# 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>.

  config KCSAN_KCOV_BROKEN
  	def_bool KCOV && CC_HAS_SANCOV_TRACE_PC
  	depends on CC_IS_CLANG
  	depends on !$(cc-option,-Werror=unused-command-line-argument -fsanitize=thread -fsanitize-coverage=trace-pc)
  	help
  	  Some versions of clang support either KCSAN and KCOV but not the
  	  combination of the two.
  	  See https://bugs.llvm.org/show_bug.cgi?id=45831 for the status
  	  in newer releases.

  menuconfig KCSAN

  	bool "KCSAN: dynamic data race detector"

  	depends on HAVE_ARCH_KCSAN && HAVE_KCSAN_COMPILER
  	depends on DEBUG_KERNEL && !KASAN

  	depends on !KCSAN_KCOV_BROKEN

  	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

  # Compiler capabilities that should not fail the test if they are unavailable.
  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))

  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_DEBUG
  	bool "Debugging of KCSAN internals"

  
  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_TEST
  	tristate "KCSAN test for integrated runtime behaviour"
  	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_WATCH_SKIP 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_WATCH_SKIP. If false, the chosen value is always
  	  KCSAN_WATCH_SKIP.

  config KCSAN_INTERRUPT_WATCHER
  	bool "Interruptible watchers"
  	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 (e.g.
  # in fuzzer configs), and are not expected to be switched frequently by other
  # users. We could turn some of them into boot parameters, but given they should
  # not be switched normally, let's keep them here to simplify configuration.
  #
  # The defaults below are chosen to be very conservative, and may 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_REPORT_VALUE_CHANGE_ONLY
  	bool "Only report races where watcher observed a data value change"
  	default y
  	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
  	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"

  	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).

  
  endif # KCSAN