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1config HAVE_ARCH_KASAN
2 bool
3
4if HAVE_ARCH_KASAN
5
6config KASAN
7 bool "KASan: runtime memory debugger"
8 depends on SLUB || (SLAB && !DEBUG_SLAB)
9 select CONSTRUCTORS
10 select STACKDEPOT
11 help
12 Enables kernel address sanitizer - runtime memory debugger,
13 designed to find out-of-bounds accesses and use-after-free bugs.
14 This is strictly a debugging feature and it requires a gcc version
15 of 4.9.2 or later. Detection of out of bounds accesses to stack or
16 global variables requires gcc 5.0 or later.
17 This feature consumes about 1/8 of available memory and brings about
18 ~x3 performance slowdown.
19 For better error detection enable CONFIG_STACKTRACE.
20 Currently CONFIG_KASAN doesn't work with CONFIG_DEBUG_SLAB
21 (the resulting kernel does not boot).
22
23config KASAN_EXTRA
24 bool "KAsan: extra checks"
25 depends on KASAN && DEBUG_KERNEL && !COMPILE_TEST
26 help
27 This enables further checks in the kernel address sanitizer, for now
28 it only includes the address-use-after-scope check that can lead
29 to excessive kernel stack usage, frame size warnings and longer
30 compile time.
31 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 has more
32
33
34choice
35 prompt "Instrumentation type"
36 depends on KASAN
37 default KASAN_OUTLINE
38
39config KASAN_OUTLINE
40 bool "Outline instrumentation"
41 help
42 Before every memory access compiler insert function call
43 __asan_load*/__asan_store*. These functions performs check
44 of shadow memory. This is slower than inline instrumentation,
45 however it doesn't bloat size of kernel's .text section so
46 much as inline does.
47
48config KASAN_INLINE
49 bool "Inline instrumentation"
50 help
51 Compiler directly inserts code checking shadow memory before
52 memory accesses. This is faster than outline (in some workloads
53 it gives about x2 boost over outline instrumentation), but
54 make kernel's .text size much bigger.
55 This requires a gcc version of 5.0 or later.
56
57endchoice
58
59config TEST_KASAN
60 tristate "Module for testing kasan for bug detection"
61 depends on m && KASAN
62 help
63 This is a test module doing various nasty things like
64 out of bounds accesses, use after free. It is useful for testing
65 kernel debugging features like kernel address sanitizer.
66
67endif
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