linux-kernel - Re: [GIT PULL] ftrace/x86: Add frames pointers to trampoline as necessary

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Message-ID: <CA+55aFx3AZpdU2YxFrNXvhWqJ2PyhyQBqTi7v_9hGH1UV-aY4g@mail.gmail.com>
Date:	Fri, 21 Nov 2014 17:35:10 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	stable <stable@...r.kernel.org>
Subject: Re: [GIT PULL] ftrace/x86: Add frames pointers to trampoline as necessary

On Fri, Nov 21, 2014 at 6:50 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> +.macro create_frame parent rip
> +#ifdef CC_USING_FENTRY
> +       pushq \parent
> +       pushq %rbp
> +       movq %rsp, %rbp

This is a very strange frame.

Why do you do the "pushq \parent" at all? Why isn't this just a *real*
frame and add it to MCOUNT_SAVE_FRAME.

You seem to create this fake frame-within-a-frame thing. It's not clear why.

                  Linus
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