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1 | # SPDX-License-Identifier: GPL-2.0-only | |
2 | # This config refers to the generic KASAN mode. | |
3 | config HAVE_ARCH_KASAN | |
4 | bool | |
5 | ||
6 | config HAVE_ARCH_KASAN_SW_TAGS | |
7 | bool | |
8 | ||
9 | config HAVE_ARCH_KASAN_HW_TAGS | |
10 | bool | |
11 | ||
12 | config HAVE_ARCH_KASAN_VMALLOC | |
13 | bool | |
14 | ||
15 | config ARCH_DISABLE_KASAN_INLINE | |
16 | bool | |
17 | help | |
18 | An architecture might not support inline instrumentation. | |
19 | When this option is selected, inline and stack instrumentation are | |
20 | disabled. | |
21 | ||
22 | config CC_HAS_KASAN_GENERIC | |
23 | def_bool $(cc-option, -fsanitize=kernel-address) | |
24 | ||
25 | config 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 don't have proper support for no_sanitize_address. | |
30 | # See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89124 for details. | |
31 | config CC_HAS_WORKING_NOSANITIZE_ADDRESS | |
32 | def_bool !CC_IS_GCC || GCC_VERSION >= 80300 | |
33 | ||
34 | menuconfig KASAN | |
35 | bool "KASAN: runtime memory debugger" | |
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 (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) | |
41 | select STACKDEPOT | |
42 | help | |
43 | Enables KASAN (KernelAddressSANitizer) - runtime memory debugger, | |
44 | designed to find out-of-bounds accesses and use-after-free bugs. | |
45 | See Documentation/dev-tools/kasan.rst for details. | |
46 | ||
47 | if KASAN | |
48 | ||
49 | choice | |
50 | prompt "KASAN mode" | |
51 | default KASAN_GENERIC | |
52 | help | |
53 | KASAN has three modes: | |
54 | 1. generic KASAN (similar to userspace ASan, | |
55 | x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC), | |
56 | 2. software tag-based KASAN (arm64 only, based on software | |
57 | memory tagging (similar to userspace HWASan), enabled with | |
58 | CONFIG_KASAN_SW_TAGS), and | |
59 | 3. hardware tag-based KASAN (arm64 only, based on hardware | |
60 | memory tagging, enabled with CONFIG_KASAN_HW_TAGS). | |
61 | ||
62 | All KASAN modes are strictly debugging features. | |
63 | ||
64 | For better error reports enable CONFIG_STACKTRACE. | |
65 | ||
66 | config KASAN_GENERIC | |
67 | bool "Generic mode" | |
68 | depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC | |
69 | select SLUB_DEBUG if SLUB | |
70 | select CONSTRUCTORS | |
71 | help | |
72 | Enables generic KASAN mode. | |
73 | ||
74 | This mode is supported in both GCC and Clang. With GCC it requires | |
75 | version 8.3.0 or later. Any supported Clang version is compatible, | |
76 | but detection of out-of-bounds accesses for global variables is | |
77 | supported only since Clang 11. | |
78 | ||
79 | This mode consumes about 1/8th of available memory at kernel start | |
80 | and introduces an overhead of ~x1.5 for the rest of the allocations. | |
81 | The performance slowdown is ~x3. | |
82 | ||
83 | Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB | |
84 | (the resulting kernel does not boot). | |
85 | ||
86 | config KASAN_SW_TAGS | |
87 | bool "Software tag-based mode" | |
88 | depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS | |
89 | select SLUB_DEBUG if SLUB | |
90 | select CONSTRUCTORS | |
91 | help | |
92 | Enables software tag-based KASAN mode. | |
93 | ||
94 | This mode require software memory tagging support in the form of | |
95 | HWASan-like compiler instrumentation. | |
96 | ||
97 | Currently this mode is only implemented for arm64 CPUs and relies on | |
98 | Top Byte Ignore. This mode requires Clang. | |
99 | ||
100 | This mode consumes about 1/16th of available memory at kernel start | |
101 | and introduces an overhead of ~20% for the rest of the allocations. | |
102 | This mode may potentially introduce problems relating to pointer | |
103 | casting and comparison, as it embeds tags into the top byte of each | |
104 | pointer. | |
105 | ||
106 | Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB | |
107 | (the resulting kernel does not boot). | |
108 | ||
109 | config KASAN_HW_TAGS | |
110 | bool "Hardware tag-based mode" | |
111 | depends on HAVE_ARCH_KASAN_HW_TAGS | |
112 | depends on SLUB | |
113 | help | |
114 | Enables hardware tag-based KASAN mode. | |
115 | ||
116 | This mode requires hardware memory tagging support, and can be used | |
117 | by any architecture that provides it. | |
118 | ||
119 | Currently this mode is only implemented for arm64 CPUs starting from | |
120 | ARMv8.5 and relies on Memory Tagging Extension and Top Byte Ignore. | |
121 | ||
122 | endchoice | |
123 | ||
124 | choice | |
125 | prompt "Instrumentation type" | |
126 | depends on KASAN_GENERIC || KASAN_SW_TAGS | |
127 | default KASAN_OUTLINE | |
128 | ||
129 | config KASAN_OUTLINE | |
130 | bool "Outline instrumentation" | |
131 | help | |
132 | Before every memory access compiler insert function call | |
133 | __asan_load*/__asan_store*. These functions performs check | |
134 | of shadow memory. This is slower than inline instrumentation, | |
135 | however it doesn't bloat size of kernel's .text section so | |
136 | much as inline does. | |
137 | ||
138 | config KASAN_INLINE | |
139 | bool "Inline instrumentation" | |
140 | depends on !ARCH_DISABLE_KASAN_INLINE | |
141 | help | |
142 | Compiler directly inserts code checking shadow memory before | |
143 | memory accesses. This is faster than outline (in some workloads | |
144 | it gives about x2 boost over outline instrumentation), but | |
145 | make kernel's .text size much bigger. | |
146 | ||
147 | endchoice | |
148 | ||
149 | config KASAN_STACK | |
150 | bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST | |
151 | depends on KASAN_GENERIC || KASAN_SW_TAGS | |
152 | depends on !ARCH_DISABLE_KASAN_INLINE | |
153 | default y if CC_IS_GCC | |
154 | help | |
155 | The LLVM stack address sanitizer has a know problem that | |
156 | causes excessive stack usage in a lot of functions, see | |
157 | https://bugs.llvm.org/show_bug.cgi?id=38809 | |
158 | Disabling asan-stack makes it safe to run kernels build | |
159 | with clang-8 with KASAN enabled, though it loses some of | |
160 | the functionality. | |
161 | This feature is always disabled when compile-testing with clang | |
162 | to avoid cluttering the output in stack overflow warnings, | |
163 | but clang users can still enable it for builds without | |
164 | CONFIG_COMPILE_TEST. On gcc it is assumed to always be safe | |
165 | to use and enabled by default. | |
166 | If the architecture disables inline instrumentation, stack | |
167 | instrumentation is also disabled as it adds inline-style | |
168 | instrumentation that is run unconditionally. | |
169 | ||
170 | config KASAN_TAGS_IDENTIFY | |
171 | bool "Enable memory corruption identification" | |
172 | depends on KASAN_SW_TAGS || KASAN_HW_TAGS | |
173 | help | |
174 | This option enables best-effort identification of bug type | |
175 | (use-after-free or out-of-bounds) at the cost of increased | |
176 | memory consumption. | |
177 | ||
178 | config KASAN_VMALLOC | |
179 | bool "Back mappings in vmalloc space with real shadow memory" | |
180 | depends on KASAN_GENERIC && HAVE_ARCH_KASAN_VMALLOC | |
181 | help | |
182 | By default, the shadow region for vmalloc space is the read-only | |
183 | zero page. This means that KASAN cannot detect errors involving | |
184 | vmalloc space. | |
185 | ||
186 | Enabling this option will hook in to vmap/vmalloc and back those | |
187 | mappings with real shadow memory allocated on demand. This allows | |
188 | for KASAN to detect more sorts of errors (and to support vmapped | |
189 | stacks), but at the cost of higher memory usage. | |
190 | ||
191 | config KASAN_KUNIT_TEST | |
192 | tristate "KUnit-compatible tests of KASAN bug detection capabilities" if !KUNIT_ALL_TESTS | |
193 | depends on KASAN && KUNIT | |
194 | default KUNIT_ALL_TESTS | |
195 | help | |
196 | This is a KUnit test suite doing various nasty things like | |
197 | out of bounds and use after free accesses. It is useful for testing | |
198 | kernel debugging features like KASAN. | |
199 | ||
200 | For more information on KUnit and unit tests in general, please refer | |
201 | to the KUnit documentation in Documentation/dev-tools/kunit. | |
202 | ||
203 | config KASAN_MODULE_TEST | |
204 | tristate "KUnit-incompatible tests of KASAN bug detection capabilities" | |
205 | depends on m && KASAN && !KASAN_HW_TAGS | |
206 | help | |
207 | This is a part of the KASAN test suite that is incompatible with | |
208 | KUnit. Currently includes tests that do bad copy_from/to_user | |
209 | accesses. | |
210 | ||
211 | endif # KASAN |