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