linux-kernel - Re: [PATCH RFC 1/4] Generic BUG handling.

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Message-Id: <20060929021833.147a17bd.akpm@osdl.org>
Date:	Fri, 29 Sep 2006 02:18:33 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Andi Kleen <ak@....de>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	linux-kernel@...r.kernel.org, Hugh Dickens <hugh@...itas.com>,
	Michael Ellerman <michael@...erman.id.au>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH RFC 1/4] Generic BUG handling.

On 29 Sep 2006 11:13:19 +0200
Andi Kleen <ak@....de> wrote:

> On Fri, Sep 29, 2006 at 02:10:19AM -0700, Andrew Morton wrote:
> > On 29 Sep 2006 10:57:45 +0200
> > Andi Kleen <ak@....de> wrote:
> > 
> > > > Some architectures (powerpc) implement WARN using the same mechanism;
> > > > if the illegal instruction was the result of a WARN, then report_bug()
> > > > returns 1; otherwise it returns 0.
> > > 
> > > In theory we could do that on x86 too (and skipping the instruction), 
> > > the only problem 
> > > is that the only guaranteed to fault opcode is ud2 :/. Ok maybe we could
> > > reserve some int XXX vector.
> > > 
> > > % gid WARN_ON | grep -v arch | wc -l
> > > 299
> > 
> > powerpc sets a bit in the __LINE__ number to indicate that it was a
> > WARN_ON.  That'll work on all architectures.
> 
> We still would need an architecture dependent way to skip the opcode
> though (just returning would raise it again). On x86
> 
> regs->eip += 2     (rip on x86-64) 
> 
> should be enough 
> 

We have all that now.  Do:

	if (report_bug(regs->eip) == BUG_TRAP_TYPE_WARN)
		regs>eip += 2;

(The powerpc is_warning_bug() implementation needs to be hoisted into
generic code)

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