[v1] ftrace: Hide a extra entry in stack trace

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

Posted by Tatsuya S 1 year, 4 months ago

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.s2862@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
 
 	preempt_disable_notrace();
-- 
2.46.1

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

Posted by Steven Rostedt 1 year, 4 months ago

On Mon, 23 Sep 2024 12:59:15 +0900
Tatsuya S <tatsuya.s2862@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.s2862@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

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

Posted by ts 1 year, 4 months ago

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

> On Mon, 23 Sep 2024 12:59:15 +0900
> Tatsuya S <tatsuya.s2862@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.s2862@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.