linux-kernel - Re: [PATCH v2 09/39] x86/ibt,paravirt: Sprinkle ENDBR

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Date:   Thu, 24 Feb 2022 16:47:35 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, joao@...rdrivepizza.com, hjl.tools@...il.com,
        jpoimboe@...hat.com, andrew.cooper3@...rix.com,
        linux-kernel@...r.kernel.org, ndesaulniers@...gle.com,
        samitolvanen@...gle.com, mark.rutland@....com,
        alyssa.milburn@...el.com, mbenes@...e.cz, rostedt@...dmis.org,
        mhiramat@...nel.org, alexei.starovoitov@...il.com
Subject: Re: [PATCH v2 09/39] x86/ibt,paravirt: Sprinkle ENDBR

On Thu, Feb 24, 2022 at 03:51:47PM +0100, Peter Zijlstra wrote:
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/x86/entry/entry_64.S                 |    1 +
>  arch/x86/include/asm/paravirt.h           |    1 +
>  arch/x86/include/asm/qspinlock_paravirt.h |    3 +++
>  arch/x86/kernel/kvm.c                     |    3 ++-
>  arch/x86/kernel/paravirt.c                |    2 ++
>  5 files changed, 9 insertions(+), 1 deletion(-)
> 
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -635,6 +635,7 @@ SYM_INNER_LABEL(restore_regs_and_return_
>  
>  SYM_INNER_LABEL_ALIGN(native_iret, SYM_L_GLOBAL)
>  	UNWIND_HINT_IRET_REGS
> +	ENDBR // paravirt_iret

If this is also setting the stage for finer grain CFI schemes, should
these macros instead be something more generically named? Like,
INDIRECT_ENTRY, or so? I imagine that'd avoid future churn, but maybe
I'm pre-optimizing... Regardless:

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

-- 
Kees Cook