linux-kernel - Re: [PATCH] x86: remove the confusing entry in call trace

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Message-ID: <20081123190444.GE21106@elte.hu>
Date:	Sun, 23 Nov 2008 20:04:44 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Alexander van Heukelum <heukelum@...lshack.com>
Cc:	jia zhang <jia.zhang2008@...il.com>, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, hpa@...or.com
Subject: Re: [PATCH] x86: remove the confusing entry in call trace


* Alexander van Heukelum <heukelum@...lshack.com> wrote:

> On Sun, Nov 23, 2008 at 10:47:10PM +0800, jia zhang wrote:
> > 
> > avoid the confusion in call trace because of the lack of padding at the tail of
> > function.
> > 
> > Signed-off-by: jia zhang <jia.zhang2008@...il.com> --- When do_exit get call,
> > the return address behind call instruction is pushed into stack. If something
> > get wrong in do_exit, for x86_64, the entry "kernel_execve +0x00/0xXX" rather
> > than "child_rip +0xYY/0xZZ" is remained in call trace. It looks confused.
> 
> It's valuable to know from where do_exit is called, so that's the
> only reason why using "call" is important. Otherwise it could just
> be changed to a jmp as do_exit does not return. It's maybe a bit
> ugly to add the padding, but it does give better traces. Maybe
> a 'ret', 'int3', or 'ud2' would be slightly less offensive?
> 
> Anyhow, I don't have a problem with the added padding, so:
> 
> Acked-by: Alexander van Heukelum <heukelum@...tmail.fm>

applied to tip/x86/debug, thanks guys!

i changed it to u2d based on your suggestion - that makes it not only 
easier to understand, but also more robust, should do_exit() return. 
(which it should never in practice)

	Ingo
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