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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
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