Re: [PATCH] kernel/extable.c: mark core_kernel_text notrace

[Masami Hiramatsu]

On Wed, 21 Jun 2017 09:03:26 +0200
Marcin Nowakowski <marcin.nowakowski@xxxxxxxxxx> wrote:

> core_kernel_text is used by MIPS in its function graph trace processing,
> so having this method traced leads to an infinite set of recursive calls
> such as:
> 
> [    2.972075] Call Trace:
> [    2.972111]
> [    2.976731] [<80506584>] ftrace_return_to_handler+0x50/0x128
> [    2.983379] [<8045478c>] core_kernel_text+0x10/0x1b8
> [    2.989146] [<804119b8>] prepare_ftrace_return+0x6c/0x114
> [    2.995402] [<80411b2c>] ftrace_graph_caller+0x20/0x44
> [    3.001362] [<80411b60>] return_to_handler+0x10/0x30
> [    3.007159] [<80411b50>] return_to_handler+0x0/0x30
> [    3.012827] [<80411b50>] return_to_handler+0x0/0x30
> [    3.018621] [<804e589c>] ftrace_ops_no_ops+0x114/0x1bc
> [    3.024602] [<8045478c>] core_kernel_text+0x10/0x1b8
> [    3.030377] [<8045478c>] core_kernel_text+0x10/0x1b8
> [    3.036140] [<8045478c>] core_kernel_text+0x10/0x1b8
> [    3.041915] [<804e589c>] ftrace_ops_no_ops+0x114/0x1bc
> [    3.047923] [<8045478c>] core_kernel_text+0x10/0x1b8
> [    3.053682] [<804119b8>] prepare_ftrace_return+0x6c/0x114
> [    3.059938] [<80411b2c>] ftrace_graph_caller+0x20/0x44
> (...)
> 
> Mark the function notrace to avoid it being traced.
> 
> Signed-off-by: Marcin Nowakowski <marcin.nowakowski@xxxxxxxxxx>

Looks correct to me.

Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

Thanks,

> ---
>  kernel/extable.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/extable.c b/kernel/extable.c
> index 2676d7f..4efaf26 100644
> --- a/kernel/extable.c
> +++ b/kernel/extable.c
> @@ -70,7 +70,7 @@ static inline int init_kernel_text(unsigned long addr)
>  	return 0;
>  }
>  
> -int core_kernel_text(unsigned long addr)
> +int notrace core_kernel_text(unsigned long addr)
>  {
>  	if (addr >= (unsigned long)_stext &&
>  	    addr < (unsigned long)_etext)
> -- 
> 2.7.4
> 


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>