linux-kernel - Re: [PATCH][RFC] getting rid of stupid loop in BUG()

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Message-ID: <20070725171956.GF27237@ftp.linux.org.uk>
Date:	Wed, 25 Jul 2007 18:19:56 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	David Miller <davem@...emloft.net>, jeremy@...p.org, hpa@...or.com,
	kaos@....com.au, xyzzy@...akeasy.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH][RFC] getting rid of stupid loop in BUG()

On Wed, Jul 25, 2007 at 09:56:12AM -0700, Linus Torvalds wrote:
> 
> 
> On Tue, 24 Jul 2007, David Miller wrote:
> >
> > From: Jeremy Fitzhardinge <jeremy@...p.org>
> > Date: Tue, 24 Jul 2007 23:24:55 -0700
> > 
> > > H. Peter Anvin wrote:
> > > > How far back was __builtin_trap() supported?
> > > 
> > > I think its relatively recent, but it might be within our supported
> > > compiler window.
> > 
> > I'm pretty sure it is.
> 
> .. and I'm pretty sure it's immaterial.
> 
> We don't just do the "ud2" instruction - we also do the file and line 
> number information after it. Which means that __builtin_trap() is useless.
> 
> So we might as well keep the loop, since both are two-byte instructions 
> that tell gcc that it will never continue.

Umm...  Actually, we might be able to do something like
{
	l: __builtin_trap();
	static struct ... v __attribute__((section(...))) = { &&l, n, file };
}

except that it would need block-local labels and those are ugly (so's
&&<label>, while we are at it)...
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