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+# SPDX-License-Identifier: GPL-2.0-only
+
+# This config refers to the generic KASAN mode.
+config HAVE_ARCH_KASAN
+ bool
+
+config HAVE_ARCH_KASAN_SW_TAGS
+ bool
+
+config HAVE_ARCH_KASAN_HW_TAGS
+ bool
+
+config HAVE_ARCH_KASAN_VMALLOC
+ bool
+
+config ARCH_DISABLE_KASAN_INLINE
+ bool
+ help
+ Disables both inline and stack instrumentation. Selected by
+ architectures that do not support these instrumentation types.
+
+config CC_HAS_KASAN_GENERIC
+ def_bool $(cc-option, -fsanitize=kernel-address)
+
+config CC_HAS_KASAN_SW_TAGS
+ def_bool $(cc-option, -fsanitize=kernel-hwaddress)
+
+# This option is only required for software KASAN modes.
+# Old GCC versions do not have proper support for no_sanitize_address.
+# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89124 for details.
+config CC_HAS_WORKING_NOSANITIZE_ADDRESS
+ def_bool !CC_IS_GCC || GCC_VERSION >= 80300
+
+menuconfig KASAN
+ bool "KASAN: dynamic memory safety error detector"
+ depends on (((HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
+ (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)) && \
+ CC_HAS_WORKING_NOSANITIZE_ADDRESS) || \
+ HAVE_ARCH_KASAN_HW_TAGS
+ depends on (SLUB && SYSFS && !SLUB_TINY) || (SLAB && !DEBUG_SLAB)
+ select STACKDEPOT_ALWAYS_INIT
+ help
+ Enables KASAN (Kernel Address Sanitizer) - a dynamic memory safety
+ error detector designed to find out-of-bounds and use-after-free bugs.
+
+ See Documentation/dev-tools/kasan.rst for details.
+
+ For better error reports, also enable CONFIG_STACKTRACE.
+
+if KASAN
+
+config CC_HAS_KASAN_MEMINTRINSIC_PREFIX
+ def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=kernel-address -mllvm -asan-kernel-mem-intrinsic-prefix=1)) || \
+ (CC_IS_GCC && $(cc-option,-fsanitize=kernel-address --param asan-kernel-mem-intrinsic-prefix=1))
+ # Don't define it if we don't need it: compilation of the test uses
+ # this variable to decide how the compiler should treat builtins.
+ depends on !KASAN_HW_TAGS
+ help
+ The compiler is able to prefix memintrinsics with __asan or __hwasan.
+
+choice
+ prompt "KASAN mode"
+ default KASAN_GENERIC
+ help
+ KASAN has three modes:
+
+ 1. Generic KASAN (supported by many architectures, enabled with
+ CONFIG_KASAN_GENERIC, similar to userspace ASan),
+ 2. Software Tag-Based KASAN (arm64 only, based on software memory
+ tagging, enabled with CONFIG_KASAN_SW_TAGS, similar to userspace
+ HWASan), and
+ 3. Hardware Tag-Based KASAN (arm64 only, based on hardware memory
+ tagging, enabled with CONFIG_KASAN_HW_TAGS).
+
+ See Documentation/dev-tools/kasan.rst for details about each mode.
+
+config KASAN_GENERIC
+ bool "Generic KASAN"
+ depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC
+ depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
+ select SLUB_DEBUG if SLUB
+ select CONSTRUCTORS
+ help
+ Enables Generic KASAN.
+
+ Requires GCC 8.3.0+ or Clang.
+
+ Consumes about 1/8th of available memory at kernel start and adds an
+ overhead of ~50% for dynamic allocations.
+ The performance slowdown is ~x3.
+
+ (Incompatible with CONFIG_DEBUG_SLAB: the kernel does not boot.)
+
+config KASAN_SW_TAGS
+ bool "Software Tag-Based KASAN"
+ depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
+ depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
+ select SLUB_DEBUG if SLUB
+ select CONSTRUCTORS
+ help
+ Enables Software Tag-Based KASAN.
+
+ Requires GCC 11+ or Clang.
+
+ Supported only on arm64 CPUs and relies on Top Byte Ignore.
+
+ Consumes about 1/16th of available memory at kernel start and
+ add an overhead of ~20% for dynamic allocations.
+
+ May potentially introduce problems related to pointer casting and
+ comparison, as it embeds a tag into the top byte of each pointer.
+
+ (Incompatible with CONFIG_DEBUG_SLAB: the kernel does not boot.)
+
+config KASAN_HW_TAGS
+ bool "Hardware Tag-Based KASAN"
+ depends on HAVE_ARCH_KASAN_HW_TAGS
+ depends on SLUB
+ help
+ Enables Hardware Tag-Based KASAN.
+
+ Requires GCC 10+ or Clang 12+.
+
+ Supported only on arm64 CPUs starting from ARMv8.5 and relies on
+ Memory Tagging Extension and Top Byte Ignore.
+
+ Consumes about 1/32nd of available memory.
+
+ May potentially introduce problems related to pointer casting and
+ comparison, as it embeds a tag into the top byte of each pointer.
+
+endchoice
+
+choice
+ prompt "Instrumentation type"
+ depends on KASAN_GENERIC || KASAN_SW_TAGS
+ default KASAN_OUTLINE
+
+config KASAN_OUTLINE
+ bool "Outline instrumentation"
+ help
+ Makes the compiler insert function calls that check whether the memory
+ is accessible before each memory access. Slower than KASAN_INLINE, but
+ does not bloat the size of the kernel's .text section so much.
+
+config KASAN_INLINE
+ bool "Inline instrumentation"
+ depends on !ARCH_DISABLE_KASAN_INLINE
+ help
+ Makes the compiler directly insert memory accessibility checks before
+ each memory access. Faster than KASAN_OUTLINE (gives ~x2 boost for
+ some workloads), but makes the kernel's .text size much bigger.
+
+endchoice
+
+config KASAN_STACK
+ bool "Stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
+ depends on KASAN_GENERIC || KASAN_SW_TAGS
+ depends on !ARCH_DISABLE_KASAN_INLINE
+ default y if CC_IS_GCC
+ help
+ Disables stack instrumentation and thus KASAN's ability to detect
+ out-of-bounds bugs in stack variables.
+
+ With Clang, stack instrumentation has a problem that causes excessive
+ stack usage, see https://bugs.llvm.org/show_bug.cgi?id=38809. Thus,
+ with Clang, this option is deemed unsafe.
+
+ This option is always disabled when compile-testing with Clang to
+ avoid cluttering the log with stack overflow warnings.
+
+ With GCC, enabling stack instrumentation is assumed to be safe.
+
+ If the architecture disables inline instrumentation via
+ ARCH_DISABLE_KASAN_INLINE, stack instrumentation gets disabled
+ as well, as it adds inline-style instrumentation that is run
+ unconditionally.
+
+config KASAN_VMALLOC
+ bool "Check accesses to vmalloc allocations"
+ depends on HAVE_ARCH_KASAN_VMALLOC
+ help
+ Makes KASAN check the validity of accesses to vmalloc allocations.
+
+ With software KASAN modes, all types vmalloc allocations are
+ checked. Enabling this option leads to higher memory usage.
+
+ With Hardware Tag-Based KASAN, only non-executable VM_ALLOC mappings
+ are checked. There is no additional memory usage.
+
+config KASAN_KUNIT_TEST
+ tristate "KUnit-compatible tests of KASAN bug detection capabilities" if !KUNIT_ALL_TESTS
+ depends on KASAN && KUNIT && TRACEPOINTS
+ default KUNIT_ALL_TESTS
+ help
+ A KUnit-based KASAN test suite. Triggers different kinds of
+ out-of-bounds and use-after-free accesses. Useful for testing whether
+ KASAN can detect certain bug types.
+
+ For more information on KUnit and unit tests in general, please refer
+ to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+config KASAN_MODULE_TEST
+ tristate "KUnit-incompatible tests of KASAN bug detection capabilities"
+ depends on m && KASAN && !KASAN_HW_TAGS
+ help
+ A part of the KASAN test suite that is not integrated with KUnit.
+ Incompatible with Hardware Tag-Based KASAN.
+
+endif # KASAN