Re: [PATCH] ftrace: Hide a extra entry in stack trace

[ts]

On 9/26/24 2:05 PM, Steven Rostedt wrote:

On Mon, 23 Sep 2024 12:59:15 +0900
Tatsuya S <tatsuya.s2...@gmail.com> wrote:

A extra entry is shown on stack trace(CONFIG_UNWINDER_ORC=y).

     [003] .....   110.171589: vfs_write <-__x64_sys_write
     [003] .....   110.171600: <stack trace>
  => XXXXXXXXX (Wrong function name)
  => vfs_write
  => __x64_sys_write
  => do_syscall_64
  => entry_SYSCALL_64_after_hwframe

To resolve this, increment skip in __ftrace_trace_stack().
The reason why skip is incremented in __ftrace_trace_stack()
is because __ftrace_trace_stack() in stack trace is the only function
that wasn't skipped from anywhere.

Signed-off-by: Tatsuya S <tatsuya.s2...@gmail.com>
---
  kernel/trace/trace.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c3b2c7dfadef..e0d98621ff23 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2919,6 +2919,8 @@ static void __ftrace_trace_stack(struct trace_buffer 
*buffer,
  #ifndef CONFIG_UNWINDER_ORC
        if (!regs)
                skip++;
+#else
+       skip++;
  #endif

The above #ifdef block should be removed and replaced with;


        if (IS_ENABLED(CONFIG_UNWINDER_ORC) || !regs)
                skip++;

preempt_disable_notrace();

-- Steve

 I will submit a new patch to fix it.

Thanks.