linux-kernel - Re: [PATCH] Put the BUG __FILE__ and __LINE_

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Message-ID: <451B708D.20505@goop.org>
Date:	Wed, 27 Sep 2006 23:49:49 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Andrew Morton <akpm@...l.org>
CC:	Andi Kleen <ak@....de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Put the BUG __FILE__ and __LINE__ info out of line

Andrew Morton wrote:
> hm.  Bigger vmlinux, smaller .text.
>   

Yep.

> It means that we'll hit handle_BUG with that extra EIP pushed on the stack.
>  What does that do to the stack trace, and to the unwinder?
>   
Dunno.  I was hoping Andi would pop up with the appropriate CFI gunk, if 
necessary.  But the reason for making it a call was to make it as 
unwindable as possible.

> It'll also muck up the displayed EIP, not that that matters a lot (well, it
> might matter a bit if the BUG is in an inlined function).
>
> We could get the correct EIP by fishing it off the stack (and subtracting
> five from it?)
>   

Yes, that's possible.

> Or we could assume that BUG doesn't return (it doesn't) and make that call
> a jmp.  But then we'd really lose the EIP.

Right.  Or it could save the EIP along with the line and filename.

    J
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