linux-kernel - Re: gas 2.16 and assembly macros -- entry

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Date:	Fri, 01 Oct 2010 16:46:51 +0100
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>, <heukelum@...tmail.fm>,
	<tglx@...utronix.de>, <akpm@...ux-foundation.org>,
	"LKML" <linux-kernel@...r.kernel.org>
Subject: Re: gas 2.16 and assembly macros -- entry_64.S build failure

>>> On 01.10.10 at 17:21, "H. Peter Anvin" <hpa@...or.com> wrote:
> On 10/01/2010 01:27 AM, Jan Beulich wrote:
>>>>> On 01.10.10 at 02:26, "H. Peter Anvin" <hpa@...or.com> wrote:
>>> ... but that doesn't work with the macros like movq_cfi.  On those, we
>> 
>> Is that only because of the register names used as operands to
>> movq_cfi etc not having the % specified right away? I don't think
>> that is really needed, i.e. the % could go there rather than being
>> added in the macro body - the .cfi_* directives are perfectly happy
>> with having the prefix there (and I don't know why it was coded
>> this way in the first place, as this made it less similar to the plain
>> movq while I thought the goal was to keep the differences to a
>> minimum).
>> 
> 
> No, and in fact the problem that spurred this discussion was in the use
> of immediates, not registers:
> 
> 	pushq_cfi $(USER_DS)
> 
> Obviously we can't add the % register prefix, since pushq can take
> either a register or an immediate (or, for that matter, a memory operand).

Perhaps a misunderstanding? I meant to move the % back into
movq_cfi's arguments, out of the macro body. pushq_cfi already
is in the shape we need for having the option of using cpp macros
when !CONFIG_AS_CFI.

>> The other alternative, albeit disliked by Ingo, continues to be to use
>> __stringify() on all non-trivial operands, which then wouldn't require
>> suppressing CONFIG_AS_CFI for pre-2.17 binutils.
> 
> You should be taken out and shot for even thinking that, never mind
> putting it in writing...

Thank you!

Jan

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