[PATCH 2/2] perf: Drop the skip argument from perf_arch_fetch_regs_caller

[PATCH 2/2] perf: Drop the skip argument from perf_arch_fetch_regs_caller

[Frederic Weisbecker]

Drop this argument now that we always want to rewind only to the
state of the first caller.
It means frame pointers are not necessary anymore to reliably get
the source of an event. But this also means we need this helper
to be a macro now, as an inline function is not an option since
we need to know when to provide a default implentation.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Miller <davem@davemloft.net>
---
 arch/powerpc/include/asm/perf_event.h |   12 ++++++++++++
 arch/powerpc/kernel/misc.S            |   26 --------------------------
 arch/sparc/include/asm/perf_event.h   |    4 ++++
 arch/sparc/kernel/helpers.S           |    6 +++---
 arch/x86/include/asm/perf_event.h     |    9 +++++++++
 arch/x86/include/asm/stacktrace.h     |    7 ++-----
 arch/x86/kernel/cpu/perf_event.c      |   12 ------------
 include/linux/perf_event.h            |   32 +++++++-------------------------
 include/trace/ftrace.h                |    2 +-
 kernel/perf_event.c                   |    5 -----
 kernel/trace/trace_event_perf.c       |    2 --
 11 files changed, 38 insertions(+), 79 deletions(-)

diff --git a/arch/powerpc/include/asm/perf_event.h b/arch/powerpc/include/asm/perf_event.h
index e6d4ce6..5c16b89 100644
--- a/arch/powerpc/include/asm/perf_event.h
+++ b/arch/powerpc/include/asm/perf_event.h
@@ -21,3 +21,15 @@
 #ifdef CONFIG_FSL_EMB_PERF_EVENT
 #include <asm/perf_event_fsl_emb.h>
 #endif
+
+#ifdef CONFIG_PERF_EVENTS
+#include <asm/ptrace.h>
+#include <asm/reg.h>
+
+#define perf_arch_fetch_caller_regs(regs, __ip)			\
+	do {							\
+		(regs)->nip = __ip;				\
+		(regs)->gpr[1] = *(unsigned long *)__get_SP();	\
+		asm volatile("mfmsr %0" : "=r" ((regs)->msr));	\
+	} while (0)
+#endif
diff --git a/arch/powerpc/kernel/misc.S b/arch/powerpc/kernel/misc.S
index 22e507c..2d29752 100644
--- a/arch/powerpc/kernel/misc.S
+++ b/arch/powerpc/kernel/misc.S
@@ -127,29 +127,3 @@ _GLOBAL(__setup_cpu_power7)
 _GLOBAL(__restore_cpu_power7)
 	/* place holder */
 	blr
-
-/*
- * Get a minimal set of registers for our caller's nth caller.
- * r3 = regs pointer, r5 = n.
- *
- * We only get R1 (stack pointer), NIP (next instruction pointer)
- * and LR (link register).  These are all we can get in the
- * general case without doing complicated stack unwinding, but
- * fortunately they are enough to do a stack backtrace, which
- * is all we need them for.
- */
-_GLOBAL(perf_arch_fetch_caller_regs)
-	mr	r6,r1
-	cmpwi	r5,0
-	mflr	r4
-	ble	2f
-	mtctr	r5
-1:	PPC_LL	r6,0(r6)
-	bdnz	1b
-	PPC_LL	r4,PPC_LR_STKOFF(r6)
-2:	PPC_LL	r7,0(r6)
-	PPC_LL	r7,PPC_LR_STKOFF(r7)
-	PPC_STL	r6,GPR1-STACK_FRAME_OVERHEAD(r3)
-	PPC_STL	r4,_NIP-STACK_FRAME_OVERHEAD(r3)
-	PPC_STL	r7,_LINK-STACK_FRAME_OVERHEAD(r3)
-	blr
diff --git a/arch/sparc/include/asm/perf_event.h b/arch/sparc/include/asm/perf_event.h
index 7e26698..7e7d4de 100644
--- a/arch/sparc/include/asm/perf_event.h
+++ b/arch/sparc/include/asm/perf_event.h
@@ -7,6 +7,10 @@ extern void set_perf_event_pending(void);
 
 #ifdef CONFIG_PERF_EVENTS
 extern void init_hw_perf_events(void);
+
+#define perf_arch_fetch_caller_regs(pt_regs, ip)	\
+	__perf_arch_fetch_caller_regs(pt_regs, ip, 1);
+#endif
 #else
 static inline void init_hw_perf_events(void)	{ }
 #endif
diff --git a/arch/sparc/kernel/helpers.S b/arch/sparc/kernel/helpers.S
index 92090cc..682fee0 100644
--- a/arch/sparc/kernel/helpers.S
+++ b/arch/sparc/kernel/helpers.S
@@ -47,9 +47,9 @@ stack_trace_flush:
 	.size		stack_trace_flush,.-stack_trace_flush
 
 #ifdef CONFIG_PERF_EVENTS
-	.globl		perf_arch_fetch_caller_regs
-	.type		perf_arch_fetch_caller_regs,#function
-perf_arch_fetch_caller_regs:
+	.globl		__perf_arch_fetch_caller_regs
+	.type		__perf_arch_fetch_caller_regs,#function
+__perf_arch_fetch_caller_regs:
 	/* We always read the %pstate into %o5 since we will use
 	 * that to construct a fake %tstate to store into the regs.
 	 */
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 254883d..ea871a5 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -140,6 +140,15 @@ extern unsigned long perf_instruction_pointer(struct pt_regs *regs);
 extern unsigned long perf_misc_flags(struct pt_regs *regs);
 #define perf_misc_flags(regs)	perf_misc_flags(regs)
 
+#include <asm/stacktrace.h>
+
+#define perf_arch_fetch_caller_regs(regs, __ip)		{	\
+	(regs)->ip = (__ip);					\
+	(regs)->bp = caller_frame_pointer();			\
+	(regs)->cs = __KERNEL_CS;				\
+	local_save_flags((regs)->flags);			\
+}
+
 #else
 static inline void init_hw_perf_events(void)		{ }
 static inline void perf_events_lapic_init(void)	{ }
diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index a957463..2b16a2a 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -78,17 +78,14 @@ struct stack_frame_ia32 {
     u32 return_address;
 };
 
-static inline unsigned long rewind_frame_pointer(int n)
+static inline unsigned long caller_frame_pointer(void)
 {
 	struct stack_frame *frame;
 
 	get_bp(frame);
 
 #ifdef CONFIG_FRAME_POINTER
-	while (n--) {
-		if (probe_kernel_address(&frame->next_frame, frame))
-			break;
-	}
+	frame = frame->next_frame;
 #endif
 
 	return (unsigned long)frame;
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 2ae6112..2c075fe 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1706,18 +1706,6 @@ struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
 	return entry;
 }
 
-void perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int skip)
-{
-	regs->ip = ip;
-	/*
-	 * perf_arch_fetch_caller_regs adds another call, we need to increment
-	 * the skip level
-	 */
-	regs->bp = rewind_frame_pointer(skip + 1);
-	regs->cs = __KERNEL_CS;
-	local_save_flags(regs->flags);
-}
-
 unsigned long perf_instruction_pointer(struct pt_regs *regs)
 {
 	unsigned long ip;
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index fe50347..49d441e 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -903,8 +903,10 @@ extern atomic_t perf_swevent_enabled[PERF_COUNT_SW_MAX];
 
 extern void __perf_sw_event(u32, u64, int, struct pt_regs *, u64);
 
-extern void
-perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int skip);
+#ifndef perf_arch_fetch_caller_regs
+static inline void
+perf_arch_fetch_caller_regs(struct regs *regs, unsigned long ip) { }
+#endif
 
 /*
  * Take a snapshot of the regs. Skip ip and frame pointer to
@@ -914,31 +916,11 @@ perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int skip);
  * - bp for callchains
  * - eflags, for future purposes, just in case
  */
-static inline void perf_fetch_caller_regs(struct pt_regs *regs, int skip)
+static inline void perf_fetch_caller_regs(struct pt_regs *regs)
 {
-	unsigned long ip;
-
 	memset(regs, 0, sizeof(*regs));
 
-	switch (skip) {
-	case 1 :
-		ip = CALLER_ADDR0;
-		break;
-	case 2 :
-		ip = CALLER_ADDR1;
-		break;
-	case 3 :
-		ip = CALLER_ADDR2;
-		break;
-	case 4:
-		ip = CALLER_ADDR3;
-		break;
-	/* No need to support further for now */
-	default:
-		ip = 0;
-	}
-
-	return perf_arch_fetch_caller_regs(regs, ip, skip);
+	perf_arch_fetch_caller_regs(regs, CALLER_ADDR0);
 }
 
 static inline void
@@ -948,7 +930,7 @@ perf_sw_event(u32 event_id, u64 nr, int nmi, struct pt_regs *regs, u64 addr)
 		struct pt_regs hot_regs;
 
 		if (!regs) {
-			perf_fetch_caller_regs(&hot_regs, 1);
+			perf_fetch_caller_regs(&hot_regs);
 			regs = &hot_regs;
 		}
 		__perf_sw_event(event_id, nr, nmi, regs, addr);
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 1016b21..976cc09 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -801,7 +801,7 @@ static notrace void perf_trace_##call(proto)				\
 	struct ftrace_event_call *event_call = &event_##call;		\
 	struct pt_regs *__regs = &get_cpu_var(perf_trace_regs);		\
 									\
-	perf_fetch_caller_regs(__regs, 1);				\
+	perf_fetch_caller_regs(__regs);					\
 									\
 	perf_trace_templ_##template(event_call, __regs, args);		\
 									\
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 45b7aec..77387fa 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2842,11 +2842,6 @@ __weak struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
 	return NULL;
 }
 
-__weak
-void perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int skip)
-{
-}
-
 
 /*
  * We assume there is only KVM supporting the callbacks.
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 89b780a..924bab2 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -12,8 +12,6 @@
 DEFINE_PER_CPU(struct pt_regs, perf_trace_regs);
 EXPORT_PER_CPU_SYMBOL_GPL(perf_trace_regs);
 
-EXPORT_SYMBOL_GPL(perf_arch_fetch_caller_regs);
-
 static char *perf_trace_buf;
 static char *perf_trace_buf_nmi;
 
-- 
1.6.2.3

Re: [PATCH 2/2] perf: Drop the skip argument from perf_arch_fetch_regs_caller

[Peter Zijlstra]

On Fri, 2010-05-21 at 10:11 +0200, Frederic Weisbecker wrote:
> +static inline void perf_fetch_caller_regs(struct pt_regs *regs)
>  {
> -       unsigned long ip;
> -
>         memset(regs, 0, sizeof(*regs));

btw, do we really need that memset?

As long as we don't actually copy out to userspace, it really doesn't
matter what is in there, and we should be setting all relevant registers
anyway.

Re: [PATCH 2/2] perf: Drop the skip argument from perf_arch_fetch_regs_caller

[Frederic Weisbecker]

On Fri, May 21, 2010 at 12:24:37PM +0200, Peter Zijlstra wrote:
> On Fri, 2010-05-21 at 10:11 +0200, Frederic Weisbecker wrote:
> > +static inline void perf_fetch_caller_regs(struct pt_regs *regs)
> >  {
> > -       unsigned long ip;
> > -
> >         memset(regs, 0, sizeof(*regs));
> 
> btw, do we really need that memset?
> 
> As long as we don't actually copy out to userspace, it really doesn't
> matter what is in there, and we should be setting all relevant registers
> anyway.


We probably need to decouple that yeah.

- If we don't do callchains, we don't need to deref bp
- If we don't copy to userspace, we don't need to zeroe

We should do the filling much later for tracepoints in fact,
but that doesn't concern syscalls or kprobes.

But well, I'll iterate that step by step.

[GIT PULL] perf updates

[Frederic Weisbecker]

Ingo,

Please pull the perf/core branch that can be found at:

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/random-tracing.git
	perf/core

Thanks,
	Frederic
---

Frederic Weisbecker (2):
      x86: Unify dumpstack.h and stacktrace.h
      perf: Drop the skip argument from perf_arch_fetch_regs_caller


 arch/powerpc/include/asm/perf_event.h |   12 +++++++
 arch/powerpc/kernel/misc.S            |   26 ---------------
 arch/sparc/include/asm/perf_event.h   |    8 +++++
 arch/sparc/kernel/helpers.S           |    6 ++--
 arch/x86/include/asm/perf_event.h     |   13 +++++++
 arch/x86/include/asm/stacktrace.h     |   49 ++++++++++++++++++++++++++++
 arch/x86/kernel/cpu/perf_event.c      |   18 ----------
 arch/x86/kernel/dumpstack.c           |    1 -
 arch/x86/kernel/dumpstack.h           |   56 ---------------------------------
 arch/x86/kernel/dumpstack_32.c        |    2 -
 arch/x86/kernel/dumpstack_64.c        |    1 -
 arch/x86/kernel/stacktrace.c          |    7 ++--
 include/linux/perf_event.h            |   32 ++++--------------
 include/trace/ftrace.h                |    2 +-
 kernel/perf_event.c                   |    5 ---
 kernel/trace/trace_event_perf.c       |    2 -
 16 files changed, 97 insertions(+), 143 deletions(-)

[PATCH 1/2] x86: Unify dumpstack.h and stacktrace.h

[Frederic Weisbecker]

arch/x86/include/asm/stacktrace.h and arch/x86/kernel/dumpstack.h
declare headers of objects that deal with the same topic.
Actually most of the files that include stacktrace.h also include
dumpstack.h

Although dumpstack.h seems more reserved for internals of stack
traces, those are quite often needed to define specialized stack
trace operations. And perf event arch headers are going to need
access to such low level operations anyway. So don't continue to
bother with dumpstack.h as it's not anymore about isolated deep
internals.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/include/asm/stacktrace.h |   52 ++++++++++++++++++++++++++++++++++
 arch/x86/kernel/cpu/perf_event.c  |    2 -
 arch/x86/kernel/dumpstack.c       |    1 -
 arch/x86/kernel/dumpstack.h       |   56 -------------------------------------
 arch/x86/kernel/dumpstack_32.c    |    2 -
 arch/x86/kernel/dumpstack_64.c    |    1 -
 arch/x86/kernel/stacktrace.c      |    7 ++--
 7 files changed, 56 insertions(+), 65 deletions(-)
 delete mode 100644 arch/x86/kernel/dumpstack.h

diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index 4dab78e..a957463 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -1,6 +1,13 @@
+/*
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *  Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
+ */
+
 #ifndef _ASM_X86_STACKTRACE_H
 #define _ASM_X86_STACKTRACE_H
 
+#include <linux/uaccess.h>
+
 extern int kstack_depth_to_print;
 
 struct thread_info;
@@ -42,4 +49,49 @@ void dump_trace(struct task_struct *tsk, struct pt_regs *regs,
 		unsigned long *stack, unsigned long bp,
 		const struct stacktrace_ops *ops, void *data);
 
+#ifdef CONFIG_X86_32
+#define STACKSLOTS_PER_LINE 8
+#define get_bp(bp) asm("movl %%ebp, %0" : "=r" (bp) :)
+#else
+#define STACKSLOTS_PER_LINE 4
+#define get_bp(bp) asm("movq %%rbp, %0" : "=r" (bp) :)
+#endif
+
+extern void
+show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
+		unsigned long *stack, unsigned long bp, char *log_lvl);
+
+extern void
+show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
+		unsigned long *sp, unsigned long bp, char *log_lvl);
+
+extern unsigned int code_bytes;
+
+/* The form of the top of the frame on the stack */
+struct stack_frame {
+	struct stack_frame *next_frame;
+	unsigned long return_address;
+};
+
+struct stack_frame_ia32 {
+    u32 next_frame;
+    u32 return_address;
+};
+
+static inline unsigned long rewind_frame_pointer(int n)
+{
+	struct stack_frame *frame;
+
+	get_bp(frame);
+
+#ifdef CONFIG_FRAME_POINTER
+	while (n--) {
+		if (probe_kernel_address(&frame->next_frame, frame))
+			break;
+	}
+#endif
+
+	return (unsigned long)frame;
+}
+
 #endif /* _ASM_X86_STACKTRACE_H */
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index c775860..9632fb6 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1585,8 +1585,6 @@ static const struct stacktrace_ops backtrace_ops = {
 	.walk_stack		= print_context_stack_bp,
 };
 
-#include "../dumpstack.h"
-
 static void
 perf_callchain_kernel(struct pt_regs *regs, struct perf_callchain_entry *entry)
 {
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index c89a386..6e8752c 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -18,7 +18,6 @@
 
 #include <asm/stacktrace.h>
 
-#include "dumpstack.h"
 
 int panic_on_unrecovered_nmi;
 int panic_on_io_nmi;
diff --git a/arch/x86/kernel/dumpstack.h b/arch/x86/kernel/dumpstack.h
deleted file mode 100644
index e1a93be..0000000
--- a/arch/x86/kernel/dumpstack.h
+++ /dev/null
@@ -1,56 +0,0 @@
-/*
- *  Copyright (C) 1991, 1992  Linus Torvalds
- *  Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
- */
-
-#ifndef DUMPSTACK_H
-#define DUMPSTACK_H
-
-#ifdef CONFIG_X86_32
-#define STACKSLOTS_PER_LINE 8
-#define get_bp(bp) asm("movl %%ebp, %0" : "=r" (bp) :)
-#else
-#define STACKSLOTS_PER_LINE 4
-#define get_bp(bp) asm("movq %%rbp, %0" : "=r" (bp) :)
-#endif
-
-#include <linux/uaccess.h>
-
-extern void
-show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
-		unsigned long *stack, unsigned long bp, char *log_lvl);
-
-extern void
-show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
-		unsigned long *sp, unsigned long bp, char *log_lvl);
-
-extern unsigned int code_bytes;
-
-/* The form of the top of the frame on the stack */
-struct stack_frame {
-	struct stack_frame *next_frame;
-	unsigned long return_address;
-};
-
-struct stack_frame_ia32 {
-    u32 next_frame;
-    u32 return_address;
-};
-
-static inline unsigned long rewind_frame_pointer(int n)
-{
-	struct stack_frame *frame;
-
-	get_bp(frame);
-
-#ifdef CONFIG_FRAME_POINTER
-	while (n--) {
-		if (probe_kernel_address(&frame->next_frame, frame))
-			break;
-	}
-#endif
-
-	return (unsigned long)frame;
-}
-
-#endif /* DUMPSTACK_H */
diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index 11540a1..0f6376f 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -16,8 +16,6 @@
 
 #include <asm/stacktrace.h>
 
-#include "dumpstack.h"
-
 
 void dump_trace(struct task_struct *task, struct pt_regs *regs,
 		unsigned long *stack, unsigned long bp,
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 272c9f1..57a21f1 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -16,7 +16,6 @@
 
 #include <asm/stacktrace.h>
 
-#include "dumpstack.h"
 
 #define N_EXCEPTION_STACKS_END \
 		(N_EXCEPTION_STACKS + DEBUG_STKSZ/EXCEPTION_STKSZ - 2)
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 922eefb..ea54d02 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -96,12 +96,13 @@ EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
 
 /* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */
 
-struct stack_frame {
+struct stack_frame_user {
 	const void __user	*next_fp;
 	unsigned long		ret_addr;
 };
 
-static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
+static int
+copy_stack_frame(const void __user *fp, struct stack_frame_user *frame)
 {
 	int ret;
 
@@ -126,7 +127,7 @@ static inline void __save_stack_trace_user(struct stack_trace *trace)
 		trace->entries[trace->nr_entries++] = regs->ip;
 
 	while (trace->nr_entries < trace->max_entries) {
-		struct stack_frame frame;
+		struct stack_frame_user frame;
 
 		frame.next_fp = NULL;
 		frame.ret_addr = 0;
-- 
1.6.2.3

[PATCH 2/2] perf: Drop the skip argument from perf_arch_fetch_regs_caller

[Frederic Weisbecker]

Drop this argument now that we always want to rewind only to the
state of the first caller.
It means frame pointers are not necessary anymore to reliably get
the source of an event. But this also means we need this helper
to be a macro now, as an inline function is not an option since
we need to know when to provide a default implentation.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Cc: David Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 arch/powerpc/include/asm/perf_event.h |   12 ++++++++++++
 arch/powerpc/kernel/misc.S            |   26 --------------------------
 arch/sparc/include/asm/perf_event.h   |    8 ++++++++
 arch/sparc/kernel/helpers.S           |    6 +++---
 arch/x86/include/asm/perf_event.h     |   13 +++++++++++++
 arch/x86/include/asm/stacktrace.h     |    7 ++-----
 arch/x86/kernel/cpu/perf_event.c      |   16 ----------------
 include/linux/perf_event.h            |   32 +++++++-------------------------
 include/trace/ftrace.h                |    2 +-
 kernel/perf_event.c                   |    5 -----
 kernel/trace/trace_event_perf.c       |    2 --
 11 files changed, 46 insertions(+), 83 deletions(-)

diff --git a/arch/powerpc/include/asm/perf_event.h b/arch/powerpc/include/asm/perf_event.h
index e6d4ce6..5c16b89 100644
--- a/arch/powerpc/include/asm/perf_event.h
+++ b/arch/powerpc/include/asm/perf_event.h
@@ -21,3 +21,15 @@
 #ifdef CONFIG_FSL_EMB_PERF_EVENT
 #include <asm/perf_event_fsl_emb.h>
 #endif
+
+#ifdef CONFIG_PERF_EVENTS
+#include <asm/ptrace.h>
+#include <asm/reg.h>
+
+#define perf_arch_fetch_caller_regs(regs, __ip)			\
+	do {							\
+		(regs)->nip = __ip;				\
+		(regs)->gpr[1] = *(unsigned long *)__get_SP();	\
+		asm volatile("mfmsr %0" : "=r" ((regs)->msr));	\
+	} while (0)
+#endif
diff --git a/arch/powerpc/kernel/misc.S b/arch/powerpc/kernel/misc.S
index 22e507c..2d29752 100644
--- a/arch/powerpc/kernel/misc.S
+++ b/arch/powerpc/kernel/misc.S
@@ -127,29 +127,3 @@ _GLOBAL(__setup_cpu_power7)
 _GLOBAL(__restore_cpu_power7)
 	/* place holder */
 	blr
-
-/*
- * Get a minimal set of registers for our caller's nth caller.
- * r3 = regs pointer, r5 = n.
- *
- * We only get R1 (stack pointer), NIP (next instruction pointer)
- * and LR (link register).  These are all we can get in the
- * general case without doing complicated stack unwinding, but
- * fortunately they are enough to do a stack backtrace, which
- * is all we need them for.
- */
-_GLOBAL(perf_arch_fetch_caller_regs)
-	mr	r6,r1
-	cmpwi	r5,0
-	mflr	r4
-	ble	2f
-	mtctr	r5
-1:	PPC_LL	r6,0(r6)
-	bdnz	1b
-	PPC_LL	r4,PPC_LR_STKOFF(r6)
-2:	PPC_LL	r7,0(r6)
-	PPC_LL	r7,PPC_LR_STKOFF(r7)
-	PPC_STL	r6,GPR1-STACK_FRAME_OVERHEAD(r3)
-	PPC_STL	r4,_NIP-STACK_FRAME_OVERHEAD(r3)
-	PPC_STL	r7,_LINK-STACK_FRAME_OVERHEAD(r3)
-	blr
diff --git a/arch/sparc/include/asm/perf_event.h b/arch/sparc/include/asm/perf_event.h
index 7e26698..74c4e0c 100644
--- a/arch/sparc/include/asm/perf_event.h
+++ b/arch/sparc/include/asm/perf_event.h
@@ -6,7 +6,15 @@ extern void set_perf_event_pending(void);
 #define	PERF_EVENT_INDEX_OFFSET	0
 
 #ifdef CONFIG_PERF_EVENTS
+#include <asm/ptrace.h>
+
 extern void init_hw_perf_events(void);
+
+extern void
+__perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int skip);
+
+#define perf_arch_fetch_caller_regs(pt_regs, ip)	\
+	__perf_arch_fetch_caller_regs(pt_regs, ip, 1);
 #else
 static inline void init_hw_perf_events(void)	{ }
 #endif
diff --git a/arch/sparc/kernel/helpers.S b/arch/sparc/kernel/helpers.S
index 92090cc..682fee0 100644
--- a/arch/sparc/kernel/helpers.S
+++ b/arch/sparc/kernel/helpers.S
@@ -47,9 +47,9 @@ stack_trace_flush:
 	.size		stack_trace_flush,.-stack_trace_flush
 
 #ifdef CONFIG_PERF_EVENTS
-	.globl		perf_arch_fetch_caller_regs
-	.type		perf_arch_fetch_caller_regs,#function
-perf_arch_fetch_caller_regs:
+	.globl		__perf_arch_fetch_caller_regs
+	.type		__perf_arch_fetch_caller_regs,#function
+__perf_arch_fetch_caller_regs:
 	/* We always read the %pstate into %o5 since we will use
 	 * that to construct a fake %tstate to store into the regs.
 	 */
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 254883d..02de298 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -140,6 +140,19 @@ extern unsigned long perf_instruction_pointer(struct pt_regs *regs);
 extern unsigned long perf_misc_flags(struct pt_regs *regs);
 #define perf_misc_flags(regs)	perf_misc_flags(regs)
 
+#include <asm/stacktrace.h>
+
+/*
+ * We abuse bit 3 from flags to pass exact information, see perf_misc_flags
+ * and the comment with PERF_EFLAGS_EXACT.
+ */
+#define perf_arch_fetch_caller_regs(regs, __ip)		{	\
+	(regs)->ip = (__ip);					\
+	(regs)->bp = caller_frame_pointer();			\
+	(regs)->cs = __KERNEL_CS;				\
+	regs->flags = 0;					\
+}
+
 #else
 static inline void init_hw_perf_events(void)		{ }
 static inline void perf_events_lapic_init(void)	{ }
diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index a957463..2b16a2a 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -78,17 +78,14 @@ struct stack_frame_ia32 {
     u32 return_address;
 };
 
-static inline unsigned long rewind_frame_pointer(int n)
+static inline unsigned long caller_frame_pointer(void)
 {
 	struct stack_frame *frame;
 
 	get_bp(frame);
 
 #ifdef CONFIG_FRAME_POINTER
-	while (n--) {
-		if (probe_kernel_address(&frame->next_frame, frame))
-			break;
-	}
+	frame = frame->next_frame;
 #endif
 
 	return (unsigned long)frame;
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 9632fb6..2c075fe 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1706,22 +1706,6 @@ struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
 	return entry;
 }
 
-void perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int skip)
-{
-	regs->ip = ip;
-	/*
-	 * perf_arch_fetch_caller_regs adds another call, we need to increment
-	 * the skip level
-	 */
-	regs->bp = rewind_frame_pointer(skip + 1);
-	regs->cs = __KERNEL_CS;
-	/*
-	 * We abuse bit 3 to pass exact information, see perf_misc_flags
-	 * and the comment with PERF_EFLAGS_EXACT.
-	 */
-	regs->flags = 0;
-}
-
 unsigned long perf_instruction_pointer(struct pt_regs *regs)
 {
 	unsigned long ip;
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index fb6c91e..bea785c 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -905,8 +905,10 @@ extern atomic_t perf_swevent_enabled[PERF_COUNT_SW_MAX];
 
 extern void __perf_sw_event(u32, u64, int, struct pt_regs *, u64);
 
-extern void
-perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int skip);
+#ifndef perf_arch_fetch_caller_regs
+static inline void
+perf_arch_fetch_caller_regs(struct regs *regs, unsigned long ip) { }
+#endif
 
 /*
  * Take a snapshot of the regs. Skip ip and frame pointer to
@@ -916,31 +918,11 @@ perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int skip);
  * - bp for callchains
  * - eflags, for future purposes, just in case
  */
-static inline void perf_fetch_caller_regs(struct pt_regs *regs, int skip)
+static inline void perf_fetch_caller_regs(struct pt_regs *regs)
 {
-	unsigned long ip;
-
 	memset(regs, 0, sizeof(*regs));
 
-	switch (skip) {
-	case 1 :
-		ip = CALLER_ADDR0;
-		break;
-	case 2 :
-		ip = CALLER_ADDR1;
-		break;
-	case 3 :
-		ip = CALLER_ADDR2;
-		break;
-	case 4:
-		ip = CALLER_ADDR3;
-		break;
-	/* No need to support further for now */
-	default:
-		ip = 0;
-	}
-
-	return perf_arch_fetch_caller_regs(regs, ip, skip);
+	perf_arch_fetch_caller_regs(regs, CALLER_ADDR0);
 }
 
 static inline void
@@ -950,7 +932,7 @@ perf_sw_event(u32 event_id, u64 nr, int nmi, struct pt_regs *regs, u64 addr)
 		struct pt_regs hot_regs;
 
 		if (!regs) {
-			perf_fetch_caller_regs(&hot_regs, 1);
+			perf_fetch_caller_regs(&hot_regs);
 			regs = &hot_regs;
 		}
 		__perf_sw_event(event_id, nr, nmi, regs, addr);
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 0152b86..5dac6b3 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -702,7 +702,7 @@ perf_trace_##call(void *__data, proto)					\
 	int __data_size;						\
 	int rctx;							\
 									\
-	perf_fetch_caller_regs(&__regs, 1);				\
+	perf_fetch_caller_regs(&__regs);				\
 									\
 	__data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
 	__entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),\
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index e099650..9ae4dbc 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2851,11 +2851,6 @@ __weak struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
 	return NULL;
 }
 
-__weak
-void perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int skip)
-{
-}
-
 
 /*
  * We assume there is only KVM supporting the callbacks.
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index cb6f365..21db1d3 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -9,8 +9,6 @@
 #include <linux/kprobes.h>
 #include "trace.h"
 
-EXPORT_SYMBOL_GPL(perf_arch_fetch_caller_regs);
-
 static char *perf_trace_buf[4];
 
 /*
-- 
1.6.2.3