linux-kernel - Re: [PATCH v2 0/3] no_profile fn attr and Kconfig for GCOV+PGO

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Message-Id: <162442894704.2888450.8087873021886781652.b4-ty@chromium.org>
Date:   Tue, 22 Jun 2021 23:15:50 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-arm-kernel@...ts.infradead.org,
        Nathan Chancellor <nathan@...nel.org>,
        Fangrui Song <maskray@...gle.com>,
        linux-kbuild@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Borislav Petkov <bp@...en8.de>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Marco Elver <elver@...gle.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Bill Wendling <wcw@...gle.com>, Arnd Bergmann <arnd@...db.de>,
        johannes.berg@...el.com, clang-built-linux@...glegroups.com,
        Jonathan Corbet <corbet@....net>,
        Martin Liska <mliska@...e.cz>,
        linux-toolchains@...r.kernel.org, x86@...nel.org,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v2 0/3] no_profile fn attr and Kconfig for GCOV+PGO

On Mon, 21 Jun 2021 16:18:19 -0700, Nick Desaulniers wrote:
> The kernel has been using noinstr for correctness to politely request
> that the compiler avoid adding various forms of instrumentation to
> certain functions.
> 
> GCOV and PGO can both instrument functions, yet the function attribute
> to disable such instrumentation (no_profile_instrument_function) was not
> being used to suppress such implementation. Also, clang only just
> recently gained support for no_profile_instrument_function. GCC has
> supported that since 7.1+.
> 
> [...]

Applied to for-next/clang/features, thanks!

[1/3] compiler_attributes.h: define __no_profile, add to noinstr
      https://git.kernel.org/kees/c/380d53c45ff2
[2/3] compiler_attributes.h: cleanups for GCC 4.9+
      https://git.kernel.org/kees/c/ae4d682dfd33
[3/3] Kconfig: add ARCH_WANTS_NO_INSTR+CC_HAS_NO_PROFILE_FN_ATTR, depend on for GCOV and PGO
      https://git.kernel.org/kees/c/51c2ee6d121c

Note that I've tweaked the series slightly to move the PGO Kconfig change into
the PGO patch.

-- 
Kees Cook