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Date:   Wed, 13 Oct 2021 12:00:38 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Sami Tolvanen <samitolvanen@google.com>
Cc:     x86@kernel.org, Josh Poimboeuf <jpoimboe@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev
Subject: Re: [PATCH v5 03/15] linkage: Add DECLARE_NOT_CALLED_FROM_C
Message-ID: <202110131200.1CAF319F@keescook>
References: <20211013181658.1020262-1-samitolvanen@google.com>
 <20211013181658.1020262-4-samitolvanen@google.com>
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On Wed, Oct 13, 2021 at 11:16:46AM -0700, Sami Tolvanen wrote:
> The kernel has several assembly functions, which are not directly
> callable from C but need to be referred to from C code. This change adds
> the DECLARE_NOT_CALLED_FROM_C macro, which allows us to declare these
> symbols using an opaque type, which makes misuse harder, and avoids the
> need to annotate references to the functions for Clang's Control-Flow
> Integrity (CFI).
> 
> Suggested-by: Andy Lutomirski <luto@amacapital.net>
> Suggested-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

I like this; I have a sense CFI won't stay the only user of this
annotation.

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

-- 
Kees Cook