+ int ret;
+
+ ret = cr_read_obj(ctx, &h, buf, n);
+ if (ret < 0)
+ return ret;
+
+ ret = -EINVAL;
+ if (h.type == type)
+ ret = h.parent;
+
+ return ret;
+}
+
+/**
+ * cr_read_string - read a string
+ * @ctx: checkpoint context
+ * @str: string buffer
+ * @len: buffer buffer length
+ */
+int cr_read_string(struct cr_ctx *ctx, void *str, int len)
+{
+ return cr_read_obj_type(ctx, str, len, CR_HDR_STRING);
+}
+
+/* read the checkpoint header */
+static int cr_read_head(struct cr_ctx *ctx)
+{
+ struct cr_hdr_head *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ int parent, ret = -EINVAL;
+
+ parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_HEAD);
+ if (parent < 0) {
+ ret = parent;
+ goto out;
+ } else if (parent != 0)
+ goto out;
+
+ if (hh->magic != CHECKPOINT_MAGIC_HEAD || hh->rev != CR_VERSION ||
+ hh->major != ((LINUX_VERSION_CODE >> 16) & 0xff) ||
+ hh->minor != ((LINUX_VERSION_CODE >> 8) & 0xff) ||
+ hh->patch != ((LINUX_VERSION_CODE) & 0xff))
+ goto out;
+
+ if (hh->flags & ~CR_CTX_CKPT)
+ goto out;
+
+ ctx->oflags = hh->flags;
+
+ /* FIX: verify compatibility of release, version and machine */
+
+ ret = 0;
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
+
+/* read the checkpoint trailer */
+static int cr_read_tail(struct cr_ctx *ctx)
+{
+ struct cr_hdr_tail *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ int parent, ret = -EINVAL;
+
+ parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_TAIL);
+ if (parent < 0) {
+ ret = parent;
+ goto out;
+ } else if (parent != 0)
+ goto out;
+
+ if (hh->magic != CHECKPOINT_MAGIC_TAIL)
+ goto out;
+
+ ret = 0;
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
+
+/* read the task_struct into the current task */
+static int cr_read_task_struct(struct cr_ctx *ctx)
+{
+ struct cr_hdr_task *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct task_struct *t = current;
+ char *buf;
+ int parent, ret = -EINVAL;
+
+ parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_TASK);
+ if (parent < 0) {
+ ret = parent;
+ goto out;
+ } else if (parent != 0)
+ goto out;
+
+ /* upper limit for task_comm_len to prevent DoS */
+ if (hh->task_comm_len < 0 || hh->task_comm_len > PAGE_SIZE)
+ goto out;
+
+ buf = kmalloc(hh->task_comm_len, GFP_KERNEL);
+ if (!buf)
+ goto out;
+ ret = cr_read_string(ctx, buf, hh->task_comm_len);
+ if (!ret) {
+ /* if t->comm is too long, silently truncate */
+ memset(t->comm, 0, TASK_COMM_LEN);
+ memcpy(t->comm, buf, min(hh->task_comm_len, TASK_COMM_LEN));
+ }
+ kfree(buf);
+
+ /* FIXME: restore remaining relevant task_struct fields */
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
+
+/* read the entire state of the current task */
+static int cr_read_task(struct cr_ctx *ctx)
+{
+ int ret;
+
+ ret = cr_read_task_struct(ctx);
+ cr_debug("ret %d\n", ret);
+
+ return ret;
+}
+
+int do_restart(struct cr_ctx *ctx)
+{
+ int ret;
+
+ ret = cr_read_head(ctx);
+ if (ret < 0)
+ goto out;
+ ret = cr_read_task(ctx);
+ if (ret < 0)
+ goto out;
+ ret = cr_read_tail(ctx);
+ if (ret < 0)
+ goto out;
+
+ /* on success, adjust the return value if needed [TODO] */
+ out:
+ return ret;
+}
diff --git a/checkpoint/sys.c b/checkpoint/sys.c
index 375129c..3ce84ba 100644
--- a/checkpoint/sys.c
+++ b/checkpoint/sys.c
@@ -10,6 +10,187 @@
#include <linux/sched.h>
#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/uaccess.h>
+#include <linux/capability.h>
+#include <linux/checkpoint.h>
+
+/*
+ * helpers to write/read to/from the image file descriptor
+ *
+ * cr_uwrite() - write a user-space buffer to the checkpoint image
+ * cr_kwrite() - write a kernel-space buffer to the checkpoint image
+ * cr_uread() - read from the checkpoint image to a user-space buffer
+ * cr_kread() - read from the checkpoint image to a kernel-space buffer
+ */
+
+int cr_uwrite(struct cr_ctx *ctx, void *buf, int count)
+{
+ struct file *file = ctx->file;
+ ssize_t nwrite;
+ int nleft;
+
+ for (nleft = count; nleft; nleft -= nwrite) {
+ loff_t pos = file_pos_read(file);
+ nwrite = vfs_write(file, (char __user *) buf, nleft, &pos);
+ file_pos_write(file, pos);
+ if (nwrite <= 0) {
+ if (nwrite == -EAGAIN)
+ nwrite = 0;
+ else
+ return nwrite;
+ }
+ buf += nwrite;
+ }
+
+ ctx->total += count;
+ return 0;
+}
+
+int cr_kwrite(struct cr_ctx *ctx, void *buf, int count)
+{
+ mm_segment_t oldfs;
+ int ret;
+
+ oldfs = get_fs();
+ set_fs(KERNEL_DS);
+ ret = cr_uwrite(ctx, buf, count);
+ set_fs(oldfs);
+
+ return ret;
+}
+
+int cr_uread(struct cr_ctx *ctx, void *buf, int count)
+{
+ struct file *file = ctx->file;
+ ssize_t nread;
+ int nleft;
+
+ for (nleft = count; nleft; nleft -= nread) {
+ loff_t pos = file_pos_read(file);
+ nread = vfs_read(file, (char __user *) buf, nleft, &pos);
+ file_pos_write(file, pos);
+ if (nread <= 0) {
+ if (nread == -EAGAIN)
+ nread = 0;
+ else
+ return nread;
+ }
+ buf += nread;
+ }
+
+ ctx->total += count;
+ return 0;
+}
+
+int cr_kread(struct cr_ctx *ctx, void *buf, int count)
+{
+ mm_segment_t oldfs;
+ int ret;
+
+ oldfs = get_fs();
+ set_fs(KERNEL_DS);
+ ret = cr_uread(ctx, buf, count);
+ set_fs(oldfs);
+
+ return ret;
+}
+
+/*
+ * During checkpoint and restart the code writes outs/reads in data
+ * to/from the checkpoint image from/to a temporary buffer (ctx->hbuf).
+ * Because operations can be nested, use cr_hbuf_get() to reserve space
+ * in the buffer, then cr_hbuf_put() when you no longer need that space.
+ */
+
+/*
+ * ctx->hbuf is used to hold headers and data of known (or bound),
+ * static sizes. In some cases, multiple headers may be allocated in
+ * a nested manner. The size should accommodate all headers, nested
+ * or not, on all archs.
+ */
+#define CR_HBUF_TOTAL (8 * 4096)
+
+/**
+ * cr_hbuf_get - reserve space on the hbuf
+ * @ctx: checkpoint context
+ * @n: number of bytes to reserve
+ *
+ * Returns pointer to reserved space
+ */
+void *cr_hbuf_get(struct cr_ctx *ctx, int n)
+{
+ void *ptr;
+
+ /*
+ * Since requests depend on logic and static header sizes (not on
+ * user data), space should always suffice, unless someone either
+ * made a structure bigger or call path deeper than expected.
+ */
+ BUG_ON(ctx->hpos + n > CR_HBUF_TOTAL);
+ ptr = ctx->hbuf + ctx->hpos;
+ ctx->hpos += n;
+ return ptr;
+}
+
+/**
+ * cr_hbuf_put - unreserve space on the hbuf
+ * @ctx: checkpoint context
+ * @n: number of bytes to reserve
+ */
+void cr_hbuf_put(struct cr_ctx *ctx, int n)
+{
+ BUG_ON(ctx->hpos < n);
+ ctx->hpos -= n;
+}
+
+/*
+ * helpers to manage C/R contexts: allocated for each checkpoint and/or
+ * restart operation, and persists until the operation is completed.
+ */
+
+/* unique checkpoint identifier (FIXME: should be per-container) */
+static atomic_t cr_ctx_count = ATOMIC_INIT(0);
+
+static void cr_ctx_free(struct cr_ctx *ctx)
+{
+ if (ctx->file)
+ fput(ctx->file);
+ kfree(ctx->hbuf);
+ kfree(ctx);
+}
+
+static struct cr_ctx *cr_ctx_alloc(pid_t pid, int fd, unsigned long flags)
+{
+ struct cr_ctx *ctx;
+ int err;
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return ERR_PTR(-ENOMEM);
+
+ ctx->pid = pid;
+ ctx->flags = flags;
+
+ err = -EBADF;
+ ctx->file = fget(fd);
+ if (!ctx->file)
+ goto err;
+
+ err = -ENOMEM;
+ ctx->hbuf = kmalloc(CR_HBUF_TOTAL, GFP_KERNEL);
+ if (!ctx->hbuf)
+ goto err;
+
+ ctx->crid = atomic_inc_return(&cr_ctx_count);
+
+ return ctx;
+
+ err:
+ cr_ctx_free(ctx);
+ return ERR_PTR(err);
+}
/**
* sys_checkpoint - checkpoint a container
@@ -22,9 +203,26 @@
*/
asmlinkage long sys_checkpoint(pid_t pid, int fd, unsigned long flags)
{
- pr_debug("sys_checkpoint not implemented yet\n");
- return -ENOSYS;
+ struct cr_ctx *ctx;
+ int ret;
+
+ /* no flags for now */
+ if (flags)
+ return -EINVAL;
+
+ ctx = cr_ctx_alloc(pid, fd, flags | CR_CTX_CKPT);
+ if (IS_ERR(ctx))
+ return PTR_ERR(ctx);
+
+ ret = do_checkpoint(ctx);
+
+ if (!ret)
+ ret = ctx->crid;
+
+ cr_ctx_free(ctx);
+ return ret;
}
+
/**
* sys_restart - restart a container
* @crid: checkpoint image identifier
@@ -36,6 +234,19 @@ asmlinkage long sys_checkpoint(pid_t pid, int fd, unsigned long flags)
*/
asmlinkage long sys_restart(int crid, int fd, unsigned long flags)
{
- pr_debug("sys_restart not implemented yet\n");
- return -ENOSYS;
+ struct cr_ctx *ctx;
+ int ret;
+
+ /* no flags for now */
+ if (flags)
+ return -EINVAL;
+
+ ctx = cr_ctx_alloc(crid, fd, flags | CR_CTX_RSTR);
+ if (IS_ERR(ctx))
+ return PTR_ERR(ctx);
+
+ ret = do_restart(ctx);
+
+ cr_ctx_free(ctx);
+ return ret;
}
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
new file mode 100644
index 0000000..0f47160
--- /dev/null
+++ b/include/linux/checkpoint.h
@@ -0,0 +1,56 @@
+#ifndef _CHECKPOINT_CKPT_H_
+#define _CHECKPOINT_CKPT_H_
+/*
+ * Generic container checkpoint-restart
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#define CR_VERSION 1
+
+struct cr_ctx {
+ pid_t pid; /* container identifier */
+ int crid; /* unique checkpoint id */
+
+ unsigned long flags;
+ unsigned long oflags; /* restart: old flags */
+
+ struct file *file;
+ int total; /* total read/written */
+
+ void *hbuf; /* temporary buffer for headers */
+ int hpos; /* position in headers buffer */
+};
+
+/* cr_ctx: flags */
+#define CR_CTX_CKPT 0x1
+#define CR_CTX_RSTR 0x2
+
+extern int cr_uwrite(struct cr_ctx *ctx, void *buf, int count);
+extern int cr_kwrite(struct cr_ctx *ctx, void *buf, int count);
+extern int cr_uread(struct cr_ctx *ctx, void *buf, int count);
+extern int cr_kread(struct cr_ctx *ctx, void *buf, int count);
+
+extern void *cr_hbuf_get(struct cr_ctx *ctx, int n);
+extern void cr_hbuf_put(struct cr_ctx *ctx, int n);
+
+struct cr_hdr;
+
+extern int cr_write_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf);
+extern int cr_write_string(struct cr_ctx *ctx, char *str, int len);
+
+extern int cr_read_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf, int n);
+extern int cr_read_obj_type(struct cr_ctx *ctx, void *buf, int n, int type);
+extern int cr_read_string(struct cr_ctx *ctx, void *str, int len);
+
+extern int do_checkpoint(struct cr_ctx *ctx);
+extern int do_restart(struct cr_ctx *ctx);
+
+#define cr_debug(fmt, args...) \
+ pr_debug("[CR:%s] " fmt, __func__, ## args)
+
+#endif /* _CHECKPOINT_CKPT_H_ */
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
new file mode 100644
index 0000000..79e4df2
--- /dev/null
+++ b/include/linux/checkpoint_hdr.h
@@ -0,0 +1,75 @@
+#ifndef _CHECKPOINT_CKPT_HDR_H_
+#define _CHECKPOINT_CKPT_HDR_H_
+/*
+ * Generic container checkpoint-restart
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/types.h>
+#include <linux/utsname.h>
+
+/*
+ * To maintain compatibility between 32-bit and 64-bit architecture flavors,
+ * keep data 64-bit aligned: use padding for structure members, and use
+ * __attribute__ ((aligned (8))) for the entire structure.
+ */
+
+/* records: generic header */
+
+struct cr_hdr {
+ __s16 type;
+ __s16 len;
+ __u32 parent;
+};
+
+/* header types */
+enum {
+ CR_HDR_HEAD = 1,
+ CR_HDR_STRING,
+
+ CR_HDR_TASK = 101,
+ CR_HDR_THREAD,
+ CR_HDR_CPU,
+
+ CR_HDR_MM = 201,
+ CR_HDR_VMA,
+ CR_HDR_MM_CONTEXT,
+
+ CR_HDR_TAIL = 5001
+};
+
+struct cr_hdr_head {
+ __u64 magic;
+
+ __u16 major;
+ __u16 minor;
+ __u16 patch;
+ __u16 rev;
+
+ __u64 time; /* when checkpoint taken */
+ __u64 flags; /* checkpoint options */
+
+ char release[__NEW_UTS_LEN];
+ char version[__NEW_UTS_LEN];
+ char machine[__NEW_UTS_LEN];
+} __attribute__((aligned(8)));
+
+struct cr_hdr_tail {
+ __u64 magic;
+} __attribute__((aligned(8)));
+
+struct cr_hdr_task {
+ __u32 state;
+ __u32 exit_state;
+ __u32 exit_code;
+ __u32 exit_signal;
+
+ __s32 task_comm_len;
+} __attribute__((aligned(8)));
+
+#endif /* _CHECKPOINT_CKPT_HDR_H_ */
diff --git a/include/linux/magic.h b/include/linux/magic.h
index 1fa0c2c..c2b811c 100644
--- a/include/linux/magic.h
+++ b/include/linux/magic.h
@@ -42,4 +42,7 @@
#define FUTEXFS_SUPER_MAGIC 0xBAD1DEA
#define INOTIFYFS_SUPER_MAGIC 0x2BAD1DEA
+#define CHECKPOINT_MAGIC_HEAD 0x00feed0cc0a2d200LL
+#define CHECKPOINT_MAGIC_TAIL 0x002d2a0cc0deef00LL
+
#endif /* __LINUX_MAGIC_H__ */
--
1.5.4.3
Restore open file descriptors: for each FD read 'struct cr_hdr_fd_ent'
and lookup objref in the hash table; if not found (first occurence), read
in 'struct cr_hdr_fd_data', create a new FD and register in the hash.
Otherwise attach the file pointer from the hash as an FD.
This patch only handles basic FDs - regular files, directories and also
symbolic links.
Changelog[v6]:
- Balance all calls to cr_hbuf_get() with matching cr_hbuf_put()
(even though it's not really needed)
Signed-off-by: Oren Laadan <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
---
checkpoint/Makefile | 2 +-
checkpoint/restart.c | 4 +
checkpoint/rstr_file.c | 246 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/checkpoint.h | 1 +
4 files changed, 252 insertions(+), 1 deletions(-)
create mode 100644 checkpoint/rstr_file.c
diff --git a/checkpoint/Makefile b/checkpoint/Makefile
index 7496695..88bbc10 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile
@@ -3,4 +3,4 @@
#
obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o objhash.o \
- ckpt_mem.o rstr_mem.o ckpt_file.o
+ ckpt_mem.o rstr_mem.o ckpt_file.o rstr_file.o
diff --git a/checkpoint/restart.c b/checkpoint/restart.c
index f4d87ba..9ff9f66 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -219,6 +219,10 @@ static int cr_read_task(struct cr_ctx *ctx)
cr_debug("memory: ret %d\n", ret);
if (ret < 0)
goto out;
+ ret = cr_read_files(ctx);
+ cr_debug("files: ret %d\n", ret);
+ if (ret < 0)
+ goto out;
ret = cr_read_thread(ctx);
cr_debug("thread: ret %d\n", ret);
if (ret < 0)
diff --git a/checkpoint/rstr_file.c b/checkpoint/rstr_file.c
new file mode 100644
index 0000000..08bb049
--- /dev/null
+++ b/checkpoint/rstr_file.c
@@ -0,0 +1,246 @@
+/*
+ * Checkpoint file descriptors
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/fsnotify.h>
+#include <linux/syscalls.h>
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+#include "checkpoint_file.h"
+
+static int cr_close_all_fds(struct files_struct *files)
+{
+ int *fdtable;
+ int nfds;
+
+ nfds = cr_scan_fds(files, &fdtable);
+ if (nfds < 0)
+ return nfds;
+ while (nfds--)
+ sys_close(fdtable[nfds]);
+ kfree(fdtable);
+ return 0;
+}
+
+/**
+ * cr_attach_file - attach a lonely file ptr to a file descriptor
+ * @file: lonely file pointer
+ */
+static int cr_attach_file(struct file *file)
+{
+ int fd = get_unused_fd_flags(0);
+
+ if (fd >= 0) {
+ fsnotify_open(file->f_path.dentry);
+ fd_install(fd, file);
+ }
+ return fd;
+}
+
+/**
+ * cr_attach_get_file - attach (and get) lonely file ptr to a file descriptor
+ * @file: lonely file pointer
+ */
+static int cr_attach_get_file(struct file *file)
+{
+ int fd = get_unused_fd_flags(0);
+
+ if (fd >= 0) {
+ fsnotify_open(file->f_path.dentry);
+ fd_install(fd, file);
+ get_file(file);
+ }
+ return fd;
+}
+
+#define CR_SETFL_MASK (O_APPEND|O_NONBLOCK|O_NDELAY|FASYNC|O_DIRECT|O_NOATIME)
+
+/* cr_read_fd_data - restore the state of a given file pointer */
+static int
+cr_read_fd_data(struct cr_ctx *ctx, struct files_struct *files, int parent)
+{
+ struct cr_hdr_fd_data *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct file *file;
+ int rparent, ret;
+ int fd = 0; /* pacify gcc warning */
+
+ rparent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_FD_DATA);
+ cr_debug("rparent %d parent %d flags %#x mode %#x how %d\n",
+ rparent, parent, hh->f_flags, hh->f_mode, hh->fd_type);
+ if (rparent < 0) {
+ ret = parent;
+ goto out;
+ }
+
+ ret = -EINVAL;
+
+ if (rparent != parent)
+ goto out;
+
+ /* FIX: more sanity checks on f_flags, f_mode etc */
+
+ switch (hh->fd_type) {
+ case CR_FD_FILE:
+ case CR_FD_DIR:
+ case CR_FD_LINK:
+ file = cr_read_open_fname(ctx, hh->f_flags, hh->f_mode);
+ break;
+ default:
+ goto out;
+ }
+
+ if (IS_ERR(file)) {
+ ret = PTR_ERR(file);
+ goto out;
+ }
+
+ /* FIX: need to restore uid, gid, owner etc */
+
+ fd = cr_attach_file(file); /* no need to cleanup 'file' below */
+ if (fd < 0) {
+ filp_close(file, NULL);
+ ret = fd;
+ goto out;
+ }
+
+ /* register new <objref, file> tuple in hash table */
+ ret = cr_obj_add_ref(ctx, (void *) file, parent, CR_OBJ_FILE, 0);
+ if (ret < 0)
+ goto out;
+ ret = sys_fcntl(fd, F_SETFL, hh->f_flags & CR_SETFL_MASK);
+ if (ret < 0)
+ goto out;
+ ret = vfs_llseek(file, hh->f_pos, SEEK_SET);
+ if (ret == -ESPIPE) /* ignore error on non-seekable files */
+ ret = 0;
+
+ ret = 0;
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret < 0 ? ret : fd;
+}
+
+/**
+ * cr_read_fd_ent - restore the state of a given file descriptor
+ * @ctx: checkpoint context
+ * @files: files_struct pointer
+ * @parent: parent objref
+ *
+ * Restores the state of a file descriptor; looks up the objref (in the
+ * header) in the hash table, and if found picks the matching file and
+ * use it; otherwise calls cr_read_fd_data to restore the file too.
+ */
+static int
+cr_read_fd_ent(struct cr_ctx *ctx, struct files_struct *files, int parent)
+{
+ struct cr_hdr_fd_ent *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct file *file;
+ int newfd, rparent, ret;
+
+ rparent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_FD_ENT);
+ cr_debug("rparent %d parent %d ref %d fd %d c.o.e %d\n",
+ rparent, parent, hh->objref, hh->fd, hh->close_on_exec);
+ if (rparent < 0) {
+ ret = rparent;
+ goto out;
+ }
+
+ ret = -EINVAL;
+
+ if (rparent != parent)
+ goto out;
+ if (hh->objref <= 0)
+ goto out;
+
+ file = cr_obj_get_by_ref(ctx, hh->objref, CR_OBJ_FILE);
+ if (IS_ERR(file)) {
+ ret = PTR_ERR(file);
+ goto out;
+ }
+
+ if (file) {
+ /* reuse file descriptor found in the hash table */
+ newfd = cr_attach_get_file(file);
+ } else {
+ /* create new file pointer (and register in hash table) */
+ newfd = cr_read_fd_data(ctx, files, hh->objref);
+ }
+
+ if (newfd < 0) {
+ ret = newfd;
+ goto out;
+ }
+
+ cr_debug("newfd got %d wanted %d\n", newfd, hh->fd);
+
+ /* if newfd isn't desired fd then reposition it */
+ if (newfd != hh->fd) {
+ ret = sys_dup2(newfd, hh->fd);
+ if (ret < 0)
+ goto out;
+ sys_close(newfd);
+ }
+
+ if (hh->close_on_exec)
+ set_close_on_exec(hh->fd, 1);
+
+ ret = 0;
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
+
+int cr_read_files(struct cr_ctx *ctx)
+{
+ struct cr_hdr_files *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct files_struct *files = current->files;
+ int i, parent, ret;
+
+ parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_FILES);
+ if (parent < 0) {
+ ret = parent;
+ goto out;
+ }
+
+ ret = -EINVAL;
+#if 0 /* activate when containers are used */
+ if (parent != task_pid_vnr(current))
+ goto out;
+#endif
+ cr_debug("objref %d nfds %d\n", hh->objref, hh->nfds);
+ if (hh->objref < 0 || hh->nfds < 0)
+ goto out;
+
+ if (hh->nfds > sysctl_nr_open) {
+ ret = -EMFILE;
+ goto out;
+ }
+
+ /* point of no return -- close all file descriptors */
+ ret = cr_close_all_fds(files);
+ if (ret < 0)
+ goto out;
+
+ for (i = 0; i < hh->nfds; i++) {
+ ret = cr_read_fd_ent(ctx, files, hh->objref);
+ if (ret < 0)
+ break;
+ }
+
+ ret = 0;
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 0856b3b..6c1e87f 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -85,6 +85,7 @@ extern int cr_write_files(struct cr_ctx *ctx, struct task_struct *t);
extern int do_restart(struct cr_ctx *ctx);
extern int cr_read_mm(struct cr_ctx *ctx);
+extern int cr_read_files(struct cr_ctx *ctx);
#define cr_debug(fmt, args...) \
pr_debug("[CR:%s] " fmt, __func__, ## args)
--
1.5.4.3
Infrastructure to handle objects that may be shared and referenced by
multiple tasks or other objects, e..g open files, memory address space
etc.
The state of shared objects is saved once. On the first encounter, the
state is dumped and the object is assigned a unique identifier (objref)
and also stored in a hash table (indexed by its physical kenrel address).
>From then on the object will be found in the hash and only its identifier
is saved.
On restart the identifier is looked up in the hash table; if not found
then the state is read, the object is created, and added to the hash
table (this time indexed by its identifier). Otherwise, the object in
the hash table is used.
Changelog[v4]:
- Fix calculation of hash table size
Changelog[v3]:
- Use standard hlist_... for hash table
Signed-off-by: Oren Laadan <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
---
checkpoint/Makefile | 2 +-
checkpoint/objhash.c | 268 ++++++++++++++++++++++++++++++++++++++++++++
checkpoint/sys.c | 6 +
include/linux/checkpoint.h | 20 ++++
4 files changed, 295 insertions(+), 1 deletions(-)
create mode 100644 checkpoint/objhash.c
diff --git a/checkpoint/Makefile b/checkpoint/Makefile
index ac35033..9843fb9 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile
@@ -2,5 +2,5 @@
# Makefile for linux checkpoint/restart.
#
-obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o \
+obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o objhash.o \
ckpt_mem.o rstr_mem.o
diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
new file mode 100644
index 0000000..05b1a1b
--- /dev/null
+++ b/checkpoint/objhash.c
@@ -0,0 +1,268 @@
+/*
+ * Checkpoint-restart - object hash infrastructure to manage shared objects
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/file.h>
+#include <linux/hash.h>
+#include <linux/checkpoint.h>
+
+struct cr_objref {
+ int objref;
+ void *ptr;
+ unsigned short type;
+ unsigned short flags;
+ struct hlist_node hash;
+};
+
+struct cr_objhash {
+ struct hlist_head *head;
+ int next_free_objref;
+};
+
+#define CR_OBJHASH_NBITS 10
+#define CR_OBJHASH_TOTAL (1UL << CR_OBJHASH_NBITS)
+
+static void cr_obj_ref_drop(struct cr_objref *obj)
+{
+ switch (obj->type) {
+ case CR_OBJ_FILE:
+ fput((struct file *) obj->ptr);
+ break;
+ default:
+ BUG();
+ }
+}
+
+static void cr_obj_ref_grab(struct cr_objref *obj)
+{
+ switch (obj->type) {
+ case CR_OBJ_FILE:
+ get_file((struct file *) obj->ptr);
+ break;
+ default:
+ BUG();
+ }
+}
+
+static void cr_objhash_clear(struct cr_objhash *objhash)
+{
+ struct hlist_head *h = objhash->head;
+ struct hlist_node *n, *t;
+ struct cr_objref *obj;
+ int i;
+
+ for (i = 0; i < CR_OBJHASH_TOTAL; i++) {
+ hlist_for_each_entry_safe(obj, n, t, &h[i], hash) {
+ cr_obj_ref_drop(obj);
+ kfree(obj);
+ }
+ }
+}
+
+void cr_objhash_free(struct cr_ctx *ctx)
+{
+ struct cr_objhash *objhash = ctx->objhash;
+
+ if (objhash) {
+ cr_objhash_clear(objhash);
+ kfree(objhash->head);
+ kfree(ctx->objhash);
+ ctx->objhash = NULL;
+ }
+}
+
+int cr_objhash_alloc(struct cr_ctx *ctx)
+{
+ struct cr_objhash *objhash;
+ struct hlist_head *head;
+
+ objhash = kzalloc(sizeof(*objhash), GFP_KERNEL);
+ if (!objhash)
+ return -ENOMEM;
+ head = kzalloc(CR_OBJHASH_TOTAL * sizeof(*head), GFP_KERNEL);
+ if (!head) {
+ kfree(objhash);
+ return -ENOMEM;
+ }
+
+ objhash->head = head;
+ objhash->next_free_objref = 1;
+
+ ctx->objhash = objhash;
+ return 0;
+}
+
+static struct cr_objref *cr_obj_find_by_ptr(struct cr_ctx *ctx, void *ptr)
+{
+ struct hlist_head *h;
+ struct hlist_node *n;
+ struct cr_objref *obj;
+
+ h = &ctx->objhash->head[hash_ptr(ptr, CR_OBJHASH_NBITS)];
+ hlist_for_each_entry(obj, n, h, hash)
+ if (obj->ptr == ptr)
+ return obj;
+ return NULL;
+}
+
+static struct cr_objref *cr_obj_find_by_objref(struct cr_ctx *ctx, int objref)
+{
+ struct hlist_head *h;
+ struct hlist_node *n;
+ struct cr_objref *obj;
+
+ h = &ctx->objhash->head[hash_ptr((void *) objref, CR_OBJHASH_NBITS)];
+ hlist_for_each_entry(obj, n, h, hash)
+ if (obj->objref == objref)
+ return obj;
+ return NULL;
+}
+
+/**
+ * cr_obj_new - allocate an object and add to the hash table
+ * @ctx: checkpoint context
+ * @ptr: pointer to object
+ * @objref: unique object reference
+ * @type: object type
+ * @flags: object flags
+ *
+ * Allocate an object referring to @ptr and add to the hash table.
+ * If @objref is zero, assign a unique object reference and use @ptr
+ * as a hash key [checkpoint]. Else use @objref as a key [restart].
+ */
+static struct cr_objref *cr_obj_new(struct cr_ctx *ctx, void *ptr, int objref,
+ unsigned short type, unsigned short flags)
+{
+ struct cr_objref *obj;
+ int i;
+
+ obj = kmalloc(sizeof(*obj), GFP_KERNEL);
+ if (!obj)
+ return NULL;
+
+ obj->ptr = ptr;
+ obj->type = type;
+ obj->flags = flags;
+
+ if (objref) {
+ /* use @objref to index (restart) */
+ obj->objref = objref;
+ i = hash_ptr((void *) objref, CR_OBJHASH_NBITS);
+ } else {
+ /* use @ptr to index, assign objref (checkpoint) */
+ obj->objref = ctx->objhash->next_free_objref++;;
+ i = hash_ptr(ptr, CR_OBJHASH_NBITS);
+ }
+
+ hlist_add_head(&obj->hash, &ctx->objhash->head[i]);
+ cr_obj_ref_grab(obj);
+ return obj;
+}
+
+/**
+ * cr_obj_add_ptr - add an object to the hash table if not already there
+ * @ctx: checkpoint context
+ * @ptr: pointer to object
+ * @objref: unique object reference [output]
+ * @type: object type
+ * @flags: object flags
+ *
+ * Look up the object pointed to by @ptr in the hash table. If it isn't
+ * already found there, then add the object to the table, and allocate a
+ * fresh unique object reference (objref). Fills the unique objref of
+ * the object into @objref.
+ * [This is used during checkpoint].
+ *
+ * Returns 0 if found, 1 if added, < 0 on error
+ */
+int cr_obj_add_ptr(struct cr_ctx *ctx, void *ptr, int *objref,
+ unsigned short type, unsigned short flags)
+{
+ struct cr_objref *obj;
+ int ret = 0;
+
+ obj = cr_obj_find_by_ptr(ctx, ptr);
+ if (!obj) {
+ obj = cr_obj_new(ctx, ptr, 0, type, flags);
+ if (!obj)
+ return -ENOMEM;
+ else
+ ret = 1;
+ } else if (obj->type != type) /* sanity check */
+ return -EINVAL;
+ *objref = obj->objref;
+ return ret;
+}
+
+/**
+ * cr_obj_add_ref - add an object with unique objref to the hash table
+ * @ctx: checkpoint context
+ * @ptr: pointer to object
+ * @objref: unique identifier - object reference
+ * @type: object type
+ * @flags: object flags
+ *
+ * Add the object pointer to by @ptr and identified by unique object
+ * reference given by @objref to the hash table (indexed by @objref).
+ * [This is used during restart].
+ */
+int cr_obj_add_ref(struct cr_ctx *ctx, void *ptr, int objref,
+ unsigned short type, unsigned short flags)
+{
+ struct cr_objref *obj;
+
+ obj = cr_obj_new(ctx, ptr, objref, type, flags);
+ return obj ? 0 : -ENOMEM;
+}
+
+/**
+ * cr_obj_get_by_ptr - find the unique object reference of an object
+ * @ctx: checkpoint context
+ * @ptr: pointer to object
+ * @type: object type
+ *
+ * Look up the unique object reference (objref) of the object pointed
+ * to by @ptr, and return that number, or 0 if not found.
+ * [This is used during checkpoint].
+ */
+int cr_obj_get_by_ptr(struct cr_ctx *ctx, void *ptr, unsigned short type)
+{
+ struct cr_objref *obj;
+
+ obj = cr_obj_find_by_ptr(ctx, ptr);
+ if (!obj)
+ return -ESRCH;
+ if (obj->type != type)
+ return -EINVAL;
+ return obj->objref;
+}
+
+/**
+ * cr_obj_get_by_ref - find an object given its unique object reference
+ * @ctx: checkpoint context
+ * @objref: unique identifier - object reference
+ * @type: object type
+ *
+ * Look up the object who is identified by unique object reference that
+ * is specified by @objref, and return a pointer to that matching object,
+ * or NULL if not found.
+ * [This is used during restart].
+ */
+void *cr_obj_get_by_ref(struct cr_ctx *ctx, int objref, unsigned short type)
+{
+ struct cr_objref *obj;
+
+ obj = cr_obj_find_by_objref(ctx, objref);
+ if (!obj)
+ return NULL;
+ if (obj->type != type)
+ return ERR_PTR(-EINVAL);
+ return obj->ptr;
+}
diff --git a/checkpoint/sys.c b/checkpoint/sys.c
index 0bcfadb..c57ae96 100644
--- a/checkpoint/sys.c
+++ b/checkpoint/sys.c
@@ -166,6 +166,7 @@ static void cr_ctx_free(struct cr_ctx *ctx)
path_put(ctx->vfsroot);
cr_pgarr_free(ctx);
+ cr_objhash_free(ctx);
kfree(ctx);
}
@@ -195,6 +196,11 @@ static struct cr_ctx *cr_ctx_alloc(pid_t pid, int fd, unsigned long flags)
if (!ctx->hbuf)
goto err;
+ if (cr_objhash_alloc(ctx) < 0) {
+ cr_ctx_free(ctx);
+ return ERR_PTR(-ENOMEM);
+ }
+
/*
* assume checkpointer is in container's root vfs
* FIXME: this works for now, but will change with real containers
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 3563bce..e85b95c 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -28,6 +28,8 @@ struct cr_ctx {
void *hbuf; /* temporary buffer for headers */
int hpos; /* position in headers buffer */
+ struct cr_objhash *objhash; /* hash for shared objects */
+
struct list_head pgarr_list; /* page array to dump VMA contents */
struct path *vfsroot; /* container root (FIXME) */
@@ -45,6 +47,24 @@ extern int cr_kread(struct cr_ctx *ctx, void *buf, int count);
extern void *cr_hbuf_get(struct cr_ctx *ctx, int n);
extern void cr_hbuf_put(struct cr_ctx *ctx, int n);
+/* shared objects handling */
+
+enum {
+ CR_OBJ_FILE = 1,
+ CR_OBJ_MAX
+};
+
+extern void cr_objhash_free(struct cr_ctx *ctx);
+extern int cr_objhash_alloc(struct cr_ctx *ctx);
+extern void *cr_obj_get_by_ref(struct cr_ctx *ctx,
+ int objref, unsigned short type);
+extern int cr_obj_get_by_ptr(struct cr_ctx *ctx,
+ void *ptr, unsigned short type);
+extern int cr_obj_add_ptr(struct cr_ctx *ctx, void *ptr, int *objref,
+ unsigned short type, unsigned short flags);
+extern int cr_obj_add_ref(struct cr_ctx *ctx, void *ptr, int objref,
+ unsigned short type, unsigned short flags);
+
struct cr_hdr;
extern int cr_write_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf);
--
1.5.4.3
These two are needed when we will use vfs_read() and vfs_write(),
in the next patch.
Signed-off-by: Oren Laadan <[email protected]>
---
fs/read_write.c | 10 ----------
include/linux/fs.h | 10 ++++++++++
2 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/fs/read_write.c b/fs/read_write.c
index 9ba495d..5d5c192 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -324,16 +324,6 @@ ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_
EXPORT_SYMBOL(vfs_write);
-static inline loff_t file_pos_read(struct file *file)
-{
- return file->f_pos;
-}
-
-static inline void file_pos_write(struct file *file, loff_t pos)
-{
- file->f_pos = pos;
-}
-
asmlinkage ssize_t sys_read(unsigned int fd, char __user * buf, size_t count)
{
struct file *file;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 580b513..5537435 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1296,6 +1296,16 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
struct iovec *fast_pointer,
struct iovec **ret_pointer);
+static inline loff_t file_pos_read(struct file *file)
+{
+ return file->f_pos;
+}
+
+static inline void file_pos_write(struct file *file, loff_t pos)
+{
+ file->f_pos = pos;
+}
+
extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
--
1.5.4.3
Now we can do "external" checkpoint, i.e. act on another task.
sys_checkpoint() now looks up the target pid (in our namespace) and
checkpoints that corresponding task. That task should be the root of
a container.
sys_restart() remains the same, as the restart is always done in the
context of the restarting task.
Signed-off-by: Oren Laadan <[email protected]>
---
checkpoint/checkpoint.c | 4 ++-
checkpoint/sys.c | 71 ++++++++++++++++++++++++++++++++++++++++++-
include/linux/checkpoint.h | 5 ++-
3 files changed, 76 insertions(+), 4 deletions(-)
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index ce622e1..f636958 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c
@@ -190,6 +190,8 @@ static int cr_write_task(struct cr_ctx *ctx, struct task_struct *t)
{
int ret ;
+ /* TODO: verity that the task is frozen (unless self) */
+
if (t->state == TASK_DEAD) {
pr_warning("C/R: task may not be in state TASK_DEAD\n");
return -EAGAIN;
@@ -227,7 +229,7 @@ int do_checkpoint(struct cr_ctx *ctx)
ret = cr_write_head(ctx);
if (ret < 0)
goto out;
- ret = cr_write_task(ctx, current);
+ ret = cr_write_task(ctx, ctx->root_task);
if (ret < 0)
goto out;
ret = cr_write_tail(ctx);
diff --git a/checkpoint/sys.c b/checkpoint/sys.c
index c57ae96..3421d47 100644
--- a/checkpoint/sys.c
+++ b/checkpoint/sys.c
@@ -9,6 +9,8 @@
*/
#include <linux/sched.h>
+#include <linux/nsproxy.h>
+#include <linux/ptrace.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/file.h>
@@ -152,6 +154,66 @@ void cr_hbuf_put(struct cr_ctx *ctx, int n)
* restart operation, and persists until the operation is completed.
*/
+static void cr_ctx_put_container(struct cr_ctx *ctx)
+{
+ if (ctx->root_nsproxy)
+ put_nsproxy(ctx->root_nsproxy);
+ if (ctx->root_task)
+ put_task_struct(ctx->root_task);
+ ctx->root_pid = 0;
+}
+
+static int cr_ctx_get_container(pid_t pid, struct cr_ctx *ctx)
+{
+ struct task_struct *task = NULL;
+ struct nsproxy *nsproxy = NULL;
+ int err = -ESRCH;
+
+ read_lock(&tasklist_lock);
+ task = find_task_by_vpid(pid);
+ if (task)
+ get_task_struct(task);
+ read_unlock(&tasklist_lock);
+
+ if (!task)
+ goto out;
+
+#if 0 /* enable to use containers */
+ if (!is_container_init(task)) {
+ err = -EINVAL;
+ goto out;
+ }
+#endif
+
+ if (!ptrace_may_access(task, PTRACE_MODE_READ)) {
+ err = -EPERM;
+ goto out;
+ }
+
+ rcu_read_lock();
+ if (task_nsproxy(task)) {
+ nsproxy = task_nsproxy(task);
+ get_nsproxy(nsproxy);
+ }
+ rcu_read_unlock();
+
+ if (!nsproxy)
+ goto out;
+
+ /* TODO: verify that the container is frozen */
+
+ ctx->root_pid = pid;
+ ctx->root_task = task;
+ ctx->root_nsproxy = nsproxy;
+
+ return 0;
+
+ out:
+ if (task)
+ put_task_struct(task);
+ return err;
+}
+
/* unique checkpoint identifier (FIXME: should be per-container) */
static atomic_t cr_ctx_count = ATOMIC_INIT(0);
@@ -168,6 +230,8 @@ static void cr_ctx_free(struct cr_ctx *ctx)
cr_pgarr_free(ctx);
cr_objhash_free(ctx);
+ cr_ctx_put_container(ctx);
+
kfree(ctx);
}
@@ -180,7 +244,6 @@ static struct cr_ctx *cr_ctx_alloc(pid_t pid, int fd, unsigned long flags)
if (!ctx)
return ERR_PTR(-ENOMEM);
- ctx->pid = pid;
ctx->flags = flags;
INIT_LIST_HEAD(&ctx->pgarr_list);
@@ -190,6 +253,10 @@ static struct cr_ctx *cr_ctx_alloc(pid_t pid, int fd, unsigned long flags)
if (!ctx->file)
goto err;
+ err = cr_ctx_get_container(pid, ctx);
+ if (err < 0)
+ goto err;
+
err = -ENOMEM;
ctx->hbuf = kmalloc(CR_HBUF_TOTAL, GFP_KERNEL);
@@ -205,7 +272,7 @@ static struct cr_ctx *cr_ctx_alloc(pid_t pid, int fd, unsigned long flags)
* assume checkpointer is in container's root vfs
* FIXME: this works for now, but will change with real containers
*/
- ctx->vfsroot = ¤t->fs->root;
+ ctx->vfsroot = &ctx->root_task->fs->root;
path_get(ctx->vfsroot);
ctx->crid = atomic_inc_return(&cr_ctx_count);
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 6c1e87f..e9d554e 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -16,9 +16,12 @@
#define CR_VERSION 2
struct cr_ctx {
- pid_t pid; /* container identifier */
int crid; /* unique checkpoint id */
+ pid_t root_pid; /* container identifier */
+ struct task_struct *root_task; /* container root task */
+ struct nsproxy *root_nsproxy; /* container root nsproxy */
+
unsigned long flags;
unsigned long oflags; /* restart: old flags */
--
1.5.4.3
Covers application checkpoint/restart, overall design, interfaces
and checkpoint image format.
Changelog[v8]:
- Split into multiple files in Documentation/checkpoint/...
- Extend documentation, fix typos and comments from feedback
Signed-off-by: Oren Laadan <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
---
Documentation/checkpoint/ckpt.c | 32 +++++++
Documentation/checkpoint/internals.txt | 125 ++++++++++++++++++++++++++
Documentation/checkpoint/readme.txt | 104 ++++++++++++++++++++++
Documentation/checkpoint/rstr.c | 20 ++++
Documentation/checkpoint/security.txt | 38 ++++++++
Documentation/checkpoint/self.c | 57 ++++++++++++
Documentation/checkpoint/test.c | 48 ++++++++++
Documentation/checkpoint/usage.txt | 153 ++++++++++++++++++++++++++++++++
8 files changed, 577 insertions(+), 0 deletions(-)
create mode 100644 Documentation/checkpoint/ckpt.c
create mode 100644 Documentation/checkpoint/internals.txt
create mode 100644 Documentation/checkpoint/readme.txt
create mode 100644 Documentation/checkpoint/rstr.c
create mode 100644 Documentation/checkpoint/security.txt
create mode 100644 Documentation/checkpoint/self.c
create mode 100644 Documentation/checkpoint/test.c
create mode 100644 Documentation/checkpoint/usage.txt
diff --git a/Documentation/checkpoint/ckpt.c b/Documentation/checkpoint/ckpt.c
new file mode 100644
index 0000000..094408c
--- /dev/null
+++ b/Documentation/checkpoint/ckpt.c
@@ -0,0 +1,32 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+
+int main(int argc, char *argv[])
+{
+ pid_t pid;
+ int ret;
+
+ if (argc != 2) {
+ printf("usage: ckpt PID\n");
+ exit(1);
+ }
+
+ pid = atoi(argv[1]);
+ if (pid <= 0) {
+ printf("invalid pid\n");
+ exit(1);
+ }
+
+ ret = syscall(__NR_checkpoint, pid, STDOUT_FILENO, 0);
+
+ if (ret < 0)
+ perror("checkpoint");
+ else
+ printf("checkpoint id %d\n", ret);
+
+ return (ret > 0 ? 0 : 1);
+}
+
diff --git a/Documentation/checkpoint/internals.txt b/Documentation/checkpoint/internals.txt
new file mode 100644
index 0000000..03a92a2
--- /dev/null
+++ b/Documentation/checkpoint/internals.txt
@@ -0,0 +1,125 @@
+
+ ===== Internals of Checkpoint-Restart =====
+
+
+(1) Order of state dump
+
+The order of operations, both save and restore, is as follows:
+
+* Header section: header, container information, etc.
+
+* Global section: [TBD] global resources such as IPC, UTS, etc.
+
+* Process forest: [TBD] tasks and their relationships
+
+* Per task data (for each task):
+ -> task state: elements of task_struct
+ -> thread state: elements of thread_struct and thread_info
+ -> CPU state: registers etc, including FPU
+ -> memory state: memory address space layout and contents
+ -> filesystem state: [TBD] filesystem namespace state, chroot, cwd, etc
+ -> files state: open file descriptors and their state
+ -> signals state: [TBD] pending signals and signal handling state
+ -> credentials state: [TBD] user and group state, statistics
+
+
+(2) Checkpoint image format
+
+The checkpoint image format is composed of records consisting of a
+pre-header that identifies its contents, followed by a payload. (The
+idea here is to enable parallel checkpointing in the future in which
+multiple threads interleave data from multiple processes into a single
+stream).
+
+The pre-header is defined by "struct cr_hdr" as follows:
+
+struct cr_hdr {
+ __s16 type;
+ __s16 len;
+ __u32 parent;
+};
+
+'type' identifies the type of the payload, 'len' tells its length in
+bytes, and 'parent' identifies the owner object instance. The meaning
+of 'parent' varies depending on the type. For example, for CR_HDR_MM,
+'parent' identifies the task to which this MM belongs. The payload
+also varies depending on the type, for instance, the data describing a
+task_struct is given by a 'struct cr_hdr_task' (type CR_HDR_TASK) and
+so on.
+
+The format of the memory dump is as follows: for each VMA, there is a
+'struct cr_vma'; if the VMA is file-mapped, it is followed by the file
+name. Following comes the actual contents, in one or more chunks: each
+chunk begins with a header that specifies how many pages it holds,
+then the virtual addresses of all the dumped pages in that chunk,
+followed by the actual contents of all the dumped pages. A header with
+zero number of pages marks the end of the contents for a particular
+VMA. Then comes the next VMA and so on.
+
+To illustrate this, consider a single simple task with two VMAs: one
+is file mapped with two dumped pages, and the other is anonymous with
+three dumped pages. The checkpoint image will look like this:
+
+cr_hdr + cr_hdr_head
+cr_hdr + cr_hdr_task
+ cr_hdr + cr_hdr_mm
+ cr_hdr + cr_hdr_vma + cr_hdr + string
+ cr_hdr_pgarr (nr_pages = 2)
+ addr1, addr2
+ page1, page2
+ cr_hdr_pgarr (nr_pages = 0)
+ cr_hdr + cr_hdr_vma
+ cr_hdr_pgarr (nr_pages = 3)
+ addr3, addr4, addr5
+ page3, page4, page5
+ cr_hdr_pgarr (nr_pages = 0)
+ cr_hdr + cr_mm_context
+ cr_hdr + cr_hdr_thread
+ cr_hdr + cr_hdr_cpu
+cr_hdr + cr_hdr_tail
+
+
+(3) Shared resources (objects)
+
+Many resources used by tasks may be shared by more than one task (e.g.
+file descriptors, memory address space, etc), or even have multiple
+references from other resources (e.g. a single inode that represents
+two ends of a pipe).
+
+Clearly, the state of shared objects need only be saved once, even if
+they occur multiple times. We use a hash table (ctx->objhash) to keep
+track of shared objects and whether they were already saved. Shared
+objects are stored in a hash table as they appear, indexed by their
+kernel address. (The hash table itself is not saved as part of the
+checkpoint image: it is constructed dynamically during both checkpoint
+and restart, and discarded at the end of the operation).
+
+Each shared object that is found is first looked up in the hash table.
+On the first encounter, the object will not be found, so its state is
+dumped, and the object is assigned a unique identifier and also stored
+in the hash table. Subsequent lookups of that object in the hash table
+will yield that entry, and then only the unique identifier is saved,
+as opposed the entire state of the object.
+
+During restart, shared objects are seen by their unique identifiers as
+assigned during the checkpoint. Each shared object that it read in is
+first looked up in the hash table. On the first encounter it will not
+be found, meaning that the object needs to be created and its state
+read in and restored. Then the object is added to the hash table, this
+time indexed by its unique identifier. Subsequent lookups of the same
+unique identifier in the hash table will yield that entry, and then
+the existing object instance is reused instead of creating another one.
+
+The interface for the hash table is the following:
+
+cr_obj_get_by_ptr() - find the unique object reference (objref)
+ of the object that is pointer to by ptr [checkpoint]
+
+cr_obj_add_ptr() - add the object pointed to by ptr to the hash table
+ if not already there, and fill its unique object reference (objref)
+
+cr_obj_get_by_ref() - return the pointer to the object whose unique
+ object reference is equal to objref [restart]
+
+cr_obj_add_ref() - add the object with given unique object reference
+ (objref), pointed to by ptr to the hash table. [restart]
diff --git a/Documentation/checkpoint/readme.txt b/Documentation/checkpoint/readme.txt
new file mode 100644
index 0000000..c7f79e9
--- /dev/null
+++ b/Documentation/checkpoint/readme.txt
@@ -0,0 +1,104 @@
+
+ ===== Checkpoint-Restart support in the Linux kernel =====
+
+Copyright (C) 2008 Oren Laadan
+
+Author: Oren Laadan <[email protected]>
+
+License: The GNU Free Documentation License, Version 1.2
+ (dual licensed under the GPL v2)
+
+Reviewers: Serge Hallyn <[email protected]>
+ Dave Hansen <[email protected]>
+
+Application checkpoint/restart [C/R] is the ability to save the state
+of a running application so that it can later resume its execution
+from the time at which it was checkpointed. An application can be
+migrated by checkpointing it on one machine and restarting it on
+another. C/R can provide many potential benefits:
+
+* Failure recovery: by rolling back to a previous checkpoint
+
+* Improved response time: by restarting applications from checkpoints
+ instead of from scratch.
+
+* Improved system utilization: by suspending long running CPU
+ intensive jobs and resuming them when load decreases.
+
+* Fault resilience: by migrating applications off faulty hosts.
+
+* Dynamic load balancing: by migrating applications to less loaded
+ hosts.
+
+* Improved service availability and administration: by migrating
+ applications before host maintenance so that they continue to run
+ with minimal downtime
+
+* Time-travel: by taking periodic checkpoints and restarting from
+ any previous checkpoint.
+
+
+=== Overall design
+
+Checkpoint and restart is done in the kernel as much as possible. The
+kernel exports a relatively opaque 'blob' of data to userspace which can
+then be handed to the new kernel at restore time. The 'blob' contains
+data and state of select portions of kernel structures such as VMAs
+and mm_structs, as well as copies of the actual memory that the tasks
+use. Any changes in this blob's format between kernel revisions can be
+handled by an in-userspace conversion program. The approach is similar
+to virtually all of the commercial C/R products out there, as well as
+the research project Zap.
+
+Two new system calls are introduced to provide C/R: sys_checkpoint()
+and sys_restart(). The checkpoint code basically serializes internal
+kernel state and writes it out to a file descriptor, and the resulting
+image is stream-able. More specifically, it consists of 5 steps:
+
+1. Pre-dump
+2. Freeze the container
+3. Dump
+4. Thaw (or kill) the container
+5. Post-dump
+
+Steps 1 and 5 are an optimization to reduce application downtime. In
+particular, "pre-dump" works before freezing the container, e.g. the
+pre-copy for live migration, and "post-dump" works after the container
+resumes execution, e.g. write-back the data to secondary storage.
+
+The restart code basically reads the saved kernel state from a file
+descriptor, and re-creates the tasks and the resources they need to
+resume execution. The restart code is executed by each task that is
+restored in a new container to reconstruct its own state.
+
+
+=== Current Implementation
+
+* How useful is this code as it stands in real-world usage?
+
+Right now, the application must be a single process that does not
+share any resources with other processes. The only file descriptors
+that may be open are simple files and directories, they may not
+include devices, sockets or pipes.
+
+For an "external" checkpoint, the caller must first freeze (or stop)
+the target process. For "self" checkpoint, the application must be
+specifically written to use the new system calls. The restart does not
+yet preserve the pid of the original process, but will use whatever
+pid it was given by the kernel.
+
+What this means in practice is that it is useful for a simple
+application doing computational work and input/output from/to files.
+
+Currently, namespaces are not saved or restored. They will be treated
+as a class of a shared object. In particular, it is assumed that the
+task's file system namespace is the "root" for the entire container.
+It is also assumed that the same file system view is available for the
+restart task(s). Otherwise, a file system snapshot is required.
+
+* What additional work needs to be done to it?
+
+We know this design can work. We have two commercial products and a
+horde of academic projects doing it today using this basic design.
+We're early in this particular implementation because we're trying to
+release early and often.
diff --git a/Documentation/checkpoint/rstr.c b/Documentation/checkpoint/rstr.c
new file mode 100644
index 0000000..288209d
--- /dev/null
+++ b/Documentation/checkpoint/rstr.c
@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/syscall.h>
+
+int main(int argc, char *argv[])
+{
+ pid_t pid = getpid();
+ int ret;
+
+ ret = syscall(__NR_restart, pid, STDIN_FILENO, 0);
+ if (ret < 0)
+ perror("restart");
+
+ printf("should not reach here !\n");
+
+ return 0;
+}
+
diff --git a/Documentation/checkpoint/security.txt b/Documentation/checkpoint/security.txt
new file mode 100644
index 0000000..e5b4107
--- /dev/null
+++ b/Documentation/checkpoint/security.txt
@@ -0,0 +1,38 @@
+
+ ===== Security consideration for Checkpoint-Restart =====
+
+The main question is whether sys_checkpoint() and sys_restart()
+require privileged or unprivileged operation.
+
+Early versions checked capable(CAP_SYS_ADMIN) assuming that we would
+attempt to remove the need for privilege, so that all users could
+safely use it. Arnd Bergmann pointed out that it'd make more sense to
+let unprivileged users use them now, so that we'll be more careful
+about the security as patches roll in.
+
+Checkpoint: the main concern is whether a task that performs the
+checkpoint of another task has sufficient privileges to access its
+state. We address this by requiring that the checkpointer task will be
+able to ptrace the target task, by means of ptrace_may_access() with
+read mode.
+
+Restart: the main concern is that we may allow an unprivileged user to
+feed the kernel with random data. To this end, the restart works in a
+way that does not skip the usual security checks. Task credentials,
+i.e. euid, reuid, and LSM security contexts currently come from the
+caller, not the checkpoint image. When restoration of credentials
+becomes supported, then definitely the ability of the task that calls
+sys_restore() to setresuid/setresgid to those values must be checked.
+
+Keeping the restart procedure to operate within the limits of the
+caller's credentials means that there various scenarios that cannot
+be supported. For instance, a setuid program that opened a protected
+log file and then dropped privileges will fail the restart, because
+the user won't have enough credentials to reopen the file. In these
+cases, we should probably treat restarting like inserting a kernel
+module: surely the user can cause havoc by providing incorrect data,
+but then again we must trust the root account.
+
+So that's why we don't want CAP_SYS_ADMIN required up-front. That way
+we will be forced to more carefully review each of those features.
+
diff --git a/Documentation/checkpoint/self.c b/Documentation/checkpoint/self.c
new file mode 100644
index 0000000..febb888
--- /dev/null
+++ b/Documentation/checkpoint/self.c
@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <math.h>
+#include <sys/syscall.h>
+
+#define OUTFILE "/tmp/cr-test.out"
+
+int main(int argc, char *argv[])
+{
+ pid_t pid = getpid();
+ FILE *file;
+ int i, ret;
+ float a;
+
+ close(0);
+ close(2);
+
+ unlink(OUTFILE);
+ file = fopen(OUTFILE, "w+");
+ if (!file) {
+ perror("open");
+ exit(1);
+ }
+ if (dup2(0, 2) < 0) {
+ perror("dup2");
+ exit(1);
+ }
+
+ a = sqrt(2.53 * (getpid() / 1.21));
+
+ fprintf(file, "hello, world (%.2f)!\n", a);
+ fflush(file);
+
+ for (i = 0; i < 1000; i++) {
+ sleep(1);
+ /* make the fpu work -> a = a + i/10 */
+ a = sqrt(a*a + 2*a*(i/10.0) + i*i/100.0);
+ fprintf(file, "count %d (%.2f)!\n", i, a);
+ fflush(file);
+
+ if (i == 2) {
+ ret = syscall(__NR_checkpoint, pid, STDOUT_FILENO, 0);
+ if (ret < 0) {
+ fprintf(file, "ckpt: %s\n", strerror(errno));
+ exit(2);
+ }
+ fprintf(file, "checkpoint ret: %d\n", ret);
+ fflush(file);
+ }
+ }
+
+ return 0;
+}
+
diff --git a/Documentation/checkpoint/test.c b/Documentation/checkpoint/test.c
new file mode 100644
index 0000000..1183655
--- /dev/null
+++ b/Documentation/checkpoint/test.c
@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <math.h>
+
+#define OUTFILE "/tmp/cr-test.out"
+
+int main(int argc, char *argv[])
+{
+ FILE *file;
+ float a;
+ int i;
+
+ close(0);
+ close(1);
+ close(2);
+
+ unlink(OUTFILE);
+ file = fopen(OUTFILE, "w+");
+ if (!file) {
+ perror("open");
+ exit(1);
+ }
+ if (dup2(0, 2) < 0) {
+ perror("dup2");
+ exit(1);
+ }
+
+ a = sqrt(2.53 * (getpid() / 1.21));
+
+ fprintf(file, "hello, world (%.2f)!\n", a);
+ fflush(file);
+
+ for (i = 0; i < 1000; i++) {
+ sleep(1);
+ /* make the fpu work -> a = a + i/10 */
+ a = sqrt(a*a + 2*a*(i/10.0) + i*i/100.0);
+ fprintf(file, "count %d (%.2f)!\n", i, a);
+ fflush(file);
+ }
+
+ fprintf(file, "world, hello (%.2f) !\n", a);
+ fflush(file);
+
+ return 0;
+}
+
diff --git a/Documentation/checkpoint/usage.txt b/Documentation/checkpoint/usage.txt
new file mode 100644
index 0000000..c126698
--- /dev/null
+++ b/Documentation/checkpoint/usage.txt
@@ -0,0 +1,153 @@
+
+ ===== How to use Checkpoint-Restart =====
+
+The API consists of two new system calls:
+
+* int sys_checkpoint(pid_t pid, int fd, unsigned long flag);
+
+ Checkpoint a container whose init task is identified by pid, to
+ the file designated by fd. 'flags' will have future meaning (must
+ be 0 for now).
+
+ Returns: a positive checkpoint identifier (crid) upon success, 0
+ if it returns from a restart, and -1 if an error occurs.
+
+ 'crid' uniquely identifies a checkpoint image. For each checkpoint
+ the kernel allocates a unique 'crid', that remains valid for as
+ long as the checkpoint is kept in the kernel (for instance, when a
+ checkpoint, or a partial checkpoint, may reside in kernel memory).
+
+* int sys_restart(int crid, int fd, unsigned long flags);
+
+ Restart a container from a checkpoint image that is read from the
+ blob stored in the file designated by fd. 'crid' will have future
+ meaning (must be 0 for now). 'flags' will have future meaning
+ (must be 0 for now).
+
+ The role of 'crid' is to identify the checkpoint image in the case
+ that it remains in kernel memory. This will be useful to restart
+ from a checkpoint image that remains in kernel memory.
+
+ Returns: -1 if an error occurs, 0 on success when restarting from
+ a "self" checkpoint, and return value of system call at the time
+ of the checkpoint when restarting from an "external" checkpoint.
+
+ If restarting from an "external" checkpoint, tasks that were
+ executing a system call will observe the return value of that
+ system call (as it was when interrupted for the act of taking the
+ checkpoint), and tasks that were executing in user space will be
+ ready to return there.
+
+ Upon successful "external" restart, the container will end up in a
+ frozen state.
+
+The granularity of a checkpoint usually is a whole container. The
+'pid' argument is interpreted in the caller's pid namespace. So to
+checkpoint a container whose init task (pid 1 in that pidns) appears
+as pid 3497 the caller's pidns, the caller must use pid 3497. Passing
+pid 1 will attempt to checkpoint the caller's container, and if the
+caller isn't privileged and init is owned by root, it will fail.
+
+If the caller passes a pid which does not refer to a container's init
+task, then sys_checkpoint() would return -EINVAL. (This is because
+with nested containers a task may belong to more than one container).
+
+Here is a code snippet that illustrates how a checkpoint is initiated
+by a process in a container - the logic is similar to fork():
+ ...
+ crid = checkpoint(1, ...);
+ switch (crid) {
+ case -1:
+ perror("checkpoint failed");
+ break;
+ default:
+ fprintf(stderr, "checkpoint succeeded, CRID=%d\n", ret);
+ /* proceed with execution after checkpoint */
+ ...
+ break;
+ case 0:
+ fprintf(stderr, "returned after restart\n");
+ /* proceed with action required following a restart */
+ ...
+ break;
+ }
+ ...
+
+And to initiate a restart, the process in an empty container can use
+logic similar to execve():
+ ...
+ if (restart(crid, ...) < 0)
+ perror("restart failed");
+ /* only get here if restart failed */
+ ...
+
+Note, that the code also supports "self" checkpoint, where a process
+can checkpoint itself. This mode does not capture the relationships
+of the task with other tasks, or any shared resources. It is useful
+for application that wish to be able to save and restore their state.
+They will either not use (or care about) shared resources, or they
+will be aware of the operations and adapt suitably after a restart.
+The code above can also be used for "self" checkpoint.
+
+To illustrate how the API works, refer to these sample programs:
+
+* ckpt.c: accepts a 'pid' argument and checkpoint that task to stdout
+* rstr.c: restarts a checkpoint image from stdin
+* self.c: a simple test program doing self-checkpoint
+* test.c: a simple test program to checkpoint
+
+"External" checkpoint:
+---------------------
+To do "external" checkpoint, you need to first freeze that other task
+either using the freezer cgroup, or by sending SIGSTOP.
+
+Restart does not preserve the original PID yet, (because we haven't
+solved yet the fork-with-specific-pid issue). In a real scenario, you
+probably want to first create a new names space, and have the init
+task there call 'sys_restart()'.
+
+I tested it this way:
+ $ ./test &
+ [1] 3493
+
+ $ kill -STOP 3493
+ $ ./ckpt 3493 > ckpt.image
+
+ $ mv /tmp/cr-test.out /tmp/cr-test.out.orig
+ $ cp /tmp/cr-test.out.orig /tmp/cr-test.out
+
+ $ kill -CONT 3493
+
+ $ ./rstr < ckpt.image
+Now compare the output of the two output files.
+
+"Self checkpoint:
+----------------
+To do "self" checkpoint, you can incorporate the code from ckpt.c into
+your application.
+
+Here is how to test the "self" checkpoint:
+ $ ./self > self.image &
+ [1] 3512
+
+ $ sleep 3
+ $ mv /tmp/cr-test.out /tmp/cr-test.out.orig
+ $ cp /tmp/cr-test.out.orig /tmp/cr-test.out
+
+ $ cat /tmp/cr-rest.out
+ hello, world (85.46)!
+ count 0 (85.46)!
+ count 1 (85.56)!
+ count 2 (85.76)!
+ count 3 (86.46)!
+
+ $ sed -i 's/count/xxxx/g' /tmp/cr-rest.out
+
+ $ ./rstr < self.image &
+Now compare the output of the two output files.
+
+Note how in test.c we close stdin, stdout, stderr - that's because
+currently we only support regular files (not ttys/ptys).
+
+If you check the output of ps, you'll see that "rstr" changed its name
+to "test" or "self", as expected.
--
1.5.4.3
Restoring the memory address space begins with nuking the existing one
of the current process, and then reading the VMA state and contents.
Call do_mmap_pgoffset() for each VMA and then read in the data.
Changelog[v7]:
- Fix argument given to kunmap_atomic() in memory dump/restore
Changelog[v6]:
- Balance all calls to cr_hbuf_get() with matching cr_hbuf_put()
(even though it's not really needed)
Changelog[v5]:
- Improve memory restore code (following Dave Hansen's comments)
- Change dump format (and code) to allow chunks of <vaddrs, pages>
instead of one long list of each
- Memory restore now maps user pages explicitly to copy data into them,
instead of reading directly to user space; got rid of mprotect_fixup()
Changelog[v4]:
- Use standard list_... for cr_pgarr
Signed-off-by: Oren Laadan <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
---
arch/x86/mm/restart.c | 64 ++++++-
checkpoint/Makefile | 2 +-
checkpoint/checkpoint_arch.h | 2 +
checkpoint/checkpoint_mem.h | 5 +
checkpoint/restart.c | 42 ++++
checkpoint/rstr_mem.c | 384 ++++++++++++++++++++++++++++++++++++++
include/asm-x86/checkpoint_hdr.h | 4 +
include/linux/checkpoint.h | 3 +
8 files changed, 503 insertions(+), 3 deletions(-)
create mode 100644 checkpoint/rstr_mem.c
diff --git a/arch/x86/mm/restart.c b/arch/x86/mm/restart.c
index bc2a502..aeae29f 100644
--- a/arch/x86/mm/restart.c
+++ b/arch/x86/mm/restart.c
@@ -53,8 +53,10 @@ int cr_read_thread(struct cr_ctx *ctx)
size = sizeof(*desc) * GDT_ENTRY_TLS_ENTRIES;
desc = kmalloc(size, GFP_KERNEL);
- if (!desc)
- return -ENOMEM;
+ if (!desc) {
+ ret = -ENOMEM;
+ goto out;
+ }
ret = cr_kread(ctx, desc, size);
if (ret >= 0) {
@@ -193,3 +195,61 @@ int cr_read_cpu(struct cr_ctx *ctx)
cr_hbuf_put(ctx, sizeof(*hh));
return ret;
}
+
+int cr_read_mm_context(struct cr_ctx *ctx, struct mm_struct *mm, int parent)
+{
+ struct cr_hdr_mm_context *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ int n, rparent, ret = -EINVAL;
+
+ rparent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_MM_CONTEXT);
+ cr_debug("parent %d rparent %d nldt %d\n", parent, rparent, hh->nldt);
+ if (rparent < 0) {
+ ret = rparent;
+ goto out;
+ }
+ if (rparent != parent)
+ goto out;
+
+ if (hh->nldt < 0 || hh->ldt_entry_size != LDT_ENTRY_SIZE)
+ goto out;
+
+ /*
+ * to utilize the syscall modify_ldt() we first convert the data
+ * in the checkpoint image from 'struct desc_struct' to 'struct
+ * user_desc' with reverse logic of include/asm/desc.h:fill_ldt()
+ */
+
+ for (n = 0; n < hh->nldt; n++) {
+ struct user_desc info;
+ struct desc_struct desc;
+ mm_segment_t old_fs;
+
+ ret = cr_kread(ctx, &desc, LDT_ENTRY_SIZE);
+ if (ret < 0)
+ goto out;
+
+ info.entry_number = n;
+ info.base_addr = desc.base0 | (desc.base1 << 16);
+ info.limit = desc.limit0;
+ info.seg_32bit = desc.d;
+ info.contents = desc.type >> 2;
+ info.read_exec_only = (desc.type >> 1) ^ 1;
+ info.limit_in_pages = desc.g;
+ info.seg_not_present = desc.p ^ 1;
+ info.useable = desc.avl;
+
+ old_fs = get_fs();
+ set_fs(get_ds());
+ ret = sys_modify_ldt(1, (struct user_desc __user *) &info,
+ sizeof(info));
+ set_fs(old_fs);
+
+ if (ret < 0)
+ goto out;
+ }
+
+ ret = 0;
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
diff --git a/checkpoint/Makefile b/checkpoint/Makefile
index 3a0df6d..ac35033 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile
@@ -3,4 +3,4 @@
#
obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o \
- ckpt_mem.o
+ ckpt_mem.o rstr_mem.o
diff --git a/checkpoint/checkpoint_arch.h b/checkpoint/checkpoint_arch.h
index 7da4ad0..018a72e 100644
--- a/checkpoint/checkpoint_arch.h
+++ b/checkpoint/checkpoint_arch.h
@@ -7,3 +7,5 @@ extern int cr_write_mm_context(struct cr_ctx *ctx,
extern int cr_read_thread(struct cr_ctx *ctx);
extern int cr_read_cpu(struct cr_ctx *ctx);
+extern int cr_read_mm_context(struct cr_ctx *ctx,
+ struct mm_struct *mm, int parent);
diff --git a/checkpoint/checkpoint_mem.h b/checkpoint/checkpoint_mem.h
index 85546f4..85a5cf3 100644
--- a/checkpoint/checkpoint_mem.h
+++ b/checkpoint/checkpoint_mem.h
@@ -38,4 +38,9 @@ static inline int cr_pgarr_is_full(struct cr_pgarr *pgarr)
return (pgarr->nr_used == CR_PGARR_TOTAL);
}
+static inline int cr_pgarr_nr_free(struct cr_pgarr *pgarr)
+{
+ return CR_PGARR_TOTAL - pgarr->nr_used;
+}
+
#endif /* _CHECKPOINT_CKPT_MEM_H_ */
diff --git a/checkpoint/restart.c b/checkpoint/restart.c
index 766e381..f4d87ba 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -78,6 +78,44 @@ int cr_read_string(struct cr_ctx *ctx, void *str, int len)
return cr_read_obj_type(ctx, str, len, CR_HDR_STRING);
}
+/**
+ * cr_read_fname - read a file name
+ * @ctx: checkpoint context
+ * @fname: buffer
+ * @n: buffer length
+ */
+int cr_read_fname(struct cr_ctx *ctx, void *fname, int flen)
+{
+ return cr_read_obj_type(ctx, fname, flen, CR_HDR_FNAME);
+}
+
+/**
+ * cr_read_open_fname - read a file name and open a file
+ * @ctx: checkpoint context
+ * @flags: file flags
+ * @mode: file mode
+ */
+struct file *cr_read_open_fname(struct cr_ctx *ctx, int flags, int mode)
+{
+ struct file *file;
+ char *fname;
+ int ret;
+
+ fname = kmalloc(PATH_MAX, GFP_KERNEL);
+ if (!fname)
+ return ERR_PTR(-ENOMEM);
+
+ ret = cr_read_fname(ctx, fname, PATH_MAX);
+ cr_debug("fname '%s' flags %#x mode %#x\n", fname, flags, mode);
+ if (ret >= 0)
+ file = filp_open(fname, flags, mode);
+ else
+ file = ERR_PTR(ret);
+
+ kfree(fname);
+ return file;
+}
+
/* read the checkpoint header */
static int cr_read_head(struct cr_ctx *ctx)
{
@@ -177,6 +215,10 @@ static int cr_read_task(struct cr_ctx *ctx)
cr_debug("task_struct: ret %d\n", ret);
if (ret < 0)
goto out;
+ ret = cr_read_mm(ctx);
+ cr_debug("memory: ret %d\n", ret);
+ if (ret < 0)
+ goto out;
ret = cr_read_thread(ctx);
cr_debug("thread: ret %d\n", ret);
if (ret < 0)
diff --git a/checkpoint/rstr_mem.c b/checkpoint/rstr_mem.c
new file mode 100644
index 0000000..062e56e
--- /dev/null
+++ b/checkpoint/rstr_mem.c
@@ -0,0 +1,384 @@
+/*
+ * Restart memory contents
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/fcntl.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/mm_types.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/err.h>
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+#include "checkpoint_arch.h"
+#include "checkpoint_mem.h"
+
+/*
+ * Unlike checkpoint, restart is executed in the context of each restarting
+ * process: vma regions are restored via a call to mmap(), and the data is
+ * read into the address space of the current process.
+ */
+
+
+/**
+ * cr_read_pages_vaddrs - read addresses of pages to page-array chain
+ * @ctx - restart context
+ * @nr_pages - number of address to read
+ */
+static int cr_read_pages_vaddrs(struct cr_ctx *ctx, unsigned long nr_pages)
+{
+ struct cr_pgarr *pgarr;
+ unsigned long *vaddrp;
+ int nr, ret;
+
+ while (nr_pages) {
+ pgarr = cr_pgarr_current(ctx);
+ if (!pgarr)
+ return -ENOMEM;
+ nr = cr_pgarr_nr_free(pgarr);
+ if (nr > nr_pages)
+ nr = nr_pages;
+ vaddrp = &pgarr->vaddrs[pgarr->nr_used];
+ ret = cr_kread(ctx, vaddrp, nr * sizeof(unsigned long));
+ if (ret < 0)
+ return ret;
+ pgarr->nr_used += nr;
+ nr_pages -= nr;
+ }
+ return 0;
+}
+
+static int cr_page_read(struct cr_ctx *ctx, struct page *page, char *buf)
+{
+ void *ptr;
+ int ret;
+
+ ret = cr_kread(ctx, buf, PAGE_SIZE);
+ if (ret < 0)
+ return ret;
+
+ ptr = kmap_atomic(page, KM_USER1);
+ memcpy(ptr, buf, PAGE_SIZE);
+ kunmap_atomic(ptr, KM_USER1);
+
+ return 0;
+}
+
+/**
+ * cr_read_pages_contents - read in data of pages in page-array chain
+ * @ctx - restart context
+ */
+static int cr_read_pages_contents(struct cr_ctx *ctx)
+{
+ struct mm_struct *mm = current->mm;
+ struct cr_pgarr *pgarr;
+ unsigned long *vaddrs;
+ char *buf;
+ int i, ret = 0;
+
+ buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ down_read(&mm->mmap_sem);
+ list_for_each_entry_reverse(pgarr, &ctx->pgarr_list, list) {
+ vaddrs = pgarr->vaddrs;
+ for (i = 0; i < pgarr->nr_used; i++) {
+ struct page *page;
+
+ ret = get_user_pages(current, mm, vaddrs[i],
+ 1, 1, 1, &page, NULL);
+ if (ret < 0)
+ goto out;
+
+ ret = cr_page_read(ctx, page, buf);
+ page_cache_release(page);
+
+ if (ret < 0)
+ goto out;
+ }
+ }
+
+ out:
+ up_read(&mm->mmap_sem);
+ kfree(buf);
+ return 0;
+}
+
+/**
+ * cr_read_private_vma_contents - restore contents of a VMA with private memory
+ * @ctx - restart context
+ *
+ * Reads a header that specifies how many pages will follow, then reads
+ * a list of virtual addresses into ctx->pgarr_list page-array chain,
+ * followed by the actual contents of the corresponding pages. Iterates
+ * these steps until reaching a header specifying "0" pages, which marks
+ * the end of the contents.
+ */
+static int cr_read_private_vma_contents(struct cr_ctx *ctx)
+{
+ struct cr_hdr_pgarr *hh;
+ unsigned long nr_pages;
+ int parent, ret = 0;
+
+ while (1) {
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_PGARR);
+ if (parent != 0) {
+ if (parent < 0)
+ ret = parent;
+ else
+ ret = -EINVAL;
+ cr_hbuf_put(ctx, sizeof(*hh));
+ break;
+ }
+
+ cr_debug("nr_pages %ld\n", (unsigned long) hh->nr_pages);
+
+ nr_pages = hh->nr_pages;
+ cr_hbuf_put(ctx, sizeof(*hh));
+
+ if (!nr_pages)
+ break;
+
+ ret = cr_read_pages_vaddrs(ctx, nr_pages);
+ if (ret < 0)
+ break;
+ ret = cr_read_pages_contents(ctx);
+ if (ret < 0)
+ break;
+ cr_pgarr_reset_all(ctx);
+ }
+
+ return ret;
+}
+
+/**
+ * cr_calc_map_prot_bits - convert vm_flags to mmap protection
+ * orig_vm_flags: source vm_flags
+ */
+static unsigned long cr_calc_map_prot_bits(unsigned long orig_vm_flags)
+{
+ unsigned long vm_prot = 0;
+
+ if (orig_vm_flags & VM_READ)
+ vm_prot |= PROT_READ;
+ if (orig_vm_flags & VM_WRITE)
+ vm_prot |= PROT_WRITE;
+ if (orig_vm_flags & VM_EXEC)
+ vm_prot |= PROT_EXEC;
+ if (orig_vm_flags & PROT_SEM) /* only (?) with IPC-SHM */
+ vm_prot |= PROT_SEM;
+
+ return vm_prot;
+}
+
+/**
+ * cr_calc_map_flags_bits - convert vm_flags to mmap flags
+ * orig_vm_flags: source vm_flags
+ */
+static unsigned long cr_calc_map_flags_bits(unsigned long orig_vm_flags)
+{
+ unsigned long vm_flags = 0;
+
+ vm_flags = MAP_FIXED;
+ if (orig_vm_flags & VM_GROWSDOWN)
+ vm_flags |= MAP_GROWSDOWN;
+ if (orig_vm_flags & VM_DENYWRITE)
+ vm_flags |= MAP_DENYWRITE;
+ if (orig_vm_flags & VM_EXECUTABLE)
+ vm_flags |= MAP_EXECUTABLE;
+ if (orig_vm_flags & VM_MAYSHARE)
+ vm_flags |= MAP_SHARED;
+ else
+ vm_flags |= MAP_PRIVATE;
+
+ return vm_flags;
+}
+
+static int cr_read_vma(struct cr_ctx *ctx, struct mm_struct *mm)
+{
+ struct cr_hdr_vma *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ unsigned long vm_size, vm_start, vm_flags, vm_prot, vm_pgoff;
+ unsigned long addr;
+ struct file *file = NULL;
+ int parent, ret = -EINVAL;
+
+ parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_VMA);
+ if (parent < 0) {
+ ret = parent;
+ goto err;
+ } else if (parent != 0)
+ goto err;
+
+ cr_debug("vma %#lx-%#lx type %d\n", (unsigned long) hh->vm_start,
+ (unsigned long) hh->vm_end, (int) hh->vma_type);
+
+ if (hh->vm_end < hh->vm_start)
+ goto err;
+
+ vm_start = hh->vm_start;
+ vm_pgoff = hh->vm_pgoff;
+ vm_size = hh->vm_end - hh->vm_start;
+ vm_prot = cr_calc_map_prot_bits(hh->vm_flags);
+ vm_flags = cr_calc_map_flags_bits(hh->vm_flags);
+
+ switch (hh->vma_type) {
+
+ case CR_VMA_ANON: /* anonymous private mapping */
+ if (vm_flags & VM_SHARED)
+ goto err;
+ /*
+ * vm_pgoff for anonymous mapping is the "global" page
+ * offset (namely from addr 0x0), so we force a zero
+ */
+ vm_pgoff = 0;
+ break;
+
+ case CR_VMA_FILE: /* private mapping from a file */
+ if (vm_flags & VM_SHARED)
+ goto err;
+ /*
+ * for private mapping using 'read-only' is sufficient
+ */
+ file = cr_read_open_fname(ctx, O_RDONLY, 0);
+ if (IS_ERR(file)) {
+ ret = PTR_ERR(file);
+ goto err;
+ }
+ break;
+
+ default:
+ goto err;
+
+ }
+
+ cr_hbuf_put(ctx, sizeof(*hh));
+
+ down_write(&mm->mmap_sem);
+ addr = do_mmap_pgoff(file, vm_start, vm_size,
+ vm_prot, vm_flags, vm_pgoff);
+ up_write(&mm->mmap_sem);
+ cr_debug("size %#lx prot %#lx flag %#lx pgoff %#lx => %#lx\n",
+ vm_size, vm_prot, vm_flags, vm_pgoff, addr);
+
+ /* the file (if opened) is now referenced by the vma */
+ if (file)
+ filp_close(file, NULL);
+
+ if (IS_ERR((void *) addr))
+ return PTR_ERR((void *) addr);
+
+ /*
+ * CR_VMA_ANON: read in memory as is
+ * CR_VMA_FILE: read in memory as is
+ * (more to follow ...)
+ */
+
+ switch (hh->vma_type) {
+ case CR_VMA_ANON:
+ case CR_VMA_FILE:
+ /* standard case: read the data into the memory */
+ ret = cr_read_private_vma_contents(ctx);
+ break;
+ }
+
+ if (ret < 0)
+ return ret;
+
+ cr_debug("vma retval %d\n", ret);
+ return 0;
+
+ err:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
+
+static int cr_destroy_mm(struct mm_struct *mm)
+{
+ struct vm_area_struct *vmnext = mm->mmap;
+ struct vm_area_struct *vma;
+ int ret;
+
+ while (vmnext) {
+ vma = vmnext;
+ vmnext = vmnext->vm_next;
+ ret = do_munmap(mm, vma->vm_start, vma->vm_end-vma->vm_start);
+ if (ret < 0) {
+ pr_debug("C/R: restart failed do_munmap (%d)\n", ret);
+ return ret;
+ }
+ }
+ return 0;
+}
+
+int cr_read_mm(struct cr_ctx *ctx)
+{
+ struct cr_hdr_mm *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct mm_struct *mm;
+ int nr, parent, ret;
+
+ parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_MM);
+ if (parent < 0) {
+ ret = parent;
+ goto out;
+ }
+
+ ret = -EINVAL;
+#if 0 /* activate when containers are used */
+ if (parent != task_pid_vnr(current))
+ goto out;
+#endif
+ cr_debug("map_count %d\n", hh->map_count);
+
+ /* XXX need more sanity checks */
+ if (hh->start_code > hh->end_code ||
+ hh->start_data > hh->end_data || hh->map_count < 0)
+ goto out;
+
+ mm = current->mm;
+
+ /* point of no return -- destruct current mm */
+ down_write(&mm->mmap_sem);
+ ret = cr_destroy_mm(mm);
+ if (ret < 0) {
+ up_write(&mm->mmap_sem);
+ goto out;
+ }
+ mm->start_code = hh->start_code;
+ mm->end_code = hh->end_code;
+ mm->start_data = hh->start_data;
+ mm->end_data = hh->end_data;
+ mm->start_brk = hh->start_brk;
+ mm->brk = hh->brk;
+ mm->start_stack = hh->start_stack;
+ mm->arg_start = hh->arg_start;
+ mm->arg_end = hh->arg_end;
+ mm->env_start = hh->env_start;
+ mm->env_end = hh->env_end;
+ up_write(&mm->mmap_sem);
+
+ /* FIX: need also mm->flags */
+
+ for (nr = hh->map_count; nr; nr--) {
+ ret = cr_read_vma(ctx, mm);
+ if (ret < 0)
+ goto out;
+ }
+
+ ret = cr_read_mm_context(ctx, mm, hh->objref);
+ out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return ret;
+}
diff --git a/include/asm-x86/checkpoint_hdr.h b/include/asm-x86/checkpoint_hdr.h
index 6bc61ac..f8eee6a 100644
--- a/include/asm-x86/checkpoint_hdr.h
+++ b/include/asm-x86/checkpoint_hdr.h
@@ -74,4 +74,8 @@ struct cr_hdr_mm_context {
__s16 nldt;
} __attribute__((aligned(8)));
+
+/* misc prototypes from kernel (not defined elsewhere) */
+asmlinkage int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount);
+
#endif /* __ASM_X86_CKPT_HDR__H */
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 70ef22f..3563bce 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -55,6 +55,9 @@ extern int cr_write_fname(struct cr_ctx *ctx,
extern int cr_read_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf, int n);
extern int cr_read_obj_type(struct cr_ctx *ctx, void *buf, int n, int type);
extern int cr_read_string(struct cr_ctx *ctx, void *str, int len);
+extern int cr_read_fname(struct cr_ctx *ctx, void *fname, int n);
+extern struct file *cr_read_open_fname(struct cr_ctx *ctx,
+ int flags, int mode);
extern int cr_write_mm(struct cr_ctx *ctx, struct task_struct *t);
extern int cr_read_mm(struct cr_ctx *ctx);
--
1.5.4.3
For each VMA, there is a 'struct cr_vma'; if the VMA is file-mapped,
it will be followed by the file name. Then comes the actual contents,
in one or more chunk: each chunk begins with a header that specifies
how many pages it holds, then the virtual addresses of all the dumped
pages in that chunk, followed by the actual contents of all dumped
pages. A header with zero number of pages marks the end of the contents.
Then comes the next VMA and so on.
Changelog[v7]:
- Fix argument given to kunmap_atomic() in memory dump/restore
Changelog[v6]:
- Balance all calls to cr_hbuf_get() with matching cr_hbuf_put()
(even though it's not really needed)
Changelog[v5]:
- Improve memory dump code (following Dave Hansen's comments)
- Change dump format (and code) to allow chunks of <vaddrs, pages>
instead of one long list of each
- Fix use of follow_page() to avoid faulting in non-present pages
Changelog[v4]:
- Use standard list_... for cr_pgarr
Signed-off-by: Oren Laadan <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
---
arch/x86/mm/checkpoint.c | 31 +++
arch/x86/mm/restart.c | 1 +
checkpoint/Makefile | 3 +-
checkpoint/checkpoint.c | 53 ++++
checkpoint/checkpoint_arch.h | 2 +
checkpoint/checkpoint_mem.h | 41 +++
checkpoint/ckpt_mem.c | 500 ++++++++++++++++++++++++++++++++++++++
checkpoint/sys.c | 19 ++
include/asm-x86/checkpoint_hdr.h | 5 +
include/linux/checkpoint.h | 12 +
include/linux/checkpoint_hdr.h | 32 +++
11 files changed, 698 insertions(+), 1 deletions(-)
create mode 100644 checkpoint/checkpoint_mem.h
create mode 100644 checkpoint/ckpt_mem.c
diff --git a/arch/x86/mm/checkpoint.c b/arch/x86/mm/checkpoint.c
index bfa7180..9a75d1d 100644
--- a/arch/x86/mm/checkpoint.c
+++ b/arch/x86/mm/checkpoint.c
@@ -198,3 +198,34 @@ int cr_write_cpu(struct cr_ctx *ctx, struct task_struct *t)
cr_hbuf_put(ctx, sizeof(*hh));
return ret;
}
+
+/* dump the mm->context state */
+int cr_write_mm_context(struct cr_ctx *ctx, struct mm_struct *mm, int parent)
+{
+ struct cr_hdr h;
+ struct cr_hdr_mm_context *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ int ret;
+
+ h.type = CR_HDR_MM_CONTEXT;
+ h.len = sizeof(*hh);
+ h.parent = parent;
+
+ mutex_lock(&mm->context.lock);
+
+ hh->ldt_entry_size = LDT_ENTRY_SIZE;
+ hh->nldt = mm->context.size;
+
+ cr_debug("nldt %d\n", hh->nldt);
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ goto out;
+
+ ret = cr_kwrite(ctx, mm->context.ldt,
+ mm->context.size * LDT_ENTRY_SIZE);
+
+ out:
+ mutex_unlock(&mm->context.lock);
+ return ret;
+}
diff --git a/arch/x86/mm/restart.c b/arch/x86/mm/restart.c
index 2bff5eb..bc2a502 100644
--- a/arch/x86/mm/restart.c
+++ b/arch/x86/mm/restart.c
@@ -8,6 +8,7 @@
* distribution for more details.
*/
+#include <linux/unistd.h>
#include <asm/desc.h>
#include <asm/i387.h>
diff --git a/checkpoint/Makefile b/checkpoint/Makefile
index d2df68c..3a0df6d 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile
@@ -2,4 +2,5 @@
# Makefile for linux checkpoint/restart.
#
-obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o
+obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o \
+ ckpt_mem.o
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index ba18e44..4cbc9c0 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c
@@ -55,6 +55,55 @@ int cr_write_string(struct cr_ctx *ctx, char *str, int len)
return cr_write_obj(ctx, &h, str);
}
+/**
+ * cr_fill_fname - return pathname of a given file
+ * @path: path name
+ * @root: relative root
+ * @buf: buffer for pathname
+ * @n: buffer length (in) and pathname length (out)
+ */
+static char *
+cr_fill_fname(struct path *path, struct path *root, char *buf, int *n)
+{
+ char *fname;
+
+ BUG_ON(!buf);
+ fname = __d_path(path, root, buf, *n);
+ if (!IS_ERR(fname))
+ *n = (buf + (*n) - fname);
+ return fname;
+}
+
+/**
+ * cr_write_fname - write a file name
+ * @ctx: checkpoint context
+ * @path: path name
+ * @root: relative root
+ */
+int cr_write_fname(struct cr_ctx *ctx, struct path *path, struct path *root)
+{
+ struct cr_hdr h;
+ char *buf, *fname;
+ int ret, flen;
+
+ flen = PATH_MAX;
+ buf = kmalloc(flen, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ fname = cr_fill_fname(path, root, buf, &flen);
+ if (!IS_ERR(fname)) {
+ h.type = CR_HDR_FNAME;
+ h.len = flen;
+ h.parent = 0;
+ ret = cr_write_obj(ctx, &h, fname);
+ } else
+ ret = PTR_ERR(fname);
+
+ kfree(buf);
+ return ret;
+}
+
/* write the checkpoint header */
static int cr_write_head(struct cr_ctx *ctx)
{
@@ -150,6 +199,10 @@ static int cr_write_task(struct cr_ctx *ctx, struct task_struct *t)
cr_debug("task_struct: ret %d\n", ret);
if (ret < 0)
goto out;
+ ret = cr_write_mm(ctx, t);
+ cr_debug("memory: ret %d\n", ret);
+ if (ret < 0)
+ goto out;
ret = cr_write_thread(ctx, t);
cr_debug("thread: ret %d\n", ret);
if (ret < 0)
diff --git a/checkpoint/checkpoint_arch.h b/checkpoint/checkpoint_arch.h
index bf2d21e..7da4ad0 100644
--- a/checkpoint/checkpoint_arch.h
+++ b/checkpoint/checkpoint_arch.h
@@ -2,6 +2,8 @@
extern int cr_write_thread(struct cr_ctx *ctx, struct task_struct *t);
extern int cr_write_cpu(struct cr_ctx *ctx, struct task_struct *t);
+extern int cr_write_mm_context(struct cr_ctx *ctx,
+ struct mm_struct *mm, int parent);
extern int cr_read_thread(struct cr_ctx *ctx);
extern int cr_read_cpu(struct cr_ctx *ctx);
diff --git a/checkpoint/checkpoint_mem.h b/checkpoint/checkpoint_mem.h
new file mode 100644
index 0000000..85546f4
--- /dev/null
+++ b/checkpoint/checkpoint_mem.h
@@ -0,0 +1,41 @@
+#ifndef _CHECKPOINT_CKPT_MEM_H_
+#define _CHECKPOINT_CKPT_MEM_H_
+/*
+ * Generic container checkpoint-restart
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/mm_types.h>
+
+/*
+ * page-array chains: each cr_pgarr describes a set of <strcut page *,vaddr>
+ * tuples (where vaddr is the virtual address of a page in a particular mm).
+ * Specifically, we use separate arrays so that all vaddrs can be written
+ * and read at once.
+ */
+
+struct cr_pgarr {
+ unsigned long *vaddrs;
+ struct page **pages;
+ unsigned int nr_used;
+ struct list_head list;
+};
+
+#define CR_PGARR_TOTAL (PAGE_SIZE / sizeof(void *))
+#define CR_PGARR_CHUNK (4 * CR_PGARR_TOTAL)
+
+extern void cr_pgarr_free(struct cr_ctx *ctx);
+extern struct cr_pgarr *cr_pgarr_current(struct cr_ctx *ctx);
+extern void cr_pgarr_reset_all(struct cr_ctx *ctx);
+
+static inline int cr_pgarr_is_full(struct cr_pgarr *pgarr)
+{
+ return (pgarr->nr_used == CR_PGARR_TOTAL);
+}
+
+#endif /* _CHECKPOINT_CKPT_MEM_H_ */
diff --git a/checkpoint/ckpt_mem.c b/checkpoint/ckpt_mem.c
new file mode 100644
index 0000000..807f8fa
--- /dev/null
+++ b/checkpoint/ckpt_mem.c
@@ -0,0 +1,500 @@
+/*
+ * Checkpoint memory contents
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/pagemap.h>
+#include <linux/mm_types.h>
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+#include "checkpoint_arch.h"
+#include "checkpoint_mem.h"
+
+/*
+ * utilities to alloc, free, and handle 'struct cr_pgarr' (page-arrays)
+ * (common to ckpt_mem.c and rstr_mem.c).
+ *
+ * The checkpoint context structure has two members for page-arrays:
+ * ctx->pgarr_list: list head of the page-array chain
+ *
+ * During checkpoint (and restart) the chain tracks the dirty pages (page
+ * pointer and virtual address) of each MM. For a particular MM, these are
+ * always added to the head of the page-array chain (ctx->pgarr_list).
+ * This "current" page-array advances as necessary, and new page-array
+ * descriptors are allocated on-demand. Before the next chunk of pages,
+ * the chain is reset but not freed (that is, dereference page pointers).
+ */
+
+/* return first page-array in the chain */
+static inline struct cr_pgarr *cr_pgarr_first(struct cr_ctx *ctx)
+{
+ if (list_empty(&ctx->pgarr_list))
+ return NULL;
+ return list_first_entry(&ctx->pgarr_list, struct cr_pgarr, list);
+}
+
+/* release pages referenced by a page-array */
+static void cr_pgarr_release_pages(struct cr_pgarr *pgarr)
+{
+ int i;
+
+ cr_debug("nr_used %d\n", pgarr->nr_used);
+ /*
+ * although both checkpoint and restart use 'nr_used', we only
+ * collect pages during checkpoint; in restart we simply return
+ */
+ if (!pgarr->pages)
+ return;
+ for (i = pgarr->nr_used; i--; /**/)
+ page_cache_release(pgarr->pages[i]);
+}
+
+/* free a single page-array object */
+static void cr_pgarr_free_one(struct cr_pgarr *pgarr)
+{
+ cr_pgarr_release_pages(pgarr);
+ kfree(pgarr->pages);
+ kfree(pgarr->vaddrs);
+ kfree(pgarr);
+}
+
+/* free a chain of page-arrays */
+void cr_pgarr_free(struct cr_ctx *ctx)
+{
+ struct cr_pgarr *pgarr, *tmp;
+
+ list_for_each_entry_safe(pgarr, tmp, &ctx->pgarr_list, list) {
+ list_del(&pgarr->list);
+ cr_pgarr_free_one(pgarr);
+ }
+}
+
+/* allocate a single page-array object */
+static struct cr_pgarr *cr_pgarr_alloc_one(unsigned long flags)
+{
+ struct cr_pgarr *pgarr;
+
+ pgarr = kzalloc(sizeof(*pgarr), GFP_KERNEL);
+ if (!pgarr)
+ return NULL;
+
+ pgarr->vaddrs = kmalloc(CR_PGARR_TOTAL * sizeof(unsigned long),
+ GFP_KERNEL);
+ if (!pgarr->vaddrs)
+ goto nomem;
+
+ /* pgarr->pages is needed only for checkpoint */
+ if (flags & CR_CTX_CKPT) {
+ pgarr->pages = kmalloc(CR_PGARR_TOTAL * sizeof(struct page *),
+ GFP_KERNEL);
+ if (!pgarr->pages)
+ goto nomem;
+ }
+
+ return pgarr;
+
+ nomem:
+ cr_pgarr_free_one(pgarr);
+ return NULL;
+}
+
+/* cr_pgarr_current - return the next available page-array in the chain
+ * @ctx: checkpoint context
+ *
+ * Returns the first page-array in the list that has space. Extends the
+ * list if none has space.
+ */
+struct cr_pgarr *cr_pgarr_current(struct cr_ctx *ctx)
+{
+ struct cr_pgarr *pgarr;
+
+ pgarr = cr_pgarr_first(ctx);
+ if (pgarr && !cr_pgarr_is_full(pgarr))
+ goto out;
+ pgarr = cr_pgarr_alloc_one(ctx->flags);
+ if (!pgarr)
+ goto out;
+ list_add(&pgarr->list, &ctx->pgarr_list);
+ out:
+ return pgarr;
+}
+
+/* reset the page-array chain (dropping page references if necessary) */
+void cr_pgarr_reset_all(struct cr_ctx *ctx)
+{
+ struct cr_pgarr *pgarr;
+
+ list_for_each_entry(pgarr, &ctx->pgarr_list, list) {
+ cr_pgarr_release_pages(pgarr);
+ pgarr->nr_used = 0;
+ }
+}
+
+/*
+ * Checkpoint is outside the context of the checkpointee, so one cannot
+ * simply read pages from user-space. Instead, we scan the address space
+ * of the target to cherry-pick pages of interest. Selected pages are
+ * enlisted in a page-array chain (attached to the checkpoint context).
+ * To save their contents, each page is mapped to kernel memory and then
+ * dumped to the file descriptor.
+ */
+
+
+/**
+ * cr_private_follow_page - return page pointer for dirty pages
+ * @vma - target vma
+ * @addr - page address
+ *
+ * Looks up the page that correspond to the address in the vma, and
+ * returns the page if it was modified (and grabs a reference to it),
+ * or otherwise returns NULL (or error).
+ *
+ * This function should _only_ called for private vma's.
+ */
+static struct page *
+cr_private_follow_page(struct vm_area_struct *vma, unsigned long addr)
+{
+ struct page *page;
+
+ BUG_ON(vma->vm_flags & (VM_SHARED | VM_MAYSHARE));
+
+ /*
+ * simplified version of get_user_pages(): already have vma,
+ * only need FOLL_ANON, and (for now) ignore fault stats.
+ *
+ * follow_page() will return NULL if the page is not present
+ * (swapped), ZERO_PAGE(0) if the pte wasn't allocated, and
+ * the actual page pointer otherwise.
+ *
+ * FIXME: consolidate with get_user_pages()
+ */
+
+ cond_resched();
+ while (!(page = follow_page(vma, addr, FOLL_ANON | FOLL_GET))) {
+ int ret;
+
+ /* the page is swapped out - bring it in (optimize ?) */
+ ret = handle_mm_fault(vma->vm_mm, vma, addr, 0);
+ if (ret & VM_FAULT_ERROR) {
+ if (ret & VM_FAULT_OOM)
+ return ERR_PTR(-ENOMEM);
+ else if (ret & VM_FAULT_SIGBUS)
+ return ERR_PTR(-EFAULT);
+ else
+ BUG();
+ break;
+ }
+ cond_resched();
+ }
+
+ if (IS_ERR(page))
+ return page;
+
+ /*
+ * We only care about dirty pages: either non-zero page, or
+ * file-backed (copy-on-write) that were touched. For the latter,
+ * the page_mapping() will be unset because it will no longer be
+ * mapped to the original file after having been modified.
+ */
+ if (page == ZERO_PAGE(0)) {
+ /* this is the zero page: ignore */
+ page_cache_release(page);
+ page = NULL;
+ } else if (vma->vm_file && (page_mapping(page) != NULL)) {
+ /* file backed clean cow: ignore */
+ page_cache_release(page);
+ page = NULL;
+ }
+
+ return page;
+}
+
+/**
+ * cr_private_vma_fill_pgarr - fill a page-array with addr/page tuples
+ * @ctx - checkpoint context
+ * @pgarr - page-array to fill
+ * @vma - vma to scan
+ * @start - start address (updated)
+ *
+ * Returns the number of pages collected
+ */
+static int
+cr_private_vma_fill_pgarr(struct cr_ctx *ctx, struct cr_pgarr *pgarr,
+ struct vm_area_struct *vma, unsigned long *start)
+{
+ unsigned long end = vma->vm_end;
+ unsigned long addr = *start;
+ int orig_used = pgarr->nr_used;
+
+ /* this function is only for private memory (anon or file-mapped) */
+ BUG_ON(vma->vm_flags & (VM_SHARED | VM_MAYSHARE));
+
+ while (addr < end) {
+ struct page *page;
+
+ page = cr_private_follow_page(vma, addr);
+ if (IS_ERR(page))
+ return PTR_ERR(page);
+
+ if (page) {
+ pgarr->pages[pgarr->nr_used] = page;
+ pgarr->vaddrs[pgarr->nr_used] = addr;
+ pgarr->nr_used++;
+ }
+
+ addr += PAGE_SIZE;
+
+ if (cr_pgarr_is_full(pgarr))
+ break;
+ }
+
+ *start = addr;
+ return pgarr->nr_used - orig_used;
+}
+
+/* dump contents of a pages: use kmap_atomic() to avoid TLB flush */
+static int cr_page_write(struct cr_ctx *ctx, struct page *page, char *buf)
+{
+ void *ptr;
+
+ ptr = kmap_atomic(page, KM_USER1);
+ memcpy(buf, ptr, PAGE_SIZE);
+ kunmap_atomic(ptr, KM_USER1);
+
+ return cr_kwrite(ctx, buf, PAGE_SIZE);
+}
+
+/**
+ * cr_vma_dump_pages - dump pages listed in the ctx page-array chain
+ * @ctx - checkpoint context
+ * @total - total number of pages
+ *
+ * First dump all virtual addresses, followed by the contents of all pages
+ */
+static int cr_vma_dump_pages(struct cr_ctx *ctx, int total)
+{
+ struct cr_pgarr *pgarr;
+ char *buf;
+ int i, ret = 0;
+
+ if (!total)
+ return 0;
+
+ list_for_each_entry_reverse(pgarr, &ctx->pgarr_list, list) {
+ ret = cr_kwrite(ctx, pgarr->vaddrs,
+ pgarr->nr_used * sizeof(*pgarr->vaddrs));
+ if (ret < 0)
+ return ret;
+ }
+
+ buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ list_for_each_entry_reverse(pgarr, &ctx->pgarr_list, list) {
+ for (i = 0; i < pgarr->nr_used; i++) {
+ ret = cr_page_write(ctx, pgarr->pages[i], buf);
+ if (ret < 0)
+ goto out;
+ }
+ }
+
+ out:
+ kfree(buf);
+ return ret;
+}
+
+/**
+ * cr_write_private_vma_contents - dump contents of a VMA with private memory
+ * @ctx - checkpoint context
+ * @vma - vma to scan
+ *
+ * Collect lists of pages that needs to be dumped, and corresponding
+ * virtual addresses into ctx->pgarr_list page-array chain. Then dump
+ * the addresses, followed by the page contents.
+ */
+static int
+cr_write_private_vma_contents(struct cr_ctx *ctx, struct vm_area_struct *vma)
+{
+ struct cr_hdr h;
+ struct cr_hdr_pgarr *hh;
+ unsigned long addr = vma->vm_start;
+ struct cr_pgarr *pgarr;
+ unsigned long cnt = 0;
+ int ret;
+
+ /*
+ * Work iteratively, collecting and dumping at most CR_PGARR_CHUNK
+ * in each round. Each iterations is divided into two steps:
+ *
+ * (1) scan: scan through the PTEs of the vma to collect the pages
+ * to dump (later we'll also make them COW), while keeping a list
+ * of pages and their corresponding addresses on ctx->pgarr_list.
+ *
+ * (2) dump: write out a header specifying how many pages, followed
+ * by the addresses of all pages in ctx->pgarr_list, followed by
+ * the actual contents of all pages. (Then, release the references
+ * to the pages and reset the page-array chain).
+ *
+ * (This split makes the logic simpler by first counting the pages
+ * that need saving. More importantly, it allows for a future
+ * optimization that will reduce application downtime by deferring
+ * the actual write-out of the data to after the application is
+ * allowed to resume execution).
+ *
+ * After dumpting the entire contents, conclude with a header that
+ * specifies 0 pages to mark the end of the contents.
+ */
+
+ h.type = CR_HDR_PGARR;
+ h.len = sizeof(*hh);
+ h.parent = 0;
+
+ while (addr < vma->vm_end) {
+ pgarr = cr_pgarr_current(ctx);
+ if (!pgarr)
+ return -ENOMEM;
+ ret = cr_private_vma_fill_pgarr(ctx, pgarr, vma, &addr);
+ if (ret < 0)
+ return ret;
+ cnt += ret;
+
+ /* did we complete a chunk, or is this the last chunk ? */
+ if (cnt >= CR_PGARR_CHUNK || (cnt && addr == vma->vm_end)) {
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ hh->nr_pages = cnt;
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ return ret;
+
+ ret = cr_vma_dump_pages(ctx, cnt);
+ if (ret < 0)
+ return ret;
+
+ cr_pgarr_reset_all(ctx);
+ }
+ }
+
+ /* mark end of contents with header saying "0" pages */
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ hh->nr_pages = 0;
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+
+ return ret;
+}
+
+static int cr_write_vma(struct cr_ctx *ctx, struct vm_area_struct *vma)
+{
+ struct cr_hdr h;
+ struct cr_hdr_vma *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ int vma_type, ret;
+
+ h.type = CR_HDR_VMA;
+ h.len = sizeof(*hh);
+ h.parent = 0;
+
+ hh->vm_start = vma->vm_start;
+ hh->vm_end = vma->vm_end;
+ hh->vm_page_prot = vma->vm_page_prot.pgprot;
+ hh->vm_flags = vma->vm_flags;
+ hh->vm_pgoff = vma->vm_pgoff;
+
+ if (vma->vm_flags & (VM_SHARED | VM_IO | VM_HUGETLB | VM_NONLINEAR)) {
+ pr_warning("C/R: unsupported VMA %#lx\n", vma->vm_flags);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return -ENOSYS;
+ }
+
+ /* by default assume anon memory */
+ vma_type = CR_VMA_ANON;
+
+ /*
+ * if there is a backing file, assume private-mapped
+ * (FIXME: check if the file is unlinked)
+ */
+ if (vma->vm_file)
+ vma_type = CR_VMA_FILE;
+
+ hh->vma_type = vma_type;
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ return ret;
+
+ /* save the file name, if relevant */
+ if (vma->vm_file) {
+ ret = cr_write_fname(ctx, &vma->vm_file->f_path, ctx->vfsroot);
+ if (ret < 0)
+ return ret;
+ }
+
+ return cr_write_private_vma_contents(ctx, vma);
+}
+
+int cr_write_mm(struct cr_ctx *ctx, struct task_struct *t)
+{
+ struct cr_hdr h;
+ struct cr_hdr_mm *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct mm_struct *mm;
+ struct vm_area_struct *vma;
+ int objref, ret;
+
+ h.type = CR_HDR_MM;
+ h.len = sizeof(*hh);
+ h.parent = task_pid_vnr(t);
+
+ mm = get_task_mm(t);
+
+ objref = 0; /* will be meaningful with multiple processes */
+ hh->objref = objref;
+
+ down_read(&mm->mmap_sem);
+
+ hh->start_code = mm->start_code;
+ hh->end_code = mm->end_code;
+ hh->start_data = mm->start_data;
+ hh->end_data = mm->end_data;
+ hh->start_brk = mm->start_brk;
+ hh->brk = mm->brk;
+ hh->start_stack = mm->start_stack;
+ hh->arg_start = mm->arg_start;
+ hh->arg_end = mm->arg_end;
+ hh->env_start = mm->env_start;
+ hh->env_end = mm->env_end;
+
+ hh->map_count = mm->map_count;
+
+ /* FIX: need also mm->flags */
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ goto out;
+
+ /* write the vma's */
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ ret = cr_write_vma(ctx, vma);
+ if (ret < 0)
+ goto out;
+ }
+
+ ret = cr_write_mm_context(ctx, mm, objref);
+
+ out:
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+ return ret;
+}
diff --git a/checkpoint/sys.c b/checkpoint/sys.c
index 3ce84ba..0bcfadb 100644
--- a/checkpoint/sys.c
+++ b/checkpoint/sys.c
@@ -16,6 +16,8 @@
#include <linux/capability.h>
#include <linux/checkpoint.h>
+#include "checkpoint_mem.h"
+
/*
* helpers to write/read to/from the image file descriptor
*
@@ -157,7 +159,14 @@ static void cr_ctx_free(struct cr_ctx *ctx)
{
if (ctx->file)
fput(ctx->file);
+
kfree(ctx->hbuf);
+
+ if (ctx->vfsroot)
+ path_put(ctx->vfsroot);
+
+ cr_pgarr_free(ctx);
+
kfree(ctx);
}
@@ -173,6 +182,8 @@ static struct cr_ctx *cr_ctx_alloc(pid_t pid, int fd, unsigned long flags)
ctx->pid = pid;
ctx->flags = flags;
+ INIT_LIST_HEAD(&ctx->pgarr_list);
+
err = -EBADF;
ctx->file = fget(fd);
if (!ctx->file)
@@ -180,9 +191,17 @@ static struct cr_ctx *cr_ctx_alloc(pid_t pid, int fd, unsigned long flags)
err = -ENOMEM;
ctx->hbuf = kmalloc(CR_HBUF_TOTAL, GFP_KERNEL);
+
if (!ctx->hbuf)
goto err;
+ /*
+ * assume checkpointer is in container's root vfs
+ * FIXME: this works for now, but will change with real containers
+ */
+ ctx->vfsroot = ¤t->fs->root;
+ path_get(ctx->vfsroot);
+
ctx->crid = atomic_inc_return(&cr_ctx_count);
return ctx;
diff --git a/include/asm-x86/checkpoint_hdr.h b/include/asm-x86/checkpoint_hdr.h
index 44a903c..6bc61ac 100644
--- a/include/asm-x86/checkpoint_hdr.h
+++ b/include/asm-x86/checkpoint_hdr.h
@@ -69,4 +69,9 @@ struct cr_hdr_cpu {
} __attribute__((aligned(8)));
+struct cr_hdr_mm_context {
+ __s16 ldt_entry_size;
+ __s16 nldt;
+} __attribute__((aligned(8)));
+
#endif /* __ASM_X86_CKPT_HDR__H */
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 0f47160..70ef22f 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -10,6 +10,9 @@
* distribution for more details.
*/
+#include <linux/path.h>
+#include <linux/fs.h>
+
#define CR_VERSION 1
struct cr_ctx {
@@ -24,6 +27,10 @@ struct cr_ctx {
void *hbuf; /* temporary buffer for headers */
int hpos; /* position in headers buffer */
+
+ struct list_head pgarr_list; /* page array to dump VMA contents */
+
+ struct path *vfsroot; /* container root (FIXME) */
};
/* cr_ctx: flags */
@@ -42,11 +49,16 @@ struct cr_hdr;
extern int cr_write_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf);
extern int cr_write_string(struct cr_ctx *ctx, char *str, int len);
+extern int cr_write_fname(struct cr_ctx *ctx,
+ struct path *path, struct path *root);
extern int cr_read_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf, int n);
extern int cr_read_obj_type(struct cr_ctx *ctx, void *buf, int n, int type);
extern int cr_read_string(struct cr_ctx *ctx, void *str, int len);
+extern int cr_write_mm(struct cr_ctx *ctx, struct task_struct *t);
+extern int cr_read_mm(struct cr_ctx *ctx);
+
extern int do_checkpoint(struct cr_ctx *ctx);
extern int do_restart(struct cr_ctx *ctx);
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 03ec72e..2b110f1 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -32,6 +32,7 @@ struct cr_hdr {
enum {
CR_HDR_HEAD = 1,
CR_HDR_STRING,
+ CR_HDR_FNAME,
CR_HDR_TASK = 101,
CR_HDR_THREAD,
@@ -39,6 +40,7 @@ enum {
CR_HDR_MM = 201,
CR_HDR_VMA,
+ CR_HDR_PGARR,
CR_HDR_MM_CONTEXT,
CR_HDR_TAIL = 5001
@@ -73,4 +75,34 @@ struct cr_hdr_task {
__s32 task_comm_len;
} __attribute__((aligned(8)));
+struct cr_hdr_mm {
+ __u32 objref; /* identifier for shared objects */
+ __u32 map_count;
+
+ __u64 start_code, end_code, start_data, end_data;
+ __u64 start_brk, brk, start_stack;
+ __u64 arg_start, arg_end, env_start, env_end;
+} __attribute__((aligned(8)));
+
+/* vma subtypes */
+enum vm_type {
+ CR_VMA_ANON = 1,
+ CR_VMA_FILE
+};
+
+struct cr_hdr_vma {
+ __u32 vma_type;
+ __u32 _padding;
+
+ __u64 vm_start;
+ __u64 vm_end;
+ __u64 vm_page_prot;
+ __u64 vm_flags;
+ __u64 vm_pgoff;
+} __attribute__((aligned(8)));
+
+struct cr_hdr_pgarr {
+ __u64 nr_pages; /* number of pages to saved */
+} __attribute__((aligned(8)));
+
#endif /* _CHECKPOINT_CKPT_HDR_H_ */
--
1.5.4.3
Dump the files_struct of a task with 'struct cr_hdr_files', followed by
all open file descriptors. Since FDs can be shared, they are assigned an
objref and registered in the object hash.
For each open FD there is a 'struct cr_hdr_fd_ent' with the FD, its objref
and its close-on-exec property. If the FD is to be saved (first time)
then this is followed by a 'struct cr_hdr_fd_data' with the FD state.
Then will come the next FD and so on.
This patch only handles basic FDs - regular files, directories and also
symbolic links.
Changelog[v8]:
- initialize 'coe' to workaround gcc false warning
Changelog[v6]:
- Balance all calls to cr_hbuf_get() with matching cr_hbuf_put()
(even though it's not really needed)
Signed-off-by: Oren Laadan <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
---
checkpoint/Makefile | 2 +-
checkpoint/checkpoint.c | 4 +
checkpoint/checkpoint_file.h | 17 +++
checkpoint/ckpt_file.c | 232 ++++++++++++++++++++++++++++++++++++++++
include/linux/checkpoint.h | 7 +-
include/linux/checkpoint_hdr.h | 32 ++++++-
6 files changed, 289 insertions(+), 5 deletions(-)
create mode 100644 checkpoint/checkpoint_file.h
create mode 100644 checkpoint/ckpt_file.c
diff --git a/checkpoint/Makefile b/checkpoint/Makefile
index 9843fb9..7496695 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile
@@ -3,4 +3,4 @@
#
obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o objhash.o \
- ckpt_mem.o rstr_mem.o
+ ckpt_mem.o rstr_mem.o ckpt_file.o
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index 4cbc9c0..ce622e1 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c
@@ -203,6 +203,10 @@ static int cr_write_task(struct cr_ctx *ctx, struct task_struct *t)
cr_debug("memory: ret %d\n", ret);
if (ret < 0)
goto out;
+ ret = cr_write_files(ctx, t);
+ cr_debug("files: ret %d\n", ret);
+ if (ret < 0)
+ goto out;
ret = cr_write_thread(ctx, t);
cr_debug("thread: ret %d\n", ret);
if (ret < 0)
diff --git a/checkpoint/checkpoint_file.h b/checkpoint/checkpoint_file.h
new file mode 100644
index 0000000..9dc3eba
--- /dev/null
+++ b/checkpoint/checkpoint_file.h
@@ -0,0 +1,17 @@
+#ifndef _CHECKPOINT_CKPT_FILE_H_
+#define _CHECKPOINT_CKPT_FILE_H_
+/*
+ * Checkpoint file descriptors
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/fdtable.h>
+
+int cr_scan_fds(struct files_struct *files, int **fdtable);
+
+#endif /* _CHECKPOINT_CKPT_FILE_H_ */
diff --git a/checkpoint/ckpt_file.c b/checkpoint/ckpt_file.c
new file mode 100644
index 0000000..5aa295f
--- /dev/null
+++ b/checkpoint/ckpt_file.c
@@ -0,0 +1,232 @@
+/*
+ * Checkpoint file descriptors
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+#include "checkpoint_file.h"
+
+#define CR_DEFAULT_FDTABLE 256 /* an initial guess */
+
+/**
+ * cr_scan_fds - scan file table and construct array of open fds
+ * @files: files_struct pointer
+ * @fdtable: (output) array of open fds
+ *
+ * Returns the number of open fds found, and also the file table
+ * array via *fdtable. The caller should free the array.
+ *
+ * The caller must validate the file descriptors collected in the
+ * array before using them, e.g. by using fcheck_files(), in case
+ * the task's fdtable changes in the meantime.
+ */
+int cr_scan_fds(struct files_struct *files, int **fdtable)
+{
+ struct fdtable *fdt;
+ int *fds;
+ int i, n = 0;
+ int tot = CR_DEFAULT_FDTABLE;
+
+ fds = kmalloc(tot * sizeof(*fds), GFP_KERNEL);
+ if (!fds)
+ return -ENOMEM;
+
+ /*
+ * We assume that the target task is frozen (or that we checkpoint
+ * ourselves), so we can safely proceed after krealloc() from where
+ * we left off; in the worst cases restart will fail.
+ */
+
+ spin_lock(&files->file_lock);
+ rcu_read_lock();
+ fdt = files_fdtable(files);
+ for (i = 0; i < fdt->max_fds; i++) {
+ if (!fcheck_files(files, i))
+ continue;
+ if (n == tot) {
+ /*
+ * fcheck_files() is safe with drop/re-acquire
+ * of the lock, because it tests: fd < max_fds
+ */
+ spin_unlock(&files->file_lock);
+ rcu_read_unlock();
+ tot *= 2; /* won't overflow: kmalloc will fail */
+ fds = krealloc(fds, tot * sizeof(*fds), GFP_KERNEL);
+ if (!fds) {
+ kfree(fds);
+ return -ENOMEM;
+ }
+ rcu_read_lock();
+ spin_lock(&files->file_lock);
+ }
+ fds[n++] = i;
+ }
+ rcu_read_unlock();
+ spin_unlock(&files->file_lock);
+
+ *fdtable = fds;
+ return n;
+}
+
+/* cr_write_fd_data - dump the state of a given file pointer */
+static int cr_write_fd_data(struct cr_ctx *ctx, struct file *file, int parent)
+{
+ struct cr_hdr h;
+ struct cr_hdr_fd_data *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct dentry *dent = file->f_dentry;
+ struct inode *inode = dent->d_inode;
+ enum fd_type fd_type;
+ int ret;
+
+ h.type = CR_HDR_FD_DATA;
+ h.len = sizeof(*hh);
+ h.parent = parent;
+
+ hh->f_flags = file->f_flags;
+ hh->f_mode = file->f_mode;
+ hh->f_pos = file->f_pos;
+ hh->f_version = file->f_version;
+ /* FIX: need also file->uid, file->gid, file->f_owner, etc */
+
+ switch (inode->i_mode & S_IFMT) {
+ case S_IFREG:
+ fd_type = CR_FD_FILE;
+ break;
+ case S_IFDIR:
+ fd_type = CR_FD_DIR;
+ break;
+ case S_IFLNK:
+ fd_type = CR_FD_LINK;
+ break;
+ default:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return -EBADF;
+ }
+
+ /* FIX: check if the file/dir/link is unlinked */
+ hh->fd_type = fd_type;
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ return ret;
+
+ return cr_write_fname(ctx, &file->f_path, ctx->vfsroot);
+}
+
+/**
+ * cr_write_fd_ent - dump the state of a given file descriptor
+ * @ctx: checkpoint context
+ * @files: files_struct pointer
+ * @fd: file descriptor
+ *
+ * Saves the state of the file descriptor; looks up the actual file
+ * pointer in the hash table, and if found saves the matching objref,
+ * otherwise calls cr_write_fd_data to dump the file pointer too.
+ */
+static int
+cr_write_fd_ent(struct cr_ctx *ctx, struct files_struct *files, int fd)
+{
+ struct cr_hdr h;
+ struct cr_hdr_fd_ent *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct file *file = NULL;
+ struct fdtable *fdt;
+ int objref, new, ret;
+ int coe = 0; /* avoid gcc warning */
+
+ rcu_read_lock();
+ fdt = files_fdtable(files);
+ file = fcheck_files(files, fd);
+ if (file) {
+ coe = FD_ISSET(fd, fdt->close_on_exec);
+ get_file(file);
+ }
+ rcu_read_unlock();
+
+ /* sanity check (although this shouldn't happen) */
+ if (!file) {
+ ret = -EBADF;
+ goto out;
+ }
+
+ new = cr_obj_add_ptr(ctx, file, &objref, CR_OBJ_FILE, 0);
+ cr_debug("fd %d objref %d file %p c-o-e %d)\n", fd, objref, file, coe);
+
+ if (new < 0) {
+ ret = new;
+ goto out;
+ }
+
+ h.type = CR_HDR_FD_ENT;
+ h.len = sizeof(*hh);
+ h.parent = 0;
+
+ hh->objref = objref;
+ hh->fd = fd;
+ hh->close_on_exec = coe;
+
+ ret = cr_write_obj(ctx, &h, hh);
+ if (ret < 0)
+ goto out;
+
+ /* new==1 if-and-only-if file was newly added to hash */
+ if (new)
+ ret = cr_write_fd_data(ctx, file, objref);
+
+out:
+ cr_hbuf_put(ctx, sizeof(*hh));
+ fput(file);
+ return ret;
+}
+
+int cr_write_files(struct cr_ctx *ctx, struct task_struct *t)
+{
+ struct cr_hdr h;
+ struct cr_hdr_files *hh = cr_hbuf_get(ctx, sizeof(*hh));
+ struct files_struct *files;
+ int *fdtable;
+ int nfds, n, ret;
+
+ h.type = CR_HDR_FILES;
+ h.len = sizeof(*hh);
+ h.parent = task_pid_vnr(t);
+
+ files = get_files_struct(t);
+
+ nfds = cr_scan_fds(files, &fdtable);
+ if (nfds < 0) {
+ put_files_struct(files);
+ return nfds;
+ }
+
+ hh->objref = 0; /* will be meaningful with multiple processes */
+ hh->nfds = nfds;
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ goto clean;
+
+ cr_debug("nfds %d\n", nfds);
+ for (n = 0; n < nfds; n++) {
+ ret = cr_write_fd_ent(ctx, files, fdtable[n]);
+ if (ret < 0)
+ break;
+ }
+
+ clean:
+ kfree(fdtable);
+ put_files_struct(files);
+ return ret;
+}
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index e85b95c..0856b3b 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -13,7 +13,7 @@
#include <linux/path.h>
#include <linux/fs.h>
-#define CR_VERSION 1
+#define CR_VERSION 2
struct cr_ctx {
pid_t pid; /* container identifier */
@@ -79,11 +79,12 @@ extern int cr_read_fname(struct cr_ctx *ctx, void *fname, int n);
extern struct file *cr_read_open_fname(struct cr_ctx *ctx,
int flags, int mode);
+extern int do_checkpoint(struct cr_ctx *ctx);
extern int cr_write_mm(struct cr_ctx *ctx, struct task_struct *t);
-extern int cr_read_mm(struct cr_ctx *ctx);
+extern int cr_write_files(struct cr_ctx *ctx, struct task_struct *t);
-extern int do_checkpoint(struct cr_ctx *ctx);
extern int do_restart(struct cr_ctx *ctx);
+extern int cr_read_mm(struct cr_ctx *ctx);
#define cr_debug(fmt, args...) \
pr_debug("[CR:%s] " fmt, __func__, ## args)
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 2b110f1..cbb920f 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -17,7 +17,7 @@
/*
* To maintain compatibility between 32-bit and 64-bit architecture flavors,
* keep data 64-bit aligned: use padding for structure members, and use
- * __attribute__ ((aligned (8))) for the entire structure.
+ * __attribute__((aligned(8))) for the entire structure.
*/
/* records: generic header */
@@ -43,6 +43,10 @@ enum {
CR_HDR_PGARR,
CR_HDR_MM_CONTEXT,
+ CR_HDR_FILES = 301,
+ CR_HDR_FD_ENT,
+ CR_HDR_FD_DATA,
+
CR_HDR_TAIL = 5001
};
@@ -105,4 +109,30 @@ struct cr_hdr_pgarr {
__u64 nr_pages; /* number of pages to saved */
} __attribute__((aligned(8)));
+struct cr_hdr_files {
+ __u32 objref; /* identifier for shared objects */
+ __u32 nfds;
+} __attribute__((aligned(8)));
+
+struct cr_hdr_fd_ent {
+ __u32 objref; /* identifier for shared objects */
+ __s32 fd;
+ __u32 close_on_exec;
+} __attribute__((aligned(8)));
+
+/* fd types */
+enum fd_type {
+ CR_FD_FILE = 1,
+ CR_FD_DIR,
+ CR_FD_LINK
+};
+
+struct cr_hdr_fd_data {
+ __u16 fd_type;
+ __u16 f_mode;
+ __u32 f_flags;
+ __u64 f_pos;
+ __u64 f_version;
+} __attribute__((aligned(8)));
+
#endif /* _CHECKPOINT_CKPT_HDR_H_ */
--
1.5.4.3
From: Dave Hansen <[email protected]>
Suggested by Ingo.
Checkpoint/restart is going to be a long effort to get things working.
We're going to have a lot of things that we know just don't work for
a long time. That doesn't mean that it will be useless, it just means
that there's some complicated features that we are going to have to
work incrementally to fix.
This patch introduces a new mechanism to help the checkpoint/restart
developers. A new function pair: task/process_deny_checkpoint() is
created. When called, these tell the kernel that we *know* that the
process has performed some activity that will keep it from being
properly checkpointed.
The 'flag' is an atomic_t for now so that we can have some level
of atomicity and make sure to only warn once.
For now, this is a one-way trip. Once a process is no longer
'may_checkpoint' capable, neither it nor its children ever will be.
This can, of course, be fixed up in the future. We might want to
reset the flag when a new pid namespace is created, for instance.
Signed-off-by: Dave Hansen <[email protected]>
Signed-off-by: Oren Laadan <[email protected]>
---
include/linux/checkpoint.h | 33 ++++++++++++++++++++++++++++++++-
include/linux/sched.h | 3 +++
kernel/fork.c | 10 ++++++++++
3 files changed, 45 insertions(+), 1 deletions(-)
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index e9d554e..70cfceb 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -10,8 +10,11 @@
* distribution for more details.
*/
-#include <linux/path.h>
#include <linux/fs.h>
+#include <linux/path.h>
+#include <linux/sched.h>
+
+#ifdef CONFIG_CHECKPOINT_RESTART
#define CR_VERSION 2
@@ -93,4 +96,32 @@ extern int cr_read_files(struct cr_ctx *ctx);
#define cr_debug(fmt, args...) \
pr_debug("[CR:%s] " fmt, __func__, ## args)
+static inline void __task_deny_checkpointing(struct task_struct *task,
+ char *file, int line)
+{
+ if (!atomic_dec_and_test(&task->may_checkpoint))
+ return;
+ printk(KERN_INFO "process performed an action that can not be "
+ "checkpointed at: %s:%d\n", file, line);
+ WARN_ON(1);
+}
+#define process_deny_checkpointing(p) \
+ __task_deny_checkpointing(p, __FILE__, __LINE__)
+
+/*
+ * For now, we're not going to have a distinction between
+ * tasks and processes for the purpose of c/r. But, allow
+ * these two calls anyway to make new users at least think
+ * about it.
+ */
+#define task_deny_checkpointing(p) \
+ __task_deny_checkpointing(p, __FILE__, __LINE__)
+
+#else
+
+static inline void task_deny_checkpointing(struct task_struct *task) {}
+static inline void process_deny_checkpointing(struct task_struct *task) {}
+
+#endif
+
#endif /* _CHECKPOINT_CKPT_H_ */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3d9120c..8c50e3b 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1301,6 +1301,9 @@ struct task_struct {
int latency_record_count;
struct latency_record latency_record[LT_SAVECOUNT];
#endif
+#ifdef CONFIG_CHECKPOINT_RESTART
+ atomic_t may_checkpoint;
+#endif
};
/*
diff --git a/kernel/fork.c b/kernel/fork.c
index 7ce2ebe..d6cf7e4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -194,6 +194,13 @@ void __init fork_init(unsigned long mempages)
init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
init_task.signal->rlim[RLIMIT_SIGPENDING] =
init_task.signal->rlim[RLIMIT_NPROC];
+
+#ifdef CONFIG_CHECKPOINT_RESTART
+ /*
+ * This probably won't stay set for long...
+ */
+ atomic_set(&init_task.may_checkpoint, 1);
+#endif
}
int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
@@ -244,6 +251,9 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
tsk->btrace_seq = 0;
#endif
tsk->splice_pipe = NULL;
+#ifdef CONFIG_CHECKPOINT_RESTART
+ atomic_set(&tsk->may_checkpoint, atomic_read(&orig->may_checkpoint));
+#endif
return tsk;
out:
--
1.5.4.3
Create trivial sys_checkpoint and sys_restore system calls. They will
enable to checkpoint and restart an entire container, to and from a
checkpoint image file descriptor.
The syscalls take a file descriptor (for the image file) and flags as
arguments. For sys_checkpoint the first argument identifies the target
container; for sys_restart it will identify the checkpoint image.
The checkpoint image is written to (and read from) the file descriptor
directly from the kernel. This way the data is generated and pushed
out naturally as resources and tasks are scanned to save their state.
This is the approach taken by, e.g., Zap and OpenVZ.
By using a return value and not a file descriptor, we can distinguish
between a return from checkpoint, a return from restart (in case of a
checkpoint that includes self, i.e. a task checkpointing its own
container, or itself), and an error condition, in a manner analogous
to a fork() call.
We don't use copyin()/copyout() because it requires holding the entire
image in user space, and does not make sense for restart. Also, we
don't use a pipe, pseudo-fs file and the like, because they work by
generating data on demand as the user pulls it (unless the entire
image is buffered in the kernel) and would require more complex logic.
They also would significantly complicate checkpoint that includes self.
Changelog[v5]:
- Config is 'def_bool n' by default
Signed-off-by: Oren Laadan <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
---
arch/x86/kernel/syscall_table_32.S | 2 +
checkpoint/Kconfig | 11 +++++++++
checkpoint/Makefile | 5 ++++
checkpoint/sys.c | 41 ++++++++++++++++++++++++++++++++++++
include/asm-x86/unistd_32.h | 2 +
include/linux/syscalls.h | 2 +
init/Kconfig | 2 +
kernel/sys_ni.c | 4 +++
8 files changed, 69 insertions(+), 0 deletions(-)
create mode 100644 checkpoint/Kconfig
create mode 100644 checkpoint/Makefile
create mode 100644 checkpoint/sys.c
diff --git a/arch/x86/kernel/syscall_table_32.S b/arch/x86/kernel/syscall_table_32.S
index d44395f..5543136 100644
--- a/arch/x86/kernel/syscall_table_32.S
+++ b/arch/x86/kernel/syscall_table_32.S
@@ -332,3 +332,5 @@ ENTRY(sys_call_table)
.long sys_dup3 /* 330 */
.long sys_pipe2
.long sys_inotify_init1
+ .long sys_checkpoint
+ .long sys_restart
diff --git a/checkpoint/Kconfig b/checkpoint/Kconfig
new file mode 100644
index 0000000..ffaa635
--- /dev/null
+++ b/checkpoint/Kconfig
@@ -0,0 +1,11 @@
+config CHECKPOINT_RESTART
+ prompt "Enable checkpoint/restart (EXPERIMENTAL)"
+ def_bool n
+ depends on X86_32 && EXPERIMENTAL
+ help
+ Application checkpoint/restart is the ability to save the
+ state of a running application so that it can later resume
+ its execution from the time at which it was checkpointed.
+
+ Turning this option on will enable checkpoint and restart
+ functionality in the kernel.
diff --git a/checkpoint/Makefile b/checkpoint/Makefile
new file mode 100644
index 0000000..07d018b
--- /dev/null
+++ b/checkpoint/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for linux checkpoint/restart.
+#
+
+obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o
diff --git a/checkpoint/sys.c b/checkpoint/sys.c
new file mode 100644
index 0000000..375129c
--- /dev/null
+++ b/checkpoint/sys.c
@@ -0,0 +1,41 @@
+/*
+ * Generic container checkpoint-restart
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/sched.h>
+#include <linux/kernel.h>
+
+/**
+ * sys_checkpoint - checkpoint a container
+ * @pid: pid of the container init(1) process
+ * @fd: file to which dump the checkpoint image
+ * @flags: checkpoint operation flags
+ *
+ * Returns positive identifier on success, 0 when returning from restart
+ * or negative value on error
+ */
+asmlinkage long sys_checkpoint(pid_t pid, int fd, unsigned long flags)
+{
+ pr_debug("sys_checkpoint not implemented yet\n");
+ return -ENOSYS;
+}
+/**
+ * sys_restart - restart a container
+ * @crid: checkpoint image identifier
+ * @fd: file from which read the checkpoint image
+ * @flags: restart operation flags
+ *
+ * Returns negative value on error, or otherwise returns in the realm
+ * of the original checkpoint
+ */
+asmlinkage long sys_restart(int crid, int fd, unsigned long flags)
+{
+ pr_debug("sys_restart not implemented yet\n");
+ return -ENOSYS;
+}
diff --git a/include/asm-x86/unistd_32.h b/include/asm-x86/unistd_32.h
index d739467..88bdec4 100644
--- a/include/asm-x86/unistd_32.h
+++ b/include/asm-x86/unistd_32.h
@@ -338,6 +338,8 @@
#define __NR_dup3 330
#define __NR_pipe2 331
#define __NR_inotify_init1 332
+#define __NR_checkpoint 333
+#define __NR_restart 334
#ifdef __KERNEL__
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index d6ff145..edc218b 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -622,6 +622,8 @@ asmlinkage long sys_timerfd_gettime(int ufd, struct itimerspec __user *otmr);
asmlinkage long sys_eventfd(unsigned int count);
asmlinkage long sys_eventfd2(unsigned int count, int flags);
asmlinkage long sys_fallocate(int fd, int mode, loff_t offset, loff_t len);
+asmlinkage long sys_checkpoint(pid_t pid, int fd, unsigned long flags);
+asmlinkage long sys_restart(int crid, int fd, unsigned long flags);
int kernel_execve(const char *filename, char *const argv[], char *const envp[]);
diff --git a/init/Kconfig b/init/Kconfig
index c11da38..fd5f7bf 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -779,6 +779,8 @@ config MARKERS
source "arch/Kconfig"
+source "checkpoint/Kconfig"
+
config PROC_PAGE_MONITOR
default y
depends on PROC_FS && MMU
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 08d6e1b..ca95c25 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -168,3 +168,7 @@ cond_syscall(compat_sys_timerfd_settime);
cond_syscall(compat_sys_timerfd_gettime);
cond_syscall(sys_eventfd);
cond_syscall(sys_eventfd2);
+
+/* checkpoint/restart */
+cond_syscall(sys_checkpoint);
+cond_syscall(sys_restart);
--
1.5.4.3
Oren,
Can you please check your git server. I can't update to the latest version:
# git-pull
fatal: The remote end hung up unexpectedly
git-clone exits with the same error.
Andrey
On Thursday 30 October 2008 16:51 Oren Laadan wrote:
> Basic checkpoint-restart [C/R]: v8 adds support for "external" checkpoint
> and improves documentation. Older announcements below.
>
> The git tree tracking v8 (branch 'ckpt-v8'), and older versions, is at:
> git://gorgona.ncl.cs.columbia.edu/pub/git/linux-cr-dev.git
>
> (or for the latest version -
> git://gorgona.ncl.cs.columbia.edu/pub/git/linux-cr.git)
>
> We'd like to see these make their way into -mm.
> As Dave Hansen put it:
>
> --
> Why do we want it? It allows containers to be moved between physical
> machines' kernels in the same way that VMWare can move VMs between
> physical machines' hypervisors. There are currently at least two
> out-of-tree implementations of this in the commercial world (IBM's
> Metacluster and Parallels' OpenVZ/Virtuozzo) and several in the academic
> world like Zap.
>
> Why do we need it in mainline now? Because we already have plenty of
> out-of-tree ones, and want to know what an in-tree one will be like. :)
> What *I* want right now is the extra review and scrutiny that comes with
> a mainline submission to make sure we're not going in a direction
> contrary to the community.
>
> This only supports pretty simple apps. But, I trust Ingo when he says:
> >> > > Generally, if something works for simple apps already (in a robust,
> >> > > compatible and supportable way) and users find it "very cool", then
> >> > > support for more complex apps is not far in the future. but if you
> >> > > want to support more complex apps straight away, it takes forever
> >> > > and gets ugly.
>
> We're *certainly* going to be changing the ABI (which is the format of
> the checkpoint). I'd like to follow the model that we used for
> ext4-dev, which is to make it very clear that this is a development-only
> feature for now. Perhaps we do that by making the interface only
> available through debugfs or something similar for now. Or, reserving
> the syscall numbers but require some runtime switch to be thrown before
> they can be used. I'm open to suggestions here.
> --
>
> Oren.
>
> --
> Todo:
> - Add support for x86-64 and improve ABI
> - Refine or change syscall interface
> - Extend to handle (multiple) tasks in a container
> - Handle multiple namespaces in a container (e.g. save the filesystem
> namespaces state with the file descriptors)
> - Security (without CAPS_SYS_ADMIN files restore may fail)
>
> Changelog:
>
> [2008-Oct-29] v8:
> - Support "external" checkpoint
> - Include Dave Hansen's 'deny-checkpoint' patch
> - Split docs in Documentation/checkpoint/..., and improve contents
>
> [2008-Oct-17] v7:
> - Fix save/restore state of FPU
> - Fix argument given to kunmap_atomic() in memory dump/restore
>
> [2008-Oct-07] v6:
> - Balance all calls to cr_hbuf_get() with matching cr_hbuf_put()
> (even though it's not really needed)
> - Add assumptions and what's-missing to documentation
> - Misc fixes and cleanups
>
> [2008-Sep-11] v5:
> - Config is now 'def_bool n' by default
> - Improve memory dump/restore code (following Dave Hansen's comments)
> - Change dump format (and code) to allow chunks of <vaddrs, pages>
> instead of one long list of each
> - Fix use of follow_page() to avoid faulting in non-present pages
> - Memory restore now maps user pages explicitly to copy data into them,
> instead of reading directly to user space; got rid of mprotect_fixup()
> - Remove preempt_disable() when restoring debug registers
> - Rename headers files s/ckpt/checkpoint/
> - Fix misc bugs in files dump/restore
> - Fixes and cleanups on some error paths
> - Fix misc coding style
>
> [2008-Sep-09] v4:
> - Various fixes and clean-ups
> - Fix calculation of hash table size
> - Fix header structure alignment
> - Use stand list_... for cr_pgarr
>
> [2008-Aug-29] v3:
> - Various fixes and clean-ups
> - Use standard hlist_... for hash table
> - Better use of standard kmalloc/kfree
>
> [2008-Aug-20] v2:
> - Added Dump and restore of open files (regular and directories)
> - Added basic handling of shared objects, and improve handling of
> 'parent tag' concept
> - Added documentation
> - Improved ABI, 64bit padding for image data
> - Improved locking when saving/restoring memory
> - Added UTS information to header (release, version, machine)
> - Cleanup extraction of filename from a file pointer
> - Refactor to allow easier reviewing
> - Remove requirement for CAPS_SYS_ADMIN until we come up with a
> security policy (this means that file restore may fail)
> - Other cleanup and response to comments for v1
>
> [2008-Jul-29] v1:
> - Initial version: support a single task with address space of only
> private anonymous or file-mapped VMAs; syscalls ignore pid/crid
> argument and act on current process.
>
> --
> At the containers mini-conference before OLS, the consensus among
> all the stakeholders was that doing checkpoint/restart in the kernel
> as much as possible was the best approach. With this approach, the
> kernel will export a relatively opaque 'blob' of data to userspace
> which can then be handed to the new kernel at restore time.
>
> This is different than what had been proposed before, which was
> that a userspace application would be responsible for collecting
> all of this data. We were also planning on adding lots of new,
> little kernel interfaces for all of the things that needed
> checkpointing. This unites those into a single, grand interface.
>
> The 'blob' will contain copies of select portions of kernel
> structures such as vmas and mm_structs. It will also contain
> copies of the actual memory that the process uses. Any changes
> in this blob's format between kernel revisions can be handled by
> an in-userspace conversion program.
>
> This is a similar approach to virtually all of the commercial
> checkpoint/restart products out there, as well as the research
> project Zap.
>
> These patches basically serialize internel kernel state and write
> it out to a file descriptor. The checkpoint and restore are done
> with two new system calls: sys_checkpoint and sys_restart.
>
> In this incarnation, they can only work checkpoint and restore a
> single task. The task's address space may consist of only private,
> simple vma's - anonymous or file-mapped. The open files may consist
> of only simple files and directories.
> --
>
> _______________________________________________
> Containers mailing list
> [email protected]
> https://lists.linux-foundation.org/mailman/listinfo/containers
>
> _______________________________________________
> Devel mailing list
> [email protected]
> https://openvz.org/mailman/listinfo/devel
Andrey Mirkin wrote:
> Oren,
>
> Can you please check your git server. I can't update to the latest version:
>
> # git-pull
> fatal: The remote end hung up unexpectedly
>
> git-clone exits with the same error.
>
> Andrey
Not sure what was the problem. It works now.
Oren.
Quoting Oren Laadan ([email protected]):
> Now we can do "external" checkpoint, i.e. act on another task.
>
> sys_checkpoint() now looks up the target pid (in our namespace) and
> checkpoints that corresponding task. That task should be the root of
> a container.
>
> sys_restart() remains the same, as the restart is always done in the
> context of the restarting task.
>
> Signed-off-by: Oren Laadan <[email protected]>
Ok, I'm at a loss right now, and I'm not sure who to blame - Oren,
Daniel, Matt, or someone else.
In one terminal I do:
lxc-execute -n nonet sleep 100
then in another terminal do
lxc-checkpoint -s -n nonet > /tmp/o
or
lxc-checkpoint -n nonet > /tmp/o
followed by ctrl-c in the lxc-execute terminal.
Without fail, the second time I do this (if not the first), I get
a BUG (see below). It really does look like it should have
nothing to do with the c/r patches, but I can't reproduce this
any other way. I've tried doing
lxc-freeze -n nonet; lxc-unfreeze -n nonet; lxc-stop -n nonet
I've tried manually doing freeze, checkpoint, unfreeze of containers
hand-crafted to look like what lxc-execute creates (two tasks in private
namespaces with private /proc mount, kill container inits of populated
containers (bc it really looks like another task-exit-vs-container-cleanup
race).
I can't find any other way to reproduce this.
(This is using Oren's patchset with freezer on top, and using
a freshly pulled liblxc from cvs)
-serge
login: ------------[ cut here ]------------
kernel BUG at fs/dcache.c:666!
invalid opcode: 0000 [#1] SMP
Modules linked in:
Pid: 2963, comm: [vinit] Not tainted (2.6.27-rc9-00020-g2265283-dirty #344)
EIP: 0060:[<c0188b5a>] EFLAGS: 00010292 CPU: 1
EIP is at shrink_dcache_for_umount_subtree+0x14b/0x1fe
EAX: 0000004e EBX: c04d22a7 ECX: 00000001 EDX: de6b5160
ESI: df4040a0 EDI: ffffffff EBP: de779d7c ESP: de779d4c
DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
Process [vinit] (pid: 2963, ti=de778000 task=de6b5160 task.ti=de778000)
Stack: c04d1eb2 df4040a0 00000001 df404118 ffffffff c04d22a7 df830698 df404118
00000004 df830400 c041e788 00000020 de779d88 c0188c3a df830400 de779d98
c017b521 00000001 c054faf0 de779da4 c017b60b df830400 de779db0 c017b64d
Call Trace:
[<c0188c3a>] ? shrink_dcache_for_umount+0x2d/0x3a
[<c017b521>] ? generic_shutdown_super+0x15/0xd3
[<c017b60b>] ? kill_anon_super+0xc/0x35
[<c017b64d>] ? kill_litter_super+0x19/0x1c
[<c017b6a3>] ? deactivate_super+0x53/0x6b
[<c018d422>] ? mntput_no_expire+0xc3/0xe7
[<c018d4b1>] ? release_mounts+0x6b/0x7a
[<c018d522>] ? __put_mnt_ns+0x62/0x70
[<c0134cad>] ? free_nsproxy+0x25/0x80
[<c0134d4c>] ? switch_task_namespaces+0x44/0x49
[<c0134d5b>] ? exit_task_namespaces+0xa/0xc
[<c012403a>] ? do_exit+0x55f/0x6c9
[<c0124202>] ? do_group_exit+0x5e/0x85
[<c012c243>] ? get_signal_to_deliver+0x2ea/0x303
[<c010232c>] ? do_notify_resume+0x6b/0x715
[<c013bcfe>] ? lock_release_holdtime+0x1a/0x153
[<c013da7e>] ? trace_hardirqs_on+0xb/0xd
[<c013da7e>] ? trace_hardirqs_on+0xb/0xd
[<c0131aa5>] ? remove_wait_queue+0x30/0x34
[<c0123903>] ? do_wait+0x1d6/0x284
[<c0152ecb>] ? audit_syscall_exit+0x2b1/0x2cc
[<c013da52>] ? trace_hardirqs_on_caller+0xe1/0x102
[<c01031a6>] ? work_notifysig+0x13/0x19
=======================
Code: 1c 8b 18 8b 46 40 89 45 ec 8b 46 28 85 c0 74 03 8b 50 20 8d 81 98 02 00 00 50 53 57 ff 75 ec 52 56 68 b2 1e 4d c0 e8 9a 04 28 00 <0f> 0b 83 c4 1c eb fe 8b 7e 34 39 f7 75 04 31 ff eb 03 f0 ff 0f
EIP: [<c0188b5a>] shrink_dcache_for_umount_subtree+0x14b/0x1fe SS:ESP 0068:de779d4c
---[ end trace 218551429ab07a44 ]---
Fixing recursive fault but reboot is needed!
Quoting Oren Laadan ([email protected]):
> Now we can do "external" checkpoint, i.e. act on another task.
>
> sys_checkpoint() now looks up the target pid (in our namespace) and
> checkpoints that corresponding task. That task should be the root of
> a container.
>
> sys_restart() remains the same, as the restart is always done in the
> context of the restarting task.
>
> Signed-off-by: Oren Laadan <[email protected]>
(Have looked this up and down, and it looks good, so while it's the
easiest piece of code to blame for the BUG() I'm getting, it doesn't
seem possible that it is)
Acked-by: Serge Hallyn <[email protected]>
thanks, Oren.
-serge
I'm still trying to figure out the cause of my BUG at dcache.c:666,
so as I walk through the code a few more nitpicks:
Quoting Oren Laadan ([email protected]):
> +int cr_scan_fds(struct files_struct *files, int **fdtable)
> +{
> + struct fdtable *fdt;
> + int *fds;
> + int i, n = 0;
> + int tot = CR_DEFAULT_FDTABLE;
> +
> + fds = kmalloc(tot * sizeof(*fds), GFP_KERNEL);
> + if (!fds)
> + return -ENOMEM;
> +
> + /*
> + * We assume that the target task is frozen (or that we checkpoint
> + * ourselves), so we can safely proceed after krealloc() from where
> + * we left off; in the worst cases restart will fail.
> + */
> +
> + spin_lock(&files->file_lock);
> + rcu_read_lock();
> + fdt = files_fdtable(files);
> + for (i = 0; i < fdt->max_fds; i++) {
> + if (!fcheck_files(files, i))
> + continue;
> + if (n == tot) {
> + /*
> + * fcheck_files() is safe with drop/re-acquire
> + * of the lock, because it tests: fd < max_fds
> + */
> + spin_unlock(&files->file_lock);
> + rcu_read_unlock();
> + tot *= 2; /* won't overflow: kmalloc will fail */
> + fds = krealloc(fds, tot * sizeof(*fds), GFP_KERNEL);
> + if (!fds) {
> + kfree(fds);
If !fds kfree(fds) :)
> + return -ENOMEM;
> + }
> + rcu_read_lock();
> + spin_lock(&files->file_lock);
> + }
> + fds[n++] = i;
> + }
> + rcu_read_unlock();
> + spin_unlock(&files->file_lock);
> +
> + *fdtable = fds;
> + return n;
> +}
> +static int
> +cr_write_fd_ent(struct cr_ctx *ctx, struct files_struct *files, int fd)
> +{
> + struct cr_hdr h;
> + struct cr_hdr_fd_ent *hh = cr_hbuf_get(ctx, sizeof(*hh));
> + struct file *file = NULL;
> + struct fdtable *fdt;
> + int objref, new, ret;
> + int coe = 0; /* avoid gcc warning */
> +
> + rcu_read_lock();
> + fdt = files_fdtable(files);
> + file = fcheck_files(files, fd);
> + if (file) {
> + coe = FD_ISSET(fd, fdt->close_on_exec);
> + get_file(file);
> + }
> + rcu_read_unlock();
> +
> + /* sanity check (although this shouldn't happen) */
> + if (!file) {
> + ret = -EBADF;
(As mentioned on irc - and probably already fixed in your v9 - you to an
fput(NULL) in this case which will bomb)
> + goto out;
> + }
> +
> + new = cr_obj_add_ptr(ctx, file, &objref, CR_OBJ_FILE, 0);
> + cr_debug("fd %d objref %d file %p c-o-e %d)\n", fd, objref, file, coe);
> +
> + if (new < 0) {
> + ret = new;
> + goto out;
> + }
> +
> + h.type = CR_HDR_FD_ENT;
> + h.len = sizeof(*hh);
> + h.parent = 0;
> +
> + hh->objref = objref;
> + hh->fd = fd;
> + hh->close_on_exec = coe;
> +
> + ret = cr_write_obj(ctx, &h, hh);
> + if (ret < 0)
> + goto out;
> +
> + /* new==1 if-and-only-if file was newly added to hash */
> + if (new)
> + ret = cr_write_fd_data(ctx, file, objref);
> +
> +out:
> + cr_hbuf_put(ctx, sizeof(*hh));
> + fput(file);
> + return ret;
> +}
> +
> +int cr_write_files(struct cr_ctx *ctx, struct task_struct *t)
> +{
> + struct cr_hdr h;
> + struct cr_hdr_files *hh = cr_hbuf_get(ctx, sizeof(*hh));
> + struct files_struct *files;
> + int *fdtable;
> + int nfds, n, ret;
> +
> + h.type = CR_HDR_FILES;
> + h.len = sizeof(*hh);
> + h.parent = task_pid_vnr(t);
> +
> + files = get_files_struct(t);
> +
> + nfds = cr_scan_fds(files, &fdtable);
> + if (nfds < 0) {
> + put_files_struct(files);
need a cr_hbuf_put()
> + return nfds;
> + }
> +
(Cause of my BUG() doesn't appear to be here :( )
thanks,
-serge
Hi Oren,
I'm now trying to port your patchset to x86_64, and find a tiny
inconsistency issue.
On 2008-10-30 at 09:51 -0400, Oren Laadan wrote:
> +/* dump the thread_struct of a given task */
> +int cr_write_thread(struct cr_ctx *ctx, struct task_struct *t)
> +{
> + struct cr_hdr h;
> + struct cr_hdr_thread *hh = cr_hbuf_get(ctx, sizeof(*hh));
> + struct thread_struct *thread;
> + struct desc_struct *desc;
> + int ntls = 0;
> + int n, ret;
> +
> + h.type = CR_HDR_THREAD;
> + h.len = sizeof(*hh);
> + h.parent = task_pid_vnr(t);
> +
> + thread = &t->thread;
> +
> + /* calculate no. of TLS entries that follow */
> + desc = thread->tls_array;
> + for (n = GDT_ENTRY_TLS_ENTRIES; n > 0; n--, desc++) {
> + if (desc->a || desc->b)
> + ntls++;
> + }
> +
> + hh->gdt_entry_tls_entries = GDT_ENTRY_TLS_ENTRIES;
> + hh->sizeof_tls_array = sizeof(thread->tls_array);
> + hh->ntls = ntls;
> +
> + ret = cr_write_obj(ctx, &h, hh);
> + cr_hbuf_put(ctx, sizeof(*hh));
> + if (ret < 0)
> + return ret;
Please add
if (ntls == 0)
return ret;
because, in restart phase, reading TLS entries from the image file
is skipped if hh->ntls == 0, which may incur inconsistency and fail
to restart.
> + /* for simplicity dump the entire array, cherry-pick upon restart */
> + ret = cr_kwrite(ctx, thread->tls_array, sizeof(thread->tls_array));
> +
> + cr_debug("ntls %d\n", ntls);
> +
> + /* IGNORE RESTART BLOCKS FOR NOW ... */
> +
> + return ret;
> +}
(snip)
> +/* read the thread_struct into the current task */
> +int cr_read_thread(struct cr_ctx *ctx)
> +{
> + struct cr_hdr_thread *hh = cr_hbuf_get(ctx, sizeof(*hh));
> + struct task_struct *t = current;
> + struct thread_struct *thread = &t->thread;
> + int parent, ret;
> +
> + parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_THREAD);
> + if (parent < 0) {
> + ret = parent;
> + goto out;
> + }
> +
> + ret = -EINVAL;
> +
> +#if 0 /* activate when containers are used */
> + if (parent != task_pid_vnr(t))
> + goto out;
> +#endif
> + cr_debug("ntls %d\n", hh->ntls);
> +
> + if (hh->gdt_entry_tls_entries != GDT_ENTRY_TLS_ENTRIES ||
> + hh->sizeof_tls_array != sizeof(thread->tls_array) ||
> + hh->ntls < 0 || hh->ntls > GDT_ENTRY_TLS_ENTRIES)
> + goto out;
> +
> + if (hh->ntls > 0) {
> + struct desc_struct *desc;
> + int size, cpu;
> +
> + /*
> + * restore TLS by hand: why convert to struct user_desc if
> + * sys_set_thread_entry() will convert it back ?
> + */
> +
> + size = sizeof(*desc) * GDT_ENTRY_TLS_ENTRIES;
> + desc = kmalloc(size, GFP_KERNEL);
> + if (!desc)
> + return -ENOMEM;
> +
> + ret = cr_kread(ctx, desc, size);
> + if (ret >= 0) {
> + /*
> + * FIX: add sanity checks (eg. that values makes
> + * sense, that we don't overwrite old values, etc
> + */
> + cpu = get_cpu();
> + memcpy(thread->tls_array, desc, size);
> + load_TLS(thread, cpu);
> + put_cpu();
> + }
> + kfree(desc);
> + }
> +
> + ret = 0;
> + out:
> + cr_hbuf_put(ctx, sizeof(*hh));
> + return ret;
> +}
Thanks,
Masahiko.
---
Masahiko Takahashi / [email protected]
Masahiko Takahashi wrote:
> Hi Oren,
>
> I'm now trying to port your patchset to x86_64, and find a tiny
> inconsistency issue.
>
>
> On 2008-10-30 at 09:51 -0400, Oren Laadan wrote:
>> +/* dump the thread_struct of a given task */
>> +int cr_write_thread(struct cr_ctx *ctx, struct task_struct *t)
>> +{
>> + struct cr_hdr h;
>> + struct cr_hdr_thread *hh = cr_hbuf_get(ctx, sizeof(*hh));
>> + struct thread_struct *thread;
>> + struct desc_struct *desc;
>> + int ntls = 0;
>> + int n, ret;
>> +
>> + h.type = CR_HDR_THREAD;
>> + h.len = sizeof(*hh);
>> + h.parent = task_pid_vnr(t);
>> +
>> + thread = &t->thread;
>> +
>> + /* calculate no. of TLS entries that follow */
>> + desc = thread->tls_array;
>> + for (n = GDT_ENTRY_TLS_ENTRIES; n > 0; n--, desc++) {
>> + if (desc->a || desc->b)
>> + ntls++;
>> + }
>> +
>> + hh->gdt_entry_tls_entries = GDT_ENTRY_TLS_ENTRIES;
>> + hh->sizeof_tls_array = sizeof(thread->tls_array);
>> + hh->ntls = ntls;
>> +
>> + ret = cr_write_obj(ctx, &h, hh);
>> + cr_hbuf_put(ctx, sizeof(*hh));
>> + if (ret < 0)
>> + return ret;
>
> Please add
> if (ntls == 0)
> return ret;
> because, in restart phase, reading TLS entries from the image file
> is skipped if hh->ntls == 0, which may incur inconsistency and fail
> to restart.
>
Will fix, thanks.
Oren.
Quoting Oren Laadan ([email protected]):
> Basic checkpoint-restart [C/R]: v8 adds support for "external" checkpoint
> and improves documentation. Older announcements below.
The following test-program seems to reliably trigger a bug. Run it in a
new set of namespaces, i.e.
ns_exec -cmpiuU ./runme > /tmp/o
then control-c it. The second time I do that, I get the dcache.c:666
BUG().
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <sys/syscall.h>
#define __NR_checkpoint 333
int main (int argc, char *argv[])
{
pid_t pid = getpid();
int ret;
close(0); close(2);
ret = syscall (__NR_checkpoint, pid, STDOUT_FILENO, 0);
if (ret < 0)
perror ("checkpoint");
else
printf ("checkpoint id %d\n", ret);
sleep(200);
return (ret > 0 ? 0 : 1);
}
-serge
Quoting Oren Laadan ([email protected]):
> Basic checkpoint-restart [C/R]: v8 adds support for "external" checkpoint
> and improves documentation. Older announcements below.
Finally!
>From 8edab186b605f7dddd612e581204f1ad8fd766be Mon Sep 17 00:00:00 2001
From: Serge Hallyn <[email protected]>
Date: Tue, 4 Nov 2008 15:28:01 -0600
Subject: [PATCH 1/1] cr: fix use of __d_path()
__d_path():
1. should be used under dcache_lock
2. can change root->{mnt,dentry} without changing refcounts
The second point was the cause of my BUGs. The ctx->root was passed
in, and do_checkpoint() had taken a path_get on the vfsroot. So now
at cleanup it was doing path_put() using another mnt+dentry.
(Why they are different, I'm not sure - but my guess would be that
stdin or stdout is inherited from the parent task in parent mntns,
hence file->mnt is different from root->mnt as it's a different
namespace.)
Signed-off-by: Serge Hallyn <[email protected]>
---
checkpoint/checkpoint.c | 13 ++++++++++++-
1 files changed, 12 insertions(+), 1 deletions(-)
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index 173b637..7f0c1e7 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c
@@ -70,9 +70,20 @@ static char *
cr_fill_fname(struct path *path, struct path *root, char *buf, int *n)
{
char *fname;
+ struct path root2;
+
+ root2.mnt = root->mnt;
+ root2.dentry = root->dentry;
BUG_ON(!buf);
- fname = __d_path(path, root, buf, *n);
+ spin_lock(&dcache_lock);
+ fname = __d_path(path, &root2, buf, *n);
+ spin_unlock(&dcache_lock);
+ if (root2.mnt != root->mnt)
+ printk(KERN_NOTICE "%s: mnt changed\n", __func__);
+ if (root2.dentry != root->dentry)
+ printk(KERN_NOTICE "%s: dentry changed\n", __func__);
+ fname = buf+10;
if (!IS_ERR(fname))
*n = (buf + (*n) - fname);
return fname;
--
1.5.6.3