From: AKASHI Takahiro <takahiro.akashi@linaro.org>
To: catalin.marinas@arm.com, will.deacon@arm.com, rostedt@goodmis.org
Cc: jungseoklee85@gmail.com, olof@lixom.net, broonie@kernel.org,
david.griego@linaro.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
AKASHI Takahiro <takahiro.akashi@linaro.org>
Subject: [RFC 1/3] ftrace: adjust a function's pc to search for in check_stack() for arm64
Date: Mon, 13 Jul 2015 14:29:33 +0900 [thread overview]
Message-ID: <1436765375-7119-2-git-send-email-takahiro.akashi@linaro.org> (raw)
In-Reply-To: <1436765375-7119-1-git-send-email-takahiro.akashi@linaro.org>
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
this_size = stack_dump_index[i++] =
(top - p) * sizeof(unsigned long);
found = 1;
--
1.7.9.5
WARNING: multiple messages have this Message-ID (diff)
From: takahiro.akashi@linaro.org (AKASHI Takahiro)
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 14:29:33 +0900 [thread overview]
Message-ID: <1436765375-7119-2-git-send-email-takahiro.akashi@linaro.org> (raw)
In-Reply-To: <1436765375-7119-1-git-send-email-takahiro.akashi@linaro.org>
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
this_size = stack_dump_index[i++] =
(top - p) * sizeof(unsigned long);
found = 1;
--
1.7.9.5
next prev parent reply other threads:[~2015-07-13 5:30 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 ` AKASHI Takahiro [this message]
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 15:24 ` Steven Rostedt
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1436765375-7119-2-git-send-email-takahiro.akashi@linaro.org \
--to=takahiro.akashi@linaro.org \
--cc=broonie@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=david.griego@linaro.org \
--cc=jungseoklee85@gmail.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=olof@lixom.net \
--cc=rostedt@goodmis.org \
--cc=will.deacon@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.