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>
diff --git a/arch/powerpc/include/asm/asm-compat.h b/arch/powerpc/include/asm/asm-compat.h
index c1b475a..a9b91ed 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