[linux-2.6-block.git] / lib / Kconfig.kasan

# This config refers to the generic KASAN mode.
config HAVE_ARCH_KASAN
	bool

config HAVE_ARCH_KASAN_SW_TAGS
	bool

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)

config KASAN
	bool "KASAN: runtime memory debugger"
	depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
		   (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)
	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
	help
	  Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
	  designed to find out-of-bounds accesses and use-after-free bugs.
	  See Documentation/dev-tools/kasan.rst for details.

choice
	prompt "KASAN mode"
	depends on KASAN
	default KASAN_GENERIC
	help
	  KASAN has two modes: generic KASAN (similar to userspace ASan,
	  x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC) and
	  software tag-based KASAN (a version based on software memory
	  tagging, arm64 only, similar to userspace HWASan, enabled with
	  CONFIG_KASAN_SW_TAGS).
	  Both generic and tag-based KASAN are strictly debugging features.

config KASAN_GENERIC
	bool "Generic mode"
	depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC
	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
	select SLUB_DEBUG if SLUB
	select CONSTRUCTORS
	select STACKDEPOT
	help
	  Enables generic KASAN mode.
	  Supported in both GCC and Clang. With GCC it requires version 4.9.2
	  or later for basic support and version 5.0 or later for detection of
	  out-of-bounds accesses for stack and global variables and for inline
	  instrumentation mode (CONFIG_KASAN_INLINE). With Clang it requires
	  version 3.7.0 or later and it doesn't support detection of
	  out-of-bounds accesses for global variables yet.
	  This mode consumes about 1/8th of available memory at kernel start
	  and introduces an overhead of ~x1.5 for the rest of the allocations.
	  The performance slowdown is ~x3.
	  For better error detection enable CONFIG_STACKTRACE.
	  Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB
	  (the resulting kernel does not boot).

config KASAN_SW_TAGS
	bool "Software tag-based mode"
	depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
	select SLUB_DEBUG if SLUB
	select CONSTRUCTORS
	select STACKDEPOT
	help
	  Enables software tag-based KASAN mode.
	  This mode requires Top Byte Ignore support by the CPU and therefore
	  is only supported for arm64.
	  This mode requires Clang version 7.0.0 or later.
	  This mode consumes about 1/16th of available memory at kernel start
	  and introduces an overhead of ~20% for the rest of the allocations.
	  This mode may potentially introduce problems relating to pointer
	  casting and comparison, as it embeds tags into the top byte of each
	  pointer.
	  For better error detection enable CONFIG_STACKTRACE.
	  Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB
	  (the resulting kernel does not boot).

endchoice

config KASAN_EXTRA
	bool "KASAN: extra checks"
	depends on KASAN_GENERIC && DEBUG_KERNEL && !COMPILE_TEST
	help
	  This enables further checks in generic KASAN, for now it only
	  includes the address-use-after-scope check that can lead to
	  excessive kernel stack usage, frame size warnings and longer
	  compile time.
	  See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715

choice
	prompt "Instrumentation type"
	depends on KASAN
	default KASAN_OUTLINE

config KASAN_OUTLINE
	bool "Outline instrumentation"
	help
	  Before every memory access compiler insert function call
	  __asan_load*/__asan_store*. These functions performs check
	  of shadow memory. This is slower than inline instrumentation,
	  however it doesn't bloat size of kernel's .text section so
	  much as inline does.

config KASAN_INLINE
	bool "Inline instrumentation"
	help
	  Compiler directly inserts code checking shadow memory before
	  memory accesses. This is faster than outline (in some workloads
	  it gives about x2 boost over outline instrumentation), but
	  make kernel's .text size much bigger.
	  For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later.

endchoice

config KASAN_S390_4_LEVEL_PAGING
	bool "KASan: use 4-level paging"
	depends on KASAN && S390
	help
	  Compiling the kernel with KASan disables automatic 3-level vs
	  4-level paging selection. 3-level paging is used by default (up
	  to 3TB of RAM with KASan enabled). This options allows to force
	  4-level paging instead.

config TEST_KASAN
	tristate "Module for testing KASAN for bug detection"
	depends on m && KASAN
	help
	  This is a test module doing various nasty things like
	  out of bounds accesses, use after free. It is useful for testing
	  kernel debugging features like KASAN.
Commit	Line	Data
2bd926b4	1	# This config refers to the generic KASAN mode.
0b24becc AR	2	config HAVE_ARCH_KASAN
	3	bool
	4
2bd926b4 AK	5	config HAVE_ARCH_KASAN_SW_TAGS
	6	bool
	7
	8	config CC_HAS_KASAN_GENERIC
	9	def_bool $(cc-option, -fsanitize=kernel-address)
	10
	11	config CC_HAS_KASAN_SW_TAGS
	12	def_bool $(cc-option, -fsanitize=kernel-hwaddress)
0b24becc AR	13
0b24becc AR	14	config KASAN
2bd926b4 AK	15	bool "KASAN: runtime memory debugger"
	16	depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) \|\| \
	17	(HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)
	18	depends on (SLUB && SYSFS) \|\| (SLAB && !DEBUG_SLAB)
	19	help
	20	Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
	21	designed to find out-of-bounds accesses and use-after-free bugs.
	22	See Documentation/dev-tools/kasan.rst for details.
	23
	24	choice
	25	prompt "KASAN mode"
	26	depends on KASAN
	27	default KASAN_GENERIC
	28	help
	29	KASAN has two modes: generic KASAN (similar to userspace ASan,
	30	x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC) and
	31	software tag-based KASAN (a version based on software memory
	32	tagging, arm64 only, similar to userspace HWASan, enabled with
	33	CONFIG_KASAN_SW_TAGS).
	34	Both generic and tag-based KASAN are strictly debugging features.
	35
	36	config KASAN_GENERIC
	37	bool "Generic mode"
	38	depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC
03758dbb	39	depends on (SLUB && SYSFS) \|\| (SLAB && !DEBUG_SLAB)
dd275caf	40	select SLUB_DEBUG if SLUB
bebf56a1	41	select CONSTRUCTORS
80a9201a	42	select STACKDEPOT
0b24becc	43	help
2bd926b4 AK	44	Enables generic KASAN mode.
	45	Supported in both GCC and Clang. With GCC it requires version 4.9.2
	46	or later for basic support and version 5.0 or later for detection of
	47	out-of-bounds accesses for stack and global variables and for inline
	48	instrumentation mode (CONFIG_KASAN_INLINE). With Clang it requires
	49	version 3.7.0 or later and it doesn't support detection of
	50	out-of-bounds accesses for global variables yet.
	51	This mode consumes about 1/8th of available memory at kernel start
	52	and introduces an overhead of ~x1.5 for the rest of the allocations.
	53	The performance slowdown is ~x3.
89d3c87e	54	For better error detection enable CONFIG_STACKTRACE.
2bd926b4	55	Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB
7ed2f9e6	56	(the resulting kernel does not boot).
0b24becc	57
2bd926b4 AK	58	config KASAN_SW_TAGS
	59	bool "Software tag-based mode"
	60	depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
	61	depends on (SLUB && SYSFS) \|\| (SLAB && !DEBUG_SLAB)
	62	select SLUB_DEBUG if SLUB
	63	select CONSTRUCTORS
	64	select STACKDEPOT
	65	help
	66	Enables software tag-based KASAN mode.
	67	This mode requires Top Byte Ignore support by the CPU and therefore
	68	is only supported for arm64.
	69	This mode requires Clang version 7.0.0 or later.
	70	This mode consumes about 1/16th of available memory at kernel start
	71	and introduces an overhead of ~20% for the rest of the allocations.
	72	This mode may potentially introduce problems relating to pointer
	73	casting and comparison, as it embeds tags into the top byte of each
	74	pointer.
	75	For better error detection enable CONFIG_STACKTRACE.
	76	Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB
	77	(the resulting kernel does not boot).
	78
	79	endchoice
	80
e7c52b84	81	config KASAN_EXTRA
2bd926b4 AK	82	bool "KASAN: extra checks"
2bd926b4 AK	83	depends on KASAN_GENERIC && DEBUG_KERNEL && !COMPILE_TEST
e7c52b84	84	help
2bd926b4 AK	85	This enables further checks in generic KASAN, for now it only
	86	includes the address-use-after-scope check that can lead to
	87	excessive kernel stack usage, frame size warnings and longer
e7c52b84	88	compile time.
2bd926b4	89	See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715
e7c52b84	90
0b24becc AR	91	choice
	92	prompt "Instrumentation type"
	93	depends on KASAN
	94	default KASAN_OUTLINE
	95
	96	config KASAN_OUTLINE
	97	bool "Outline instrumentation"
	98	help
	99	Before every memory access compiler insert function call
	100	__asan_load/__asan_store. These functions performs check
	101	of shadow memory. This is slower than inline instrumentation,
	102	however it doesn't bloat size of kernel's .text section so
	103	much as inline does.
	104
	105	config KASAN_INLINE
	106	bool "Inline instrumentation"
	107	help
	108	Compiler directly inserts code checking shadow memory before
	109	memory accesses. This is faster than outline (in some workloads
	110	it gives about x2 boost over outline instrumentation), but
	111	make kernel's .text size much bigger.
2bd926b4	112	For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later.
0b24becc AR	113
	114	endchoice
	115
5dff0381 VG	116	config KASAN_S390_4_LEVEL_PAGING
	117	bool "KASan: use 4-level paging"
	118	depends on KASAN && S390
	119	help
	120	Compiling the kernel with KASan disables automatic 3-level vs
	121	4-level paging selection. 3-level paging is used by default (up
	122	to 3TB of RAM with KASan enabled). This options allows to force
	123	4-level paging instead.
	124
3f15801c	125	config TEST_KASAN
2bd926b4	126	tristate "Module for testing KASAN for bug detection"
3f15801c AR	127	depends on m && KASAN
	128	help
	129	This is a test module doing various nasty things like
	130	out of bounds accesses, use after free. It is useful for testing
2bd926b4	131	kernel debugging features like KASAN.