linux-kernel - Re: [RFT PATCH v3 00/21] x86: strict separation of startup code

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Message-ID: <CAMj1kXHRgrmD41cNHnkBTMKfZjfRTm6uCx8XhGHZg6+iaY0x_w@mail.gmail.com>
Date: Tue, 13 May 2025 22:31:47 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Ingo Molnar <mingo@...nel.org>, Ard Biesheuvel <ardb+git@...gle.com>, linux-kernel@...r.kernel.org, 
	linux-efi@...r.kernel.org, x86@...nel.org, 
	Dionna Amalie Glaze <dionnaglaze@...gle.com>, Kevin Loughlin <kevinloughlin@...gle.com>, 
	Tom Lendacky <thomas.lendacky@....com>, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFT PATCH v3 00/21] x86: strict separation of startup code

On Tue, 13 May 2025 at 17:44, Borislav Petkov <bp@...en8.de> wrote:
>
...
> > I've done a preliminary pass upstream with RIP_REL_REF() and
> > rip_rel_ptr() and the use of the .head.text section for startup code
> > to ensure that we detect such issues at build time, and it has already
> > resulted in a number of true positives where the code in question
> > would have failed at boot time. At this point, I'm not aware of any
> > issues caused by absolute references going undetected.
> >
> > However, Linus kindly indicated that the resulting diagnostics
> > produced by the relocs tool do not meet his high standards, and so I
> > proposed another approach, which I am implementing now (see cover
> > letter for details). Note that this approach is also much more robust,
> > as annotating things as __head by hand to get it emitted into the
> > section to which the diagnostics are applied is obviously not
> > foolproof.
>
> AFAIR, this is what you've done for arm64 too, right?
>

The new approach proposed in this series is what I implemented before
for arm64, yes.