From: Steven Rostedt <rostedt@goodmis.org>
To: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: catalin.marinas@arm.com, will.deacon@arm.com,
jungseoklee85@gmail.com, olof@lixom.net, broonie@kernel.org,
david.griego@linaro.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC 1/3] ftrace: adjust a function's pc to search for in check_stack() for arm64
Date: Mon, 13 Jul 2015 11:24:39 -0400 [thread overview]
Message-ID: <20150713112439.079d275d@gandalf.local.home> (raw)
In-Reply-To: <1436765375-7119-2-git-send-email-takahiro.akashi@linaro.org>
On Mon, 13 Jul 2015 14:29:33 +0900
AKASHI Takahiro <takahiro.akashi@linaro.org> wrote:
> Ftace's stack tracer on arm64 returns wrong information about call stacks:
>
> Depth Size Location (50 entries)
> ----- ---- --------
> 0) 5256 0 notifier_call_chain+0x30/0x94
> 1) 5256 0 ftrace_call+0x0/0x4
> 2) 5256 0 notifier_call_chain+0x2c/0x94
> 3) 5256 0 raw_notifier_call_chain+0x34/0x44
> 4) 5256 0 timekeeping_update.constprop.9+0xb8/0x114
> 5) 5256 0 update_wall_time+0x408/0x6dc
>
> Most of 'Size' fields are unexpectedly zero.
>
> This is because stack tracer fails to recognize each function's stack frame
> in check_stack(). Stack tracer searches for a function's pc in the stack
> based on the list returned by save_stack_trace(), but save_stack_trace() on
> arm64 does not return the exact return address saved in a stack frame, but
> a value decrmented by 4 (which means a branch instruction's address).
> This behavior was introduced by
> commit e306dfd06fcb ("ARM64: unwind: Fix PC calculation")
>
> So the matching doesn't succeed in most cases.
>
> This problem can be fixed either by
> a) reverting the commit above
> b) adding an arm64-specific hack to check_patch()
>
> This patch does b).
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> ---
> kernel/trace/trace_stack.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
> index 3f34496..7086fc3 100644
> --- a/kernel/trace/trace_stack.c
> +++ b/kernel/trace/trace_stack.c
> @@ -143,7 +143,11 @@ check_stack(unsigned long ip, unsigned long *stack)
> p = start;
>
> for (; p < top && i < max_stack_trace.nr_entries; p++) {
> +#ifdef CONFIG_ARM64
> + if (*p == (stack_dump_trace[i] + 4)) {
> +#else
> if (*p == stack_dump_trace[i]) {
> +#endif
Instead of the ugly #ifdef in this code, please add a macro
FTRACE_STACK_FRAME_OFFSET
Then in include/linux/ftrace.h have:
#ifndef FTRACE_STACK_FRAME_OFFSET
# define FTRACE_STACK_FRAME_OFFSET 0
#endif
And in arch/arm64/include/asm/ftrace.h
#define FTRACE_STACK_FRAME_OFFSET 4
And then just do:
if (*p == (stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET)) {
-- Steve
> this_size = stack_dump_index[i++] =
> (top - p) * sizeof(unsigned long);
> found = 1;
WARNING: multiple messages have this Message-ID (diff)
From: rostedt@goodmis.org (Steven Rostedt)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC 1/3] ftrace: adjust a function's pc to search for in check_stack() for arm64
Date: Mon, 13 Jul 2015 11:24:39 -0400 [thread overview]
Message-ID: <20150713112439.079d275d@gandalf.local.home> (raw)
In-Reply-To: <1436765375-7119-2-git-send-email-takahiro.akashi@linaro.org>
On Mon, 13 Jul 2015 14:29:33 +0900
AKASHI Takahiro <takahiro.akashi@linaro.org> wrote:
> Ftace's stack tracer on arm64 returns wrong information about call stacks:
>
> Depth Size Location (50 entries)
> ----- ---- --------
> 0) 5256 0 notifier_call_chain+0x30/0x94
> 1) 5256 0 ftrace_call+0x0/0x4
> 2) 5256 0 notifier_call_chain+0x2c/0x94
> 3) 5256 0 raw_notifier_call_chain+0x34/0x44
> 4) 5256 0 timekeeping_update.constprop.9+0xb8/0x114
> 5) 5256 0 update_wall_time+0x408/0x6dc
>
> Most of 'Size' fields are unexpectedly zero.
>
> This is because stack tracer fails to recognize each function's stack frame
> in check_stack(). Stack tracer searches for a function's pc in the stack
> based on the list returned by save_stack_trace(), but save_stack_trace() on
> arm64 does not return the exact return address saved in a stack frame, but
> a value decrmented by 4 (which means a branch instruction's address).
> This behavior was introduced by
> commit e306dfd06fcb ("ARM64: unwind: Fix PC calculation")
>
> So the matching doesn't succeed in most cases.
>
> This problem can be fixed either by
> a) reverting the commit above
> b) adding an arm64-specific hack to check_patch()
>
> This patch does b).
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> ---
> kernel/trace/trace_stack.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
> index 3f34496..7086fc3 100644
> --- a/kernel/trace/trace_stack.c
> +++ b/kernel/trace/trace_stack.c
> @@ -143,7 +143,11 @@ check_stack(unsigned long ip, unsigned long *stack)
> p = start;
>
> for (; p < top && i < max_stack_trace.nr_entries; p++) {
> +#ifdef CONFIG_ARM64
> + if (*p == (stack_dump_trace[i] + 4)) {
> +#else
> if (*p == stack_dump_trace[i]) {
> +#endif
Instead of the ugly #ifdef in this code, please add a macro
FTRACE_STACK_FRAME_OFFSET
Then in include/linux/ftrace.h have:
#ifndef FTRACE_STACK_FRAME_OFFSET
# define FTRACE_STACK_FRAME_OFFSET 0
#endif
And in arch/arm64/include/asm/ftrace.h
#define FTRACE_STACK_FRAME_OFFSET 4
And then just do:
if (*p == (stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET)) {
-- Steve
> this_size = stack_dump_index[i++] =
> (top - p) * sizeof(unsigned long);
> found = 1;
next prev parent reply other threads:[~2015-07-13 15:24 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-13 5:29 [RFC 0/3] arm64: ftrace: fix incorrect output from stack tracer AKASHI Takahiro
2015-07-13 5:29 ` AKASHI Takahiro
2015-07-13 5:29 ` [RFC 1/3] ftrace: adjust a function's pc to search for in check_stack() for arm64 AKASHI Takahiro
2015-07-13 5:29 ` AKASHI Takahiro
2015-07-13 15:24 ` Steven Rostedt [this message]
2015-07-13 15:24 ` Steven Rostedt
2015-07-15 0:22 ` AKASHI Takahiro
2015-07-15 0:22 ` AKASHI Takahiro
2015-07-13 5:29 ` [RFC 2/3] arm64: refactor save_stack_trace() AKASHI Takahiro
2015-07-13 5:29 ` AKASHI Takahiro
2015-07-14 12:47 ` Jungseok Lee
2015-07-14 12:47 ` Jungseok Lee
2015-07-14 13:31 ` Steven Rostedt
2015-07-14 13:31 ` Steven Rostedt
2015-07-15 0:20 ` AKASHI Takahiro
2015-07-15 0:20 ` AKASHI Takahiro
2015-07-15 2:51 ` Steven Rostedt
2015-07-15 2:51 ` Steven Rostedt
2015-07-15 11:41 ` AKASHI Takahiro
2015-07-15 11:41 ` AKASHI Takahiro
2015-07-15 14:55 ` Steven Rostedt
2015-07-15 14:55 ` Steven Rostedt
2015-07-15 16:13 ` Steven Rostedt
2015-07-15 16:13 ` Steven Rostedt
2015-07-16 0:27 ` AKASHI Takahiro
2015-07-16 0:27 ` AKASHI Takahiro
2015-07-16 1:08 ` AKASHI Takahiro
2015-07-16 1:08 ` AKASHI Takahiro
2015-07-16 1:38 ` Steven Rostedt
2015-07-16 1:38 ` Steven Rostedt
2015-07-17 10:46 ` Will Deacon
2015-07-17 10:46 ` Will Deacon
2015-07-16 13:29 ` Jungseok Lee
2015-07-16 13:29 ` Jungseok Lee
2015-07-16 13:54 ` Jungseok Lee
2015-07-16 13:54 ` Jungseok Lee
2015-07-16 14:24 ` Steven Rostedt
2015-07-16 14:24 ` Steven Rostedt
2015-07-16 15:01 ` Jungseok Lee
2015-07-16 15:01 ` Jungseok Lee
2015-07-16 15:31 ` Steven Rostedt
2015-07-16 15:31 ` Steven Rostedt
2015-07-16 15:52 ` Jungseok Lee
2015-07-16 15:52 ` Jungseok Lee
2015-07-16 20:22 ` Steven Rostedt
2015-07-16 20:22 ` Steven Rostedt
2015-07-17 2:49 ` AKASHI Takahiro
2015-07-17 2:49 ` AKASHI Takahiro
2015-07-17 3:21 ` Steven Rostedt
2015-07-17 3:21 ` Steven Rostedt
2015-07-16 16:16 ` Steven Rostedt
2015-07-16 16:16 ` Steven Rostedt
2015-07-17 12:40 ` Mark Rutland
2015-07-17 12:40 ` Mark Rutland
2015-07-17 12:51 ` Steven Rostedt
2015-07-17 12:51 ` Steven Rostedt
2015-07-17 13:00 ` Steven Rostedt
2015-07-17 13:00 ` Steven Rostedt
2015-07-17 14:28 ` Jungseok Lee
2015-07-17 14:28 ` Jungseok Lee
2015-07-17 14:41 ` Steven Rostedt
2015-07-17 14:41 ` Steven Rostedt
2015-07-17 14:59 ` Jungseok Lee
2015-07-17 14:59 ` Jungseok Lee
2015-07-17 15:34 ` Jungseok Lee
2015-07-17 15:34 ` Jungseok Lee
2015-07-17 16:01 ` Steven Rostedt
2015-07-17 16:01 ` Steven Rostedt
2015-07-20 16:20 ` Will Deacon
2015-07-20 16:20 ` Will Deacon
2015-07-20 23:53 ` AKASHI Takahiro
2015-07-20 23:53 ` AKASHI Takahiro
2015-07-21 10:26 ` AKASHI Takahiro
2015-07-21 10:26 ` AKASHI Takahiro
2015-07-21 14:34 ` Jungseok Lee
2015-07-21 14:34 ` Jungseok Lee
2015-08-03 9:09 ` Will Deacon
2015-08-03 9:09 ` Will Deacon
2015-08-03 14:01 ` Steven Rostedt
2015-08-03 14:01 ` Steven Rostedt
2015-08-03 14:04 ` Will Deacon
2015-08-03 14:04 ` Will Deacon
2015-08-03 16:30 ` Jungseok Lee
2015-08-03 16:30 ` Jungseok Lee
2015-08-03 16:57 ` Steven Rostedt
2015-08-03 16:57 ` Steven Rostedt
2015-08-03 17:22 ` Jungseok Lee
2015-08-03 17:22 ` Jungseok Lee
2015-08-03 17:32 ` Steven Rostedt
2015-08-03 17:32 ` Steven Rostedt
2015-08-04 7:41 ` AKASHI Takahiro
2015-08-04 7:41 ` AKASHI Takahiro
2015-07-17 2:04 ` AKASHI Takahiro
2015-07-17 2:04 ` AKASHI Takahiro
2015-07-17 14:38 ` Jungseok Lee
2015-07-17 14:38 ` Jungseok Lee
2015-07-16 14:28 ` Mark Rutland
2015-07-16 14:28 ` Mark Rutland
2015-07-16 14:34 ` Steven Rostedt
2015-07-16 14:34 ` Steven Rostedt
2015-07-17 2:09 ` AKASHI Takahiro
2015-07-17 2:09 ` AKASHI Takahiro
2015-07-13 5:29 ` [RFC 3/3] arm64: ftrace: mcount() should not create a stack frame AKASHI Takahiro
2015-07-13 5:29 ` AKASHI Takahiro
2015-07-13 15:01 ` [RFC 0/3] arm64: ftrace: fix incorrect output from stack tracer Jungseok Lee
2015-07-13 15:01 ` Jungseok Lee
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