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Date:   Thu, 26 May 2022 08:04:07 -0700
From:   Josh Poimboeuf <jpoimboe@kernel.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     x86@kernel.org, jpoimboe@redhat.com, linux-kernel@vger.kernel.org,
        elver@google.com, jbaron@akamai.com, rostedt@goodmis.org,
        ardb@kernel.org, mark.rutland@arm.com
Subject: Re: [PATCH 1/7] x86/entry: Anchor annotation
Message-ID: <20220526150407.bsagwksr5osgde62@treble>
References: <20220526105252.440440893@infradead.org>
 <20220526105957.754830839@infradead.org>
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On Thu, May 26, 2022 at 12:52:53PM +0200, Peter Zijlstra wrote:
> x86_64-allmodconfig gives:
> 
>   vmlinux.o: warning: objtool: entry_SYSCALL_compat+0x0: ANNOTATE_NOENDBR on ENDBR
> 
> This is due to:
> 
> 	ANNOTATE_NOENDBR
> SYM_CODE_END(entry_SYSENTER_compat)
> SYM_CODE_START(entry_SYSCALL_compat)
> 	UNWIND_HINT_EMPTY
> 	ENDBR
> 
> And the hint then landing on the first instruction of the next symbol,
> which happens to be ENDBR. Stick in an int3 to anchor the annotation
> in the previous symbol.
> 
> Fixes: 3e3f06950434 ("x86/ibt: Annotate text references")
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
>  arch/x86/entry/entry_64_compat.S |    1 +
>  1 file changed, 1 insertion(+)
> 
> --- a/arch/x86/entry/entry_64_compat.S
> +++ b/arch/x86/entry/entry_64_compat.S
> @@ -124,6 +124,7 @@ SYM_INNER_LABEL(entry_SYSENTER_compat_af
>  	jmp	.Lsysenter_flags_fixed
>  SYM_INNER_LABEL(__end_entry_SYSENTER_compat, SYM_L_GLOBAL)
>  	ANNOTATE_NOENDBR // is_sysenter_singlestep
> +	int3
>  SYM_CODE_END(entry_SYSENTER_compat)

Hm, I get the feeling this warning is pretty much useless anyway.  Can
we just get rid of the warning instead?

-- 
Josh