linux-kernel - Re: [PATCH 0/3] Ensure default return thunk isn't used at runtime

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Message-ID: <20231010175207.GH14330@noisy.programming.kicks-ass.net>
Date:   Tue, 10 Oct 2023 19:52:07 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     David Kaplan <david.kaplan@....com>
Cc:     x86@...nel.org, luto@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] Ensure default return thunk isn't used at runtime

On Tue, Oct 10, 2023 at 12:10:17PM -0500, David Kaplan wrote:

> David Kaplan (3):
>   Revert "x86/retpoline: Remove .text..__x86.return_thunk section"
>   x86/vdso: Run objtool on vdso32-setup
>   x86/retpoline: Ensure default return thunk isn't used at runtime
> 
>  arch/x86/entry/vdso/Makefile  |  3 ++-
>  arch/x86/kernel/vmlinux.lds.S |  3 +++
>  arch/x86/lib/retpoline.S      | 10 +++++++---
>  3 files changed, 12 insertions(+), 4 deletions(-)

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

That said, I'm afraid we might have broken rethunk for i386 somewhere
along the SRSO series.

I suspect the easiest fix is to make CONFIG_RETHUNK hard depend on
x86_64 or something.