linux-kernel - Re: [PATCH v3 09/16] x86: Use an opaque type for functions not callable from C

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Message-ID: <202109141233.01761C8@keescook>
Date:   Tue, 14 Sep 2021 12:33:33 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     x86@...nel.org, Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH v3 09/16] x86: Use an opaque type for functions not
 callable from C

On Tue, Sep 14, 2021 at 12:10:38PM -0700, Sami Tolvanen wrote:
> The kernel has several assembly functions that are not directly callable
> from C. Use an opaque type for these function prototypes to make misuse
> harder, and to avoid the need to annotate references to these functions
> for Clang's Control-Flow Integrity (CFI).
> 
> Suggested-by: Andy Lutomirski <luto@...capital.net>
> Suggested-by: Alexander Lobakin <alobakin@...me>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

This looks clean to me.

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

-- 
Kees Cook