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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 && (SLAB || SLUB)
+ 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