1# 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"
8	depends on HAVE_ARCH_KFENCE
9	select STACKTRACE
10	select IRQ_WORK
11	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
17	  See <file:Documentation/dev-tools/kfence.rst> for more details.
18
19	  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
28config 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
48config 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
60config 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
75config 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
86config 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
99endif # KFENCE
100