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 <[email protected]> --- 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
