linux-kernel - Re: [RFC][PATCH] objtool,ftrace: Implement UNWIND_HINT_RET

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Message-ID: <20200331202642.2hkn33dbsjgnsg7q@treble>
Date:   Tue, 31 Mar 2020 15:26:42 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, x86@...nel.org, mhiramat@...nel.org,
        mbenes@...e.cz
Subject: Re: [RFC][PATCH] objtool,ftrace: Implement UNWIND_HINT_RET_OFFSET

On Tue, Mar 31, 2020 at 09:58:41PM +0200, Peter Zijlstra wrote:
> On Tue, Mar 31, 2020 at 11:31:36AM -0400, Steven Rostedt wrote:
> 
> > Can you send this change as a separate patch as it has nothing to do with
> > this current change, and is a clean up patch that stands on its own.
> 
> I also found this.. should I write it up?
> 
> ---
> diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
> index 369e61faacfe..0f108096f278 100644
> --- a/arch/x86/kernel/ftrace_64.S
> +++ b/arch/x86/kernel/ftrace_64.S
> @@ -23,7 +23,7 @@
>  #endif /* CONFIG_FRAME_POINTER */
> 
>  /* Size of stack used to save mcount regs in save_mcount_regs */
> -#define MCOUNT_REG_SIZE		(SS+8 + MCOUNT_FRAME_SIZE)
> +#define MCOUNT_REG_SIZE		(SIZEOF_PTREGS + MCOUNT_FRAME_SIZE)
> 
>  /*
>   * gcc -pg option adds a call to 'mcount' in most functions.
> @@ -77,7 +77,7 @@
>  	/*
>  	 * We add enough stack to save all regs.
>  	 */
> -	subq $(MCOUNT_REG_SIZE - MCOUNT_FRAME_SIZE), %rsp
> +	subq $(SIZEOF_PTREGS), %rsp
>  	movq %rax, RAX(%rsp)
>  	movq %rcx, RCX(%rsp)
>  	movq %rdx, RDX(%rsp)

I was going to suggest the same thing :-)

Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>

-- 
Josh