linux-kernel - [tip: locking/kcsan] kcsan: Remove 'noinline' from __no_kcsan_or

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Message-ID: <159016372746.17951.1491330046676441338.tip-bot2@tip-bot2>
Date:   Fri, 22 May 2020 16:08:47 -0000
From:   "tip-bot2 for Marco Elver" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Marco Elver <elver@...gle.com>, Borislav Petkov <bp@...e.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Will Deacon <will@...nel.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: locking/kcsan] kcsan: Remove 'noinline' from __no_kcsan_or_inline

The following commit has been merged into the locking/kcsan branch of tip:

Commit-ID:     f487a549ea30ee894055d8d20e81c1996a6e10a0
Gitweb:        https://git.kernel.org/tip/f487a549ea30ee894055d8d20e81c1996a6e10a0
Author:        Marco Elver <elver@...gle.com>
AuthorDate:    Thu, 21 May 2020 16:20:41 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Fri, 22 May 2020 15:12:39 +02:00

kcsan: Remove 'noinline' from __no_kcsan_or_inline

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 versions of Clang are unaffected, and
never inline 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, give the compiler
the ability to inline and generate the expected code in __no_kcsan
functions.

Signed-off-by: Marco Elver <elver@...gle.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Will Deacon <will@...nel.org>
Link: https://lkml.kernel.org/r/CANpmjNNOpJk0tprXKB_deiNAv_UmmORf1-2uajLhnLWQQ1hvoA@mail.gmail.com
Link: https://lkml.kernel.org/r/20200521142047.169334-6-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 e24cc3a..17c98b2 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