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

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Message-ID: <46A6DB04.3000003@zytor.com>
Date:	Tue, 24 Jul 2007 22:09:24 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Keith Owens <kaos@....com.au>
CC:	Trent Piepho <xyzzy@...akeasy.org>,
	Al Viro <viro@....linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH][RFC] getting rid of stupid loop in BUG()

Keith Owens wrote:
> Trent Piepho (on Tue, 24 Jul 2007 19:31:36 -0700 (PDT)) wrote:
>> Adding __builtin_trap after the
>> asm might be an ok fix.  It will emit a spurious int 6, but that won't even be
>> reached since the asm doesn't return, and it probably be less extra code than
>> the loop.
> 
> int 6 is a two byte instruction, the loop generates jmp with an 8 bit
> offset, also two bytes.  No change in code size.
> 

INT 6 is #UD, so the __builtin_trap() replaces the ud2a as well as the loop.

How far back was __builtin_trap() supported?

	-hpa
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