linux-kernel - Re: [PATCH] Partially revert patch that encloses asm-offset.h numbers in brackets

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Date:	Mon, 25 Oct 2010 16:43:03 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jan Beulich <JBeulich@...ell.com>
Cc:	akpm@...ux-foundation.org, torvalds@...l.org,
	David Howells <dhowells@...hat.com>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	"H. Peter Anvin" <hpa@...ux.intel.com>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Partially revert patch that encloses asm-offset.h
 numbers in brackets


* Jan Beulich <JBeulich@...ell.com> wrote:

> >>> On 25.10.10 at 16:02, David Howells <dhowells@...hat.com> wrote:
> > Partially revert patch:
> > 
> > 	commit 3234282f33b29d349bcada40204fc7c8fda7fe72
> > 	Author: Jan Beulich <JBeulich@...ell.com>
> > 	Date:   Tue Oct 19 14:52:26 2010 +0100
> > 	x86, asm: Fix CFI macro invocations to deal with shortcomings in gas
> 
> No, that's not going to work for x86. You're removing the parentheses again, which 
> were added intentionally.

But that's not a valid argument - MN10300 worked before and we broke it => that's a 
regression.

> > This breaks MN10300 arch as this changes many instances of instructions similar 
> > to the following:
> > 
> > 	MOV	number,D0
> > 
> > which represents an immediate value load into:
> > 
> > 	MOV	(number),D0
> > 
> > which the assembler then interprets as a load from absolute address.
> > 
> > arch/mn10300/kernel/entry.S:64: Error: Invalid opcode/operands
> > arch/mn10300/kernel/entry.S:65: Error: junk at end of line, first 
> > unrecognized character is `0'
> > arch/mn10300/kernel/entry.S:74: Error: Invalid opcode/operands
> > arch/mn10300/kernel/entry.S:74: Error: junk at end of line, first 
> > unrecognized character is `1'
> > arch/mn10300/kernel/entry.S:75: Error: Invalid opcode/operands
> > arch/mn10300/kernel/entry.S:76: Error: junk at end of line, first 
> > unrecognized character is `0'
> 
> Isn't this a gas bug then? Anywhere you use a plain number you should also be 
> permitted to use an expression.

This argument is not valid either - we added this change to fix a GAS bug to begin 
with ...

> >  	"/^->/{s:->#\(.*\):/* \1 */:; \
> > -	s:^->\([^ ]*\) [\$$#]*\([-0-9]*\) \(.*\):#define \1 (\2) /* \3 */:; \
> > +	s:^->\([^ ]*\) [\$$#]*\([-0-9]*\) \(.*\):#define \1 \2 /* \3 */:; \
> 
> This basically gets us back to the way things were before, thus
> reverting to the state we had before the patch that changed this.

Correct - we should apply David's partial revert and then we'll need to solve our 
x86 quirk differently: for example by using a x86 and broken-GAS specific quirk.

Thanks,

	Ingo
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