linux-kernel - Re: [PATCH] ftrace/x86: Fix missing ops arg on static function tracing

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Message-ID: <20151116105453.3de46887@gandalf.local.home>
Date:	Mon, 16 Nov 2015 10:54:53 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ftrace/x86: Fix missing ops arg on static function
 tracing

On Sat, 14 Nov 2015 18:32:28 +0900
Namhyung Kim <namhyung@...nel.org> wrote:

> The commit f1ab00af816e ("ftrace/x86: Get rid of ftrace_caller_setup")
> moved code that loads ftrace_ops into 3rd parameter but it missed to do
> for static tracing.
> 
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  arch/x86/kernel/mcount_64.S | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S
> index 94ea120fa21f..6c1ccf9e5427 100644
> --- a/arch/x86/kernel/mcount_64.S
> +++ b/arch/x86/kernel/mcount_64.S
> @@ -278,6 +278,9 @@ trace:
>  	/* save_mcount_regs fills in first two parameters */
>  	save_mcount_regs
>  
> +	/* Load the ftrace_ops into the 3rd parameter */
> +	movq function_trace_op(%rip), %rdx
> +
>  	call   *ftrace_trace_function

This isn't needed, nor will the parameter be used if added. A comment
should probably be added here instead.

/*
 * When DYNAMIC_FTRACE is not defined, ARCH_SUPPORTS_FTRACE_OPS is not
 * set (see include/asm/ftrace.h). Only the ip and parent ip are used
 * and the list function is called when function tracing is enabled.
 */

-- Steve

>  
>  	restore_mcount_regs

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