From b3eac0265bf6258f08dcd4ac7fa7f87cc050defc Mon Sep 17 00:00:00 2001 From: Hou Pengyang Date: Fri, 8 May 2015 06:43:03 +0100 Subject: [PATCH] arm: perf: Fix callchain parse error with kernel tracepoint events For ARM, when tracing with tracepoint events, the IP and cpsr are set to 0, preventing the perf code parsing the callchain and resolving the symbols correctly. ./perf record -e sched:sched_switch -g --call-graph dwarf ls [ perf record: Captured and wrote 0.006 MB perf.data ] ./perf report -f Samples: 5 of event 'sched:sched_switch', Event count (approx.): 5 Children Self Command Shared Object Symbol 100.00% 100.00% ls [unknown] [.] 00000000 The fix is to implement perf_arch_fetch_caller_regs for ARM, which fills several necessary registers used for callchain unwinding, including pc,sp, fp and cpsr. With this patch, callchain can be parsed correctly as : ..... - 100.00% 100.00% ls [kernel.kallsyms] [k] __sched_text_start + __sched_text_start + 20.00% 0.00% ls libc-2.18.so [.] _dl_addr + 20.00% 0.00% ls libc-2.18.so [.] write ..... Jean Pihet found this in ARM and come up with a patch: http://thread.gmane.org/gmane.linux.kernel/1734283/focus=1734280 This patch rewrite Jean's patch in C. Signed-off-by: Hou Pengyang Signed-off-by: Will Deacon --- arch/arm/include/asm/perf_event.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/arm/include/asm/perf_event.h b/arch/arm/include/asm/perf_event.h index d9cf138fd7d4..4f9dec489931 100644 --- a/arch/arm/include/asm/perf_event.h +++ b/arch/arm/include/asm/perf_event.h @@ -19,4 +19,11 @@ extern unsigned long perf_misc_flags(struct pt_regs *regs); #define perf_misc_flags(regs) perf_misc_flags(regs) #endif +#define perf_arch_fetch_caller_regs(regs, __ip) { \ + (regs)->ARM_pc = (__ip); \ + (regs)->ARM_fp = (unsigned long) __builtin_frame_address(0); \ + (regs)->ARM_sp = current_stack_pointer; \ + (regs)->ARM_cpsr = SVC_MODE; \ +} + #endif /* __ARM_PERF_EVENT_H__ */