xref: /linux/lib/Kconfig.kasan (revision ec8c17e5ecb4a5a74069687ccb6d2cfe1851302e)
1# SPDX-License-Identifier: GPL-2.0-only
2
3# This config refers to the generic KASAN mode.
4config HAVE_ARCH_KASAN
5	bool
6
7config HAVE_ARCH_KASAN_SW_TAGS
8	bool
9
10config HAVE_ARCH_KASAN_HW_TAGS
11	bool
12
13config HAVE_ARCH_KASAN_VMALLOC
14	bool
15
16config ARCH_DISABLE_KASAN_INLINE
17	bool
18	help
19	  Disables both inline and stack instrumentation. Selected by
20	  architectures that do not support these instrumentation types.
21
22config CC_HAS_KASAN_GENERIC
23	def_bool $(cc-option, -fsanitize=kernel-address)
24
25config CC_HAS_KASAN_SW_TAGS
26	def_bool $(cc-option, -fsanitize=kernel-hwaddress)
27
28# This option is only required for software KASAN modes.
29# Old GCC versions do not have proper support for no_sanitize_address.
30# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89124 for details.
31config CC_HAS_WORKING_NOSANITIZE_ADDRESS
32	def_bool !CC_IS_GCC || GCC_VERSION >= 80300
33
34menuconfig KASAN
35	bool "KASAN: dynamic memory safety error detector"
36	depends on (((HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
37		     (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)) && \
38		    CC_HAS_WORKING_NOSANITIZE_ADDRESS) || \
39		   HAVE_ARCH_KASAN_HW_TAGS
40	depends on SYSFS && !SLUB_TINY
41	select STACKDEPOT_ALWAYS_INIT
42	help
43	  Enables KASAN (Kernel Address Sanitizer) - a dynamic memory safety
44	  error detector designed to find out-of-bounds and use-after-free bugs.
45
46	  See Documentation/dev-tools/kasan.rst for details.
47
48	  For better error reports, also enable CONFIG_STACKTRACE.
49
50if KASAN
51
52config CC_HAS_KASAN_MEMINTRINSIC_PREFIX
53	def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=kernel-address -mllvm -asan-kernel-mem-intrinsic-prefix=1)) || \
54		 (CC_IS_GCC && $(cc-option,-fsanitize=kernel-address --param asan-kernel-mem-intrinsic-prefix=1))
55	# Don't define it if we don't need it: compilation of the test uses
56	# this variable to decide how the compiler should treat builtins.
57	depends on !KASAN_HW_TAGS
58	help
59	  The compiler is able to prefix memintrinsics with __asan or __hwasan.
60
61choice
62	prompt "KASAN mode"
63	default KASAN_GENERIC
64	help
65	  KASAN has three modes:
66
67	  1. Generic KASAN (supported by many architectures, enabled with
68	     CONFIG_KASAN_GENERIC, similar to userspace ASan),
69	  2. Software Tag-Based KASAN (arm64 only, based on software memory
70	     tagging, enabled with CONFIG_KASAN_SW_TAGS, similar to userspace
71	     HWASan), and
72	  3. Hardware Tag-Based KASAN (arm64 only, based on hardware memory
73	     tagging, enabled with CONFIG_KASAN_HW_TAGS).
74
75	  See Documentation/dev-tools/kasan.rst for details about each mode.
76
77config KASAN_GENERIC
78	bool "Generic KASAN"
79	depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC
80	depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
81	select SLUB_DEBUG
82	select CONSTRUCTORS
83	help
84	  Enables Generic KASAN.
85
86	  Requires GCC 8.3.0+ or Clang.
87
88	  Consumes about 1/8th of available memory at kernel start and adds an
89	  overhead of ~50% for dynamic allocations.
90	  The performance slowdown is ~x3.
91
92config KASAN_SW_TAGS
93	bool "Software Tag-Based KASAN"
94	depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
95	depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
96	select SLUB_DEBUG
97	select CONSTRUCTORS
98	help
99	  Enables Software Tag-Based KASAN.
100
101	  Requires GCC 11+ or Clang.
102
103	  Supported only on arm64 CPUs and relies on Top Byte Ignore.
104
105	  Consumes about 1/16th of available memory at kernel start and
106	  add an overhead of ~20% for dynamic allocations.
107
108	  May potentially introduce problems related to pointer casting and
109	  comparison, as it embeds a tag into the top byte of each pointer.
110
111config KASAN_HW_TAGS
112	bool "Hardware Tag-Based KASAN"
113	depends on HAVE_ARCH_KASAN_HW_TAGS
114	help
115	  Enables Hardware Tag-Based KASAN.
116
117	  Requires GCC 10+ or Clang 12+.
118
119	  Supported only on arm64 CPUs starting from ARMv8.5 and relies on
120	  Memory Tagging Extension and Top Byte Ignore.
121
122	  Consumes about 1/32nd of available memory.
123
124	  May potentially introduce problems related to pointer casting and
125	  comparison, as it embeds a tag into the top byte of each pointer.
126
127endchoice
128
129choice
130	prompt "Instrumentation type"
131	depends on KASAN_GENERIC || KASAN_SW_TAGS
132	default KASAN_INLINE if !ARCH_DISABLE_KASAN_INLINE
133
134config KASAN_OUTLINE
135	bool "Outline instrumentation"
136	help
137	  Makes the compiler insert function calls that check whether the memory
138	  is accessible before each memory access. Slower than KASAN_INLINE, but
139	  does not bloat the size of the kernel's .text section so much.
140
141config KASAN_INLINE
142	bool "Inline instrumentation"
143	depends on !ARCH_DISABLE_KASAN_INLINE
144	help
145	  Makes the compiler directly insert memory accessibility checks before
146	  each memory access. Faster than KASAN_OUTLINE (gives ~x2 boost for
147	  some workloads), but makes the kernel's .text size much bigger.
148
149endchoice
150
151config KASAN_STACK
152	bool "Stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
153	depends on KASAN_GENERIC || KASAN_SW_TAGS
154	depends on !ARCH_DISABLE_KASAN_INLINE
155	default y if CC_IS_GCC
156	help
157	  Disables stack instrumentation and thus KASAN's ability to detect
158	  out-of-bounds bugs in stack variables.
159
160	  With Clang, stack instrumentation has a problem that causes excessive
161	  stack usage, see https://llvm.org/pr38809. Thus,
162	  with Clang, this option is deemed unsafe.
163
164	  This option is always disabled when compile-testing with Clang to
165	  avoid cluttering the log with stack overflow warnings.
166
167	  With GCC, enabling stack instrumentation is assumed to be safe.
168
169	  If the architecture disables inline instrumentation via
170	  ARCH_DISABLE_KASAN_INLINE, stack instrumentation gets disabled
171	  as well, as it adds inline-style instrumentation that is run
172	  unconditionally.
173
174config KASAN_VMALLOC
175	bool "Check accesses to vmalloc allocations"
176	depends on HAVE_ARCH_KASAN_VMALLOC
177	help
178	  Makes KASAN check the validity of accesses to vmalloc allocations.
179
180	  With software KASAN modes, all types vmalloc allocations are
181	  checked. Enabling this option leads to higher memory usage.
182
183	  With Hardware Tag-Based KASAN, only non-executable VM_ALLOC mappings
184	  are checked. There is no additional memory usage.
185
186config KASAN_KUNIT_TEST
187	tristate "KUnit-compatible tests of KASAN bug detection capabilities" if !KUNIT_ALL_TESTS
188	depends on KASAN && KUNIT && TRACEPOINTS
189	default KUNIT_ALL_TESTS
190	help
191	  A KUnit-based KASAN test suite. Triggers different kinds of
192	  out-of-bounds and use-after-free accesses. Useful for testing whether
193	  KASAN can detect certain bug types.
194
195	  For more information on KUnit and unit tests in general, please refer
196	  to the KUnit documentation in Documentation/dev-tools/kunit/.
197
198config KASAN_EXTRA_INFO
199	bool "Record and report more information"
200	depends on KASAN
201	help
202	  Record and report more information to help us find the cause of the
203	  bug and to help us correlate the error with other system events.
204
205	  Currently, the CPU number and timestamp are additionally
206	  recorded for each heap block at allocation and free time, and
207	  8 bytes will be added to each metadata structure that records
208	  allocation or free information.
209
210	  In Generic KASAN, each kmalloc-8 and kmalloc-16 object will add
211	  16 bytes of additional memory consumption, and each kmalloc-32
212	  object will add 8 bytes of additional memory consumption, not
213	  affecting other larger objects.
214
215	  In SW_TAGS KASAN and HW_TAGS KASAN, depending on the stack_ring_size
216	  boot parameter, it will add 8 * stack_ring_size bytes of additional
217	  memory consumption.
218
219endif # KASAN
220