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05f9a40679
KCSAN data-race reports can occur quite frequently, so much so as to render the system useless. This commit therefore adds support for time-based rate-limiting KCSAN reports, with the time interval specified by a new KCSAN_REPORT_ONCE_IN_MS Kconfig option. The default is 3000 milliseconds, also known as three seconds. Because KCSAN must detect data races in allocators and in other contexts where use of allocation is ill-advised, a fixed-size array is used to buffer reports during each reporting interval. To reduce the number of reports lost due to array overflow, this commit stores only one instance of duplicate reports, which has the benefit of further reducing KCSAN's console output rate. Reported-by: Qian Cai <cai@lca.pw> Suggested-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
127 lines
4.5 KiB
Plaintext
127 lines
4.5 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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config HAVE_ARCH_KCSAN
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bool
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menuconfig KCSAN
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bool "KCSAN: watchpoint-based dynamic data race detector"
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depends on HAVE_ARCH_KCSAN && !KASAN && STACKTRACE
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help
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Kernel Concurrency Sanitizer is a dynamic data race detector, which
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uses a watchpoint-based sampling approach to detect races. See
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<file:Documentation/dev-tools/kcsan.rst> for more details.
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if KCSAN
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config KCSAN_DEBUG
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bool "Debugging of KCSAN internals"
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config KCSAN_SELFTEST
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bool "Perform short selftests on boot"
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default y
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help
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Run KCSAN selftests on boot. On test failure, causes the kernel to panic.
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config KCSAN_EARLY_ENABLE
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bool "Early enable during boot"
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default y
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help
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If KCSAN should be enabled globally as soon as possible. KCSAN can
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later be enabled/disabled via debugfs.
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config KCSAN_NUM_WATCHPOINTS
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int "Number of available watchpoints"
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default 64
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help
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Total number of available watchpoints. An address range maps into a
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specific watchpoint slot as specified in kernel/kcsan/encoding.h.
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Although larger number of watchpoints may not be usable due to
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limited number of CPUs, a larger value helps to improve performance
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due to reducing cache-line contention. The chosen default is a
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conservative value; we should almost never observe "no_capacity"
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events (see /sys/kernel/debug/kcsan).
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config KCSAN_UDELAY_TASK
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int "Delay in microseconds (for tasks)"
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default 80
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help
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For tasks, the microsecond delay after setting up a watchpoint.
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config KCSAN_UDELAY_INTERRUPT
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int "Delay in microseconds (for interrupts)"
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default 20
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help
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For interrupts, the microsecond delay after setting up a watchpoint.
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Interrupts have tighter latency requirements, and their delay should
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be lower than for tasks.
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config KCSAN_DELAY_RANDOMIZE
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bool "Randomize above delays"
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default y
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help
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If delays should be randomized, where the maximum is KCSAN_UDELAY_*.
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If false, the chosen delays are always the KCSAN_UDELAY_* values
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as defined above.
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config KCSAN_SKIP_WATCH
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int "Skip instructions before setting up watchpoint"
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default 4000
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help
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The number of per-CPU memory operations to skip, before another
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watchpoint is set up, i.e. one in KCSAN_WATCH_SKIP per-CPU
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memory operations are used to set up a watchpoint. A smaller value
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results in more aggressive race detection, whereas a larger value
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improves system performance at the cost of missing some races.
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config KCSAN_SKIP_WATCH_RANDOMIZE
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bool "Randomize watchpoint instruction skip count"
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default y
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help
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If instruction skip count should be randomized, where the maximum is
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KCSAN_WATCH_SKIP. If false, the chosen value is always
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KCSAN_WATCH_SKIP.
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config KCSAN_REPORT_ONCE_IN_MS
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int "Duration in milliseconds, in which any given data race is only reported once"
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default 3000
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help
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Any given data race is only reported once in the defined time window.
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Different data races may still generate reports within a duration
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that is smaller than the duration defined here. This allows rate
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limiting reporting to avoid flooding the console with reports.
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Setting this to 0 disables rate limiting.
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# Note that, while some of the below options could be turned into boot
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# parameters, to optimize for the common use-case, we avoid this because: (a)
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# it would impact performance (and we want to avoid static branch for all
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# {READ,WRITE}_ONCE, atomic_*, bitops, etc.), and (b) complicate the design
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# without real benefit. The main purpose of the below options is for use in
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# fuzzer configs to control reported data races, and they are not expected
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# to be switched frequently by a user.
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config KCSAN_REPORT_RACE_UNKNOWN_ORIGIN
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bool "Report races of unknown origin"
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default y
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help
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If KCSAN should report races where only one access is known, and the
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conflicting access is of unknown origin. This type of race is
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reported if it was only possible to infer a race due to a data value
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change while an access is being delayed on a watchpoint.
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config KCSAN_REPORT_VALUE_CHANGE_ONLY
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bool "Only report races where watcher observed a data value change"
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default y
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help
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If enabled and a conflicting write is observed via a watchpoint, but
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the data value of the memory location was observed to remain
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unchanged, do not report the data race.
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config KCSAN_IGNORE_ATOMICS
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bool "Do not instrument marked atomic accesses"
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help
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If enabled, never instruments marked atomic accesses. This results in
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not reporting data races where one access is atomic and the other is
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a plain access.
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endif # KCSAN
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