linux-kernel - Re: [RFC PATCH] ARM: Use generic BUG() handler

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Date:	Tue, 1 Mar 2011 10:12:40 +0100
From:	Mikael Pettersson <mikpe@...uu.se>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Simon Glass <sjg@...omium.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Phil Carmody <ext-phil.2.carmody@...ia.com>,
	Tony Lindgren <tony@...mide.com>,
	Catalin Marinas <catalin.marinas@....com>,
	linux-kernel@...r.kernel.org, Rabin Vincent <rabin@....in>,
	Alexander Shishkin <virtuoso@...nd.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Joe Perches <joe@...ches.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH] ARM: Use generic BUG() handler

Russell King - ARM Linux writes:
 > On Tue, Mar 01, 2011 at 08:49:49AM +0000, Russell King - ARM Linux wrote:
 > > On Mon, Feb 28, 2011 at 04:27:43PM -0800, Simon Glass wrote:
 > > > +	asm volatile("1:\t.word %c3\n"				\
 > > > +		     ".pushsection __bug_table,\"a\"\n"		\
 > > > +		     "2:\t.word 1b, %c0\n"			\
 > > > +		     "\t.hword %c1, 0\n"			\
 > > > +		     "\t.org 2b+%c2\n"				\
 > > 
 > > %c doesn't work on lots of versions of gcc, which is why we can't use
 > > the generic bug support.  There's no way to reliably generate constants
 > > without many compiler versions spitting out a '#' before them.
 > 
 > gcc 4.3.2:
 > 
 > asm(".word %c0" : : "i" (0));
 > 
 > produces:
 > 
 >         .word #0
 > 
 > which gas chokes on:
 > 
 > /tmp/cc2hGOHd.s:12: Error: bad expression
 > /tmp/cc2hGOHd.s:12: Error: junk at end of line, first unrecognized character is `0'
 > 
 > So what this means is that it's impossible to generate constants in
 > assembly with GCC targetting ARM without having them prefixed by '#',
 > which in turn makes it impossible to use the generic BUG support.
 > 
 > I reported this bug to gcc folk many years ago.  I've no idea which
 > version it has been fixed in or if it's even been fixed.

What's the gcc bugzilla bug number?
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