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From:   Sami Tolvanen <samitolvanen@google.com>
Date:   Mon, 4 Apr 2022 12:40:46 -0700
Message-ID: <CABCJKudaQJ0_e290gD+rG8SwEembd33ua1MG-w2OKRq3es8Kjw@mail.gmail.com>
Subject: Re: [PATCH 1/3] kbuild: Change CFI_CLANG to depend on __builtin_function_start
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     Kees Cook <keescook@chromium.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Will Deacon <will@kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        llvm@lists.linux.dev
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On Sat, Apr 2, 2022 at 6:32 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Sat, Apr 2, 2022 at 5:19 AM Sami Tolvanen <samitolvanen@google.com> wrote:
> >
> > Clang 14 added support for the __builtin_function_start()
> > built-in function, which allows us to implement function_nocfi()
> > without architecture-specific inline assembly. This patch changes
> > CONFIG_CFI_CLANG to depend on the built-in and effectively upgrades
> > the minimum supported compiler version for CFI to Clang 14.
>
> From this description, I think the straight-forward change would be:
>
>     depends on CLANG_VERSION >= 120000
> -->
>     depends on CLANG_VERSION >= 140000
>
> Any reason to avoid this?

I thought testing for the compiler feature was preferred, but I can
certainly just increase the minimum version number here too.

Sami