linux-kernel - Re: [PATCH 02/17] x86, lto: Mark all top level asm statements as .text

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Date:   Wed, 27 Mar 2019 23:50:37 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andi Kleen <ak@...ux.intel.com>
cc:     Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH 02/17] x86, lto: Mark all top level asm statements as
 .text

On Wed, 27 Mar 2019, Andi Kleen wrote:

> > > I checked the code general and with the .globl in NATIVE_LABEL the
> > 
> > With or without? I removed that as well.
> 
> With.
> 
> LTO would still need the .globls because the variable and the asm
> statement can end up in different assembler files, and resolution
> would rely on the linker.

This really sucks. As this is a constant source of trouble, we might better
bite the bullet and get rid of this fancy macro completely. It's not that
we add these patch patterns every other day.

So a good old:

/* xor %eax %ex */
static const unsigend char patch_qspinlock[] = { 0x31, 0xc0 };

and then in the patch code:

	return paravirt_patch_insns(ibuf, len, patch_qspinlock,
    	   			    patch_qspinlock + ARRAY_SIZE(patch_qspinlock));

might be less trouble than dealing with that clever inline assembly
forever.

Thanks,

	tglx