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author | AKASHI Takahiro <takahiro.akashi@linaro.org> | 2015-12-15 17:33:41 +0900 |
---|---|---|
committer | Will Deacon <will.deacon@arm.com> | 2015-12-21 17:26:02 +0000 |
commit | 20380bb390a443b2c5c8800cec59743faf8151b4 (patch) | |
tree | 3f9d14ec8f265c8969f322a8cd239f3e946e18bb /arch/arm64/kernel/time.c | |
parent | fe13f95b720075327a761fe6ddb45b0c90cab504 (diff) | |
download | linux-stable-20380bb390a443b2c5c8800cec59743faf8151b4.tar.gz linux-stable-20380bb390a443b2c5c8800cec59743faf8151b4.tar.bz2 linux-stable-20380bb390a443b2c5c8800cec59743faf8151b4.zip |
arm64: ftrace: fix a stack tracer's output under function graph tracer
Function graph tracer modifies a return address (LR) in a stack frame
to hook a function return. This will result in many useless entries
(return_to_handler) showing up in
a) a stack tracer's output
b) perf call graph (with perf record -g)
c) dump_backtrace (at panic et al.)
For example, in case of a),
$ echo function_graph > /sys/kernel/debug/tracing/current_tracer
$ echo 1 > /proc/sys/kernel/stack_trace_enabled
$ cat /sys/kernel/debug/tracing/stack_trace
Depth Size Location (54 entries)
----- ---- --------
0) 4504 16 gic_raise_softirq+0x28/0x150
1) 4488 80 smp_cross_call+0x38/0xb8
2) 4408 48 return_to_handler+0x0/0x40
3) 4360 32 return_to_handler+0x0/0x40
...
In case of b),
$ echo function_graph > /sys/kernel/debug/tracing/current_tracer
$ perf record -e mem:XXX:x -ag -- sleep 10
$ perf report
...
| | |--0.22%-- 0x550f8
| | | 0x10888
| | | el0_svc_naked
| | | sys_openat
| | | return_to_handler
| | | return_to_handler
...
In case of c),
$ echo function_graph > /sys/kernel/debug/tracing/current_tracer
$ echo c > /proc/sysrq-trigger
...
Call trace:
[<ffffffc00044d3ac>] sysrq_handle_crash+0x24/0x30
[<ffffffc000092250>] return_to_handler+0x0/0x40
[<ffffffc000092250>] return_to_handler+0x0/0x40
...
This patch replaces such entries with real addresses preserved in
current->ret_stack[] at unwind_frame(). This way, we can cover all
the cases.
Reviewed-by: Jungseok Lee <jungseoklee85@gmail.com>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
[will: fixed minor context changes conflicting with irq stack bits]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/time.c')
-rw-r--r-- | arch/arm64/kernel/time.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c index 6e5c521f123a..59779699a1a4 100644 --- a/arch/arm64/kernel/time.c +++ b/arch/arm64/kernel/time.c @@ -52,6 +52,9 @@ unsigned long profile_pc(struct pt_regs *regs) frame.fp = regs->regs[29]; frame.sp = regs->sp; frame.pc = regs->pc; +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + frame.graph = -1; /* no task info */ +#endif do { int ret = unwind_frame(NULL, &frame); if (ret < 0) |