[PATCH v5] arm64: perf: Fix callchain parse error with kernel tracepoint events

From: Hou Pengyang
Date: Sun May 10 2015 - 07:09:20 EST


For ARM64, when tracing with tracepoint events, the IP and pstate 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 0.146 MB perf.data ]
./perf report -f
Samples: 194 of event 'sched:sched_switch', Event count (approx.): 194
Children Self Command Shared Object Symbol
100.00% 100.00% ls [unknown] [.] 0000000000000000

The fix is to implement perf_arch_fetch_caller_regs for ARM64, which fills
several necessary registers used for callchain unwinding, including pc,sp,
fp and spsr .

With this patch, callchain can be parsed correctly as follows:

......
+ 2.63% 0.00% ls [kernel.kallsyms] [k] vfs_symlink
+ 2.63% 0.00% ls [kernel.kallsyms] [k] follow_down
+ 2.63% 0.00% ls [kernel.kallsyms] [k] pfkey_get
+ 2.63% 0.00% ls [kernel.kallsyms] [k] do_execveat_common.isra.33
- 2.63% 0.00% ls [kernel.kallsyms] [k] pfkey_send_policy_notify
pfkey_send_policy_notify
pfkey_get
v9fs_vfs_rename
page_follow_link_light
link_path_walk
el0_svc_naked
.......

Signed-off-by: Hou Pengyang <houpengyang@xxxxxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
---
arch/arm64/include/asm/perf_event.h | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/arm64/include/asm/perf_event.h b/arch/arm64/include/asm/perf_event.h
index d26d1d5..6471773 100644
--- a/arch/arm64/include/asm/perf_event.h
+++ b/arch/arm64/include/asm/perf_event.h
@@ -24,4 +24,11 @@ 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)->pc = (__ip); \
+ (regs)->regs[29] = (unsigned long) __builtin_frame_address(0); \
+ (regs)->sp = current_stack_pointer; \
+ (regs)->pstate = PSR_MODE_EL1h; \
+}
+
#endif
--
1.8.5.2

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