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 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
  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
  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 config 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
 111 config 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
 127 endchoice
 128
 129 choice
 130         prompt "Instrumentation type"
 131         depends on KASAN_GENERIC || KASAN_SW_TAGS
 132         default KASAN_INLINE if !ARCH_DISABLE_KASAN_INLINE
 133
 134 config 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
 141 config 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
 149 endchoice
 150
 151 config 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://bugs.llvm.org/show_bug.cgi?id=38809. 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
 174 config 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
 186 config 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
 198 config KASAN_MODULE_TEST
 199         tristate "KUnit-incompatible tests of KASAN bug detection capabilities"
 200         depends on m && KASAN && !KASAN_HW_TAGS
 201         help
 202           A part of the KASAN test suite that is not integrated with KUnit.
 203           Incompatible with Hardware Tag-Based KASAN.
 204
 205 config KASAN_EXTRA_INFO
 206         bool "Record and report more information"
 207         depends on KASAN
 208         help
 209           Record and report more information to help us find the cause of the
 210           bug and to help us correlate the error with other system events.
 211
 212           Currently, the CPU number and timestamp are additionally
 213           recorded for each heap block at allocation and free time, and
 214           8 bytes will be added to each metadata structure that records
 215           allocation or free information.
 216
 217           In Generic KASAN, each kmalloc-8 and kmalloc-16 object will add
 218           16 bytes of additional memory consumption, and each kmalloc-32
 219           object will add 8 bytes of additional memory consumption, not
 220           affecting other larger objects.
 221
 222           In SW_TAGS KASAN and HW_TAGS KASAN, depending on the stack_ring_size
 223           boot parameter, it will add 8 * stack_ring_size bytes of additional
 224           memory consumption.
 225
 226 endif # KASAN