linux-kernel - Re: [tip: x86/asm] x86/asm: Make ASM_CALL_CONSTRAINT conditional on frame pointers

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Message-ID: <20250307232157.comm4lycebr7zmre@jpoimboe>
Date: Fri, 7 Mar 2025 15:21:57 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	tip-bot2 for Josh Poimboeuf <tip-bot2@...utronix.de>,
	linux-tip-commits@...r.kernel.org,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Brian Gerst <brgerst@...il.com>, x86@...nel.org
Subject: Re: [tip: x86/asm] x86/asm: Make ASM_CALL_CONSTRAINT conditional on
 frame pointers

On Sat, Mar 08, 2025 at 12:05:29AM +0100, Ingo Molnar wrote:
> 
> * H. Peter Anvin <hpa@...or.com> wrote:
> 
> > > #endif /* __ASSEMBLY__ */
> > 
> > So we are going to be using this version despite the gcc maintainers 
> > telling us it is not supported?
> 
> No, neither patches are in the x86 tree at the moment.

FWIW, the existing ASM_CALL_CONSTRAINT is also not supported, so this
patch wouldn't have changed anything in that respect.

Regardless I plan to post a new patch set soon with a bunch of cleanups.

It will keep the existing ASM_CALL_CONSTRAINT in place for GCC, and will
use the new __builtin_frame_address(0) input constraint for Clang only.

There will be a new asm_call() interface to hide the mess.

-- 
Josh