lib/Kconfig.kasan

   1 # SPDX-License-Identifier: GPL-2.0-only
   2
   3 # This config refers to the generic KASAN mode.
   4 config HAVE_ARCH_KASAN
   5         bool
   6
   7 config HAVE_ARCH_KASAN_SW_TAGS
   8         bool
   9
  10 config HAVE_ARCH_KASAN_HW_TAGS
  11         bool
  12
  13 config HAVE_ARCH_KASAN_VMALLOC
  14         bool
  15
  16 config 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
  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 do not 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: 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 (SLUB && SYSFS && !SLUB_TINY) || (SLAB && !DEBUG_SLAB)
  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
  50 if KASAN
  51
  52 config 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
  61 choice
  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
  77 config 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 if SLUB
  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
  92           (Incompatible with CONFIG_DEBUG_SLAB: the kernel does not boot.)
  93
  94 config KASAN_SW_TAGS
  95         bool "Software Tag-Based KASAN"
  96         depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
  97         depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
  98         select SLUB_DEBUG if SLUB
  99         select CONSTRUCTORS
 100         help
 101           Enables Software Tag-Based KASAN.
 102
 103           Requires GCC 11+ or Clang.
 104
 105           Supported only on arm64 CPUs and relies on Top Byte Ignore.
 106
 107           Consumes about 1/16th of available memory at kernel start and
 108           add an overhead of ~20% for dynamic allocations.
 109
 110           May potentially introduce problems related to pointer casting and
 111           comparison, as it embeds a tag into the top byte of each pointer.
 112
 113           (Incompatible with CONFIG_DEBUG_SLAB: the kernel does not boot.)
 114
 115 config KASAN_HW_TAGS
 116         bool "Hardware Tag-Based KASAN"
 117         depends on HAVE_ARCH_KASAN_HW_TAGS
 118         depends on SLUB
 119         help
 120           Enables Hardware Tag-Based KASAN.
 121
 122           Requires GCC 10+ or Clang 12+.
 123
 124           Supported only on arm64 CPUs starting from ARMv8.5 and relies on
 125           Memory Tagging Extension and Top Byte Ignore.
 126
 127           Consumes about 1/32nd of available memory.
 128
 129           May potentially introduce problems related to pointer casting and
 130           comparison, as it embeds a tag into the top byte of each pointer.
 131
 132 endchoice
 133
 134 choice
 135         prompt "Instrumentation type"
 136         depends on KASAN_GENERIC || KASAN_SW_TAGS
 137         default KASAN_OUTLINE
 138
 139 config KASAN_OUTLINE
 140         bool "Outline instrumentation"
 141         help
 142           Makes the compiler insert function calls that check whether the memory
 143           is accessible before each memory access. Slower than KASAN_INLINE, but
 144           does not bloat the size of the kernel's .text section so much.
 145
 146 config KASAN_INLINE
 147         bool "Inline instrumentation"
 148         depends on !ARCH_DISABLE_KASAN_INLINE
 149         help
 150           Makes the compiler directly insert memory accessibility checks before
 151           each memory access. Faster than KASAN_OUTLINE (gives ~x2 boost for
 152           some workloads), but makes the kernel's .text size much bigger.
 153
 154 endchoice
 155
 156 config KASAN_STACK
 157         bool "Stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
 158         depends on KASAN_GENERIC || KASAN_SW_TAGS
 159         depends on !ARCH_DISABLE_KASAN_INLINE
 160         default y if CC_IS_GCC
 161         help
 162           Disables stack instrumentation and thus KASAN's ability to detect
 163           out-of-bounds bugs in stack variables.
 164
 165           With Clang, stack instrumentation has a problem that causes excessive
 166           stack usage, see https://bugs.llvm.org/show_bug.cgi?id=38809. Thus,
 167           with Clang, this option is deemed unsafe.
 168
 169           This option is always disabled when compile-testing with Clang to
 170           avoid cluttering the log with stack overflow warnings.
 171
 172           With GCC, enabling stack instrumentation is assumed to be safe.
 173
 174           If the architecture disables inline instrumentation via
 175           ARCH_DISABLE_KASAN_INLINE, stack instrumentation gets disabled
 176           as well, as it adds inline-style instrumentation that is run
 177           unconditionally.
 178
 179 config KASAN_VMALLOC
 180         bool "Check accesses to vmalloc allocations"
 181         depends on HAVE_ARCH_KASAN_VMALLOC
 182         help
 183           Makes KASAN check the validity of accesses to vmalloc allocations.
 184
 185           With software KASAN modes, all types vmalloc allocations are
 186           checked. Enabling this option leads to higher memory usage.
 187
 188           With Hardware Tag-Based KASAN, only non-executable VM_ALLOC mappings
 189           are checked. There is no additional 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 && TRACEPOINTS
 194         default KUNIT_ALL_TESTS
 195         help
 196           A KUnit-based KASAN test suite. Triggers different kinds of
 197           out-of-bounds and use-after-free accesses. Useful for testing whether
 198           KASAN can detect certain bug types.
 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           A part of the KASAN test suite that is not integrated with KUnit.
 208           Incompatible with Hardware Tag-Based KASAN.
 209
 210 endif # KASAN