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# SPDX-License-Identifier: GPL-2.0-only config HAVE_ARCH_KFENCE bool menuconfig KFENCE bool "KFENCE: low-overhead sampling-based memory safety error detector" depends on HAVE_ARCH_KFENCE select STACKTRACE select IRQ_WORK help KFENCE is a low-overhead sampling-based detector of heap out-of-bounds access, use-after-free, and invalid-free errors. KFENCE is designed to have negligible cost to permit enabling it in production environments. See <file:Documentation/dev-tools/kfence.rst> for more details. Note that, KFENCE is not a substitute for explicit testing with tools such as KASAN. KFENCE can detect a subset of bugs that KASAN can detect, albeit at very different performance profiles. If you can afford to use KASAN, continue using KASAN, for example in test environments. If your kernel targets production use, and cannot enable KASAN due to its cost, consider using KFENCE. if KFENCE config KFENCE_SAMPLE_INTERVAL int "Default sample interval in milliseconds" default 100 help The KFENCE sample interval determines the frequency with which heap allocations will be guarded by KFENCE. May be overridden via boot parameter "kfence.sample_interval". Set this to 0 to disable KFENCE by default, in which case only setting "kfence.sample_interval" to a non-zero value enables KFENCE. config KFENCE_NUM_OBJECTS int "Number of guarded objects available" range 1 65535 default 255 help The number of guarded objects available. For each KFENCE object, 2 pages are required; with one containing the object and two adjacent ones used as guard pages. config KFENCE_DEFERRABLE bool "Use a deferrable timer to trigger allocations" help Use a deferrable timer to trigger allocations. This avoids forcing CPU wake-ups if the system is idle, at the risk of a less predictable sample interval. Warning: The KUnit test suite fails with this option enabled - due to the unpredictability of the sample interval! Say N if you are unsure. config KFENCE_STATIC_KEYS bool "Use static keys to set up allocations" if EXPERT depends on JUMP_LABEL help Use static keys (static branches) to set up KFENCE allocations. This option is only recommended when using very large sample intervals, or performance has carefully been evaluated with this option. Using static keys comes with trade-offs that need to be carefully evaluated given target workloads and system architectures. Notably, enabling and disabling static keys invoke IPI broadcasts, the latency and impact of which is much harder to predict than a dynamic branch. Say N if you are unsure. config KFENCE_STRESS_TEST_FAULTS int "Stress testing of fault handling and error reporting" if EXPERT default 0 help The inverse probability with which to randomly protect KFENCE object pages, resulting in spurious use-after-frees. The main purpose of this option is to stress test KFENCE with concurrent error reports and allocations/frees. A value of 0 disables stress testing logic. Only for KFENCE testing; set to 0 if you are not a KFENCE developer. config KFENCE_KUNIT_TEST tristate "KFENCE integration test suite" if !KUNIT_ALL_TESTS default KUNIT_ALL_TESTS depends on TRACEPOINTS && KUNIT help Test suite for KFENCE, testing various error detection scenarios with various allocation types, and checking that reports are correctly output to console. 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. endif # KFENCE