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Date: Thu, 19 Feb 2009 12:07:11 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Jeremy Fitzhardinge <jeremy@goop.org>
CC: Ingo Molnar <mingo@elte.hu>, Petr Tesarik <ptesarik@suse.cz>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: Definition of BUG on x86
References: <20090219121027.GB1703@elte.hu> <1235045971.15053.42.camel@nathan.suse.cz> <20090219122211.GE1703@elte.hu> <1235047082.15053.49.camel@nathan.suse.cz> <20090219124702.GC22044@elte.hu> <1235048535.15053.52.camel@nathan.suse.cz> <20090219144902.GA8650@elte.hu> <499D7B9D.7060001@goop.org> <20090219153544.GA31637@elte.hu> <1235059883.15053.68.camel@nathan.suse.cz> <20090219161649.GC9556@elte.hu> <499D8A0C.5030908@goop.org>
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Jeremy Fitzhardinge wrote:
> Ingo Molnar wrote:
>> Well, the important question is thatGCC will optimize out whatever 
>> comes after the __builtin_trap(), right? To guarantee an assert we can 
>> do something like:
>>
>>      __builtin_trap();
>>     panic("should never get here");
>>
>> to guarantee a message. (But realistically GCC will at most generate a 
>> build error.)
>>   
> 
> Ah, right, I remember the problem.  There's no guaranteed way of getting 
> the address of the ud2a instruction __builtin_trap generates to put it 
> into the bug table.
> 

Did we actually run into any instance where that failed?

It's true that it's not guaranteed, but it seems highly unlikely that it 
would happen in real life.  We *could* do a forward search at that 
point, that should catch the vast majority of the failing cases, again, 
but once again there are no guarantees.

I guess I should ask the gcc people...

	-hpa