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