linux-kernel - Re: [PATCH v5 0/6] x86: Refactor and consolidate startup code

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Message-ID: <CAMj1kXEALOpMggoxx6wVTdpTR14krSSrxFKoOKWAfh15x9z4CQ@mail.gmail.com>
Date: Tue, 22 Apr 2025 23:09:19 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org, x86@...nel.org, 
	Tom Lendacky <thomas.lendacky@....com>, Dionna Amalie Glaze <dionnaglaze@...gle.com>, 
	Kevin Loughlin <kevinloughlin@...gle.com>
Subject: Re: [PATCH v5 0/6] x86: Refactor and consolidate startup code

On Tue, 22 Apr 2025 at 21:55, Ingo Molnar <mingo@...nel.org> wrote:
>
>
> * Ard Biesheuvel <ardb+git@...gle.com> wrote:
>
> >  10 files changed, 1757 insertions(+), 1724 deletions(-)
>
> So I think this is a new build warning/failure (config attached),
> from objtool:
>
>   arch/x86/boot/startup/sev-startup.o: warning: objtool: vc_check_opcode_bytes+0x53: can't find switch jump table
>
> Note that it's a randconfig.
>
> No such warning triggers on:
>
>   a1b582a3ff61 Merge branch 'x86/urgent' into x86/boot, to merge dependent commit and upstream fixes
>
> which is the base of the commits:
>
>   ff4c0560ab02 x86/asm: Retire RIP_REL_REF()
>   681e2901330c x86/boot: Drop RIP_REL_REF() uses from early SEV code
>   a3cbbb4717e1 x86/boot: Move SEV startup code into startup/
>   234cf67fc3bd x86/sev: Split off startup code from core code
>   b66fcee1574e x86/sev: Move noinstr NMI handling code into separate source file
>   092071e0f63c vmlinux.lds: Include .data.rel[.local] into .data section
>   a1b582a3ff61 Merge branch 'x86/urgent' into x86/boot, to merge dependent commit and upstream fixes
>
> Unsurprisingly:
>
>   starship:~/tip> git bisect bad
>
>   a3cbbb4717e120f9e53fa7685909b310f7e99bf5 is the first bad commit
>   commit a3cbbb4717e120f9e53fa7685909b310f7e99bf5 (HEAD)
>   Author: Ard Biesheuvel <ardb@...nel.org>
>   Date:   Fri Apr 18 16:12:58 2025 +0200
>
>     x86/boot: Move SEV startup code into startup/
>

Yeah, my bad - I forgot to disable jump tables, which objtool doesn't
handle well to begin with, but this is much more difficult for jump
tables emitted under -fPIC

I've sent a patch to disable them.