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From: Nick Desaulniers <ndesaulniers@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Bill Wendling <wcw@google.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	Peter Oberparleiter <oberpar@linux.ibm.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	Ard Biesheuvel <ardb@kernel.org>, Will Deacon <will@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
	x86@kernel.org, Borislav Petkov <bp@alien8.de>,
	Martin Liska <mliska@suse.cz>, Marco Elver <elver@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Fangrui Song <maskray@google.com>,
	linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org,
	Dmitry Vyukov <dvyukov@google.com>,
	johannes.berg@intel.com, linux-toolchains@vger.kernel.org,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	linux-s390@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Nick Desaulniers <ndesaulniers@google.com>
Subject: [PATCH v2 0/3] no_profile fn attr and Kconfig for GCOV+PGO
Date: Mon, 21 Jun 2021 16:18:19 -0700	[thread overview]
Message-ID: <20210621231822.2848305-1-ndesaulniers@google.com> (raw)

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+.

Add a new function annotation __no_profile that expands to
__attribute__((__no_profile_instrument_function__)) and Kconfig values
CC_HAS_NO_PROFILE_FN_ATTR and ARCH_WANTS_NO_INSTR. Make GCOV and PGO
depend on either !ARCH_WANTS_NO_INSTR or CC_HAS_NO_PROFILE_FN_ATTR.

Changes V1 -> V2:
* s/no_profile/no_profile_instrument_function/
* fix trailing double underscore on GCC 4 define, as per Fangrui+Miguel.
* Pick up Fangrui + Miguel's reviewed-by tag.
* Add link to GCC's doc.
* Fix clang's doc format; will appear once clang-13 is released.
* New cleanup patch 2/3. Orthogonal to the series, but while I'm here...

Base is
https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/log/?h=for-next/clang/pgo.

Nick Desaulniers (3):
  compiler_attributes.h: define __no_profile, add to noinstr
  compiler_attributes.h: cleanups for GCC 4.9+
  Kconfig: add ARCH_WANTS_NO_INSTR+CC_HAS_NO_PROFILE_FN_ATTR, depend on
    for GCOV and PGO

 arch/Kconfig                        |  7 +++++++
 arch/arm64/Kconfig                  |  1 +
 arch/s390/Kconfig                   |  1 +
 arch/x86/Kconfig                    |  1 +
 include/linux/compiler_attributes.h | 19 ++++++++++++++++---
 include/linux/compiler_types.h      |  2 +-
 init/Kconfig                        |  3 +++
 kernel/gcov/Kconfig                 |  1 +
 kernel/pgo/Kconfig                  |  3 ++-
 9 files changed, 33 insertions(+), 5 deletions(-)


base-commit: 4356bc4c0425c81e204f561acf4dd0095544a6cb
-- 
2.32.0.288.g62a8d224e6-goog


             reply	other threads:[~2021-06-21 23:18 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-21 23:18 Nick Desaulniers [this message]
2021-06-21 23:18 ` [PATCH v2 1/3] compiler_attributes.h: define __no_profile, add to noinstr Nick Desaulniers
2021-06-21 23:41   ` Nathan Chancellor
2021-06-21 23:18 ` [PATCH v2 2/3] compiler_attributes.h: cleanups for GCC 4.9+ Nick Desaulniers
2021-06-21 23:31   ` Miguel Ojeda
2021-06-21 23:42   ` Nathan Chancellor
2021-06-21 23:18 ` [PATCH v2 3/3] Kconfig: add ARCH_WANTS_NO_INSTR+CC_HAS_NO_PROFILE_FN_ATTR, depend on for GCOV and PGO Nick Desaulniers
2021-06-21 23:45   ` Nathan Chancellor
2021-06-22  7:25   ` Peter Zijlstra
2021-06-22  8:09     ` Marco Elver
2021-06-22  9:05   ` Mark Rutland
2021-06-22 11:10     ` Will Deacon
2021-06-22  9:33   ` Heiko Carstens
2021-06-22  9:35   ` Peter Oberparleiter
2021-06-22  7:25 ` [PATCH v2 0/3] no_profile fn attr and Kconfig for GCOV+PGO Peter Zijlstra
2021-06-22 18:19 ` Kees Cook
2021-06-23  6:15 ` Kees Cook
2021-06-24 19:36   ` Nick Desaulniers

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