linux-kernel - Re: [PATCH v6 06/15] x86/module: Deal with GOT based stack cookie load on Clang

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Message-ID: <CAMzpN2i7-=2BU=4_SY_hxPHU+n5MMGRwS7BzApy-TGoeWTZHog@mail.gmail.com>
Date: Tue, 18 Feb 2025 09:05:37 -0500
From: Brian Gerst <brgerst@...il.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, 
	"H . Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, 
	Ard Biesheuvel <ardb@...nel.org>, Uros Bizjak <ubizjak@...il.com>
Subject: Re: [PATCH v6 06/15] x86/module: Deal with GOT based stack cookie
 load on Clang < 17

On Tue, Feb 18, 2025 at 4:07 AM Ingo Molnar <mingo@...nel.org> wrote:
>
>
> * Brian Gerst <brgerst@...il.com> wrote:
>
> >  #define R_X86_64_GOTPCREL    9       /* 32 bit signed pc relative
> > -                                        offset to GOT */
> > +#define R_X86_64_GOTPCRELX   41         offset to GOT */
>                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > +#define R_X86_64_REX_GOTPCRELX       42
>
> Uhm, I'm pretty sure this won't even build, should any code use
> R_X86_64_GOTPCRELX - which it doesn't currently...
>
> Also, each entry here has a comment explaining it - except these two
> new GOTPCREL variants.

Should we remove the non-REX version that isn't used by the kernel?
This header is not exported to userspace.


Brian Gerst