Commit 9eff26ea authored by Paul Mackerras's avatar Paul Mackerras Committed by Ingo Molnar
Browse files

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: default avatarPaul Mackerras <paulus@samba.org>
Acked-by: default avatarBenjamin 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: default avatarIngo Molnar <mingo@elte.hu>
parent 00909e95

arch/powerpc/include/asm/asm-compat.h

+2 −0
Original line number Diff line number Diff line
@@ -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

arch/powerpc/kernel/misc.S

+28 −0
Original line number Diff line number Diff line
@@ -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 */

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