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Alexander Potapenko0ce20dd2021-02-25 17:18:53 -08001# SPDX-License-Identifier: GPL-2.0-only
2
3config HAVE_ARCH_KFENCE
4 bool
5
6menuconfig KFENCE
7 bool "KFENCE: low-overhead sampling-based memory safety error detector"
Alexander Potapenko2b830522021-02-25 17:19:21 -08008 depends on HAVE_ARCH_KFENCE && (SLAB || SLUB)
Alexander Potapenko0ce20dd2021-02-25 17:18:53 -08009 select STACKTRACE
Marco Elver407f1d82021-05-04 18:40:21 -070010 select IRQ_WORK
Alexander Potapenko0ce20dd2021-02-25 17:18:53 -080011 help
12 KFENCE is a low-overhead sampling-based detector of heap out-of-bounds
13 access, use-after-free, and invalid-free errors. KFENCE is designed
14 to have negligible cost to permit enabling it in production
15 environments.
16
Marco Elver10efe552021-02-25 17:19:26 -080017 See <file:Documentation/dev-tools/kfence.rst> for more details.
18
Alexander Potapenko0ce20dd2021-02-25 17:18:53 -080019 Note that, KFENCE is not a substitute for explicit testing with tools
20 such as KASAN. KFENCE can detect a subset of bugs that KASAN can
21 detect, albeit at very different performance profiles. If you can
22 afford to use KASAN, continue using KASAN, for example in test
23 environments. If your kernel targets production use, and cannot
24 enable KASAN due to its cost, consider using KFENCE.
25
26if KFENCE
27
Alexander Potapenko0ce20dd2021-02-25 17:18:53 -080028config KFENCE_SAMPLE_INTERVAL
29 int "Default sample interval in milliseconds"
30 default 100
31 help
32 The KFENCE sample interval determines the frequency with which heap
33 allocations will be guarded by KFENCE. May be overridden via boot
34 parameter "kfence.sample_interval".
35
36 Set this to 0 to disable KFENCE by default, in which case only
37 setting "kfence.sample_interval" to a non-zero value enables KFENCE.
38
39config KFENCE_NUM_OBJECTS
40 int "Number of guarded objects available"
41 range 1 65535
42 default 255
43 help
44 The number of guarded objects available. For each KFENCE object, 2
45 pages are required; with one containing the object and two adjacent
46 ones used as guard pages.
47
Marco Elver737b6a12022-03-22 14:48:25 -070048config KFENCE_DEFERRABLE
49 bool "Use a deferrable timer to trigger allocations"
50 help
51 Use a deferrable timer to trigger allocations. This avoids forcing
52 CPU wake-ups if the system is idle, at the risk of a less predictable
53 sample interval.
54
55 Warning: The KUnit test suite fails with this option enabled - due to
56 the unpredictability of the sample interval!
57
58 Say N if you are unsure.
59
Marco Elver4f612ed2021-11-05 13:45:49 -070060config KFENCE_STATIC_KEYS
61 bool "Use static keys to set up allocations" if EXPERT
62 depends on JUMP_LABEL
63 help
64 Use static keys (static branches) to set up KFENCE allocations. This
65 option is only recommended when using very large sample intervals, or
66 performance has carefully been evaluated with this option.
67
68 Using static keys comes with trade-offs that need to be carefully
69 evaluated given target workloads and system architectures. Notably,
70 enabling and disabling static keys invoke IPI broadcasts, the latency
71 and impact of which is much harder to predict than a dynamic branch.
72
73 Say N if you are unsure.
74
Alexander Potapenko0ce20dd2021-02-25 17:18:53 -080075config KFENCE_STRESS_TEST_FAULTS
76 int "Stress testing of fault handling and error reporting" if EXPERT
77 default 0
78 help
79 The inverse probability with which to randomly protect KFENCE object
80 pages, resulting in spurious use-after-frees. The main purpose of
81 this option is to stress test KFENCE with concurrent error reports
82 and allocations/frees. A value of 0 disables stress testing logic.
83
84 Only for KFENCE testing; set to 0 if you are not a KFENCE developer.
85
Marco Elverbc8fbc52021-02-25 17:19:31 -080086config KFENCE_KUNIT_TEST
87 tristate "KFENCE integration test suite" if !KUNIT_ALL_TESTS
88 default KUNIT_ALL_TESTS
89 depends on TRACEPOINTS && KUNIT
90 help
91 Test suite for KFENCE, testing various error detection scenarios with
92 various allocation types, and checking that reports are correctly
93 output to console.
94
95 Say Y here if you want the test to be built into the kernel and run
96 during boot; say M if you want the test to build as a module; say N
97 if you are unsure.
98
Alexander Potapenko0ce20dd2021-02-25 17:18:53 -080099endif # KFENCE