Messages in this thread Patch in this message | | | Date | Fri, 22 May 2020 16:08:48 -0000 | From | "tip-bot2 for Marco Elver" <> | Subject | [tip: locking/kcsan] kcsan: Restrict supported compilers |
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The following commit has been merged into the locking/kcsan branch of tip:
Commit-ID: 0d473b1d6e5c240f8ffed02715c718024802d0fa Gitweb: https://git.kernel.org/tip/0d473b1d6e5c240f8ffed02715c718024802d0fa Author: Marco Elver <elver@google.com> AuthorDate: Thu, 21 May 2020 16:20:42 +02:00 Committer: Borislav Petkov <bp@suse.de> CommitterDate: Fri, 22 May 2020 14:46:02 +02:00
kcsan: Restrict supported compilers
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.
Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lkml.kernel.org/r/CANpmjNMTsY_8241bS7=XAfqvZHFLrVEkv_uM4aDUWE_kh3Rvbw@mail.gmail.com Link: https://lkml.kernel.org/r/20200521142047.169334-7-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 b5d88ac..5ee88e5 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
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