lib/Kconfig.kcsan

   1 # SPDX-License-Identifier: GPL-2.0-only
   2
   3 config HAVE_ARCH_KCSAN
   4         bool
   5
   6 menuconfig KCSAN
   7         bool "KCSAN: watchpoint-based dynamic data race detector"
   8         depends on HAVE_ARCH_KCSAN && !KASAN && STACKTRACE
   9         help
  10           Kernel Concurrency Sanitizer is a dynamic data race detector, which
  11           uses a watchpoint-based sampling approach to detect races. See
  12           <file:Documentation/dev-tools/kcsan.rst> for more details.
  13
  14 if KCSAN
  15
  16 config KCSAN_DEBUG
  17         bool "Debugging of KCSAN internals"
  18
  19 config KCSAN_SELFTEST
  20         bool "Perform short selftests on boot"
  21         default y
  22         help
  23           Run KCSAN selftests on boot. On test failure, causes the kernel to panic.
  24
  25 config KCSAN_EARLY_ENABLE
  26         bool "Early enable during boot"
  27         default y
  28         help
  29           If KCSAN should be enabled globally as soon as possible. KCSAN can
  30           later be enabled/disabled via debugfs.
  31
  32 config KCSAN_NUM_WATCHPOINTS
  33         int "Number of available watchpoints"
  34         default 64
  35         help
  36           Total number of available watchpoints. An address range maps into a
  37           specific watchpoint slot as specified in kernel/kcsan/encoding.h.
  38           Although larger number of watchpoints may not be usable due to
  39           limited number of CPUs, a larger value helps to improve performance
  40           due to reducing cache-line contention. The chosen default is a
  41           conservative value; we should almost never observe "no_capacity"
  42           events (see /sys/kernel/debug/kcsan).
  43
  44 config KCSAN_UDELAY_TASK
  45         int "Delay in microseconds (for tasks)"
  46         default 80
  47         help
  48           For tasks, the microsecond delay after setting up a watchpoint.
  49
  50 config KCSAN_UDELAY_INTERRUPT
  51         int "Delay in microseconds (for interrupts)"
  52         default 20
  53         help
  54           For interrupts, the microsecond delay after setting up a watchpoint.
  55           Interrupts have tighter latency requirements, and their delay should
  56           be lower than for tasks.
  57
  58 config KCSAN_DELAY_RANDOMIZE
  59         bool "Randomize above delays"
  60         default y
  61         help
  62           If delays should be randomized, where the maximum is KCSAN_UDELAY_*.
  63           If false, the chosen delays are always the KCSAN_UDELAY_* values
  64           as defined above.
  65
  66 config KCSAN_SKIP_WATCH
  67         int "Skip instructions before setting up watchpoint"
  68         default 4000
  69         help
  70           The number of per-CPU memory operations to skip, before another
  71           watchpoint is set up, i.e. one in KCSAN_WATCH_SKIP per-CPU
  72           memory operations are used to set up a watchpoint. A smaller value
  73           results in more aggressive race detection, whereas a larger value
  74           improves system performance at the cost of missing some races.
  75
  76 config KCSAN_SKIP_WATCH_RANDOMIZE
  77         bool "Randomize watchpoint instruction skip count"
  78         default y
  79         help
  80           If instruction skip count should be randomized, where the maximum is
  81           KCSAN_WATCH_SKIP. If false, the chosen value is always
  82           KCSAN_WATCH_SKIP.
  83
  84 # Note that, while some of the below options could be turned into boot
  85 # parameters, to optimize for the common use-case, we avoid this because: (a)
  86 # it would impact performance (and we want to avoid static branch for all
  87 # {READ,WRITE}_ONCE, atomic_*, bitops, etc.), and (b) complicate the design
  88 # without real benefit. The main purpose of the below options is for use in
  89 # fuzzer configs to control reported data races, and they are not expected
  90 # to be switched frequently by a user.
  91
  92 config KCSAN_REPORT_RACE_UNKNOWN_ORIGIN
  93         bool "Report races of unknown origin"
  94         default y
  95         help
  96           If KCSAN should report races where only one access is known, and the
  97           conflicting access is of unknown origin. This type of race is
  98           reported if it was only possible to infer a race due to a data value
  99           change while an access is being delayed on a watchpoint.
 100
 101 config KCSAN_REPORT_VALUE_CHANGE_ONLY
 102         bool "Only report races where watcher observed a data value change"
 103         default y
 104         help
 105           If enabled and a conflicting write is observed via a watchpoint, but
 106           the data value of the memory location was observed to remain
 107           unchanged, do not report the data race.
 108
 109 config KCSAN_IGNORE_ATOMICS
 110         bool "Do not instrument marked atomic accesses"
 111         help
 112           If enabled, never instruments marked atomic accesses. This results in
 113           not reporting data races where one access is atomic and the other is
 114           a plain access.
 115
 116 endif # KCSAN