linux-hardening - Re: [PATCH v6 3/4] Compiler Attributes: Add __diagnose

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Message-ID: <CAKwvOdm7LUUotbk+mQbzXR6=UC+oEBNtq_mQbCUt0arqAbw43Q@mail.gmail.com>
Date:   Thu, 3 Feb 2022 12:28:41 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>, llvm@...ts.linux.dev,
        George Burgess IV <gbiv@...gle.com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v6 3/4] Compiler Attributes: Add __diagnose_as for Clang

On Thu, Feb 3, 2022 at 9:33 AM Kees Cook <keescook@...omium.org> wrote:
>
> Clang will perform various compile-time diagnostics on uses of various
> functions (e.g. simple bounds-checking on strcpy(), etc). These
> diagnostics can be assigned to other functions (for example, new
> implementations of the string functions under CONFIG_FORTIFY_SOURCE)
> using the "diagnose_as_builtin" attribute. This allows those functions
> to retain their compile-time diagnostic warnings.
>
> Cc: Miguel Ojeda <ojeda@...nel.org>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Cc: Nathan Chancellor <nathan@...nel.org>
> Cc: llvm@...ts.linux.dev
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>  include/linux/compiler_attributes.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
> index dc3bf2a6e1c9..df9c7e5e8818 100644
> --- a/include/linux/compiler_attributes.h
> +++ b/include/linux/compiler_attributes.h
> @@ -100,6 +100,19 @@
>  # define __copy(symbol)
>  #endif
>
> +/*
> + * Optional: not supported by gcc
> + * Optional: only supported since clang >= 14.0
> + * Optional: not supported by icc
> + *
> + * clang: https://clang.llvm.org/docs/AttributeReference.html#diagnose_as_builtin
> + */
> +#if __has_attribute(__diagnose_as_builtin__)
> +# define __diagnose_as(builtin...)     __attribute__((__diagnose_as_builtin__(builtin)))
> +#else
> +# define __diagnose_as(builtin...)
> +#endif
> +
>  /*
>   * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
>   * attribute warnings entirely and for good") for more information.
> --
> 2.30.2
>


-- 
Thanks,
~Nick Desaulniers