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>

1 files changed, 31 insertions, 22 deletions

diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index 69552a39951d..25c259df8ffa 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
-ifdef CONFIG_KASAN
+ifdef CONFIG_KASAN_GENERIC
+
 ifdef CONFIG_KASAN_INLINE
 	call_threshold := 10000
 else
@@ -12,36 +13,44 @@ CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
 
 cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))
 
-ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
-   ifneq ($(CONFIG_COMPILE_TEST),y)
-        $(warning Cannot use CONFIG_KASAN: \
-            -fsanitize=kernel-address is not supported by compiler)
-   endif
-else
-   # -fasan-shadow-offset fails without -fsanitize
-   CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
+# -fasan-shadow-offset fails without -fsanitize
+CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
 			-fasan-shadow-offset=$(KASAN_SHADOW_OFFSET), \
 			$(call cc-option, -fsanitize=kernel-address \
 			-mllvm -asan-mapping-offset=$(KASAN_SHADOW_OFFSET)))
 
-   ifeq ($(strip $(CFLAGS_KASAN_SHADOW)),)
-      CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
-   else
-      # Now add all the compiler specific options that are valid standalone
-      CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
-	$(call cc-param,asan-globals=1) \
-	$(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
-	$(call cc-param,asan-stack=1) \
-	$(call cc-param,asan-use-after-scope=1) \
-	$(call cc-param,asan-instrument-allocas=1)
-   endif
-
+ifeq ($(strip $(CFLAGS_KASAN_SHADOW)),)
+	CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
+else
+	# Now add all the compiler specific options that are valid standalone
+	CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
+	 $(call cc-param,asan-globals=1) \
+	 $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
+	 $(call cc-param,asan-stack=1) \
+	 $(call cc-param,asan-use-after-scope=1) \
+	 $(call cc-param,asan-instrument-allocas=1)
 endif
 
 ifdef CONFIG_KASAN_EXTRA
 CFLAGS_KASAN += $(call cc-option, -fsanitize-address-use-after-scope)
 endif
 
-CFLAGS_KASAN_NOSANITIZE := -fno-builtin
+endif # CONFIG_KASAN_GENERIC
 
+ifdef CONFIG_KASAN_SW_TAGS
+
+ifdef CONFIG_KASAN_INLINE
+    instrumentation_flags := -mllvm -hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET)
+else
+    instrumentation_flags := -mllvm -hwasan-instrument-with-calls=1
+endif
+
+CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
+		-mllvm -hwasan-instrument-stack=0 \
+		$(instrumentation_flags)
+
+endif # CONFIG_KASAN_SW_TAGS
+
+ifdef CONFIG_KASAN
+CFLAGS_KASAN_NOSANITIZE := -fno-builtin
 endif