For ARM64, 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 0.146 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 psr .
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
.......
For tracepoint event, stack parsing also doesn't work well for ARM. Jean Pihet
comed up a patch:
http://thread.gmane.org/gmane.linux.kernel/1734283/focus=1734280
Signed-off-by: Hou Pengyang <houpengy...@huawei.com>
---
arch/arm64/include/asm/perf_event.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/arch/arm64/include/asm/perf_event.h
b/arch/arm64/include/asm/perf_event.h
index d26d1d5..16a074f 100644
--- a/arch/arm64/include/asm/perf_event.h
+++ b/arch/arm64/include/asm/perf_event.h
@@ -24,4 +24,20 @@ 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) { \
+ unsigned long sp; \
+ __asm__ ("mov %[sp], sp\n" : [sp] "=r" (sp)); \
+ (regs)->pc = (__ip); \
+ __asm__ ( \
+ "str %[sp], %[_arm64_sp] \n\t" \
+ "str x29, %[_arm64_fp] \n\t" \
+ "mrs %[_arm64_cpsr], spsr_el1 \n\t" \
+ : [_arm64_sp] "=m" (regs->sp), \
+ [_arm64_fp] "=m" (regs->regs[29]), \
+ [_arm64_cpsr] "=r" (regs->pstate) \
+ : [sp] "r" (sp) \
+ ); \
+}
+
+
#endif
--
1.8.3.4
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
