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Diffstat (limited to 'lib/Kconfig.kcsan')
| -rw-r--r-- | lib/Kconfig.kcsan | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan new file mode 100644 index 000000000..f271ff5fb --- /dev/null +++ b/lib/Kconfig.kcsan @@ -0,0 +1,226 @@ +# 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 |