linux-kernel - RE: x86/boot: Avoid using Intel mnemonics in AT&T syntax asm

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Message-ID: <23d1f8db268d43afa332517779b0ef95@AcuMS.aculab.com>
Date:   Tue, 10 Jan 2023 14:01:50 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Borislav Petkov' <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>
CC:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: x86/boot: Avoid using Intel mnemonics in AT&T syntax asm

From: Borislav Petkov
> Sent: 10 January 2023 11:37
> 
> On Tue, Jan 10, 2023 at 12:15:40PM +0100, Peter Zijlstra wrote:
> >
> > With 'GNU assembler (GNU Binutils for Debian) 2.39.90.20221231' the
> > build now reports:
> >
> >   arch/x86/realmode/rm/../../boot/bioscall.S: Assembler messages:
> >   arch/x86/realmode/rm/../../boot/bioscall.S:35: Warning: found `movsd'; assuming `movsl' was meant
> >   arch/x86/realmode/rm/../../boot/bioscall.S:70: Warning: found `movsd'; assuming `movsl' was meant
> >
> >   arch/x86/boot/bioscall.S: Assembler messages:
> >   arch/x86/boot/bioscall.S:35: Warning: found `movsd'; assuming `movsl' was meant
> >   arch/x86/boot/bioscall.S:70: Warning: found `movsd'; assuming `movsl' was meant
> >
> > Which is due to:
> >
> >   PR gas/29525
> >
> >   Note that with the dropped CMPSD and MOVSD Intel Syntax string insn
> >   templates taking operands, mixed IsString/non-IsString template groups
> >   (with memory operands) cannot occur anymore. With that
> >   maybe_adjust_templates() becomes unnecessary (and is hence being
> >   removed).
> >
> > More details: https://sourceware.org/bugzilla/show_bug.cgi?id=29525
> 
> Right, I'm being told the particular problem here is is that the 'd' suffix is
> "conflicting" in the sense that you can have SSE mnemonics like movsD %xmm...
> and the same thing also for string ops (which is the case here) so apparently
> the agreement in binutils land is to use the always accepted suffixes 'l' or 'q'
> and phase out 'd' slowly...
> 
> Which is basically what the PR text says above but more understanable. :-)
> 
> Might wanna add that to the commit message.

Can they be changed to movsq ?
movsl has an implied 32bitness about it.

	David

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