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Date:   Sat, 14 May 2022 14:56:50 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Sami Tolvanen <samitolvanen@google.com>
Cc:     linux-kernel@vger.kernel.org, Josh Poimboeuf <jpoimboe@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>, x86@kernel.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Joao Moreira <joao@overdrivepizza.com>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-hardening@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev
Subject: Re: [RFC PATCH v2 15/21] objtool: Don't warn about __cfi_ preambles
 falling through
Message-ID: <202205141456.72950C77B@keescook>
References: <20220513202159.1550547-1-samitolvanen@google.com>
 <20220513202159.1550547-16-samitolvanen@google.com>
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On Fri, May 13, 2022 at 01:21:53PM -0700, Sami Tolvanen wrote:
> The __cfi_ preambles contain valid instructions, which embed KCFI
> type information in the following format:
> 
>   __cfi_function:
>     int3
>     int3
>     mov <id>, %eax
>     int3
>     int3
>   function:
>     ...
> 
> While the preambles are STT_FUNC and contain valid instructions,
> they are not executed and always fall through. Skip the warning for
> them.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

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

-- 
Kees Cook