From: Marco Elver <elver@google.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kees Cook <keescook@chromium.org>,
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>, 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,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH 2/2] Kconfig: CC_HAS_NO_PROFILE_FN_ATTR, depend on for GCOV and PGO
Date: Sat, 19 Jun 2021 08:23:23 +0200 [thread overview]
Message-ID: <CANpmjNNK-iYXucjz7Degh1kJPF_Z_=8+2vNLtUW17x0UnfgtPg@mail.gmail.com> (raw)
In-Reply-To: <20210618233023.1360185-3-ndesaulniers@google.com>
On Sat, 19 Jun 2021 at 01:30, Nick Desaulniers <ndesaulniers@google.com> wrote:
>
> We don't want compiler instrumentation to touch noinstr functions, which
> are annotated with the no_profile function attribute. Add a Kconfig test
> for this and make PGO and GCOV depend on it.
>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
> Link: https://lore.kernel.org/lkml/YMTn9yjuemKFLbws@hirez.programming.kicks-ass.net/
> Link: https://lore.kernel.org/lkml/YMcssV%2Fn5IBGv4f0@hirez.programming.kicks-ass.net/
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
> init/Kconfig | 3 +++
> kernel/gcov/Kconfig | 1 +
> kernel/pgo/Kconfig | 3 ++-
> 3 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/init/Kconfig b/init/Kconfig
> index 1ea12c64e4c9..540f862b40c6 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -83,6 +83,9 @@ config TOOLS_SUPPORT_RELR
> config CC_HAS_ASM_INLINE
> def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
>
> +config CC_HAS_NO_PROFILE_FN_ATTR
> + def_bool $(success,echo '__attribute__((no_profile)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
> +
> config CONSTRUCTORS
> bool
>
> diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig
> index 58f87a3092f3..19facd4289cd 100644
> --- a/kernel/gcov/Kconfig
> +++ b/kernel/gcov/Kconfig
> @@ -5,6 +5,7 @@ config GCOV_KERNEL
> bool "Enable gcov-based kernel profiling"
> depends on DEBUG_FS
> depends on !CC_IS_CLANG || CLANG_VERSION >= 110000
> + depends on !X86 || (X86 && CC_HAS_NO_PROFILE_FN_ATTR)
[+Cc Mark]
arm64 is also starting to rely on noinstr working properly.
This should probably be a 'select ARCH_HAS_GCOV_PROFILE_ALL if
CC_HAS_NO_PROFILE_FN_ATTR' in the relevant arch/../Kconfig.
Alternatively, using:
https://lkml.kernel.org/r/YMcssV/n5IBGv4f0@hirez.programming.kicks-ass.net
But I'd probably not overcomplicate things at this point and just use
ARCH_HAS_GCOV_PROFILE_ALL, because GCOV seems to be a) rarely used,
and b) if someone decides to selectively instrument stuff like entry
code, we can just say it's user error.
> select CONSTRUCTORS
> default n
> help
> diff --git a/kernel/pgo/Kconfig b/kernel/pgo/Kconfig
> index d2053df1111c..26f75ac4c6c1 100644
> --- a/kernel/pgo/Kconfig
> +++ b/kernel/pgo/Kconfig
> @@ -8,7 +8,8 @@ config PGO_CLANG
> bool "Enable clang's PGO-based kernel profiling"
> depends on DEBUG_FS
> depends on ARCH_SUPPORTS_PGO_CLANG
> - depends on CC_IS_CLANG && CLANG_VERSION >= 120000
> + depends on CC_IS_CLANG
> + depends on CC_HAS_NO_PROFILE_FN_ATTR
> help
> This option enables clang's PGO (Profile Guided Optimization) based
> code profiling to better optimize the kernel.
> --
> 2.32.0.288.g62a8d224e6-goog
>
next prev parent reply other threads:[~2021-06-19 6:23 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-18 23:30 [PATCH 0/2] no_profile fn attr and Kconfig for GCOV+PGO Nick Desaulniers
2021-06-18 23:30 ` [PATCH 1/2] compiler_attributes.h: define __no_profile, add to noinstr Nick Desaulniers
2021-06-19 11:26 ` Miguel Ojeda
2021-06-19 11:32 ` Miguel Ojeda
2021-06-21 18:10 ` Nick Desaulniers
2021-06-21 18:24 ` Fangrui Song
2021-06-21 19:09 ` Miguel Ojeda
2021-06-18 23:30 ` [PATCH 2/2] Kconfig: CC_HAS_NO_PROFILE_FN_ATTR, depend on for GCOV and PGO Nick Desaulniers
2021-06-19 6:23 ` Marco Elver [this message]
2021-06-21 18:22 ` Nick Desaulniers
2021-06-21 18:50 ` Bill Wendling
2021-06-21 20:43 ` Nick Desaulniers
2021-06-21 21:15 ` Nathan Chancellor
2021-06-22 9:25 ` Catalin Marinas
2021-06-22 9:29 ` Mark Rutland
2021-06-22 9:32 ` Catalin Marinas
2021-06-18 23:52 ` [PATCH 0/2] no_profile fn attr and Kconfig for GCOV+PGO Fangrui Song
2021-06-19 2:45 ` Kees Cook
2021-06-20 8:08 ` Bill Wendling
2021-06-20 14:53 ` Miguel Ojeda
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