# SPDX-License-Identifier: GPL-2.0-only config HAVE_ARCH_KCSAN	bool config HAVE_KCSAN_COMPILER	def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=thread -mllvm -tsan-distinguish-volatile=1)) || \		 (CC_IS_GCC && $(cc-option,-fsanitize=thread --param tsan-distinguish-volatile=1))	help	  For the list of compilers that support KCSAN, please see	  <file:Documentation/dev-tools/kcsan.rst>. menuconfig KCSAN	bool "KCSAN: dynamic data race detector"	depends on HAVE_ARCH_KCSAN && HAVE_KCSAN_COMPILER	depends on DEBUG_KERNEL && !KASAN	select CONSTRUCTORS	select STACKTRACE	help	  The Kernel Concurrency Sanitizer (KCSAN) is a dynamic	  data-race detector that relies on compile-time instrumentation.	  KCSAN uses a watchpoint-based sampling approach to detect races. 	  While KCSAN's primary purpose is to detect data races, it	  also provides assertions to check data access constraints.	  These assertions can expose bugs that do not manifest as	  data races. 	  See <file:Documentation/dev-tools/kcsan.rst> for more details. if KCSAN config CC_HAS_TSAN_COMPOUND_READ_BEFORE_WRITE	def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=thread -mllvm -tsan-compound-read-before-write=1)) || \		 (CC_IS_GCC && $(cc-option,-fsanitize=thread --param tsan-compound-read-before-write=1))	help	  The compiler instruments plain compound read-write operations	  differently (++, --, +=, -=, |=, &=, etc.), which allows KCSAN to	  distinguish them from other plain accesses. This is currently	  supported by Clang 12 or later. config KCSAN_VERBOSE	bool "Show verbose reports with more information about system state"	depends on PROVE_LOCKING	help	  If enabled, reports show more information about the system state that	  may help better analyze and debug races. This includes held locks and	  IRQ trace events. 	  While this option should generally be benign, we call into more	  external functions on report generation; if a race report is	  generated from any one of them, system stability may suffer due to	  deadlocks or recursion.  If in doubt, say N. config KCSAN_SELFTEST	bool "Perform short selftests on boot"	default y	help	  Run KCSAN selftests on boot. On test failure, causes the kernel to	  panic. Recommended to be enabled, ensuring critical functionality	  works as intended. config KCSAN_KUNIT_TEST	tristate "KCSAN test for integrated runtime behaviour" if !KUNIT_ALL_TESTS	default KUNIT_ALL_TESTS	depends on TRACEPOINTS && KUNIT	select TORTURE_TEST	help	  KCSAN test focusing on behaviour of the integrated runtime. Tests	  various race scenarios, and verifies the reports generated to	  console. Makes use of KUnit for test organization, and the Torture	  framework for test thread control. 	  Each test case may run at least up to KCSAN_REPORT_ONCE_IN_MS	  milliseconds. Test run duration may be optimized by building the	  kernel and KCSAN test with KCSAN_REPORT_ONCE_IN_MS set to a lower	  than default value. 	  Say Y here if you want the test to be built into the kernel and run	  during boot; say M if you want the test to build as a module; say N	  if you are unsure. config KCSAN_EARLY_ENABLE	bool "Early enable during boot"	default y	help	  If KCSAN should be enabled globally as soon as possible. KCSAN can	  later be enabled/disabled via debugfs. config KCSAN_NUM_WATCHPOINTS	int "Number of available watchpoints"	default 64	help	  Total number of available watchpoints. An address range maps into a	  specific watchpoint slot as specified in kernel/kcsan/encoding.h.	  Although larger number of watchpoints may not be usable due to	  limited number of CPUs, a larger value helps to improve performance	  due to reducing cache-line contention. The chosen default is a	  conservative value; we should almost never observe "no_capacity"	  events (see /sys/kernel/debug/kcsan). config KCSAN_UDELAY_TASK	int "Delay in microseconds (for tasks)"	default 80	help	  For tasks, the microsecond delay after setting up a watchpoint. config KCSAN_UDELAY_INTERRUPT	int "Delay in microseconds (for interrupts)"	default 20	help	  For interrupts, the microsecond delay after setting up a watchpoint.	  Interrupts have tighter latency requirements, and their delay should	  be lower than for tasks. config KCSAN_DELAY_RANDOMIZE	bool "Randomize above delays"	default y	help	  If delays should be randomized, where the maximum is KCSAN_UDELAY_*.	  If false, the chosen delays are always the KCSAN_UDELAY_* values	  as defined above. config KCSAN_SKIP_WATCH	int "Skip instructions before setting up watchpoint"	default 4000	help	  The number of per-CPU memory operations to skip, before another	  watchpoint is set up, i.e. one in KCSAN_SKIP_WATCH per-CPU	  memory operations are used to set up a watchpoint. A smaller value	  results in more aggressive race detection, whereas a larger value	  improves system performance at the cost of missing some races. config KCSAN_SKIP_WATCH_RANDOMIZE	bool "Randomize watchpoint instruction skip count"	default y	help	  If instruction skip count should be randomized, where the maximum is	  KCSAN_SKIP_WATCH. If false, the chosen value is always	  KCSAN_SKIP_WATCH. config KCSAN_INTERRUPT_WATCHER	bool "Interruptible watchers" if !KCSAN_STRICT	default KCSAN_STRICT	help	  If enabled, a task that set up a watchpoint may be interrupted while	  delayed. This option will allow KCSAN to detect races between	  interrupted tasks and other threads of execution on the same CPU. 	  Currently disabled by default, because not all safe per-CPU access	  primitives and patterns may be accounted for, and therefore could	  result in false positives. config KCSAN_REPORT_ONCE_IN_MS	int "Duration in milliseconds, in which any given race is only reported once"	default 3000	help	  Any given race is only reported once in the defined time window.	  Different races may still generate reports within a duration that is	  smaller than the duration defined here. This allows rate limiting	  reporting to avoid flooding the console with reports.  Setting this	  to 0 disables rate limiting. # The main purpose of the below options is to control reported data races, and# are not expected to be switched frequently by non-testers or at runtime.# The defaults are chosen to be conservative, and can miss certain bugs. config KCSAN_REPORT_RACE_UNKNOWN_ORIGIN	bool "Report races of unknown origin"	default y	help	  If KCSAN should report races where only one access is known, and the	  conflicting access is of unknown origin. This type of race is	  reported if it was only possible to infer a race due to a data value	  change while an access is being delayed on a watchpoint. config KCSAN_STRICT	bool "Strict data-race checking"	help	  KCSAN will report data races with the strictest possible rules, which	  closely aligns with the rules defined by the Linux-kernel memory	  consistency model (LKMM). config KCSAN_WEAK_MEMORY	bool "Enable weak memory modeling to detect missing memory barriers"	default y	depends on KCSAN_STRICT	help	  Enable support for modeling a subset of weak memory, which allows	  detecting a subset of data races due to missing memory barriers. 	  Depends on KCSAN_STRICT, because the options strengthening certain	  plain accesses by default (depending on !KCSAN_STRICT) reduce the	  ability to detect any data races invoving reordered accesses, in	  particular reordered writes. 	  Weak memory modeling relies on additional instrumentation and may	  affect performance. config KCSAN_REPORT_VALUE_CHANGE_ONLY	bool "Only report races where watcher observed a data value change"	default y	depends on !KCSAN_STRICT	help	  If enabled and a conflicting write is observed via a watchpoint, but	  the data value of the memory location was observed to remain	  unchanged, do not report the data race. config KCSAN_ASSUME_PLAIN_WRITES_ATOMIC	bool "Assume that plain aligned writes up to word size are atomic"	default y	depends on !KCSAN_STRICT	help	  Assume that plain aligned writes up to word size are atomic by	  default, and also not subject to other unsafe compiler optimizations	  resulting in data races. This will cause KCSAN to not report data	  races due to conflicts where the only plain accesses are aligned	  writes up to word size: conflicts between marked reads and plain	  aligned writes up to word size will not be reported as data races;	  notice that data races between two conflicting plain aligned writes	  will also not be reported. config KCSAN_IGNORE_ATOMICS	bool "Do not instrument marked atomic accesses"	depends on !KCSAN_STRICT	help	  Never instrument marked atomic accesses. This option can be used for	  additional filtering. Conflicting marked atomic reads and plain	  writes will never be reported as a data race, however, will cause	  plain reads and marked writes to result in "unknown origin" reports.	  If combined with CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN=n, data	  races where at least one access is marked atomic will never be	  reported. 	  Similar to KCSAN_ASSUME_PLAIN_WRITES_ATOMIC, but including unaligned	  accesses, conflicting marked atomic reads and plain writes will not	  be reported as data races; however, unlike that option, data races	  due to two conflicting plain writes will be reported (aligned and	  unaligned, if CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=n). config KCSAN_PERMISSIVE	bool "Enable all additional permissive rules"	depends on KCSAN_REPORT_VALUE_CHANGE_ONLY	help	  Enable additional permissive rules to ignore certain classes of data	  races (also see kernel/kcsan/permissive.h). None of the permissive	  rules imply that such data races are generally safe, but can be used	  to further reduce reported data races due to data-racy patterns	  common across the kernel. endif # KCSAN