linux-kernel - Re: [PATCH 1/1] fentry: x86, cleanup function

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Date:   Wed, 15 Mar 2017 11:40:17 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jiri Slaby <jslaby@...e.cz>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 1/1] fentry: x86, cleanup function_hook uses

On Wed, 15 Mar 2017 14:44:36 +0100
Jiri Slaby <jslaby@...e.cz> wrote:

> @@ -16,14 +17,6 @@
>  
>  #ifdef CONFIG_FUNCTION_TRACER
>  
> -#ifdef CC_USING_FENTRY
> -# define function_hook	__fentry__
> -EXPORT_SYMBOL(__fentry__)

There's a reason the export symbols are here.

> -#else
> -# define function_hook	mcount
> -EXPORT_SYMBOL(mcount)
> -#endif
> -
>  /* All cases save the original rbp (8 bytes) */
>  #ifdef CONFIG_FRAME_POINTER
>  # ifdef CC_USING_FENTRY
> @@ -297,6 +290,7 @@ trace:
>  	jmp fgraph_trace
>  END(function_hook)
>  #endif /* CONFIG_DYNAMIC_FTRACE */
> +EXPORT_SYMBOL(function_hook)

Under certain configs, this will fail the build. EXPORT_SYMBOL() does
not take the function_hook as a macro nicely. See commit 5de0a8c0c24033.

-- Steve

>  #endif /* CONFIG_FUNCTION_TRACER */
>  
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER