kasan: introduce CONFIG_KASAN_HW_TAGS

This patch adds a configuration option for a new KASAN mode called
hardware tag-based KASAN.  This mode uses the memory tagging approach like
the software tag-based mode, but relies on arm64 Memory Tagging Extension
feature for tag management and access checking.

Link: https://lkml.kernel.org/r/44906a209d3a44f9c6f5a21841e90988e365601e.1606161801.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Co-developed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Vasily Gorbik <gor@linux.ibm.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>

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index c0e9e78..f5fa4ba 100644 (file)
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -6,7 +6,10 @@ config HAVE_ARCH_KASAN
 config HAVE_ARCH_KASAN_SW_TAGS
        bool
 
-config HAVE_ARCH_KASAN_VMALLOC
+config HAVE_ARCH_KASAN_HW_TAGS
+       bool
+
+config HAVE_ARCH_KASAN_VMALLOC
        bool
 
 config CC_HAS_KASAN_GENERIC
@@ -15,16 +18,19 @@ config CC_HAS_KASAN_GENERIC
 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 don't 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: runtime memory debugger"
-       depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
-                  (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)
+       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) || (SLAB && !DEBUG_SLAB)
-       depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
-       select CONSTRUCTORS
        select STACKDEPOT
        help
          Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
@@ -37,18 +43,24 @@ choice
        prompt "KASAN mode"
        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).
+         KASAN has three modes:
+         1. generic KASAN (similar to userspace ASan,
+            x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC),
+         2. software tag-based KASAN (arm64 only, based on software
+            memory tagging (similar to userspace HWASan), enabled with
+            CONFIG_KASAN_SW_TAGS), and
+         3. hardware tag-based KASAN (arm64 only, based on hardware
+            memory tagging, enabled with CONFIG_KASAN_HW_TAGS).
+
+         All KASAN modes are strictly debugging features.
 
-         Both generic and tag-based KASAN are strictly debugging features.
+         For better error reports enable CONFIG_STACKTRACE.
 
 config KASAN_GENERIC
        bool "Generic mode"
        depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC
        select SLUB_DEBUG if SLUB
+       select CONSTRUCTORS
        help
          Enables generic KASAN mode.
 
@@ -61,8 +73,6 @@ config KASAN_GENERIC
          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).
 
@@ -70,11 +80,15 @@ config KASAN_SW_TAGS
        bool "Software tag-based mode"
        depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
        select SLUB_DEBUG if SLUB
+       select CONSTRUCTORS
        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.
+         This mode require software memory tagging support in the form of
+         HWASan-like compiler instrumentation.
+
+         Currently this mode is only implemented for arm64 CPUs and relies on
+         Top Byte Ignore. This mode requires Clang.
 
          This mode consumes about 1/16th of available memory at kernel start
          and introduces an overhead of ~20% for the rest of the allocations.
@@ -82,15 +96,27 @@ config KASAN_SW_TAGS
          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).
 
+config KASAN_HW_TAGS
+       bool "Hardware tag-based mode"
+       depends on HAVE_ARCH_KASAN_HW_TAGS
+       depends on SLUB
+       help
+         Enables hardware tag-based KASAN mode.
+
+         This mode requires hardware memory tagging support, and can be used
+         by any architecture that provides it.
+
+         Currently this mode is only implemented for arm64 CPUs starting from
+         ARMv8.5 and relies on Memory Tagging Extension and Top Byte Ignore.
+
 endchoice
 
 choice
        prompt "Instrumentation type"
+       depends on KASAN_GENERIC || KASAN_SW_TAGS
        default KASAN_OUTLINE
 
 config KASAN_OUTLINE
@@ -114,6 +140,7 @@ endchoice
 
 config KASAN_STACK_ENABLE
        bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
+       depends on KASAN_GENERIC || KASAN_SW_TAGS
        help
          The LLVM stack address sanitizer has a know problem that
          causes excessive stack usage in a lot of functions, see