linux-kernel - Re: [PATCH] ftrace/samples: Add missing prototype for my_direct

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Message-ID: <20211101113127.19148268@gandalf.local.home>
Date:   Mon, 1 Nov 2021 11:31:27 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Ingo Molnar <mingo@...hat.com>, kernel test robot <lkp@...el.com>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ftrace/samples: Add missing prototype for
 my_direct_func

On Mon,  1 Nov 2021 16:20:02 +0100
Jiri Olsa <jolsa@...hat.com> wrote:

> There's compilation fail reported kernel test robot for W=1 build:
> 
>   >> samples/ftrace/ftrace-direct-multi.c:8:6: warning: no previous  
>   prototype for function 'my_direct_func' [-Wmissing-prototypes]
>      void my_direct_func(unsigned long ip)
> 
> The inlined assembly is used outside function, so we can't make
> my_direct_func static and pass it as asm input argument.
> 
> However my_tramp is already extern so I think there's no problem
> keeping my_direct_func extern as well and just add its prototype.
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Fixes: 5fae941b9a6f ("ftrace/samples: Add multi direct interface test module")
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  samples/ftrace/ftrace-direct-multi.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
> index 2a5b1fb7ac14..e0ccf43da0c9 100644
> --- a/samples/ftrace/ftrace-direct-multi.c
> +++ b/samples/ftrace/ftrace-direct-multi.c
> @@ -10,6 +10,7 @@ void my_direct_func(unsigned long ip)
>  	trace_printk("ip %lx\n", ip);
>  }
>  
> +extern void my_direct_func(unsigned long ip);
>  extern void my_tramp(void *);

Except that I believe that the prototype must come before it is used.

I don't think this will fix the warning.

-- Steve


>  
>  asm (