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authorAndrey Konovalov <andreyknvl@google.com>2018-12-28 00:29:53 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-12-28 12:11:43 -0800
commit2bd926b439b4cb6b9ed240a9781cd01958b53d85 (patch)
treebfdd9f2a3f0111b3a3510032aabdc6f90ce73ed4 /lib
parentb938fcf42739de8270e6ea41593722929c8a7dd0 (diff)
downloadlinux-stericsson-2bd926b439b4cb6b9ed240a9781cd01958b53d85.tar.gz
kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS
This commit splits the current CONFIG_KASAN config option into two: 1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one that exists now); 2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode. The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have another hardware tag-based KASAN mode, that will rely on hardware memory tagging support in arm64. With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to instrument kernel files with -fsantize=kernel-hwaddress (except the ones for which KASAN_SANITIZE := n is set). Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes. This commit also adds empty placeholder (for now) implementation of tag-based KASAN specific hooks inserted by the compiler and adjusts common hooks implementation. While this commit adds the CONFIG_KASAN_SW_TAGS config option, this option is not selectable, as it depends on HAVE_ARCH_KASAN_SW_TAGS, which we will enable once all the infrastracture code has been added. Link: http://lkml.kernel.org/r/b2550106eb8a68b10fefbabce820910b115aa853.1544099024.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.kasan98
1 files changed, 76 insertions, 22 deletions
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index d0bad1bd9a2b..d8c474b6691e 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -1,36 +1,92 @@
+# This config refers to the generic KASAN mode.
config HAVE_ARCH_KASAN
bool
-if HAVE_ARCH_KASAN
+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"
+ 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 kernel address sanitizer - runtime memory debugger,
- designed to find out-of-bounds accesses and use-after-free bugs.
- This is strictly a debugging feature and it requires a gcc version
- of 4.9.2 or later. Detection of out of bounds accesses to stack or
- global variables requires gcc 5.0 or later.
- This feature consumes about 1/8 of available memory and brings about
- ~x3 performance slowdown.
+ 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 doesn't work with CONFIG_DEBUG_SLAB
+ 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 && DEBUG_KERNEL && !COMPILE_TEST
+ bool "KASAN: extra checks"
+ depends on KASAN_GENERIC && DEBUG_KERNEL && !COMPILE_TEST
help
- This enables further checks in the kernel address sanitizer, for now
- it only includes the address-use-after-scope check that can lead
- to excessive kernel stack usage, frame size warnings and longer
+ 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.
- https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 has more
-
+ See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715
choice
prompt "Instrumentation type"
@@ -53,7 +109,7 @@ config KASAN_INLINE
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.
- This requires a gcc version of 5.0 or later.
+ For CONFIG_KASAN_GENERIC this requires GCC 5.0 or later.
endchoice
@@ -67,11 +123,9 @@ config KASAN_S390_4_LEVEL_PAGING
4-level paging instead.
config TEST_KASAN
- tristate "Module for testing kasan for bug detection"
+ 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 kernel address sanitizer.
-
-endif
+ kernel debugging features like KASAN.