This is the V3 patchset of the kprobes jump optimization
(a.k.a OPTPROBES)for powerpc. Kprobe being an inevitable tool
for kernel developers, enhancing the performance of kprobe has
got much importance.
Currently kprobes inserts a trap instruction to probe a running kernel.
Jump optimization allows kprobes to replace the trap with a branch,
reducing the probe overhead drastically.
In this series, conditional branch instructions are not considered for
optimization as they have to be assessed carefully in SMP systems.
The kprobe placed on the kretprobe_trampoline during boot time, is also
optimized in this series. Patch 4/4 furnishes this.
The first two patches can go independently of the series. The helper
functions in these patches are invoked in patch 3/4.
Performance:
============
An optimized kprobe in powerpc is 1.05 to 4.7 times faster than a kprobe.
Example:
Placed a probe at an offset 0x50 in _do_fork().
*Time Diff here is, difference in time before hitting the probe and
after the probed instruction. mftb() is employed in kernel/fork.c for
this purpose.
# echo 0 > /proc/sys/debug/kprobes-optimization
Kprobes globally unoptimized
[ 233.607120] Time Diff = 0x1f0
[ 233.608273] Time Diff = 0x1ee
[ 233.609228] Time Diff = 0x203
[ 233.610400] Time Diff = 0x1ec
[ 233.611335] Time Diff = 0x200
[ 233.612552] Time Diff = 0x1f0
[ 233.613386] Time Diff = 0x1ee
[ 233.614547] Time Diff = 0x212
[ 233.615570] Time Diff = 0x206
[ 233.616819] Time Diff = 0x1f3
[ 233.617773] Time Diff = 0x1ec
[ 233.618944] Time Diff = 0x1fb
[ 233.619879] Time Diff = 0x1f0
[ 233.621066] Time Diff = 0x1f9
[ 233.621999] Time Diff = 0x283
[ 233.623281] Time Diff = 0x24d
[ 233.624172] Time Diff = 0x1ea
[ 233.625381] Time Diff = 0x1f0
[ 233.626358] Time Diff = 0x200
[ 233.627572] Time Diff = 0x1ed
# echo 1 > /proc/sys/debug/kprobes-optimization
Kprobes globally optimized
[ 70.797075] Time Diff = 0x103
[ 70.799102] Time Diff = 0x181
[ 70.801861] Time Diff = 0x15e
[ 70.803466] Time Diff = 0xf0
[ 70.804348] Time Diff = 0xd0
[ 70.805653] Time Diff = 0xad
[ 70.806477] Time Diff = 0xe0
[ 70.807725] Time Diff = 0xbe
[ 70.808541] Time Diff = 0xc3
[ 70.810191] Time Diff = 0xc7
[ 70.811007] Time Diff = 0xc0
[ 70.812629] Time Diff = 0xc0
[ 70.813640] Time Diff = 0xda
[ 70.814915] Time Diff = 0xbb
[ 70.815726] Time Diff = 0xc4
[ 70.816955] Time Diff = 0xc0
[ 70.817778] Time Diff = 0xcd
[ 70.818999] Time Diff = 0xcd
[ 70.820099] Time Diff = 0xcb
[ 70.821333] Time Diff = 0xf0
Implementation:
===================
The trap instruction is replaced by a branch to a detour buffer. To address
the limitation of branch instruction in power architecture, detour buffer
slot is allocated from a reserved area. This will ensure that the branch
is within ± 32 MB range. The existing generic approach for kprobes insn
cache uses module_alloc() to allocate memory area for insn slots. This will
always be beyond ± 32MB range.
The detour buffer contains a call to optimized_callback() which in turn
call the pre_handler(). Once the pre-handler is run, the original
instruction is emulated from the detour buffer itself. Also the detour
buffer is equipped with a branch back to the normal work flow after the
probed instruction is emulated. Before preparing optimization, Kprobes
inserts original(breakpoint instruction)kprobe on the specified address.
So, even if the kprobe is not possible to be optimized, it just uses a
normal kprobe.
Limitations:
==============
- Number of probes which can be optimized is limited by the size of the
area reserved.
- Currently instructions which can be emulated using analyse_instr() are
the only candidates for optimization.
- Conditional branch instructions are not optimized.
- Probes on kernel module region are not considered for optimization now.
Link for the V1 patchset:
https://lkml.org/lkml/2016/9/7/171
https://lkml.org/lkml/2016/9/7/174
https://lkml.org/lkml/2016/9/7/172
https://lkml.org/lkml/2016/9/7/173
Changes from v1:
- Merged the three patches in V1 into a single patch.
- Comments by Masami are addressed.
- Some helper functions are implemented in separate patches.
- Optimization for kprobe placed on the kretprobe_trampoline during
boot time is implemented.
Changes from v2:
- Comments by Masami are addressed.
- Description in the cover letter is modified a bit.
Kindly let me know your suggestions and comments.
Thanks,
-Anju
Anju T Sudhakar (2):
arch/powerpc: Implement Optprobes
arch/powerpc: Optimize kprobe in kretprobe_trampoline
Naveen N. Rao (2):
powerpc: asm/ppc-opcode.h: introduce __PPC_SH64()
powerpc: add helper to check if offset is within rel branch range
.../features/debug/optprobes/arch-support.txt | 2 +-
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/code-patching.h | 1 +
arch/powerpc/include/asm/kprobes.h | 24 +-
arch/powerpc/include/asm/ppc-opcode.h | 1 +
arch/powerpc/include/asm/sstep.h | 1 +
arch/powerpc/kernel/Makefile | 1 +
arch/powerpc/kernel/kprobes.c | 8 +
arch/powerpc/kernel/optprobes.c | 330 +++++++++++++++++++++
arch/powerpc/kernel/optprobes_head.S | 135 +++++++++
arch/powerpc/lib/code-patching.c | 24 +-
arch/powerpc/lib/sstep.c | 21 ++
arch/powerpc/net/bpf_jit.h | 11 +-
13 files changed, 551 insertions(+), 9 deletions(-)
create mode 100644 arch/powerpc/kernel/optprobes.c
create mode 100644 arch/powerpc/kernel/optprobes_head.S
--
2.7.4
Detour buffer contains instructions to create an in memory pt_regs.
After the execution of the pre-handler, a call is made for instruction emulation.
The NIP is determined in advanced through dummy instruction emulation and a branch
instruction is created to the NIP at the end of the trampoline.
Instruction slot for detour buffer is allocated from the reserved area.
For the time being, 64KB is reserved in memory for this purpose.
Instructions which can be emulated using analyse_instr() are suppliants
for optimization. Before optimization ensure that the address range
between the detour buffer allocated and the instruction being probed
is within ± 32MB.
Signed-off-by: Anju T Sudhakar <[email protected]>
Signed-off-by: Naveen N. Rao <[email protected]>
---
.../features/debug/optprobes/arch-support.txt | 2 +-
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/kprobes.h | 24 +-
arch/powerpc/include/asm/sstep.h | 1 +
arch/powerpc/kernel/Makefile | 1 +
arch/powerpc/kernel/optprobes.c | 331 +++++++++++++++++++++
arch/powerpc/kernel/optprobes_head.S | 135 +++++++++
arch/powerpc/lib/sstep.c | 21 ++
8 files changed, 514 insertions(+), 2 deletions(-)
create mode 100644 arch/powerpc/kernel/optprobes.c
create mode 100644 arch/powerpc/kernel/optprobes_head.S
diff --git a/Documentation/features/debug/optprobes/arch-support.txt b/Documentation/features/debug/optprobes/arch-support.txt
index b8999d8..45bc99d 100644
--- a/Documentation/features/debug/optprobes/arch-support.txt
+++ b/Documentation/features/debug/optprobes/arch-support.txt
@@ -27,7 +27,7 @@
| nios2: | TODO |
| openrisc: | TODO |
| parisc: | TODO |
- | powerpc: | TODO |
+ | powerpc: | ok |
| s390: | TODO |
| score: | TODO |
| sh: | TODO |
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 65fba4c..f7e9296 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -98,6 +98,7 @@ config PPC
select HAVE_IOREMAP_PROT
select HAVE_EFFICIENT_UNALIGNED_ACCESS if !(CPU_LITTLE_ENDIAN && POWER7_CPU)
select HAVE_KPROBES
+ select HAVE_OPTPROBES if PPC64
select HAVE_ARCH_KGDB
select HAVE_KRETPROBES
select HAVE_ARCH_TRACEHOOK
diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h
index 2c9759bd..0cf640b 100644
--- a/arch/powerpc/include/asm/kprobes.h
+++ b/arch/powerpc/include/asm/kprobes.h
@@ -38,7 +38,23 @@ struct pt_regs;
struct kprobe;
typedef ppc_opcode_t kprobe_opcode_t;
-#define MAX_INSN_SIZE 1
+
+extern kprobe_opcode_t optinsn_slot;
+
+/* Optinsn template address */
+extern kprobe_opcode_t optprobe_template_entry[];
+extern kprobe_opcode_t optprobe_template_op_address[];
+extern kprobe_opcode_t optprobe_template_call_handler[];
+extern kprobe_opcode_t optprobe_template_insn[];
+extern kprobe_opcode_t optprobe_template_call_emulate[];
+extern kprobe_opcode_t optprobe_template_ret[];
+extern kprobe_opcode_t optprobe_template_end[];
+
+/* Fixed instruction size for powerpc */
+#define MAX_INSN_SIZE 1
+#define MAX_OPTIMIZED_LENGTH sizeof(kprobe_opcode_t) /* 4 bytes */
+#define MAX_OPTINSN_SIZE (optprobe_template_end - optprobe_template_entry)
+#define RELATIVEJUMP_SIZE sizeof(kprobe_opcode_t) /* 4 bytes */
#ifdef PPC64_ELF_ABI_v2
/* PPC64 ABIv2 needs local entry point */
@@ -124,6 +140,12 @@ struct kprobe_ctlblk {
struct prev_kprobe prev_kprobe;
};
+struct arch_optimized_insn {
+ kprobe_opcode_t copied_insn[1];
+ /* detour buffer */
+ kprobe_opcode_t *insn;
+};
+
extern int kprobe_exceptions_notify(struct notifier_block *self,
unsigned long val, void *data);
extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
diff --git a/arch/powerpc/include/asm/sstep.h b/arch/powerpc/include/asm/sstep.h
index d3a42cc..f7ad425 100644
--- a/arch/powerpc/include/asm/sstep.h
+++ b/arch/powerpc/include/asm/sstep.h
@@ -87,3 +87,4 @@ struct instruction_op {
extern int analyse_instr(struct instruction_op *op, struct pt_regs *regs,
unsigned int instr);
+extern bool is_conditional_branch(unsigned int instr);
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 1925341..54f0f47 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -98,6 +98,7 @@ obj-$(CONFIG_KGDB) += kgdb.o
obj-$(CONFIG_BOOTX_TEXT) += btext.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_KPROBES) += kprobes.o
+obj-$(CONFIG_OPTPROBES) += optprobes.o optprobes_head.o
obj-$(CONFIG_UPROBES) += uprobes.o
obj-$(CONFIG_PPC_UDBG_16550) += legacy_serial.o udbg_16550.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
new file mode 100644
index 0000000..fb5e62d
--- /dev/null
+++ b/arch/powerpc/kernel/optprobes.c
@@ -0,0 +1,331 @@
+/*
+ * Code for Kernel probes Jump optimization.
+ *
+ * Copyright 2016, Anju T, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/kprobes.h>
+#include <linux/jump_label.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <asm/kprobes.h>
+#include <asm/ptrace.h>
+#include <asm/cacheflush.h>
+#include <asm/code-patching.h>
+#include <asm/sstep.h>
+#include <asm/ppc-opcode.h>
+
+#define TMPL_CALL_HDLR_IDX \
+ (optprobe_template_call_handler - optprobe_template_entry)
+#define TMPL_EMULATE_IDX \
+ (optprobe_template_call_emulate - optprobe_template_entry)
+#define TMPL_RET_IDX \
+ (optprobe_template_ret - optprobe_template_entry)
+#define TMPL_OP_IDX \
+ (optprobe_template_op_address - optprobe_template_entry)
+#define TMPL_INSN_IDX \
+ (optprobe_template_insn - optprobe_template_entry)
+#define TMPL_END_IDX \
+ (optprobe_template_end - optprobe_template_entry)
+
+DEFINE_INSN_CACHE_OPS(ppc_optinsn);
+
+static bool insn_page_in_use;
+
+static void *__ppc_alloc_insn_page(void)
+{
+ if (insn_page_in_use)
+ return NULL;
+ insn_page_in_use = true;
+ return &optinsn_slot;
+}
+
+static void __ppc_free_insn_page(void *page __maybe_unused)
+{
+ insn_page_in_use = false;
+}
+
+struct kprobe_insn_cache kprobe_ppc_optinsn_slots = {
+ .mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex),
+ .pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages),
+ /* insn_size initialized later */
+ .alloc = __ppc_alloc_insn_page,
+ .free = __ppc_free_insn_page,
+ .nr_garbage = 0,
+};
+
+/*
+ * Check if we can optimize this probe. Returns NIP post-emulation if this can
+ * be optimized and 0 otherwise.
+ */
+static unsigned long can_optimize(struct kprobe *p)
+{
+ struct pt_regs regs;
+ struct instruction_op op;
+ unsigned long nip = 0;
+
+ /*
+ * kprobe placed for kretprobe during boot time
+ * is not optimizing now.
+ *
+ * TODO: Optimize kprobe in kretprobe_trampoline
+ */
+ if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
+ return 0;
+
+ /*
+ * We only support optimizing kernel addresses, but not
+ * module addresses.
+ */
+ if (!is_kernel_addr((unsigned long)p->addr))
+ return 0;
+
+ regs.nip = (unsigned long)p->addr;
+ regs.trap = 0x0;
+ regs.msr = MSR_KERNEL;
+
+ /*
+ * Ensure that the instruction is not a conditional branch,
+ * and that can be emulated.
+ */
+ if (!is_conditional_branch(*p->ainsn.insn) &&
+ analyse_instr(&op, ®s, *p->ainsn.insn))
+ nip = regs.nip;
+
+ return nip;
+}
+
+static void optimized_callback(struct optimized_kprobe *op,
+ struct pt_regs *regs)
+{
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+ unsigned long flags;
+
+ /* This is possible if op is under delayed unoptimizing */
+ if (kprobe_disabled(&op->kp))
+ return;
+
+ local_irq_save(flags);
+
+ if (kprobe_running()) {
+ kprobes_inc_nmissed_count(&op->kp);
+ } else {
+ __this_cpu_write(current_kprobe, &op->kp);
+ regs->nip = (unsigned long)op->kp.addr;
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+ opt_pre_handler(&op->kp, regs);
+ __this_cpu_write(current_kprobe, NULL);
+ }
+ local_irq_restore(flags);
+}
+NOKPROBE_SYMBOL(optimized_callback);
+
+void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
+{
+ if (op->optinsn.insn) {
+ free_ppc_optinsn_slot(op->optinsn.insn, 1);
+ op->optinsn.insn = NULL;
+ }
+}
+
+/*
+ * emulate_step() requires insn to be emulated as
+ * second parameter. Load register 'r4' with the
+ * instruction.
+ */
+void patch_imm32_load_insns(unsigned int val, kprobe_opcode_t *addr)
+{
+ /* addis r4,0,(insn)@h */
+ *addr++ = PPC_INST_ADDIS | ___PPC_RT(4) |
+ ((val >> 16) & 0xffff);
+
+ /* ori r4,r4,(insn)@l */
+ *addr = PPC_INST_ORI | ___PPC_RA(4) | ___PPC_RS(4) |
+ (val & 0xffff);
+}
+
+/*
+ * Generate instructions to load provided immediate 64-bit value
+ * to register 'r3' and patch these instructions at 'addr'.
+ */
+void patch_imm64_load_insns(unsigned long val, kprobe_opcode_t *addr)
+{
+ /* lis r3,(op)@highest */
+ *addr++ = PPC_INST_ADDIS | ___PPC_RT(3) |
+ ((val >> 48) & 0xffff);
+
+ /* ori r3,r3,(op)@higher */
+ *addr++ = PPC_INST_ORI | ___PPC_RA(3) | ___PPC_RS(3) |
+ ((val >> 32) & 0xffff);
+
+ /* rldicr r3,r3,32,31 */
+ *addr++ = PPC_INST_RLDICR | ___PPC_RA(3) | ___PPC_RS(3) |
+ __PPC_SH64(32) | __PPC_ME64(31);
+
+ /* oris r3,r3,(op)@h */
+ *addr++ = PPC_INST_ORIS | ___PPC_RA(3) | ___PPC_RS(3) |
+ ((val >> 16) & 0xffff);
+
+ /* ori r3,r3,(op)@l */
+ *addr = PPC_INST_ORI | ___PPC_RA(3) | ___PPC_RS(3) |
+ (val & 0xffff);
+}
+
+int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
+{
+ kprobe_opcode_t *buff, branch_op_callback, branch_emulate_step;
+ kprobe_opcode_t *op_callback_addr, *emulate_step_addr;
+ long b_offset;
+ unsigned long nip;
+
+ kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
+
+ nip = can_optimize(p);
+ if (!nip)
+ return -EILSEQ;
+
+ /* Allocate instruction slot for detour buffer */
+ buff = get_ppc_optinsn_slot();
+ if (!buff)
+ return -ENOMEM;
+
+ /*
+ * OPTPROBE uses 'b' instruction to branch to optinsn.insn.
+ *
+ * The target address has to be relatively nearby, to permit use
+ * of branch instruction in powerpc, because the address is specified
+ * in an immediate field in the instruction opcode itself, ie 24 bits
+ * in the opcode specify the address. Therefore the address should
+ * be within 32MB on either side of the current instruction.
+ */
+ b_offset = (unsigned long)buff - (unsigned long)p->addr;
+ if (!is_offset_in_branch_range(b_offset))
+ goto error;
+
+ /* Check if the return address is also within 32MB range */
+ b_offset = (unsigned long)(buff + TMPL_RET_IDX) -
+ (unsigned long)nip;
+ if (!is_offset_in_branch_range(b_offset))
+ goto error;
+
+ /* Setup template */
+ memcpy(buff, optprobe_template_entry,
+ TMPL_END_IDX * sizeof(kprobe_opcode_t));
+
+ /*
+ * Fixup the template with instructions to:
+ * 1. load the address of the actual probepoint
+ */
+ patch_imm64_load_insns((unsigned long)op, buff + TMPL_OP_IDX);
+
+ /*
+ * 2. branch to optimized_callback() and emulate_step()
+ */
+ kprobe_lookup_name("optimized_callback", op_callback_addr);
+ kprobe_lookup_name("emulate_step", emulate_step_addr);
+ if (!op_callback_addr || !emulate_step_addr) {
+ WARN(1, "kprobe_lookup_name() failed\n");
+ goto error;
+ }
+
+ branch_op_callback = create_branch((unsigned int *)buff + TMPL_CALL_HDLR_IDX,
+ (unsigned long)op_callback_addr,
+ BRANCH_SET_LINK);
+
+ branch_emulate_step = create_branch((unsigned int *)buff + TMPL_EMULATE_IDX,
+ (unsigned long)emulate_step_addr,
+ BRANCH_SET_LINK);
+
+ if (!branch_op_callback || !branch_emulate_step)
+ goto error;
+
+ buff[TMPL_CALL_HDLR_IDX] = branch_op_callback;
+ buff[TMPL_EMULATE_IDX] = branch_emulate_step;
+
+ /*
+ * 3. load instruction to be emulated into relevant register, and
+ */
+ patch_imm32_load_insns(*p->ainsn.insn, buff + TMPL_INSN_IDX);
+
+ /*
+ * 4. branch back from trampoline
+ */
+ buff[TMPL_RET_IDX] = create_branch((unsigned int *)buff + TMPL_RET_IDX,
+ (unsigned long)nip, 0);
+
+ flush_icache_range((unsigned long)buff,
+ (unsigned long)(&buff[TMPL_END_IDX]));
+
+ op->optinsn.insn = buff;
+
+ return 0;
+
+ error:
+ free_ppc_optinsn_slot(buff, 0);
+ return -ERANGE;
+
+}
+
+int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
+{
+ return optinsn->insn != NULL;
+}
+
+/*
+ * On powerpc, Optprobes always replaces one instruction (4 bytes
+ * aligned and 4 bytes long). It is impossible to encounter another
+ * kprobe in this address range. So always return 0.
+ */
+int arch_check_optimized_kprobe(struct optimized_kprobe *op)
+{
+ return 0;
+}
+
+void arch_optimize_kprobes(struct list_head *oplist)
+{
+ struct optimized_kprobe *op;
+ struct optimized_kprobe *tmp;
+
+ list_for_each_entry_safe(op, tmp, oplist, list) {
+ /*
+ * Backup instructions which will be replaced
+ * by jump address
+ */
+ memcpy(op->optinsn.copied_insn, op->kp.addr,
+ RELATIVEJUMP_SIZE);
+ patch_instruction(op->kp.addr,
+ create_branch((unsigned int *)op->kp.addr,
+ (unsigned long)op->optinsn.insn, 0));
+ list_del_init(&op->list);
+ }
+}
+
+void arch_unoptimize_kprobe(struct optimized_kprobe *op)
+{
+ arch_arm_kprobe(&op->kp);
+}
+
+void arch_unoptimize_kprobes(struct list_head *oplist,
+ struct list_head *done_list)
+{
+ struct optimized_kprobe *op;
+ struct optimized_kprobe *tmp;
+
+ list_for_each_entry_safe(op, tmp, oplist, list) {
+ arch_unoptimize_kprobe(op);
+ list_move(&op->list, done_list);
+ }
+}
+
+int arch_within_optimized_kprobe(struct optimized_kprobe *op,
+ unsigned long addr)
+{
+ return ((unsigned long)op->kp.addr <= addr &&
+ (unsigned long)op->kp.addr + RELATIVEJUMP_SIZE > addr);
+}
diff --git a/arch/powerpc/kernel/optprobes_head.S b/arch/powerpc/kernel/optprobes_head.S
new file mode 100644
index 0000000..c86976b
--- /dev/null
+++ b/arch/powerpc/kernel/optprobes_head.S
@@ -0,0 +1,135 @@
+/*
+ * Code to prepare detour buffer for optprobes in Kernel.
+ *
+ * Copyright 2016, Anju T, IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <asm/ppc_asm.h>
+#include <asm/ptrace.h>
+#include <asm/asm-offsets.h>
+
+#define OPT_SLOT_SIZE 65536
+
+ .balign 4
+
+ /*
+ * Reserve an area to allocate slots for detour buffer.
+ * This is part of .text section (rather than vmalloc area)
+ * as this needs to be within 32MB of the probed address.
+ */
+ .global optinsn_slot
+optinsn_slot:
+ .space OPT_SLOT_SIZE
+
+ /*
+ * Optprobe template:
+ * This template gets copied into one of the slots in optinsn_slot
+ * and gets fixed up with real optprobe structures et al.
+ */
+ .global optprobe_template_entry
+optprobe_template_entry:
+ /* Create an in-memory pt_regs */
+ stdu r1,-INT_FRAME_SIZE(r1)
+ SAVE_GPR(0,r1)
+ /* Save the previous SP into stack */
+ addi r0,r1,INT_FRAME_SIZE
+ std r0,GPR1(r1)
+ SAVE_10GPRS(2,r1)
+ SAVE_10GPRS(12,r1)
+ SAVE_10GPRS(22,r1)
+ /* Save SPRS */
+ mfmsr r5
+ std r5,_MSR(r1)
+ li r5,0x700
+ std r5,_TRAP(r1)
+ li r5,0
+ std r5,ORIG_GPR3(r1)
+ std r5,RESULT(r1)
+ mfctr r5
+ std r5,_CTR(r1)
+ mflr r5
+ std r5,_LINK(r1)
+ mfspr r5,SPRN_XER
+ std r5,_XER(r1)
+ mfcr r5
+ std r5,_CCR(r1)
+ lbz r5,PACASOFTIRQEN(r13)
+ std r5,SOFTE(r1)
+ mfdar r5
+ std r5,_DAR(r1)
+ mfdsisr r5
+ std r5,_DSISR(r1)
+
+ .global optprobe_template_op_address
+optprobe_template_op_address:
+ /*
+ * Parameters to optimized_callback():
+ * 1. optimized_kprobe structure in r3
+ */
+ nop
+ nop
+ nop
+ nop
+ nop
+ /* 2. pt_regs pointer in r4 */
+ addi r4,r1,STACK_FRAME_OVERHEAD
+
+ .global optprobe_template_call_handler
+optprobe_template_call_handler:
+ /* Branch to optimized_callback() */
+ nop
+
+ /*
+ * Parameters for instruction emulation:
+ * 1. Pass SP in register r3.
+ */
+ addi r3,r1,STACK_FRAME_OVERHEAD
+
+ .global optprobe_template_insn
+optprobe_template_insn:
+ /* 2, Pass instruction to be emulated in r4 */
+ nop
+ nop
+
+ .global optprobe_template_call_emulate
+optprobe_template_call_emulate:
+ /* Branch to emulate_step() */
+ nop
+
+ /*
+ * All done.
+ * Now, restore the registers...
+ */
+ ld r5,_MSR(r1)
+ mtmsr r5
+ ld r5,_CTR(r1)
+ mtctr r5
+ ld r5,_LINK(r1)
+ mtlr r5
+ ld r5,_XER(r1)
+ mtxer r5
+ ld r5,_CCR(r1)
+ mtcr r5
+ ld r5,_DAR(r1)
+ mtdar r5
+ ld r5,_DSISR(r1)
+ mtdsisr r5
+ REST_GPR(0,r1)
+ REST_10GPRS(2,r1)
+ REST_10GPRS(12,r1)
+ REST_10GPRS(22,r1)
+ /* Restore the previous SP */
+ addi r1,r1,INT_FRAME_SIZE
+
+ .global optprobe_template_ret
+optprobe_template_ret:
+ /* ... and jump back from trampoline */
+ nop
+
+ .global optprobe_template_end
+optprobe_template_end:
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index 3362299..895dcdd 100644
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -618,6 +618,27 @@ static int __kprobes trap_compare(long v1, long v2)
}
/*
+ * Helper to check if a given instruction is a conditional branch
+ * Derived from the conditional checks in analyse_instr()
+ */
+bool __kprobes is_conditional_branch(unsigned int instr)
+{
+ unsigned int opcode = instr >> 26;
+
+ if (opcode == 16) /* bc, bca, bcl, bcla */
+ return true;
+ if (opcode == 19) {
+ switch ((instr >> 1) & 0x3ff) {
+ case 16: /* bclr, bclrl */
+ case 528: /* bcctr, bcctrl */
+ case 560: /* bctar, bctarl */
+ return true;
+ }
+ }
+ return false;
+}
+
+/*
* Elements of 32-bit rotate and mask instructions.
*/
#define MASK32(mb, me) ((0xffffffffUL >> (mb)) + \
--
2.7.4
From: "Naveen N. Rao" <[email protected]>
To permit the use of relative branch instruction in powerpc, the target
address has to be relatively nearby, since the address is specified in an
immediate field (24 bit filed) in the instruction opcode itself. Here
nearby refers to 32MB on either side of the current instruction.
This patch verifies whether the target address is within +/- 32MB
range or not.
Signed-off-by: Naveen N. Rao <[email protected]>
Signed-off-by: Anju T Sudhakar <[email protected]>
---
arch/powerpc/include/asm/code-patching.h | 1 +
arch/powerpc/lib/code-patching.c | 24 +++++++++++++++++++++++-
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index 2015b07..75ee4f4 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -22,6 +22,7 @@
#define BRANCH_SET_LINK 0x1
#define BRANCH_ABSOLUTE 0x2
+bool is_offset_in_branch_range(long offset);
unsigned int create_branch(const unsigned int *addr,
unsigned long target, int flags);
unsigned int create_cond_branch(const unsigned int *addr,
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index d5edbeb..f643451 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -32,6 +32,28 @@ int patch_branch(unsigned int *addr, unsigned long target, int flags)
return patch_instruction(addr, create_branch(addr, target, flags));
}
+bool is_offset_in_branch_range(long offset)
+{
+ /*
+ * Powerpc branch instruction is :
+ *
+ * 0 6 30 31
+ * +---------+----------------+---+---+
+ * | opcode | LI |AA |LK |
+ * +---------+----------------+---+---+
+ * Where AA = 0 and LK = 0
+ *
+ * LI is a signed 24 bits integer. The real branch offset is computed
+ * by: imm32 = SignExtend(LI:'0b00', 32);
+ *
+ * So the maximum forward branch should be:
+ * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc
+ * The maximum backward branch should be:
+ * (0xff800000 << 2) = 0xfe000000 = -0x2000000
+ */
+ return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
+}
+
unsigned int create_branch(const unsigned int *addr,
unsigned long target, int flags)
{
@@ -43,7 +65,7 @@ unsigned int create_branch(const unsigned int *addr,
offset = offset - (unsigned long)addr;
/* Check we can represent the target in the instruction format */
- if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3)
+ if (!is_offset_in_branch_range(offset))
return 0;
/* Mask out the flags and target, so they don't step on each other. */
--
2.7.4
Kprobe placed on the kretprobe_trampoline during boot time can be
optimized, since the instruction at probe point is a 'nop'.
Signed-off-by: Anju T Sudhakar <[email protected]>
Acked-by: Masami Hiramatsu <[email protected]>
---
arch/powerpc/kernel/kprobes.c | 8 ++++++++
arch/powerpc/kernel/optprobes.c | 7 +++----
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index e785cc9..5b0fd07 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -282,6 +282,7 @@ asm(".global kretprobe_trampoline\n"
".type kretprobe_trampoline, @function\n"
"kretprobe_trampoline:\n"
"nop\n"
+ "blr\n"
".size kretprobe_trampoline, .-kretprobe_trampoline\n");
/*
@@ -334,6 +335,13 @@ static int __kprobes trampoline_probe_handler(struct kprobe *p,
kretprobe_assert(ri, orig_ret_address, trampoline_address);
regs->nip = orig_ret_address;
+ /*
+ * Make LR point to the orig_ret_address.
+ * When the 'nop' inside the kretprobe_trampoline
+ * is optimized, we can do a 'blr' after executing the
+ * detour buffer code.
+ */
+ regs->link = orig_ret_address;
reset_current_kprobe();
kretprobe_hash_unlock(current, &flags);
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
index ecba221..5e4c254 100644
--- a/arch/powerpc/kernel/optprobes.c
+++ b/arch/powerpc/kernel/optprobes.c
@@ -72,12 +72,11 @@ static unsigned long can_optimize(struct kprobe *p)
/*
* kprobe placed for kretprobe during boot time
- * is not optimizing now.
- *
- * TODO: Optimize kprobe in kretprobe_trampoline
+ * has a 'nop' instruction, which can be emulated.
+ * So further checks can be skipped.
*/
if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
- return 0;
+ return (unsigned long)p->addr + sizeof(kprobe_opcode_t);
/*
* We only support optimizing kernel addresses, but not
--
2.7.4
From: "Naveen N. Rao" <[email protected]>
Introduce __PPC_SH64() as a 64-bit variant to encode shift field in some
of the shift and rotate instructions operating on double-words. Convert
some of the BPF instruction macros to use the same.
Signed-off-by: Naveen N. Rao <[email protected]>
---
arch/powerpc/include/asm/ppc-opcode.h | 1 +
arch/powerpc/net/bpf_jit.h | 11 +++++------
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index 0132831..630127b 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -306,6 +306,7 @@
#define __PPC_WC(w) (((w) & 0x3) << 21)
#define __PPC_WS(w) (((w) & 0x1f) << 11)
#define __PPC_SH(s) __PPC_WS(s)
+#define __PPC_SH64(s) (__PPC_SH(s) | (((s) & 0x20) >> 4))
#define __PPC_MB(s) (((s) & 0x1f) << 6)
#define __PPC_ME(s) (((s) & 0x1f) << 1)
#define __PPC_MB64(s) (__PPC_MB(s) | ((s) & 0x20))
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index 89f7007..30cf03f 100644
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -157,8 +157,7 @@
#define PPC_SRAD(d, a, s) EMIT(PPC_INST_SRAD | ___PPC_RA(d) | \
___PPC_RS(a) | ___PPC_RB(s))
#define PPC_SRADI(d, a, i) EMIT(PPC_INST_SRADI | ___PPC_RA(d) | \
- ___PPC_RS(a) | __PPC_SH(i) | \
- (((i) & 0x20) >> 4))
+ ___PPC_RS(a) | __PPC_SH64(i))
#define PPC_RLWINM(d, a, i, mb, me) EMIT(PPC_INST_RLWINM | ___PPC_RA(d) | \
___PPC_RS(a) | __PPC_SH(i) | \
__PPC_MB(mb) | __PPC_ME(me))
@@ -166,11 +165,11 @@
___PPC_RS(a) | __PPC_SH(i) | \
__PPC_MB(mb) | __PPC_ME(me))
#define PPC_RLDICL(d, a, i, mb) EMIT(PPC_INST_RLDICL | ___PPC_RA(d) | \
- ___PPC_RS(a) | __PPC_SH(i) | \
- __PPC_MB64(mb) | (((i) & 0x20) >> 4))
+ ___PPC_RS(a) | __PPC_SH64(i) | \
+ __PPC_MB64(mb))
#define PPC_RLDICR(d, a, i, me) EMIT(PPC_INST_RLDICR | ___PPC_RA(d) | \
- ___PPC_RS(a) | __PPC_SH(i) | \
- __PPC_ME64(me) | (((i) & 0x20) >> 4))
+ ___PPC_RS(a) | __PPC_SH64(i) | \
+ __PPC_ME64(me))
/* slwi = rlwinm Rx, Ry, n, 0, 31-n */
#define PPC_SLWI(d, a, i) PPC_RLWINM(d, a, i, 0, 31-(i))
--
2.7.4
On Mon, 19 Dec 2016 18:48:24 +0530
Anju T Sudhakar <[email protected]> wrote:
> Detour buffer contains instructions to create an in memory pt_regs.
> After the execution of the pre-handler, a call is made for instruction emulation.
> The NIP is determined in advanced through dummy instruction emulation and a branch
> instruction is created to the NIP at the end of the trampoline.
>
> Instruction slot for detour buffer is allocated from the reserved area.
> For the time being, 64KB is reserved in memory for this purpose.
>
> Instructions which can be emulated using analyse_instr() are suppliants
> for optimization. Before optimization ensure that the address range
> between the detour buffer allocated and the instruction being probed
> is within $B!^(B 32MB.
>
> Signed-off-by: Anju T Sudhakar <[email protected]>
> Signed-off-by: Naveen N. Rao <[email protected]>
Looks good to me :)
Acked-by: Masami Hiramatsu <[email protected]>
Thanks!
> ---
> .../features/debug/optprobes/arch-support.txt | 2 +-
> arch/powerpc/Kconfig | 1 +
> arch/powerpc/include/asm/kprobes.h | 24 +-
> arch/powerpc/include/asm/sstep.h | 1 +
> arch/powerpc/kernel/Makefile | 1 +
> arch/powerpc/kernel/optprobes.c | 331 +++++++++++++++++++++
> arch/powerpc/kernel/optprobes_head.S | 135 +++++++++
> arch/powerpc/lib/sstep.c | 21 ++
> 8 files changed, 514 insertions(+), 2 deletions(-)
> create mode 100644 arch/powerpc/kernel/optprobes.c
> create mode 100644 arch/powerpc/kernel/optprobes_head.S
>
> diff --git a/Documentation/features/debug/optprobes/arch-support.txt b/Documentation/features/debug/optprobes/arch-support.txt
> index b8999d8..45bc99d 100644
> --- a/Documentation/features/debug/optprobes/arch-support.txt
> +++ b/Documentation/features/debug/optprobes/arch-support.txt
> @@ -27,7 +27,7 @@
> | nios2: | TODO |
> | openrisc: | TODO |
> | parisc: | TODO |
> - | powerpc: | TODO |
> + | powerpc: | ok |
> | s390: | TODO |
> | score: | TODO |
> | sh: | TODO |
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 65fba4c..f7e9296 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -98,6 +98,7 @@ config PPC
> select HAVE_IOREMAP_PROT
> select HAVE_EFFICIENT_UNALIGNED_ACCESS if !(CPU_LITTLE_ENDIAN && POWER7_CPU)
> select HAVE_KPROBES
> + select HAVE_OPTPROBES if PPC64
> select HAVE_ARCH_KGDB
> select HAVE_KRETPROBES
> select HAVE_ARCH_TRACEHOOK
> diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h
> index 2c9759bd..0cf640b 100644
> --- a/arch/powerpc/include/asm/kprobes.h
> +++ b/arch/powerpc/include/asm/kprobes.h
> @@ -38,7 +38,23 @@ struct pt_regs;
> struct kprobe;
>
> typedef ppc_opcode_t kprobe_opcode_t;
> -#define MAX_INSN_SIZE 1
> +
> +extern kprobe_opcode_t optinsn_slot;
> +
> +/* Optinsn template address */
> +extern kprobe_opcode_t optprobe_template_entry[];
> +extern kprobe_opcode_t optprobe_template_op_address[];
> +extern kprobe_opcode_t optprobe_template_call_handler[];
> +extern kprobe_opcode_t optprobe_template_insn[];
> +extern kprobe_opcode_t optprobe_template_call_emulate[];
> +extern kprobe_opcode_t optprobe_template_ret[];
> +extern kprobe_opcode_t optprobe_template_end[];
> +
> +/* Fixed instruction size for powerpc */
> +#define MAX_INSN_SIZE 1
> +#define MAX_OPTIMIZED_LENGTH sizeof(kprobe_opcode_t) /* 4 bytes */
> +#define MAX_OPTINSN_SIZE (optprobe_template_end - optprobe_template_entry)
> +#define RELATIVEJUMP_SIZE sizeof(kprobe_opcode_t) /* 4 bytes */
>
> #ifdef PPC64_ELF_ABI_v2
> /* PPC64 ABIv2 needs local entry point */
> @@ -124,6 +140,12 @@ struct kprobe_ctlblk {
> struct prev_kprobe prev_kprobe;
> };
>
> +struct arch_optimized_insn {
> + kprobe_opcode_t copied_insn[1];
> + /* detour buffer */
> + kprobe_opcode_t *insn;
> +};
> +
> extern int kprobe_exceptions_notify(struct notifier_block *self,
> unsigned long val, void *data);
> extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
> diff --git a/arch/powerpc/include/asm/sstep.h b/arch/powerpc/include/asm/sstep.h
> index d3a42cc..f7ad425 100644
> --- a/arch/powerpc/include/asm/sstep.h
> +++ b/arch/powerpc/include/asm/sstep.h
> @@ -87,3 +87,4 @@ struct instruction_op {
>
> extern int analyse_instr(struct instruction_op *op, struct pt_regs *regs,
> unsigned int instr);
> +extern bool is_conditional_branch(unsigned int instr);
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index 1925341..54f0f47 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -98,6 +98,7 @@ obj-$(CONFIG_KGDB) += kgdb.o
> obj-$(CONFIG_BOOTX_TEXT) += btext.o
> obj-$(CONFIG_SMP) += smp.o
> obj-$(CONFIG_KPROBES) += kprobes.o
> +obj-$(CONFIG_OPTPROBES) += optprobes.o optprobes_head.o
> obj-$(CONFIG_UPROBES) += uprobes.o
> obj-$(CONFIG_PPC_UDBG_16550) += legacy_serial.o udbg_16550.o
> obj-$(CONFIG_STACKTRACE) += stacktrace.o
> diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
> new file mode 100644
> index 0000000..fb5e62d
> --- /dev/null
> +++ b/arch/powerpc/kernel/optprobes.c
> @@ -0,0 +1,331 @@
> +/*
> + * Code for Kernel probes Jump optimization.
> + *
> + * Copyright 2016, Anju T, IBM Corp.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <linux/kprobes.h>
> +#include <linux/jump_label.h>
> +#include <linux/types.h>
> +#include <linux/slab.h>
> +#include <linux/list.h>
> +#include <asm/kprobes.h>
> +#include <asm/ptrace.h>
> +#include <asm/cacheflush.h>
> +#include <asm/code-patching.h>
> +#include <asm/sstep.h>
> +#include <asm/ppc-opcode.h>
> +
> +#define TMPL_CALL_HDLR_IDX \
> + (optprobe_template_call_handler - optprobe_template_entry)
> +#define TMPL_EMULATE_IDX \
> + (optprobe_template_call_emulate - optprobe_template_entry)
> +#define TMPL_RET_IDX \
> + (optprobe_template_ret - optprobe_template_entry)
> +#define TMPL_OP_IDX \
> + (optprobe_template_op_address - optprobe_template_entry)
> +#define TMPL_INSN_IDX \
> + (optprobe_template_insn - optprobe_template_entry)
> +#define TMPL_END_IDX \
> + (optprobe_template_end - optprobe_template_entry)
> +
> +DEFINE_INSN_CACHE_OPS(ppc_optinsn);
> +
> +static bool insn_page_in_use;
> +
> +static void *__ppc_alloc_insn_page(void)
> +{
> + if (insn_page_in_use)
> + return NULL;
> + insn_page_in_use = true;
> + return &optinsn_slot;
> +}
> +
> +static void __ppc_free_insn_page(void *page __maybe_unused)
> +{
> + insn_page_in_use = false;
> +}
> +
> +struct kprobe_insn_cache kprobe_ppc_optinsn_slots = {
> + .mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex),
> + .pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages),
> + /* insn_size initialized later */
> + .alloc = __ppc_alloc_insn_page,
> + .free = __ppc_free_insn_page,
> + .nr_garbage = 0,
> +};
> +
> +/*
> + * Check if we can optimize this probe. Returns NIP post-emulation if this can
> + * be optimized and 0 otherwise.
> + */
> +static unsigned long can_optimize(struct kprobe *p)
> +{
> + struct pt_regs regs;
> + struct instruction_op op;
> + unsigned long nip = 0;
> +
> + /*
> + * kprobe placed for kretprobe during boot time
> + * is not optimizing now.
> + *
> + * TODO: Optimize kprobe in kretprobe_trampoline
> + */
> + if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
> + return 0;
> +
> + /*
> + * We only support optimizing kernel addresses, but not
> + * module addresses.
> + */
> + if (!is_kernel_addr((unsigned long)p->addr))
> + return 0;
> +
> + regs.nip = (unsigned long)p->addr;
> + regs.trap = 0x0;
> + regs.msr = MSR_KERNEL;
> +
> + /*
> + * Ensure that the instruction is not a conditional branch,
> + * and that can be emulated.
> + */
> + if (!is_conditional_branch(*p->ainsn.insn) &&
> + analyse_instr(&op, ®s, *p->ainsn.insn))
> + nip = regs.nip;
> +
> + return nip;
> +}
> +
> +static void optimized_callback(struct optimized_kprobe *op,
> + struct pt_regs *regs)
> +{
> + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> + unsigned long flags;
> +
> + /* This is possible if op is under delayed unoptimizing */
> + if (kprobe_disabled(&op->kp))
> + return;
> +
> + local_irq_save(flags);
> +
> + if (kprobe_running()) {
> + kprobes_inc_nmissed_count(&op->kp);
> + } else {
> + __this_cpu_write(current_kprobe, &op->kp);
> + regs->nip = (unsigned long)op->kp.addr;
> + kcb->kprobe_status = KPROBE_HIT_ACTIVE;
> + opt_pre_handler(&op->kp, regs);
> + __this_cpu_write(current_kprobe, NULL);
> + }
> + local_irq_restore(flags);
> +}
> +NOKPROBE_SYMBOL(optimized_callback);
> +
> +void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
> +{
> + if (op->optinsn.insn) {
> + free_ppc_optinsn_slot(op->optinsn.insn, 1);
> + op->optinsn.insn = NULL;
> + }
> +}
> +
> +/*
> + * emulate_step() requires insn to be emulated as
> + * second parameter. Load register 'r4' with the
> + * instruction.
> + */
> +void patch_imm32_load_insns(unsigned int val, kprobe_opcode_t *addr)
> +{
> + /* addis r4,0,(insn)@h */
> + *addr++ = PPC_INST_ADDIS | ___PPC_RT(4) |
> + ((val >> 16) & 0xffff);
> +
> + /* ori r4,r4,(insn)@l */
> + *addr = PPC_INST_ORI | ___PPC_RA(4) | ___PPC_RS(4) |
> + (val & 0xffff);
> +}
> +
> +/*
> + * Generate instructions to load provided immediate 64-bit value
> + * to register 'r3' and patch these instructions at 'addr'.
> + */
> +void patch_imm64_load_insns(unsigned long val, kprobe_opcode_t *addr)
> +{
> + /* lis r3,(op)@highest */
> + *addr++ = PPC_INST_ADDIS | ___PPC_RT(3) |
> + ((val >> 48) & 0xffff);
> +
> + /* ori r3,r3,(op)@higher */
> + *addr++ = PPC_INST_ORI | ___PPC_RA(3) | ___PPC_RS(3) |
> + ((val >> 32) & 0xffff);
> +
> + /* rldicr r3,r3,32,31 */
> + *addr++ = PPC_INST_RLDICR | ___PPC_RA(3) | ___PPC_RS(3) |
> + __PPC_SH64(32) | __PPC_ME64(31);
> +
> + /* oris r3,r3,(op)@h */
> + *addr++ = PPC_INST_ORIS | ___PPC_RA(3) | ___PPC_RS(3) |
> + ((val >> 16) & 0xffff);
> +
> + /* ori r3,r3,(op)@l */
> + *addr = PPC_INST_ORI | ___PPC_RA(3) | ___PPC_RS(3) |
> + (val & 0xffff);
> +}
> +
> +int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
> +{
> + kprobe_opcode_t *buff, branch_op_callback, branch_emulate_step;
> + kprobe_opcode_t *op_callback_addr, *emulate_step_addr;
> + long b_offset;
> + unsigned long nip;
> +
> + kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
> +
> + nip = can_optimize(p);
> + if (!nip)
> + return -EILSEQ;
> +
> + /* Allocate instruction slot for detour buffer */
> + buff = get_ppc_optinsn_slot();
> + if (!buff)
> + return -ENOMEM;
> +
> + /*
> + * OPTPROBE uses 'b' instruction to branch to optinsn.insn.
> + *
> + * The target address has to be relatively nearby, to permit use
> + * of branch instruction in powerpc, because the address is specified
> + * in an immediate field in the instruction opcode itself, ie 24 bits
> + * in the opcode specify the address. Therefore the address should
> + * be within 32MB on either side of the current instruction.
> + */
> + b_offset = (unsigned long)buff - (unsigned long)p->addr;
> + if (!is_offset_in_branch_range(b_offset))
> + goto error;
> +
> + /* Check if the return address is also within 32MB range */
> + b_offset = (unsigned long)(buff + TMPL_RET_IDX) -
> + (unsigned long)nip;
> + if (!is_offset_in_branch_range(b_offset))
> + goto error;
> +
> + /* Setup template */
> + memcpy(buff, optprobe_template_entry,
> + TMPL_END_IDX * sizeof(kprobe_opcode_t));
> +
> + /*
> + * Fixup the template with instructions to:
> + * 1. load the address of the actual probepoint
> + */
> + patch_imm64_load_insns((unsigned long)op, buff + TMPL_OP_IDX);
> +
> + /*
> + * 2. branch to optimized_callback() and emulate_step()
> + */
> + kprobe_lookup_name("optimized_callback", op_callback_addr);
> + kprobe_lookup_name("emulate_step", emulate_step_addr);
> + if (!op_callback_addr || !emulate_step_addr) {
> + WARN(1, "kprobe_lookup_name() failed\n");
> + goto error;
> + }
> +
> + branch_op_callback = create_branch((unsigned int *)buff + TMPL_CALL_HDLR_IDX,
> + (unsigned long)op_callback_addr,
> + BRANCH_SET_LINK);
> +
> + branch_emulate_step = create_branch((unsigned int *)buff + TMPL_EMULATE_IDX,
> + (unsigned long)emulate_step_addr,
> + BRANCH_SET_LINK);
> +
> + if (!branch_op_callback || !branch_emulate_step)
> + goto error;
> +
> + buff[TMPL_CALL_HDLR_IDX] = branch_op_callback;
> + buff[TMPL_EMULATE_IDX] = branch_emulate_step;
> +
> + /*
> + * 3. load instruction to be emulated into relevant register, and
> + */
> + patch_imm32_load_insns(*p->ainsn.insn, buff + TMPL_INSN_IDX);
> +
> + /*
> + * 4. branch back from trampoline
> + */
> + buff[TMPL_RET_IDX] = create_branch((unsigned int *)buff + TMPL_RET_IDX,
> + (unsigned long)nip, 0);
> +
> + flush_icache_range((unsigned long)buff,
> + (unsigned long)(&buff[TMPL_END_IDX]));
> +
> + op->optinsn.insn = buff;
> +
> + return 0;
> +
> + error:
> + free_ppc_optinsn_slot(buff, 0);
> + return -ERANGE;
> +
> +}
> +
> +int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
> +{
> + return optinsn->insn != NULL;
> +}
> +
> +/*
> + * On powerpc, Optprobes always replaces one instruction (4 bytes
> + * aligned and 4 bytes long). It is impossible to encounter another
> + * kprobe in this address range. So always return 0.
> + */
> +int arch_check_optimized_kprobe(struct optimized_kprobe *op)
> +{
> + return 0;
> +}
> +
> +void arch_optimize_kprobes(struct list_head *oplist)
> +{
> + struct optimized_kprobe *op;
> + struct optimized_kprobe *tmp;
> +
> + list_for_each_entry_safe(op, tmp, oplist, list) {
> + /*
> + * Backup instructions which will be replaced
> + * by jump address
> + */
> + memcpy(op->optinsn.copied_insn, op->kp.addr,
> + RELATIVEJUMP_SIZE);
> + patch_instruction(op->kp.addr,
> + create_branch((unsigned int *)op->kp.addr,
> + (unsigned long)op->optinsn.insn, 0));
> + list_del_init(&op->list);
> + }
> +}
> +
> +void arch_unoptimize_kprobe(struct optimized_kprobe *op)
> +{
> + arch_arm_kprobe(&op->kp);
> +}
> +
> +void arch_unoptimize_kprobes(struct list_head *oplist,
> + struct list_head *done_list)
> +{
> + struct optimized_kprobe *op;
> + struct optimized_kprobe *tmp;
> +
> + list_for_each_entry_safe(op, tmp, oplist, list) {
> + arch_unoptimize_kprobe(op);
> + list_move(&op->list, done_list);
> + }
> +}
> +
> +int arch_within_optimized_kprobe(struct optimized_kprobe *op,
> + unsigned long addr)
> +{
> + return ((unsigned long)op->kp.addr <= addr &&
> + (unsigned long)op->kp.addr + RELATIVEJUMP_SIZE > addr);
> +}
> diff --git a/arch/powerpc/kernel/optprobes_head.S b/arch/powerpc/kernel/optprobes_head.S
> new file mode 100644
> index 0000000..c86976b
> --- /dev/null
> +++ b/arch/powerpc/kernel/optprobes_head.S
> @@ -0,0 +1,135 @@
> +/*
> + * Code to prepare detour buffer for optprobes in Kernel.
> + *
> + * Copyright 2016, Anju T, IBM Corp.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <asm/ppc_asm.h>
> +#include <asm/ptrace.h>
> +#include <asm/asm-offsets.h>
> +
> +#define OPT_SLOT_SIZE 65536
> +
> + .balign 4
> +
> + /*
> + * Reserve an area to allocate slots for detour buffer.
> + * This is part of .text section (rather than vmalloc area)
> + * as this needs to be within 32MB of the probed address.
> + */
> + .global optinsn_slot
> +optinsn_slot:
> + .space OPT_SLOT_SIZE
> +
> + /*
> + * Optprobe template:
> + * This template gets copied into one of the slots in optinsn_slot
> + * and gets fixed up with real optprobe structures et al.
> + */
> + .global optprobe_template_entry
> +optprobe_template_entry:
> + /* Create an in-memory pt_regs */
> + stdu r1,-INT_FRAME_SIZE(r1)
> + SAVE_GPR(0,r1)
> + /* Save the previous SP into stack */
> + addi r0,r1,INT_FRAME_SIZE
> + std r0,GPR1(r1)
> + SAVE_10GPRS(2,r1)
> + SAVE_10GPRS(12,r1)
> + SAVE_10GPRS(22,r1)
> + /* Save SPRS */
> + mfmsr r5
> + std r5,_MSR(r1)
> + li r5,0x700
> + std r5,_TRAP(r1)
> + li r5,0
> + std r5,ORIG_GPR3(r1)
> + std r5,RESULT(r1)
> + mfctr r5
> + std r5,_CTR(r1)
> + mflr r5
> + std r5,_LINK(r1)
> + mfspr r5,SPRN_XER
> + std r5,_XER(r1)
> + mfcr r5
> + std r5,_CCR(r1)
> + lbz r5,PACASOFTIRQEN(r13)
> + std r5,SOFTE(r1)
> + mfdar r5
> + std r5,_DAR(r1)
> + mfdsisr r5
> + std r5,_DSISR(r1)
> +
> + .global optprobe_template_op_address
> +optprobe_template_op_address:
> + /*
> + * Parameters to optimized_callback():
> + * 1. optimized_kprobe structure in r3
> + */
> + nop
> + nop
> + nop
> + nop
> + nop
> + /* 2. pt_regs pointer in r4 */
> + addi r4,r1,STACK_FRAME_OVERHEAD
> +
> + .global optprobe_template_call_handler
> +optprobe_template_call_handler:
> + /* Branch to optimized_callback() */
> + nop
> +
> + /*
> + * Parameters for instruction emulation:
> + * 1. Pass SP in register r3.
> + */
> + addi r3,r1,STACK_FRAME_OVERHEAD
> +
> + .global optprobe_template_insn
> +optprobe_template_insn:
> + /* 2, Pass instruction to be emulated in r4 */
> + nop
> + nop
> +
> + .global optprobe_template_call_emulate
> +optprobe_template_call_emulate:
> + /* Branch to emulate_step() */
> + nop
> +
> + /*
> + * All done.
> + * Now, restore the registers...
> + */
> + ld r5,_MSR(r1)
> + mtmsr r5
> + ld r5,_CTR(r1)
> + mtctr r5
> + ld r5,_LINK(r1)
> + mtlr r5
> + ld r5,_XER(r1)
> + mtxer r5
> + ld r5,_CCR(r1)
> + mtcr r5
> + ld r5,_DAR(r1)
> + mtdar r5
> + ld r5,_DSISR(r1)
> + mtdsisr r5
> + REST_GPR(0,r1)
> + REST_10GPRS(2,r1)
> + REST_10GPRS(12,r1)
> + REST_10GPRS(22,r1)
> + /* Restore the previous SP */
> + addi r1,r1,INT_FRAME_SIZE
> +
> + .global optprobe_template_ret
> +optprobe_template_ret:
> + /* ... and jump back from trampoline */
> + nop
> +
> + .global optprobe_template_end
> +optprobe_template_end:
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index 3362299..895dcdd 100644
> --- a/arch/powerpc/lib/sstep.c
> +++ b/arch/powerpc/lib/sstep.c
> @@ -618,6 +618,27 @@ static int __kprobes trap_compare(long v1, long v2)
> }
>
> /*
> + * Helper to check if a given instruction is a conditional branch
> + * Derived from the conditional checks in analyse_instr()
> + */
> +bool __kprobes is_conditional_branch(unsigned int instr)
> +{
> + unsigned int opcode = instr >> 26;
> +
> + if (opcode == 16) /* bc, bca, bcl, bcla */
> + return true;
> + if (opcode == 19) {
> + switch ((instr >> 1) & 0x3ff) {
> + case 16: /* bclr, bclrl */
> + case 528: /* bcctr, bcctrl */
> + case 560: /* bctar, bctarl */
> + return true;
> + }
> + }
> + return false;
> +}
> +
> +/*
> * Elements of 32-bit rotate and mask instructions.
> */
> #define MASK32(mb, me) ((0xffffffffUL >> (mb)) + \
> --
> 2.7.4
>
--
Masami Hiramatsu <[email protected]>