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authorPaul Mackerras <paulus@samba.org>2010-03-18 16:05:13 +1100
committerIngo Molnar <mingo@elte.hu>2010-03-18 06:48:29 +0100
commit9eff26ea48bfbe2885b158742a7512a097ec911b (patch)
treea914f959b78bdf4ee9eca897a743d727c27faf4f
parent00909e955125e90a6ebb34671c56c4c851e62951 (diff)
powerpc/perf_events: Fix call-graph recording, add perf_arch_fetch_caller_regs
This implements a powerpc version of perf_arch_fetch_caller_regs to get correct call-graphs. It's implemented in assembly because that way we can be sure there isn't a stack frame for perf_arch_fetch_caller_regs. If it was in C, gcc might or might not create a stack frame for it, which would affect the number of levels we have to skip. With this, we see results from perf record -e lock:lock_acquire like this: # Samples: 24878 # # Overhead Command Shared Object Symbol # ........ .............. ................. ...... # 14.99% perf [kernel.kallsyms] [k] ._raw_spin_lock | --- ._raw_spin_lock | |--25.00%-- .alloc_fd | (nil) | | | |--50.00%-- .anon_inode_getfd | | .sys_perf_event_open | | syscall_exit | | syscall | | create_counter | | __cmd_record | | run_builtin | | main | | 0xfd2e704 | | 0xfd2e8c0 | | (nil) ... etc. Signed-off-by: Paul Mackerras <paulus@samba.org> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: anton@samba.org Cc: linuxppc-dev@ozlabs.org Cc: Peter Zijlstra <peterz@infradead.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <20100318050513.GA6575@drongo> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--arch/powerpc/include/asm/asm-compat.h2
-rw-r--r--arch/powerpc/kernel/misc.S28
2 files changed, 30 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/asm-compat.h b/arch/powerpc/include/asm/asm-compat.h
index c1b475a941eb..a9b91ed3d4b9 100644
--- a/arch/powerpc/include/asm/asm-compat.h
+++ b/arch/powerpc/include/asm/asm-compat.h
@@ -28,6 +28,7 @@
#define PPC_LLARX(t, a, b, eh) PPC_LDARX(t, a, b, eh)
#define PPC_STLCX stringify_in_c(stdcx.)
#define PPC_CNTLZL stringify_in_c(cntlzd)
+#define PPC_LR_STKOFF 16
/* Move to CR, single-entry optimized version. Only available
* on POWER4 and later.
@@ -51,6 +52,7 @@
#define PPC_STLCX stringify_in_c(stwcx.)
#define PPC_CNTLZL stringify_in_c(cntlzw)
#define PPC_MTOCRF stringify_in_c(mtcrf)
+#define PPC_LR_STKOFF 4
#endif
diff --git a/arch/powerpc/kernel/misc.S b/arch/powerpc/kernel/misc.S
index 2d29752cbe16..b485a87c94e1 100644
--- a/arch/powerpc/kernel/misc.S
+++ b/arch/powerpc/kernel/misc.S
@@ -127,3 +127,31 @@ _GLOBAL(__setup_cpu_power7)
_GLOBAL(__restore_cpu_power7)
/* place holder */
blr
+
+#ifdef CONFIG_EVENT_TRACING
+/*
+ * 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
+#endif /* CONFIG_EVENT_TRACING */