linux-kernel - Re: [PATCH 07/19] ftrace/x86_32: Simplify parameter setup for ftrace_regs

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Date:	Mon, 23 Jul 2012 13:06:13 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Uros Bizjak <ubizjak@...il.com>,
	yrl.pp-manager.tt@...achi.com
Subject: Re: [PATCH 07/19] ftrace/x86_32: Simplify parameter setup for
 ftrace_regs_caller

(2012/07/21 11:19), Steven Rostedt wrote:
> From: Uros Bizjak <ubizjak@...il.com>
> 
> The final position of the stack after saving regs and setting up
> the parameters for ftrace_regs_call, is the position of the pt_regs
> needed for the 4th parameter. Instead of saving it into a temporary
> reg and pushing the reg, simply push the stack pointer.
> 
> Link: http://lkml.kernel.org/r/1342702344.12353.16.camel@gandalf.stny.rr.com
> 

Looks simple and readable :)

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

Thanks!

> Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---
>  arch/x86/kernel/entry_32.S |    5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
> index 46caa56..4dc3017 100644
> --- a/arch/x86/kernel/entry_32.S
> +++ b/arch/x86/kernel/entry_32.S
> @@ -1169,10 +1169,9 @@ ENTRY(ftrace_regs_caller)
>  	movl $__KERNEL_CS,13*4(%esp)
>  
>  	movl 12*4(%esp), %eax	/* Load ip (1st parameter) */
> -	movl 0x4(%ebp), %edx	/* Load parent ip (2cd parameter) */
> -	lea  (%esp), %ecx
> -	pushl %ecx		/* Save pt_regs as 4th parameter */
> +	movl 0x4(%ebp), %edx	/* Load parent ip (2nd parameter) */
>  	leal function_trace_op, %ecx /* Save ftrace_pos in 3rd parameter */
> +	pushl %esp		/* Save pt_regs as 4th parameter */
>  
>  GLOBAL(ftrace_regs_call)
>  	call ftrace_stub
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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