On 2015/5/6 1:00, Will Deacon wrote:
On Sat, May 02, 2015 at 06:58:17AM +0100, Hou Pengyang wrote:
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 <houpengy...@huawei.com>
---
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..cc92021 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)->ARM_pc = (__ip); \
+ (regs)->ARM_fp = (unsigned long) __builtin_frame_address(0); \
+ (regs)->ARM_sp = current_stack_pointer; \
+ (regs)->ARM_cpsr = PSR_MODE_EL1h; \
+}
This can't possibly compile, therefore you can't possibly have tested it.
I am so sorry. I did test the patch, but on mainline 4.0 +
David long's patches for ARM64 kprobe which are not included in
mainline now. In David's patches, there are macros like ARM_pc, ARM_fp,
ARM_sp and ARM_cpsr, my patch incorrectly used these macros which
results in such compile errors if applied to 4.0 directly:
error: 'struct pt_regs' has no member named 'ARM_pc'
error: 'struct pt_regs' has no member named 'ARM_fp'
error: 'struct pt_regs' has no member named 'ARM_sp'
error: 'struct pt_regs' has no member named 'ARM_cpsr'
I will fix the code and do more test.
Please fix the code and actually check that you're getting sensible
callchains before sending a new version of the patch.
Thanks,
Will
.
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