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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 v3 06/11] kcsan: Restrict supported compilers
Date: Thu, 21 May 2020 16:20:42 +0200
Message-ID: <20200521142047.169334-7-elver@google.com> (raw)
In-Reply-To: <20200521142047.169334-1-elver@google.com>

The first version of Clang that supports -tsan-distinguish-volatile will
be able to support KCSAN. The first Clang release to do so, will be
Clang 11. This is due to satisfying all the following requirements:

1. Never emit calls to __tsan_func_{entry,exit}.

2. __no_kcsan functions should not call anything, not even
   kcsan_{enable,disable}_current(), when using __{READ,WRITE}_ONCE => Requires
   leaving them plain!

3. Support atomic_{read,set}*() with KCSAN, which rely on
   arch_atomic_{read,set}*() using __{READ,WRITE}_ONCE() => Because of
   #2, rely on Clang 11's -tsan-distinguish-volatile support. We will
   double-instrument atomic_{read,set}*(), but that's reasonable given
   it's still lower cost than the data_race() variant due to avoiding 2
   extra calls (kcsan_{en,dis}able_current() calls).

4. __always_inline functions inlined into __no_kcsan functions are never
   instrumented.

5. __always_inline functions inlined into instrumented functions are
   instrumented.

6. __no_kcsan_or_inline functions may be inlined into __no_kcsan functions =>
   Implies leaving 'noinline' off of __no_kcsan_or_inline.

7. Because of #6, __no_kcsan and __no_kcsan_or_inline functions should never be
   spuriously inlined into instrumented functions, causing the accesses of the
   __no_kcsan function to be instrumented.

Older versions of Clang do not satisfy #3. The latest GCC currently doesn't
support at least #1, #3, and #7.

Link: https://lkml.kernel.org/r/CANpmjNMTsY_8241bS7=XAfqvZHFLrVEkv_uM4aDUWE_kh3Rvbw@mail.gmail.com
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Marco Elver <elver@google.com>
---
 lib/Kconfig.kcsan | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index a7276035ca0d..3f3b5bca7a8f 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -3,6 +3,12 @@
 config HAVE_ARCH_KCSAN
 	bool
 
+config HAVE_KCSAN_COMPILER
+	def_bool CC_IS_CLANG && $(cc-option,-fsanitize=thread -mllvm -tsan-distinguish-volatile=1)
+	help
+	  For the list of compilers that support KCSAN, please see
+	  <file:Documentation/dev-tools/kcsan.rst>.
+
 config KCSAN_KCOV_BROKEN
 	def_bool KCOV && CC_HAS_SANCOV_TRACE_PC
 	depends on CC_IS_CLANG
@@ -15,7 +21,8 @@ config KCSAN_KCOV_BROKEN
 
 menuconfig KCSAN
 	bool "KCSAN: dynamic data race detector"
-	depends on HAVE_ARCH_KCSAN && DEBUG_KERNEL && !KASAN
+	depends on HAVE_ARCH_KCSAN && HAVE_KCSAN_COMPILER
+	depends on DEBUG_KERNEL && !KASAN
 	depends on !KCSAN_KCOV_BROKEN
 	select STACKTRACE
 	help
-- 
2.26.2.761.g0e0b3e54be-goog


  parent reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-21 14:20 [PATCH -tip v3 00/11] Fix KCSAN for new ONCE (require Clang 11) Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 01/11] ubsan, kcsan: don't combine sanitizer with kcov on clang Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 02/11] kcsan: Avoid inserting __tsan_func_entry/exit if possible Marco Elver
2020-05-22 16:08   ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 03/11] kcsan: Support distinguishing volatile accesses Marco Elver
2020-05-22 10:26   ` Borislav Petkov
2020-05-22 10:34     ` Marco Elver
2020-05-22 10:47       ` Borislav Petkov
2020-05-22 16:08   ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 04/11] kcsan: Pass option tsan-instrument-read-before-write to Clang Marco Elver
2020-05-22 16:08   ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 05/11] kcsan: Remove 'noinline' from __no_kcsan_or_inline Marco Elver
2020-05-29 17:07   ` Peter Zijlstra
2020-05-29 18:36     ` Marco Elver
2020-05-29 18:59       ` Peter Zijlstra
2020-05-21 14:20 ` Marco Elver [this message]
2020-05-21 14:20 ` [PATCH -tip v3 07/11] kcsan: Update Documentation to change supported compilers Marco Elver
2020-05-22 16:08   ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 08/11] READ_ONCE, WRITE_ONCE: Remove data_race() and unnecessary checks Marco Elver
2020-05-22 16:08   ` [tip: locking/kcsan] compiler.h: Remove data_race() and unnecessary checks from {READ,WRITE}_ONCE() tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 09/11] data_race: Avoid nested statement expression Marco Elver
2020-05-21 20:21   ` Nick Desaulniers
2020-05-26 10:42     ` Arnd Bergmann
2020-05-26 12:02       ` Will Deacon
2020-05-26 12:19         ` Arnd Bergmann
2020-05-26 13:12           ` Marco Elver
2020-05-26 17:33             ` Marco Elver
2020-05-26 19:00               ` Arnd Bergmann
2020-05-26 23:10                 ` Arnd Bergmann
2020-05-27  7:22                   ` Will Deacon
2020-05-27  7:44                     ` Marco Elver
2020-05-27  9:26                       ` Arnd Bergmann
2020-05-28 12:53                         ` Stephen Rothwell
2020-05-26 21:36               ` Peter Zijlstra
2020-05-21 14:20 ` [PATCH -tip v3 10/11] compiler.h: Move function attributes to compiler_types.h Marco Elver
2020-05-22 16:08   ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 11/11] compiler_types.h, kasan: Use __SANITIZE_ADDRESS__ instead of CONFIG_KASAN to decide inlining Marco Elver
2020-05-22 16:08   ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-22 11:35 ` [PATCH -tip v3 00/11] Fix KCSAN for new ONCE (require Clang 11) Peter Zijlstra

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