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737b6a10ac
Allow the use of a deferrable timer, which does not force CPU wake-ups when the system is idle. A consequence is that the sample interval becomes very unpredictable, to the point that it is not guaranteed that the KFENCE KUnit test still passes. Nevertheless, on power-constrained systems this may be preferable, so let's give the user the option should they accept the above trade-off. Link: https://lkml.kernel.org/r/20220308141415.3168078-1-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
100 lines
3.6 KiB
Plaintext
100 lines
3.6 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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config HAVE_ARCH_KFENCE
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bool
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menuconfig KFENCE
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bool "KFENCE: low-overhead sampling-based memory safety error detector"
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depends on HAVE_ARCH_KFENCE && (SLAB || SLUB)
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select STACKTRACE
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select IRQ_WORK
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help
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KFENCE is a low-overhead sampling-based detector of heap out-of-bounds
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access, use-after-free, and invalid-free errors. KFENCE is designed
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to have negligible cost to permit enabling it in production
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environments.
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See <file:Documentation/dev-tools/kfence.rst> for more details.
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Note that, KFENCE is not a substitute for explicit testing with tools
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such as KASAN. KFENCE can detect a subset of bugs that KASAN can
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detect, albeit at very different performance profiles. If you can
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afford to use KASAN, continue using KASAN, for example in test
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environments. If your kernel targets production use, and cannot
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enable KASAN due to its cost, consider using KFENCE.
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if KFENCE
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config KFENCE_SAMPLE_INTERVAL
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int "Default sample interval in milliseconds"
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default 100
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help
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The KFENCE sample interval determines the frequency with which heap
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allocations will be guarded by KFENCE. May be overridden via boot
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parameter "kfence.sample_interval".
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Set this to 0 to disable KFENCE by default, in which case only
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setting "kfence.sample_interval" to a non-zero value enables KFENCE.
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config KFENCE_NUM_OBJECTS
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int "Number of guarded objects available"
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range 1 65535
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default 255
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help
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The number of guarded objects available. For each KFENCE object, 2
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pages are required; with one containing the object and two adjacent
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ones used as guard pages.
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config KFENCE_DEFERRABLE
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bool "Use a deferrable timer to trigger allocations"
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help
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Use a deferrable timer to trigger allocations. This avoids forcing
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CPU wake-ups if the system is idle, at the risk of a less predictable
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sample interval.
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Warning: The KUnit test suite fails with this option enabled - due to
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the unpredictability of the sample interval!
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Say N if you are unsure.
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config KFENCE_STATIC_KEYS
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bool "Use static keys to set up allocations" if EXPERT
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depends on JUMP_LABEL
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help
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Use static keys (static branches) to set up KFENCE allocations. This
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option is only recommended when using very large sample intervals, or
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performance has carefully been evaluated with this option.
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Using static keys comes with trade-offs that need to be carefully
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evaluated given target workloads and system architectures. Notably,
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enabling and disabling static keys invoke IPI broadcasts, the latency
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and impact of which is much harder to predict than a dynamic branch.
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Say N if you are unsure.
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config KFENCE_STRESS_TEST_FAULTS
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int "Stress testing of fault handling and error reporting" if EXPERT
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default 0
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help
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The inverse probability with which to randomly protect KFENCE object
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pages, resulting in spurious use-after-frees. The main purpose of
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this option is to stress test KFENCE with concurrent error reports
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and allocations/frees. A value of 0 disables stress testing logic.
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Only for KFENCE testing; set to 0 if you are not a KFENCE developer.
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config KFENCE_KUNIT_TEST
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tristate "KFENCE integration test suite" if !KUNIT_ALL_TESTS
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default KUNIT_ALL_TESTS
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depends on TRACEPOINTS && KUNIT
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help
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Test suite for KFENCE, testing various error detection scenarios with
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various allocation types, and checking that reports are correctly
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output to console.
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Say Y here if you want the test to be built into the kernel and run
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during boot; say M if you want the test to build as a module; say N
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if you are unsure.
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endif # KFENCE
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