LinuxLists.cc - [PATCH 0/4] resend: ppc64 LE ABI v2 ftrace-with-regs implementation

2015-06-11 09:53:47

Subject: [PATCH 0/4] resend: ppc64 LE ABI v2 ftrace-with-regs implementation

Hi again,

with the previous submission I was too much into the details to
state a few obvious things. Now with nicer explanations and
changelog.

Torsten

2015-06-11 09:58:35

by Torsten Duwe

[permalink] [raw]

Subject: [PATCH 1/4] ppc64 FTRACE_WITH_REGS implementation

Implement FTRACE_WITH_REGS for powerpc64, on ELF ABI v2.
Initial work started by Vojtech Pavlik, used with permission.

* arch/powerpc/kernel/entry_64.S:
- enhance _mcount with a stub to test (ftrace_trace_function == &ftrace_stub)
as suggested in Documentation/trace/ftrace-design.txt
(for reference only, patched out at runtime)
- Implement an effective ftrace_caller that works from within the kernel
binary as well as from modules.
* arch/powerpc/kernel/ftrace.c:
- be prepared to deal with ppc64 ELV ABI v2, especially calls to _mcount
that result from gcc -mprofile-kernel
* arch/powerpc/kernel/module_64.c:
- do not save the TOC pointer on the trampoline when the destination
is ftrace_caller. This trampoline jump happens from a function prologue
before a new stack frame is set up, so bad things may happen otherwise...
- relax is_module_trampoline() to recognise the modified trampoline.

Signed-off-by: Torsten Duwe <[email protected]>
--
arch/powerpc/include/asm/ftrace.h | 5 +
arch/powerpc/kernel/entry_64.S | 112 +++++++++++++++++++++++++++++++-------
arch/powerpc/kernel/ftrace.c | 67 ++++++++++++++++++++--
arch/powerpc/kernel/module_64.c | 33 ++++++++++-
4 files changed, 186 insertions(+), 31 deletions(-)
--
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index e366187..6111191 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -46,6 +46,8 @@
extern void _mcount(void);

#ifdef CONFIG_DYNAMIC_FTRACE
+# define FTRACE_ADDR ((unsigned long)ftrace_caller+8)
+# define FTRACE_REGS_ADDR FTRACE_ADDR
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
/* reloction of mcount call site is the same as the address */
@@ -58,6 +60,9 @@ struct dyn_arch_ftrace {
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* __ASSEMBLY__ */

+#ifdef CONFIG_DYNAMIC_FTRACE
+#define ARCH_SUPPORTS_FTRACE_OPS 1
+#endif
#endif

#if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64) && !defined(__ASSEMBLY__)
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index d180caf..a4132ef 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -1152,32 +1152,107 @@ _GLOBAL(enter_prom)

#ifdef CONFIG_FUNCTION_TRACER
#ifdef CONFIG_DYNAMIC_FTRACE
-_GLOBAL(mcount)
+
+#define TOCSAVE 24
+
_GLOBAL(_mcount)
- blr
+ nop // REQUIRED for ftrace, to calculate local/global entry diff
+.localentry _mcount,.-_mcount
+ mflr r0
+ mtctr r0
+
+ LOAD_REG_ADDR_PIC(r12,ftrace_trace_function)
+ ld r12,0(r12)
+ LOAD_REG_ADDR_PIC(r0,ftrace_stub)
+ cmpd r0,r12
+ ld r0,LRSAVE(r1)
+ bne- 2f
+
+ mtlr r0
+ bctr
+
+2: /* here we have (*ftrace_trace_function)() in r12,
+ "selfpc" in CTR
+ and "frompc" in r0 */
+
+ mtlr r0
+ bctr
+
+_GLOBAL(ftrace_caller)
+ mr r0,r2 // global (module) call: save module TOC
+ b 1f
+.localentry ftrace_caller,.-ftrace_caller
+ mr r0,r2 // local call: callee's TOC == our TOC
+ b 2f
+
+1: addis r2,r12,(.TOC.-0b)@ha
+ addi r2,r2,(.TOC.-0b)@l
+
+2: // Here we have our proper TOC ptr in R2,
+ // and the one we need to restore on return in r0.
+
+ ld r12, 16(r1) // get caller's adress
+
+ stdu r1,-SWITCH_FRAME_SIZE(r1)
+
+ std r12, _LINK(r1)
+ SAVE_8GPRS(0,r1)
+ std r0,TOCSAVE(r1)
+ SAVE_8GPRS(8,r1)
+ SAVE_8GPRS(16,r1)
+ SAVE_8GPRS(24,r1)
+
+
+ LOAD_REG_IMMEDIATE(r3,function_trace_op)
+ ld r5,0(r3)
+
+ mflr r3
+ std r3, _NIP(r1)
+ std r3, 16(r1)
+ subi r3, r3, MCOUNT_INSN_SIZE
+ mfmsr r4
+ std r4, _MSR(r1)
+ mfctr r4
+ std r4, _CTR(r1)
+ mfxer r4
+ std r4, _XER(r1)
+ mr r4, r12
+ addi r6, r1 ,STACK_FRAME_OVERHEAD

-_GLOBAL_TOC(ftrace_caller)
- /* Taken from output of objdump from lib64/glibc */
- mflr r3
- ld r11, 0(r1)
- stdu r1, -112(r1)
- std r3, 128(r1)
- ld r4, 16(r11)
- subi r3, r3, MCOUNT_INSN_SIZE
.globl ftrace_call
ftrace_call:
bl ftrace_stub
nop
+
+ ld r3, _NIP(r1)
+ mtlr r3
+
+ REST_8GPRS(0,r1)
+ REST_8GPRS(8,r1)
+ REST_8GPRS(16,r1)
+ REST_8GPRS(24,r1)
+
+ addi r1, r1, SWITCH_FRAME_SIZE
+
+ ld r12, 16(r1) // get caller's adress
+ mr r2,r0 // restore callee's TOC
+ mflr r0 // move this LR to CTR
+ mtctr r0
+ mr r0,r12 // restore callee's lr at _mcount site
+ mtlr r0
+ bctr // jump after _mcount site
+
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.globl ftrace_graph_call
ftrace_graph_call:
b ftrace_graph_stub
_GLOBAL(ftrace_graph_stub)
#endif
- ld r0, 128(r1)
- mtlr r0
- addi r1, r1, 112
+
_GLOBAL(ftrace_stub)
+ nop
+ nop
+.localentry ftrace_stub,.-ftrace_stub
blr
#else
_GLOBAL_TOC(_mcount)
@@ -1211,12 +1286,12 @@ _GLOBAL(ftrace_stub)
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
_GLOBAL(ftrace_graph_caller)
/* load r4 with local address */
- ld r4, 128(r1)
+ ld r4, LRSAVE+SWITCH_FRAME_SIZE(r1)
subi r4, r4, MCOUNT_INSN_SIZE

/* Grab the LR out of the caller stack frame */
- ld r11, 112(r1)
- ld r3, 16(r11)
+ ld r11, SWITCH_FRAME_SIZE(r1)
+ ld r3, LRSAVE(r11)

bl prepare_ftrace_return
nop
@@ -1228,10 +1303,7 @@ _GLOBAL(ftrace_graph_caller)
ld r11, 112(r1)
std r3, 16(r11)

- ld r0, 128(r1)
- mtlr r0
- addi r1, r1, 112
- blr
+ b ftrace_graph_stub

_GLOBAL(return_to_handler)
/* need to save return values */
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 44d4d8e..349d07c 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -61,8 +61,11 @@ ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new)
return -EFAULT;

/* Make sure it is what we expect it to be */
- if (replaced != old)
+ if (replaced != old) {
+ printk(KERN_ERR "%p: replaced (%#x) != old (%#x)",
+ (void *)ip, replaced, old);
return -EINVAL;
+ }

/* replace the text with the new text */
if (patch_instruction((unsigned int *)ip, new))
@@ -106,14 +109,16 @@ static int
__ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
- unsigned int op;
+ unsigned int op, op0, op1, pop;
unsigned long entry, ptr;
unsigned long ip = rec->ip;
void *tramp;

/* read where this goes */
- if (probe_kernel_read(&op, (void *)ip, sizeof(int)))
+ if (probe_kernel_read(&op, (void *)ip, sizeof(int))) {
+ printk(KERN_ERR "Fetching opcode failed.\n");
return -EFAULT;
+ }

/* Make sure that that this is still a 24bit jump */
if (!is_bl_op(op)) {
@@ -158,10 +163,42 @@ __ftrace_make_nop(struct module *mod,
*
* Use a b +8 to jump over the load.
*/
- op = 0x48000008; /* b +8 */

- if (patch_instruction((unsigned int *)ip, op))
+ pop = 0x48000008; /* b +8 */
+
+ /*
+ * Check what is in the next instruction. We can see ld r2,40(r1), but
+ * on first pass after boot we will see mflr r0.
+ */
+ if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE)) {
+ printk(KERN_ERR "Fetching op failed.\n");
+ return -EFAULT;
+ }
+
+ if (op != 0xe8410028) { /* ld r2,STACK_OFFSET(r1) */
+
+ if (probe_kernel_read(&op0, (void *)(ip-8), MCOUNT_INSN_SIZE)) {
+ printk(KERN_ERR "Fetching op0 failed.\n");
+ return -EFAULT;
+ }
+
+ if (probe_kernel_read(&op1, (void *)(ip-4), MCOUNT_INSN_SIZE)) {
+ printk(KERN_ERR "Fetching op1 failed.\n");
+ return -EFAULT;
+ }
+
+ if (op0 != 0x7c0802a6 && op1 != 0xf8010010) { /* mflr r0 ; std r0,LRSAVE(r1) */
+ printk(KERN_ERR "Unexpected instructions around bl when enabling dynamic ftrace! (%08x,%08x,bl,%08x)\n", op0, op1, op);
+ return -EINVAL;
+ }
+
+ pop = PPC_INST_NOP; /* When using -mkernel_profile there is no load to jump over */
+ }
+
+ if (patch_instruction((unsigned int *)ip, pop)) {
+ printk(KERN_ERR "Patching NOP failed.\n");
return -EPERM;
+ }

return 0;
}
@@ -287,6 +324,13 @@ int ftrace_make_nop(struct module *mod,

#ifdef CONFIG_MODULES
#ifdef CONFIG_PPC64
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+ unsigned long addr)
+{
+ return ftrace_make_call(rec, addr);
+}
+#endif
static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
@@ -306,11 +350,18 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
* The load offset is different depending on the ABI. For simplicity
* just mask it out when doing the compare.
*/
+#if 0 // -pg, no -mprofile-kernel
if ((op[0] != 0x48000008) || ((op[1] & 0xffff0000) != 0xe8410000)) {
- pr_err("Unexpected call sequence: %x %x\n", op[0], op[1]);
+ pr_err("Unexpected call sequence at %p: %x %x\n", ip, op[0], op[1]);
return -EINVAL;
}
-
+#else
+ /* look for patched "NOP" on ppc64 with -mprofile-kernel */
+ if ((op[0] != 0x60000000) ) {
+ pr_err("Unexpected call at %p: %x\n", ip, op[0]);
+ return -EINVAL;
+ }
+#endif
/* If we never set up a trampoline to ftrace_caller, then bail */
if (!rec->arch.mod->arch.tramp) {
pr_err("No ftrace trampoline\n");
@@ -330,7 +381,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)

return 0;
}
-#else
+#else /* !CONFIG_PPC64: */
static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 6838451..1428ad8 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -138,12 +138,22 @@ static u32 ppc64_stub_insns[] = {
0x4e800420 /* bctr */
};

+/* In case of _mcount calls or dynamic ftracing, Do not save the
+ current callee's TOC (in R2) again into the original caller's stack
+ frame during this trampoline hop. The stack frame already holds
+ that of the original caller. _mcount and ftrace_caller will take
+ care of this TOC value themselves.
+*/
+#define SQUASH_TOC_SAVE_INSN(trampoline_addr) \
+ ((struct ppc64_stub_entry*)(trampoline_addr))-> \
+ jump[2] = PPC_INST_NOP;
+
#ifdef CONFIG_DYNAMIC_FTRACE

static u32 ppc64_stub_mask[] = {
0xffff0000,
0xffff0000,
- 0xffffffff,
+ 0x00000000,
0xffffffff,
#if !defined(_CALL_ELF) || _CALL_ELF != 2
0xffffffff,
@@ -170,6 +180,9 @@ bool is_module_trampoline(u32 *p)
if ((insna & mask) != (insnb & mask))
return false;
}
+ if (insns[2] != ppc64_stub_insns[2] &&
+ insns[2] != PPC_INST_NOP )
+ return false;

return true;
}
@@ -475,6 +488,14 @@ static unsigned long stub_for_addr(Elf64_Shdr *sechdrs,
static int restore_r2(u32 *instruction, struct module *me)
{
if (*instruction != PPC_INST_NOP) {
+
+ /* -mprofile_kernel sequence starting with mflr r0; std r0, LRSAVE(r1) */
+ if (instruction[-3] == 0x7c0802a6 && instruction[-2] == 0xf8010010) {
+ /* Nothing to be done here, it's a _mcount call location
+ and r2 will have to be restored in the _mcount function */
+ return 2;
+ };
+
pr_err("%s: Expect noop after relocate, got %08x\n",
me->name, *instruction);
return 0;
@@ -490,7 +511,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
unsigned int relsec,
struct module *me)
{
- unsigned int i;
+ unsigned int i, r2;
Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr;
Elf64_Sym *sym;
unsigned long *location;
@@ -603,8 +624,11 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
value = stub_for_addr(sechdrs, value, me);
if (!value)
return -ENOENT;
- if (!restore_r2((u32 *)location + 1, me))
+ if (!(r2 = restore_r2((u32 *)location + 1, me)))
return -ENOEXEC;
+ /* Squash the TOC saver for profiler calls */
+ if (!strcmp("_mcount", strtab+sym->st_name))
+ SQUASH_TOC_SAVE_INSN(value);
} else
value += local_entry_offset(sym);

@@ -665,6 +689,9 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
me->arch.tramp = stub_for_addr(sechdrs,
(unsigned long)ftrace_caller,
me);
+ /* ftrace_caller will take care of the TOC;
+ do not clobber original caller's value. */
+ SQUASH_TOC_SAVE_INSN(me->arch.tramp);
#endif

return 0;

2015-06-11 10:00:08

by Torsten Duwe

[permalink] [raw]

Subject: [PATCH 2/4] ppc64 ftrace_with_regs configuration variables

* Makefile:
- globally use -mprofile-kernel in case it's configured.
* arch/powerpc/Kconfig / kernel/trace/Kconfig:
- declare that ppc64 HAVE_MPROFILE_KERNEL and HAVE_DYNAMIC_FTRACE_WITH_REGS,
and use it.

Signed-off-by: Torsten Duwe <[email protected]>
--
Makefile | 5 ++++-
arch/powerpc/Kconfig | 2 ++
kernel/trace/Kconfig | 5 +++++
3 files changed, 11 insertions(+), 1 deletion(-)
--
diff --git a/Makefile b/Makefile
index 3d16bcc..bbd5e87 100644
--- a/Makefile
+++ b/Makefile
@@ -733,7 +733,10 @@ export CC_FLAGS_FTRACE
ifdef CONFIG_HAVE_FENTRY
CC_USING_FENTRY := $(call cc-option, -mfentry -DCC_USING_FENTRY)
endif
-KBUILD_CFLAGS += $(CC_FLAGS_FTRACE) $(CC_USING_FENTRY)
+ifdef CONFIG_HAVE_MPROFILE_KERNEL
+CC_USING_MPROFILE_KERNEL := $(call cc-option, -mprofile-kernel -DCC_USING_MPROFILE_KERNEL)
+endif
+KBUILD_CFLAGS += $(CC_FLAGS_FTRACE) $(CC_USING_FENTRY) $(CC_USING_MPROFILE_KERNEL)
KBUILD_AFLAGS += $(CC_USING_FENTRY)
ifdef CONFIG_DYNAMIC_FTRACE
ifdef CONFIG_HAVE_C_RECORDMCOUNT
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 22b0940..566f204 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -94,8 +94,10 @@ config PPC
select OF_RESERVED_MEM
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_DYNAMIC_FTRACE
+ select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_FUNCTION_TRACER
select HAVE_FUNCTION_GRAPH_TRACER
+ select HAVE_MPROFILE_KERNEL
select SYSCTL_EXCEPTION_TRACE
select ARCH_WANT_OPTIONAL_GPIOLIB
select VIRT_TO_BUS if !PPC64
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index a5da09c..dd53f3d 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -52,6 +52,11 @@ config HAVE_FENTRY
help
Arch supports the gcc options -pg with -mfentry

+config HAVE_MPROFILE_KERNEL
+ bool
+ help
+ Arch supports the gcc options -pg with -mprofile-kernel
+
config HAVE_C_RECORDMCOUNT
bool
help

2015-06-11 10:01:33

by Torsten Duwe

[permalink] [raw]

Subject: [PATCH 3/4] ppc64 ftrace_with_regs: spare early boot and low level code

Using -mprofile-kernel on early boot code not only confuses the checker
but is also useless, as the infrastructure is not yet in place. Proceed
like with -pg (remove it from CFLAGS), equally with time.o and ftrace itself.

* arch/powerpc/kernel/Makefile:
- remove -mprofile-kernel from low level and boot code objects' CFLAGS
for FUNCTION_TRACER configurations.

Signed-off-by: Torsten Duwe <[email protected]>
--
arch/powerpc/kernel/Makefile | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
--
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 502cf69..fb33fc5 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -17,14 +17,14 @@ endif

ifdef CONFIG_FUNCTION_TRACER
# Do not trace early boot code
-CFLAGS_REMOVE_cputable.o = -pg -mno-sched-epilog
-CFLAGS_REMOVE_prom_init.o = -pg -mno-sched-epilog
-CFLAGS_REMOVE_btext.o = -pg -mno-sched-epilog
-CFLAGS_REMOVE_prom.o = -pg -mno-sched-epilog
+CFLAGS_REMOVE_cputable.o = -pg -mno-sched-epilog -mprofile-kernel
+CFLAGS_REMOVE_prom_init.o = -pg -mno-sched-epilog -mprofile-kernel
+CFLAGS_REMOVE_btext.o = -pg -mno-sched-epilog -mprofile-kernel
+CFLAGS_REMOVE_prom.o = -pg -mno-sched-epilog -mprofile-kernel
# do not trace tracer code
-CFLAGS_REMOVE_ftrace.o = -pg -mno-sched-epilog
+CFLAGS_REMOVE_ftrace.o = -pg -mno-sched-epilog -mprofile-kernel
# timers used by tracing
-CFLAGS_REMOVE_time.o = -pg -mno-sched-epilog
+CFLAGS_REMOVE_time.o = -pg -mno-sched-epilog -mprofile-kernel
endif

obj-y := cputable.o ptrace.o syscalls.o \

2015-06-11 10:03:10

by Torsten Duwe

[permalink] [raw]

Subject: [PATCH 4/4] ppc64 ftrace_with_regs recursion protection

This is an *emergency* parachute to avoid an endless recursion and
consecutively a kernel stack overflow, should any function within some
ftrace framework cause an access fault, which calls _mcount / ftrace_caller
in return and so on. It might also call an ftrace'd function directly.

As Michael Ellerman pointed out, it is a tedious and error-prone task
to maintain a complete list of those functions that _might_ get called
from *_access_fault or any dynamic tracer function. So we'll
concentrate on the most frequent cases to enhance performance later,
while for now sticking with this fill-in. It will later serve as a backup
protection.

* arch/powerpc/kernel/entry_64.S:
- test-and-set TRACE_FTRACE_BIT in task_struct's trace_recursion,
do not call the actual tracer function if set, clear flag on return.

Signed-off-by: Torsten Duwe <[email protected]>
--
arch/powerpc/kernel/asm-offsets.c | 1 +
arch/powerpc/kernel/entry_64.S | 15 +++++++++++++--
2 files changed, 14 insertions(+), 2 deletions(-)
--
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 4717859..ae10752 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -72,6 +72,7 @@ int main(void)
DEFINE(THREAD, offsetof(struct task_struct, thread));
DEFINE(MM, offsetof(struct task_struct, mm));
DEFINE(MMCONTEXTID, offsetof(struct mm_struct, context.id));
+ DEFINE(TASK_TRACEREC, offsetof(struct task_struct, trace_recursion));
#ifdef CONFIG_PPC64
DEFINE(AUDITCONTEXT, offsetof(struct task_struct, audit_context));
DEFINE(SIGSEGV, SIGSEGV);
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index a4132ef..4768104 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -1202,7 +1202,13 @@ _GLOBAL(ftrace_caller)
SAVE_8GPRS(16,r1)
SAVE_8GPRS(24,r1)

-
+ ld r3, PACACURRENT(r13)
+ ld r4, TASK_TRACEREC(r3)
+ andi. r5, r4, 0x0010 // ( 1 << TRACE_FTRACE_BIT )
+ ori r4, r4, 0x0010
+ std r4, TASK_TRACEREC(r3)
+ bne- 3f // ftrace in progress - avoid recursion!
+
LOAD_REG_IMMEDIATE(r3,function_trace_op)
ld r5,0(r3)

@@ -1224,9 +1230,14 @@ ftrace_call:
bl ftrace_stub
nop

+ ld r3, PACACURRENT(r13)
+ ld r4, TASK_TRACEREC(r3)
+ andi. r4, r4, 0xffef // ~( 1 << TRACE_FTRACE_BIT )
+ std r4, TASK_TRACEREC(r3)
+
ld r3, _NIP(r1)
mtlr r3
-
+3:
REST_8GPRS(0,r1)
REST_8GPRS(8,r1)
REST_8GPRS(16,r1)

2015-06-18 16:17:36

by Torsten Duwe

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Subject: [RESEND PATCH 0/4] ppc64 LE ABI v2 ftrace-with-regs implementation

Did I miss anything else? I have the notrace optimisations and
kernel live patching in the queue, which depends on this, so I'd
really appreciate a comment whether it is acceptable in this form
or not. Thanks in advance!

Torsten

2015-06-18 16:21:16

by Torsten Duwe

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Subject: [RESEND PATCH 1/4] ppc64 FTRACE_WITH_REGS implementation

2015-06-18 16:22:48

by Torsten Duwe

[permalink] [raw]

Subject: [RESEND PATCH 2/4] ppc64 ftrace_with_regs configuration variables

2015-06-18 16:24:44

by Torsten Duwe

[permalink] [raw]

Subject: [RESEND PATCH 3/4] ppc64 ftrace_with_regs: spare early boot and low level code

2015-06-18 16:25:40

by Torsten Duwe

[permalink] [raw]

Subject: [RESEND PATCH 4/4] ppc64 ftrace_with_regs recursion protection

2015-06-18 16:49:06

by Steven Rostedt

[permalink] [raw]

Subject: Re: [RESEND PATCH 1/4] ppc64 FTRACE_WITH_REGS implementation

On Thu, 18 Jun 2015 18:21:07 +0200
Torsten Duwe <[email protected]> wrote:

> +
> _GLOBAL(ftrace_stub)
> + nop
> + nop
> +.localentry ftrace_stub,.-ftrace_stub

You might want to run checkpatch and fix your whitespace errors.

-- Steve

> blr
> #else
> _GLOBAL_TOC(_mcount)
> @@ -1211,12 +1286,12 @@ _GLOBAL(ftrace_stub)

2015-06-18 16:55:51

by Steven Rostedt

[permalink] [raw]

Subject: Re: [RESEND PATCH 0/4] ppc64 LE ABI v2 ftrace-with-regs implementation

On Thu, 18 Jun 2015 18:17:27 +0200
Torsten Duwe <[email protected]> wrote:

> Did I miss anything else? I have the notrace optimisations and
> kernel live patching in the queue, which depends on this, so I'd
> really appreciate a comment whether it is acceptable in this form
> or not. Thanks in advance!
>
> Torsten

I applied these patches against v4.1-rc8 and I get this compiling it
for my electra:

/work/autotest/nobackup/powerpc-test.git/arch/powerpc/kernel/entry_64.S: Assembler messages:
/work/autotest/nobackup/powerpc-test.git/arch/powerpc/kernel/entry_64.S:1165: Error: unknown pseudo-op: `.localentry'
/work/autotest/nobackup/powerpc-test.git/arch/powerpc/kernel/entry_64.S:1189: Error: unknown pseudo-op: `.localentry'
/work/autotest/nobackup/powerpc-test.git/arch/powerpc/kernel/entry_64.S:1271: Error: unknown pseudo-op: `.localentry'
/work/autotest/nobackup/powerpc-test.git/scripts/Makefile.build:294: recipe for target 'arch/powerpc/kernel/entry_64.o' failed
make[2]: *** [arch/powerpc/kernel/entry_64.o] Error 1

Config attached.

-- Steve

Attachments:

(No filename) (1.03 kB)
config.gz (16.83 kB)
Download all attachments

2015-06-19 02:50:05

by Michael Ellerman

[permalink] [raw]

Subject: Re: [RESEND PATCH 0/4] ppc64 LE ABI v2 ftrace-with-regs implementation

On Thu, 2015-06-18 at 18:17 +0200, Torsten Duwe wrote:
> Did I miss anything else? I have the notrace optimisations and
> kernel live patching in the queue, which depends on this, so I'd
> really appreciate a comment whether it is acceptable in this form
> or not. Thanks in advance!

Hi Torsten,

Sorry I just haven't had time to look at it this week while I've been doing
linux-next.

I'll try and review it next week.

There's no need to resend, we keep track of things in patchwork:

http://patchwork.ozlabs.org/project/linuxppc-dev/list/?submitter=2722

cheers

2015-06-19 07:15:51

by Denis Kirjanov

[permalink] [raw]

Subject: Re: [RESEND PATCH 0/4] ppc64 LE ABI v2 ftrace-with-regs implementation

On 6/18/15, Torsten Duwe <[email protected]> wrote:
> Did I miss anything else? I have the notrace optimisations and
> kernel live patching in the queue, which depends on this, so I'd
> really appreciate a comment whether it is acceptable in this form
> or not. Thanks in advance!

Hi Torsten,

could you provide a description how you did test that.

Thanks.
>
> Torsten
>
> _______________________________________________
> Linuxppc-dev mailing list
> [email protected]
> https://lists.ozlabs.org/listinfo/linuxppc-dev

2015-06-19 12:00:55

by Torsten Duwe

[permalink] [raw]

Subject: Re: [RESEND PATCH 0/4] ppc64 LE ABI v2 ftrace-with-regs implementation

On Thu, Jun 18, 2015 at 12:55:39PM -0400, Steven Rostedt wrote:
>
> I applied these patches against v4.1-rc8 and I get this compiling it
> for my electra:
>
> /work/autotest/nobackup/powerpc-test.git/arch/powerpc/kernel/entry_64.S: Assembler messages:
> /work/autotest/nobackup/powerpc-test.git/arch/powerpc/kernel/entry_64.S:1165: Error: unknown pseudo-op: `.localentry'
> /work/autotest/nobackup/powerpc-test.git/arch/powerpc/kernel/entry_64.S:1189: Error: unknown pseudo-op: `.localentry'
> /work/autotest/nobackup/powerpc-test.git/arch/powerpc/kernel/entry_64.S:1271: Error: unknown pseudo-op: `.localentry'
> /work/autotest/nobackup/powerpc-test.git/scripts/Makefile.build:294: recipe for target 'arch/powerpc/kernel/entry_64.o' failed
> make[2]: *** [arch/powerpc/kernel/entry_64.o] Error 1

After removing your cross compile prefix, with your config I get:

| kernel/bounds.c:1:0: error: -mcall-aixdesc incompatible with -mabi=elfv2

Are you building ppc64, little endian, ELF ABIv2 ?
Is your cross compiler working properly?

I'm compiling natively on that platform (faster for me than an x86 ;-)
| GNU assembler (GNU Binutils; SUSE Linux Enterprise 12) 2.24.0.20140403-7
| gcc (SUSE Linux) 4.8.3 20140627 [gcc-4_8-branch revision 212064]

4.1.0-rc8 config attached.

HTH,
Torsten

Attachments:

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2015-06-19 12:02:01

by Torsten Duwe

[permalink] [raw]

Subject: Re: [RESEND PATCH 1/4] ppc64 FTRACE_WITH_REGS implementation

On Thu, Jun 18, 2015 at 12:49:00PM -0400, Steven Rostedt wrote:
> On Thu, 18 Jun 2015 18:21:07 +0200
> Torsten Duwe <[email protected]> wrote:
>
> > +
> > _GLOBAL(ftrace_stub)
> > + nop
> > + nop
> > +.localentry ftrace_stub,.-ftrace_stub
>
> You might want to run checkpatch and fix your whitespace errors.

Right. Will do.
Thanks,

Torsten

2015-06-19 12:17:15

by Torsten Duwe

[permalink] [raw]

Subject: Re: [RESEND PATCH 0/4] ppc64 LE ABI v2 ftrace-with-regs implementation

On Fri, Jun 19, 2015 at 10:15:44AM +0300, Denis Kirjanov wrote:
>
> Hi Torsten,
>
> could you provide a description how you did test that.

Vanilla kernel, those patches on top, built as described to
Steven in the previous mail (.config attached there, built
natively on ppc64le ABIv2, mentioned tool versions)

make vmlinux, make modules, build initrd
qemu-system-ppc64 -no-reboot -enable-kvm -m 20480 -kernel vmlinux
-initrd initrd.gz -append console=hvc0 -nographic -vga none
inside:
cd /sys/kernel/debug/tracing
mkdir instances/Foo
cd instances/Foo
echo function > current_tracer

current_tracer holds "nop" or "function"; the transition is accompanied
by heavy binary patching. When the function tracer is active, almost all
calls go through ftrace_caller. This should be enough for a start; the
proper stack frame layout details for the tracer functions still remain
to be checked...

Torsten

2015-06-19 12:40:09

by Steven Rostedt

[permalink] [raw]

Subject: Re: [RESEND PATCH 0/4] ppc64 LE ABI v2 ftrace-with-regs implementation

On Fri, 19 Jun 2015 14:00:44 +0200
Torsten Duwe <[email protected]> wrote:

> | kernel/bounds.c:1:0: error: -mcall-aixdesc incompatible with -mabi=elfv2
>
> Are you building ppc64, little endian, ELF ABIv2 ?

It's big endian.

> Is your cross compiler working properly?

Well, just before applying your patches, I built and booted 4.1-rc8 on
that box. Then I applied the patches and got the error on build.

I just reverted your patches, and it builds again.

>
> I'm compiling natively on that platform (faster for me than an x86 ;-)

x86 is bit faster for me to compile.

> | GNU assembler (GNU Binutils; SUSE Linux Enterprise 12) 2.24.0.20140403-7
> | gcc (SUSE Linux) 4.8.3 20140627 [gcc-4_8-branch revision 212064]

I'm using the cross tool chains from kernel.org

https://www.kernel.org/pub/tools/crosstool/files/bin/x86_64/4.6.3/

powerpc64-linux-gcc (GCC) 4.6.3

>
> 4.1.0-rc8 config attached.

Um, what do you want me to do with your config? If your patches don't
build on my box when vanilla does, it's a regression. In other words,
you broke my machine.

-- Steve

2015-06-19 12:41:12

by Steven Rostedt

[permalink] [raw]

Subject: Re: [RESEND PATCH 0/4] ppc64 LE ABI v2 ftrace-with-regs implementation

On Fri, 19 Jun 2015 14:17:03 +0200
Torsten Duwe <[email protected]> wrote:

> On Fri, Jun 19, 2015 at 10:15:44AM +0300, Denis Kirjanov wrote:
> >
> > Hi Torsten,
> >
> > could you provide a description how you did test that.
>
> Vanilla kernel, those patches on top, built as described to
> Steven in the previous mail (.config attached there, built
> natively on ppc64le ABIv2, mentioned tool versions)
>

Great that you got it working on your machine. But you need to do it in
a way that you don't break builds of existing machines, with existing
(still supported) compilers.

-- Steve

> make vmlinux, make modules, build initrd
> qemu-system-ppc64 -no-reboot -enable-kvm -m 20480 -kernel vmlinux
> -initrd initrd.gz -append console=hvc0 -nographic -vga none
> inside:
> cd /sys/kernel/debug/tracing
> mkdir instances/Foo
> cd instances/Foo
> echo function > current_tracer
>
> current_tracer holds "nop" or "function"; the transition is accompanied
> by heavy binary patching. When the function tracer is active, almost all
> calls go through ftrace_caller. This should be enough for a start; the
> proper stack frame layout details for the tracer functions still remain
> to be checked...
>
> Torsten

2015-06-19 13:18:46

by Torsten Duwe

[permalink] [raw]

Subject: Re: [RESEND PATCH 0/4] ppc64 LE ABI v2 ftrace-with-regs implementation

On Fri, Jun 19, 2015 at 08:40:44AM -0400, Steven Rostedt wrote:
> On Fri, 19 Jun 2015 14:00:44 +0200
> Torsten Duwe <[email protected]> wrote:
>
>
> > | kernel/bounds.c:1:0: error: -mcall-aixdesc incompatible with -mabi=elfv2
> >
> > Are you building ppc64, little endian, ELF ABIv2 ?
>
> It's big endian.

And ABIv1, consequently, and then you probably don't have .localentry.
The code inherently assumes ABIv2, v1 does not work.

I'll add a dependency on v2 then, if possible.

Torsten

2015-06-19 13:25:54

by Steven Rostedt

[permalink] [raw]

Subject: Re: [RESEND PATCH 1/4] ppc64 FTRACE_WITH_REGS implementation

On Thu, 18 Jun 2015 18:21:07 +0200
Torsten Duwe <[email protected]> wrote:

> Implement FTRACE_WITH_REGS for powerpc64, on ELF ABI v2.
> Initial work started by Vojtech Pavlik, used with permission.
>
> * arch/powerpc/kernel/entry_64.S:
> - enhance _mcount with a stub to test (ftrace_trace_function == &ftrace_stub)
> as suggested in Documentation/trace/ftrace-design.txt
> (for reference only, patched out at runtime)
> - Implement an effective ftrace_caller that works from within the kernel
> binary as well as from modules.
> * arch/powerpc/kernel/ftrace.c:
> - be prepared to deal with ppc64 ELV ABI v2, especially calls to _mcount
> that result from gcc -mprofile-kernel
> * arch/powerpc/kernel/module_64.c:
> - do not save the TOC pointer on the trampoline when the destination
> is ftrace_caller. This trampoline jump happens from a function prologue
> before a new stack frame is set up, so bad things may happen otherwise...
> - relax is_module_trampoline() to recognise the modified trampoline.
>
> Signed-off-by: Torsten Duwe <[email protected]>
> --

FYI, the standard notation after the change log is '---' not '--'. That
way git will chop off this from the change log. When I did a git am -s
on this patch I had:

Signed-off-by: Torsten Duwe <[email protected]>
--
arch/powerpc/include/asm/ftrace.h | 5 +
arch/powerpc/kernel/entry_64.S | 112 +++++++++++++++++++++++++++++++-------
arch/powerpc/kernel/ftrace.c | 67 ++++++++++++++++++++--
arch/powerpc/kernel/module_64.c | 33 ++++++++++-
4 files changed, 186 insertions(+), 31 deletions(-)
--
Signed-off-by: Steven Rostedt <[email protected]>

-- Steve

> arch/powerpc/include/asm/ftrace.h | 5 +
> arch/powerpc/kernel/entry_64.S | 112 +++++++++++++++++++++++++++++++-------
> arch/powerpc/kernel/ftrace.c | 67 ++++++++++++++++++++--
> arch/powerpc/kernel/module_64.c | 33 ++++++++++-
> 4 files changed, 186 insertions(+), 31 deletions(-)
> --
> diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
> index e366187..6111191 100644
> --- a/arch/powerpc/include/asm/ftrace.h
> +++ b/arch/powerpc/include/asm/ftrace.h