linux-kernel - Re: [PATCH v10 02/15] x86/asm: Introduce inline memcpy and memset

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Message-ID: <714268c1-b78e-4096-a40b-b9c3861d4446@intel.com>
Date: Tue, 21 Oct 2025 11:06:03 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: Borislav Petkov <bp@...en8.de>
CC: <x86@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, "Thomas
 Gleixner" <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "Jonathan
 Corbet" <corbet@....net>, "H . Peter Anvin" <hpa@...or.com>, Andy Lutomirski
	<luto@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>, Peter Zijlstra
	<peterz@...radead.org>, Ard Biesheuvel <ardb@...nel.org>, "Kirill A .
 Shutemov" <kas@...nel.org>, Xin Li <xin@...or.com>, David Woodhouse
	<dwmw@...zon.co.uk>, Sean Christopherson <seanjc@...gle.com>, Rick Edgecombe
	<rick.p.edgecombe@...el.com>, Vegard Nossum <vegard.nossum@...cle.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>, David Laight
	<david.laight.linux@...il.com>, Randy Dunlap <rdunlap@...radead.org>, "Geert
 Uytterhoeven" <geert@...ux-m68k.org>, Kees Cook <kees@...nel.org>, Tony Luck
	<tony.luck@...el.com>, Alexander Shishkin
	<alexander.shishkin@...ux.intel.com>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-efi@...r.kernel.org>
Subject: Re: [PATCH v10 02/15] x86/asm: Introduce inline memcpy and memset

On 10/21/2025 5:47 AM, Borislav Petkov wrote:
> On Mon, Oct 06, 2025 at 11:51:06PM -0700, Sohil Mehta wrote:
>> From: "Peter Zijlstra (Intel)" <peterz@...radead.org>
>>
>> Provide inline memcpy and memset functions that can be used instead of
>> the GCC builtins when necessary. The immediate use case is for the text
>> poking functions to avoid the standard memcpy()/memset() calls within an
>> RFLAGS.AC=1 context.
> 
> ... because objtool does not allow function calls with AC=1 because... see
> objtool/Documentation/objtool.txt, warning type 9, yadda yadda...
> 

Sure, will add some notes here as well as in the next patch where it is
used.