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From: Marco Elver <elver@google.com>
To: elver@google.com
Cc: paulmck@kernel.org, dvyukov@google.com, glider@google.com,
	andreyknvl@google.com, kasan-dev@googlegroups.com,
	linux-kernel@vger.kernel.org, tglx@linutronix.de,
	mingo@kernel.org, peterz@infradead.org, will@kernel.org,
	clang-built-linux@googlegroups.com, bp@alien8.de
Subject: [PATCH -tip v2 05/11] kcsan: Remove 'noinline' from __no_kcsan_or_inline
Date: Thu, 21 May 2020 13:08:48 +0200	[thread overview]
Message-ID: <20200521110854.114437-6-elver@google.com> (raw)
In-Reply-To: <20200521110854.114437-1-elver@google.com>

Some compilers incorrectly inline small __no_kcsan functions, which then
results in instrumenting the accesses. For this reason, the 'noinline'
attribute was added to __no_kcsan_or_inline. All known versions of GCC
are affected by this. Supported version of Clang are unaffected, and
never inlines a no_sanitize function.

However, the attribute 'noinline' in __no_kcsan_or_inline causes
unexpected code generation in functions that are __no_kcsan and call a
__no_kcsan_or_inline function.

In certain situations it is expected that the __no_kcsan_or_inline
function is actually inlined by the __no_kcsan function, and *no* calls
are emitted. By removing the 'noinline' attribute we give the compiler
the ability to inline and generate the expected code in __no_kcsan
functions.

Link: https://lkml.kernel.org/r/CANpmjNNOpJk0tprXKB_deiNAv_UmmORf1-2uajLhnLWQQ1hvoA@mail.gmail.com
Signed-off-by: Marco Elver <elver@google.com>
---
 include/linux/compiler.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index e24cc3a2bc3e..17c98b215572 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -276,11 +276,9 @@ do {									\
 #ifdef __SANITIZE_THREAD__
 /*
  * Rely on __SANITIZE_THREAD__ instead of CONFIG_KCSAN, to avoid not inlining in
- * compilation units where instrumentation is disabled. The attribute 'noinline'
- * is required for older compilers, where implicit inlining of very small
- * functions renders __no_sanitize_thread ineffective.
+ * compilation units where instrumentation is disabled.
  */
-# define __no_kcsan_or_inline __no_kcsan noinline notrace __maybe_unused
+# define __no_kcsan_or_inline __no_kcsan notrace __maybe_unused
 # define __no_sanitize_or_inline __no_kcsan_or_inline
 #else
 # define __no_kcsan_or_inline __always_inline
-- 
2.26.2.761.g0e0b3e54be-goog


  parent reply	other threads:[~2020-05-21 11:10 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-21 11:08 [PATCH -tip v2 00/11] Fix KCSAN for new ONCE (require Clang 11) Marco Elver
2020-05-21 11:08 ` [PATCH -tip v2 01/11] ubsan, kcsan: don't combine sanitizer with kcov on clang Marco Elver
2020-05-21 11:08 ` [PATCH -tip v2 02/11] kcsan: Avoid inserting __tsan_func_entry/exit if possible Marco Elver
2020-05-21 11:08 ` [PATCH -tip v2 03/11] kcsan: Support distinguishing volatile accesses Marco Elver
2020-05-21 13:18   ` Will Deacon
2020-05-21 13:26     ` Marco Elver
2020-05-21 11:08 ` [PATCH -tip v2 04/11] kcsan: Pass option tsan-instrument-read-before-write to Clang Marco Elver
2020-05-21 11:08 ` Marco Elver [this message]
2020-05-21 11:08 ` [PATCH -tip v2 06/11] kcsan: Restrict supported compilers Marco Elver
2020-05-21 11:08 ` [PATCH -tip v2 07/11] kcsan: Update Documentation to change " Marco Elver
2020-05-21 13:33   ` Will Deacon
2020-05-21 13:35     ` Marco Elver
2020-05-21 11:08 ` [PATCH -tip v2 08/11] READ_ONCE, WRITE_ONCE: Remove data_race() and unnecessary checks Marco Elver
2020-05-21 11:08 ` [PATCH -tip v2 09/11] data_race: Avoid nested statement expression Marco Elver
2020-05-21 13:31   ` Will Deacon
2020-05-21 13:39     ` Marco Elver
2020-05-21 11:08 ` [PATCH -tip v2 10/11] compiler.h: Move function attributes to compiler_types.h Marco Elver
2020-05-21 11:08 ` [PATCH -tip v2 11/11] compiler_types.h, kasan: Use __SANITIZE_ADDRESS__ instead of CONFIG_KASAN to decide inlining Marco Elver
2020-05-21 13:36 ` [PATCH -tip v2 00/11] Fix KCSAN for new ONCE (require Clang 11) Will Deacon
2020-05-21 13:42   ` Marco Elver
2020-05-21 13:42     ` Will Deacon

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