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Date:   Fri, 18 Jun 2021 16:30:22 -0700
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Subject: [PATCH 1/2] compiler_attributes.h: define __no_profile, add to noinstr
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,
        Nick Desaulniers <ndesaulniers@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

noinstr implies that we would like the compiler to avoid instrumenting a
function.  Add support for the compiler attribute no_profile to
compiler_attributes.h, then add __no_profile to the definition of
noinstr.

Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Link: https://lore.kernel.org/lkml/20210614162018.GD68749@worktop.programming.kicks-ass.net/
Link: https://reviews.llvm.org/D104475
Link: https://reviews.llvm.org/D104257
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80223
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 include/linux/compiler_attributes.h | 12 ++++++++++++
 include/linux/compiler_types.h      |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index c043b8d2b17b..cf584a1908b3 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -33,6 +33,7 @@
 # define __GCC4_has_attribute___externally_visible__  1
 # define __GCC4_has_attribute___no_caller_saved_registers__ 0
 # define __GCC4_has_attribute___noclone__             1
+# define __GCC4_has_attribute___no_profile            0
 # define __GCC4_has_attribute___nonstring__           0
 # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
 # define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
@@ -237,6 +238,17 @@
 # define __nonstring
 #endif
 
+/*
+ * Optional: only supported since clang >= 13
+ *      gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80223
+ *    clang: https://clang.llvm.org/docs/AttributeReference.html#no_profile
+ */
+#if __has_attribute(__no_profile__)
+# define __no_profile                  __attribute__((__no_profile__))
+#else
+# define __no_profile
+#endif
+
 /*
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
  * clang: https://clang.llvm.org/docs/AttributeReference.html#noreturn
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index d29bda7f6ebd..d509169860f1 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -210,7 +210,7 @@ struct ftrace_likely_data {
 /* Section for code which can't be instrumented at all */
 #define noinstr								\
 	noinline notrace __attribute((__section__(".noinstr.text")))	\
-	__no_kcsan __no_sanitize_address
+	__no_kcsan __no_sanitize_address __no_profile
 
 #endif /* __KERNEL__ */
 
-- 
2.32.0.288.g62a8d224e6-goog