1# SPDX-License-Identifier: GPL-2.0-only 2 3config HAVE_ARCH_KCSAN 4 bool 5 6config HAVE_KCSAN_COMPILER 7 def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=thread -mllvm -tsan-distinguish-volatile=1)) || \ 8 (CC_IS_GCC && $(cc-option,-fsanitize=thread --param tsan-distinguish-volatile=1)) 9 help 10 For the list of compilers that support KCSAN, please see 11 <file:Documentation/dev-tools/kcsan.rst>. 12 13config KCSAN_KCOV_BROKEN 14 def_bool KCOV && CC_HAS_SANCOV_TRACE_PC 15 depends on CC_IS_CLANG 16 depends on !$(cc-option,-Werror=unused-command-line-argument -fsanitize=thread -fsanitize-coverage=trace-pc) 17 help 18 Some versions of clang support either KCSAN and KCOV but not the 19 combination of the two. 20 See https://bugs.llvm.org/show_bug.cgi?id=45831 for the status 21 in newer releases. 22 23menuconfig KCSAN 24 bool "KCSAN: dynamic data race detector" 25 depends on HAVE_ARCH_KCSAN && HAVE_KCSAN_COMPILER 26 depends on DEBUG_KERNEL && !KASAN 27 depends on !KCSAN_KCOV_BROKEN 28 select STACKTRACE 29 help 30 The Kernel Concurrency Sanitizer (KCSAN) is a dynamic 31 data-race detector that relies on compile-time instrumentation. 32 KCSAN uses a watchpoint-based sampling approach to detect races. 33 34 While KCSAN's primary purpose is to detect data races, it 35 also provides assertions to check data access constraints. 36 These assertions can expose bugs that do not manifest as 37 data races. 38 39 See <file:Documentation/dev-tools/kcsan.rst> for more details. 40 41if KCSAN 42 43# Compiler capabilities that should not fail the test if they are unavailable. 44config CC_HAS_TSAN_COMPOUND_READ_BEFORE_WRITE 45 def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=thread -mllvm -tsan-compound-read-before-write=1)) || \ 46 (CC_IS_GCC && $(cc-option,-fsanitize=thread --param tsan-compound-read-before-write=1)) 47 48config KCSAN_VERBOSE 49 bool "Show verbose reports with more information about system state" 50 depends on PROVE_LOCKING 51 help 52 If enabled, reports show more information about the system state that 53 may help better analyze and debug races. This includes held locks and 54 IRQ trace events. 55 56 While this option should generally be benign, we call into more 57 external functions on report generation; if a race report is 58 generated from any one of them, system stability may suffer due to 59 deadlocks or recursion. If in doubt, say N. 60 61config KCSAN_DEBUG 62 bool "Debugging of KCSAN internals" 63 64config KCSAN_SELFTEST 65 bool "Perform short selftests on boot" 66 default y 67 help 68 Run KCSAN selftests on boot. On test failure, causes the kernel to 69 panic. Recommended to be enabled, ensuring critical functionality 70 works as intended. 71 72config KCSAN_TEST 73 tristate "KCSAN test for integrated runtime behaviour" 74 depends on TRACEPOINTS && KUNIT 75 select TORTURE_TEST 76 help 77 KCSAN test focusing on behaviour of the integrated runtime. Tests 78 various race scenarios, and verifies the reports generated to 79 console. Makes use of KUnit for test organization, and the Torture 80 framework for test thread control. 81 82 Each test case may run at least up to KCSAN_REPORT_ONCE_IN_MS 83 milliseconds. Test run duration may be optimized by building the 84 kernel and KCSAN test with KCSAN_REPORT_ONCE_IN_MS set to a lower 85 than default value. 86 87 Say Y here if you want the test to be built into the kernel and run 88 during boot; say M if you want the test to build as a module; say N 89 if you are unsure. 90 91config KCSAN_EARLY_ENABLE 92 bool "Early enable during boot" 93 default y 94 help 95 If KCSAN should be enabled globally as soon as possible. KCSAN can 96 later be enabled/disabled via debugfs. 97 98config KCSAN_NUM_WATCHPOINTS 99 int "Number of available watchpoints" 100 default 64 101 help 102 Total number of available watchpoints. An address range maps into a 103 specific watchpoint slot as specified in kernel/kcsan/encoding.h. 104 Although larger number of watchpoints may not be usable due to 105 limited number of CPUs, a larger value helps to improve performance 106 due to reducing cache-line contention. The chosen default is a 107 conservative value; we should almost never observe "no_capacity" 108 events (see /sys/kernel/debug/kcsan). 109 110config KCSAN_UDELAY_TASK 111 int "Delay in microseconds (for tasks)" 112 default 80 113 help 114 For tasks, the microsecond delay after setting up a watchpoint. 115 116config KCSAN_UDELAY_INTERRUPT 117 int "Delay in microseconds (for interrupts)" 118 default 20 119 help 120 For interrupts, the microsecond delay after setting up a watchpoint. 121 Interrupts have tighter latency requirements, and their delay should 122 be lower than for tasks. 123 124config KCSAN_DELAY_RANDOMIZE 125 bool "Randomize above delays" 126 default y 127 help 128 If delays should be randomized, where the maximum is KCSAN_UDELAY_*. 129 If false, the chosen delays are always the KCSAN_UDELAY_* values 130 as defined above. 131 132config KCSAN_SKIP_WATCH 133 int "Skip instructions before setting up watchpoint" 134 default 4000 135 help 136 The number of per-CPU memory operations to skip, before another 137 watchpoint is set up, i.e. one in KCSAN_WATCH_SKIP per-CPU 138 memory operations are used to set up a watchpoint. A smaller value 139 results in more aggressive race detection, whereas a larger value 140 improves system performance at the cost of missing some races. 141 142config KCSAN_SKIP_WATCH_RANDOMIZE 143 bool "Randomize watchpoint instruction skip count" 144 default y 145 help 146 If instruction skip count should be randomized, where the maximum is 147 KCSAN_WATCH_SKIP. If false, the chosen value is always 148 KCSAN_WATCH_SKIP. 149 150config KCSAN_INTERRUPT_WATCHER 151 bool "Interruptible watchers" 152 help 153 If enabled, a task that set up a watchpoint may be interrupted while 154 delayed. This option will allow KCSAN to detect races between 155 interrupted tasks and other threads of execution on the same CPU. 156 157 Currently disabled by default, because not all safe per-CPU access 158 primitives and patterns may be accounted for, and therefore could 159 result in false positives. 160 161config KCSAN_REPORT_ONCE_IN_MS 162 int "Duration in milliseconds, in which any given race is only reported once" 163 default 3000 164 help 165 Any given race is only reported once in the defined time window. 166 Different races may still generate reports within a duration that is 167 smaller than the duration defined here. This allows rate limiting 168 reporting to avoid flooding the console with reports. Setting this 169 to 0 disables rate limiting. 170 171# The main purpose of the below options is to control reported data races (e.g. 172# in fuzzer configs), and are not expected to be switched frequently by other 173# users. We could turn some of them into boot parameters, but given they should 174# not be switched normally, let's keep them here to simplify configuration. 175# 176# The defaults below are chosen to be very conservative, and may miss certain 177# bugs. 178 179config KCSAN_REPORT_RACE_UNKNOWN_ORIGIN 180 bool "Report races of unknown origin" 181 default y 182 help 183 If KCSAN should report races where only one access is known, and the 184 conflicting access is of unknown origin. This type of race is 185 reported if it was only possible to infer a race due to a data value 186 change while an access is being delayed on a watchpoint. 187 188config KCSAN_REPORT_VALUE_CHANGE_ONLY 189 bool "Only report races where watcher observed a data value change" 190 default y 191 help 192 If enabled and a conflicting write is observed via a watchpoint, but 193 the data value of the memory location was observed to remain 194 unchanged, do not report the data race. 195 196config KCSAN_ASSUME_PLAIN_WRITES_ATOMIC 197 bool "Assume that plain aligned writes up to word size are atomic" 198 default y 199 help 200 Assume that plain aligned writes up to word size are atomic by 201 default, and also not subject to other unsafe compiler optimizations 202 resulting in data races. This will cause KCSAN to not report data 203 races due to conflicts where the only plain accesses are aligned 204 writes up to word size: conflicts between marked reads and plain 205 aligned writes up to word size will not be reported as data races; 206 notice that data races between two conflicting plain aligned writes 207 will also not be reported. 208 209config KCSAN_IGNORE_ATOMICS 210 bool "Do not instrument marked atomic accesses" 211 help 212 Never instrument marked atomic accesses. This option can be used for 213 additional filtering. Conflicting marked atomic reads and plain 214 writes will never be reported as a data race, however, will cause 215 plain reads and marked writes to result in "unknown origin" reports. 216 If combined with CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN=n, data 217 races where at least one access is marked atomic will never be 218 reported. 219 220 Similar to KCSAN_ASSUME_PLAIN_WRITES_ATOMIC, but including unaligned 221 accesses, conflicting marked atomic reads and plain writes will not 222 be reported as data races; however, unlike that option, data races 223 due to two conflicting plain writes will be reported (aligned and 224 unaligned, if CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=n). 225 226endif # KCSAN 227