linux-kernel - Re: [PATCH 1/1] x86/elf: Add a new .note section containing Xfeatures information to x86 core files

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Message-ID: <20240314160824.GDZfMg-J1VOyjxIMiV@fat_crate.local>
Date: Thu, 14 Mar 2024 17:08:24 +0100
From: Borislav Petkov <bp@...en8.de>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Vignesh Balasubramanian <vigbalas@....com>,
	linux-kernel@...r.kernel.org, linux-toolchains@...r.kernel.org,
	mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
	aneesh.kumar@...nel.org, naveen.n.rao@...ux.ibm.com,
	ebiederm@...ssion.com, keescook@...omium.org, x86@...nel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-mm@...ck.org, bpetkov@....com,
	jinisusan.george@....com, matz@...e.de, binutils@...rceware.org,
	jhb@...ebsd.org, felix.willgerodt@...el.com
Subject: Re: [PATCH 1/1] x86/elf: Add a new .note section containing
 Xfeatures information to x86 core files

On Thu, Mar 14, 2024 at 08:37:09AM -0700, Dave Hansen wrote:
> This is pretty close to just a raw dump of the XSAVE CPUID leaves.
> Rather than come up with an XSAVE-specific ABI that depends on CPUID
> *ANYWAY* (because it dumps the "flags" register aka. ECX), maybe we
> should just bite the bullet and dump out (some of) the raw CPUID space.

Funny you should say that. This was what they had done originally but if
you dump CPUID and you want to add another component in the future which
is *not* described by CPUID, your scheme breaks.

So the idea is to have a self-describing buffers layout, independent
from any x86-ism. You can extend this in a straight-forward way then
later.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette