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From: l00383200 <liucheng32@huawei.com>
To: <rmk+kernel@arm.linux.org.uk>, <tglx@linutronix.de>
Cc: <peterz@infradead.org>, <gregkh@linuxfoundation.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <liucheng32@huawei.com>
Subject: [PATCH] Stacktrace in ARM32 architecture has jumped the first 2 layers, which may ignore the display of save_stack_trace_tsk.
Date: Thu, 30 May 2019 23:06:39 +0800	[thread overview]
Message-ID: <1559228799-84473-1-git-send-email-liucheng32@huawei.com> (raw)

Without optimization, both save_stack_trace_tsk and __save_stack_trace
will have stacktrace information in ARM32.

In this situation, "data.skip += 2" operation will skip the first two layers,
which may make the stacktrace strange and different from other architectures.

A simple example is as follows:
In ARM32 architecture:
[<ffffff80083cb3f8>] proc_pid_stack+0xac/0x12c
[<ffffff80083c7c70>] proc_single_show+0x5c/0xa8
[<ffffff800838aca8>] seq_read+0x130/0x420
[<ffffff8008365c54>] __vfs_read+0x60/0x11c
[<ffffff80083665dc>] vfs_read+0x8c/0x140
[<ffffff800836717c>] SyS_read+0x6c/0xcc
[<ffffff8008202cb8>] __sys_trace_return+0x0/0x4
[<ffffffffffffffff>] 0xffffffffffffffff

In some other architectures(ARM64):
[<ffffff8008209be0>] save_stack_trace_tsk+0x0/0xf0
[<ffffff80083cb3f8>] proc_pid_stack+0xac/0x12c
[<ffffff80083c7c70>] proc_single_show+0x5c/0xa8
[<ffffff800838aca8>] seq_read+0x130/0x420
[<ffffff8008365c54>] __vfs_read+0x60/0x11c
[<ffffff80083665dc>] vfs_read+0x8c/0x140
[<ffffff800836717c>] SyS_read+0x6c/0xcc
[<ffffff8008202cb8>] __sys_trace_return+0x0/0x4
[<ffffffffffffffff>] 0xffffffffffffffff

Therefore, we'd better just jump only one layer to ensure accuracy and consistency.

Signed-off-by: liucheng <liucheng32@huawei.com>
---
 arch/arm/kernel/stacktrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index 71778bb..bb3da38 100644
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -125,7 +125,7 @@ static noinline void __save_stack_trace(struct task_struct *tsk,
 #endif
 	} else {
 		/* We don't want this function nor the caller */
-		data.skip += 2;
+		data.skip += 1;
 		frame.fp = (unsigned long)__builtin_frame_address(0);
 		frame.sp = current_stack_pointer;
 		frame.lr = (unsigned long)__builtin_return_address(0);
-- 
1.8.5.6


WARNING: multiple messages have this Message-ID (diff)
From: l00383200 <liucheng32@huawei.com>
To: <rmk+kernel@arm.linux.org.uk>, <tglx@linutronix.de>
Cc: peterz@infradead.org, gregkh@linuxfoundation.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, liucheng32@huawei.com
Subject: [PATCH] Stacktrace in ARM32 architecture has jumped the first 2 layers, which may ignore the display of save_stack_trace_tsk.
Date: Thu, 30 May 2019 23:06:39 +0800	[thread overview]
Message-ID: <1559228799-84473-1-git-send-email-liucheng32@huawei.com> (raw)

Without optimization, both save_stack_trace_tsk and __save_stack_trace
will have stacktrace information in ARM32.

In this situation, "data.skip += 2" operation will skip the first two layers,
which may make the stacktrace strange and different from other architectures.

A simple example is as follows:
In ARM32 architecture:
[<ffffff80083cb3f8>] proc_pid_stack+0xac/0x12c
[<ffffff80083c7c70>] proc_single_show+0x5c/0xa8
[<ffffff800838aca8>] seq_read+0x130/0x420
[<ffffff8008365c54>] __vfs_read+0x60/0x11c
[<ffffff80083665dc>] vfs_read+0x8c/0x140
[<ffffff800836717c>] SyS_read+0x6c/0xcc
[<ffffff8008202cb8>] __sys_trace_return+0x0/0x4
[<ffffffffffffffff>] 0xffffffffffffffff

In some other architectures(ARM64):
[<ffffff8008209be0>] save_stack_trace_tsk+0x0/0xf0
[<ffffff80083cb3f8>] proc_pid_stack+0xac/0x12c
[<ffffff80083c7c70>] proc_single_show+0x5c/0xa8
[<ffffff800838aca8>] seq_read+0x130/0x420
[<ffffff8008365c54>] __vfs_read+0x60/0x11c
[<ffffff80083665dc>] vfs_read+0x8c/0x140
[<ffffff800836717c>] SyS_read+0x6c/0xcc
[<ffffff8008202cb8>] __sys_trace_return+0x0/0x4
[<ffffffffffffffff>] 0xffffffffffffffff

Therefore, we'd better just jump only one layer to ensure accuracy and consistency.

Signed-off-by: liucheng <liucheng32@huawei.com>
---
 arch/arm/kernel/stacktrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index 71778bb..bb3da38 100644
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -125,7 +125,7 @@ static noinline void __save_stack_trace(struct task_struct *tsk,
 #endif
 	} else {
 		/* We don't want this function nor the caller */
-		data.skip += 2;
+		data.skip += 1;
 		frame.fp = (unsigned long)__builtin_frame_address(0);
 		frame.sp = current_stack_pointer;
 		frame.lr = (unsigned long)__builtin_return_address(0);
-- 
1.8.5.6


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

             reply	other threads:[~2019-05-30 15:06 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-30 15:06 l00383200 [this message]
2019-05-30 15:06 ` [PATCH] Stacktrace in ARM32 architecture has jumped the first 2 layers, which may ignore the display of save_stack_trace_tsk l00383200
2019-05-30 16:22 ` Russell King - ARM Linux admin
2019-05-30 16:22   ` Russell King - ARM Linux admin
2019-05-31  8:27   ` Peter Zijlstra
2019-05-31  8:27     ` Peter Zijlstra

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