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 && (SLAB || SLUB)
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_STATIC_KEYS
49	bool "Use static keys to set up allocations" if EXPERT
50	depends on JUMP_LABEL
51	help
52	  Use static keys (static branches) to set up KFENCE allocations. This
53	  option is only recommended when using very large sample intervals, or
54	  performance has carefully been evaluated with this option.
55
56	  Using static keys comes with trade-offs that need to be carefully
57	  evaluated given target workloads and system architectures. Notably,
58	  enabling and disabling static keys invoke IPI broadcasts, the latency
59	  and impact of which is much harder to predict than a dynamic branch.
60
61	  Say N if you are unsure.
62
63config KFENCE_STRESS_TEST_FAULTS
64	int "Stress testing of fault handling and error reporting" if EXPERT
65	default 0
66	help
67	  The inverse probability with which to randomly protect KFENCE object
68	  pages, resulting in spurious use-after-frees. The main purpose of
69	  this option is to stress test KFENCE with concurrent error reports
70	  and allocations/frees. A value of 0 disables stress testing logic.
71
72	  Only for KFENCE testing; set to 0 if you are not a KFENCE developer.
73
74config KFENCE_KUNIT_TEST
75	tristate "KFENCE integration test suite" if !KUNIT_ALL_TESTS
76	default KUNIT_ALL_TESTS
77	depends on TRACEPOINTS && KUNIT
78	help
79	  Test suite for KFENCE, testing various error detection scenarios with
80	  various allocation types, and checking that reports are correctly
81	  output to console.
82
83	  Say Y here if you want the test to be built into the kernel and run
84	  during boot; say M if you want the test to build as a module; say N
85	  if you are unsure.
86
87endif # KFENCE
88