linux-kernel - Re: [PATCH 2/3] x86: Use -mindirect-branch-cs-prefix for RETPOLINE builds

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Message-ID: <202111190910.73331E48D@keescook>
Date:   Fri, 19 Nov 2021 09:10:48 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, hjl.tools@...il.com,
        andrew.cooper3@...rix.com, mark.rutland@....com, will@...nel.org,
        ndesaulniers@...gle.com
Subject: Re: [PATCH 2/3] x86: Use -mindirect-branch-cs-prefix for RETPOLINE
 builds

On Fri, Nov 19, 2021 at 05:50:25PM +0100, Peter Zijlstra wrote:
> In order to further enable commit:
> 
>   bbe2df3f6b6d ("x86/alternative: Try inline spectre_v2=retpoline,amd")
> 
> add the new GCC flag -mindirect-branch-cs-prefix:
> 
>   https://gcc.gnu.org/g:2196a681d7810ad8b227bf983f38ba716620545e
>   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102952
>   https://bugs.llvm.org/show_bug.cgi?id=52323
> 
> to RETPOLINE=y builds. This should allow fully inlining retpoline,amd
> for GCC builds.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook