linux-kernel - Re: [PATCH] x86/boot: Remove x86

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Date:   Tue, 29 Nov 2022 08:24:14 -0500
From:   Brian Gerst <brgerst@...il.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Uros Bizjak <ubizjak@...il.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86/boot: Remove x86_32 PIC using ebx workaround

On Tue, Nov 29, 2022 at 3:32 AM Borislav Petkov <bp@...en8.de> wrote:
>
> On Mon, Nov 28, 2022 at 10:41:11PM -0500, Brian Gerst wrote:
> > x86-64 uses a PIC register for the medium and large PIC code models,
> > where offsets can be larger than +/- 2GB.
>
> Right but 64-bit is built with -mcmodel=kernel which obviously generates
> rip-relative.

Correct.  He quoted the specific part of the GCC changelog that fixed
the issue for the 32-bit kernel, but it's not applicable to the 64-bit
kernel.  Perhaps the commit message should be more apparent that it's
quoting the GCC changelog verbatim, or better yet, reference the
specific commit or bug number instead of the general release notes.

--
Brian Gerst