kasan: allow enabling stack tagging for tag-based mode

Use CONFIG_KASAN_STACK to enable stack tagging.

Note, that HWASAN short granules [1] are disabled. Supporting those will
require more kernel changes.

[1] https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html

Signed-off-by: Andrey Konovalov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Elena Petrova <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: Walter Wu <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Link: http://lkml.kernel.org/r/e7febb907b539c3730780df587ce0b38dc558c3d.1596199677.git.andreyknvl@google.com
Link: http://lkml.kernel.org/r/99f7d90a4237431bf5988599fb41358e92876eb0.1596544734.git.andreyknvl@google.com
Signed-off-by: Linus Torvalds <[email protected]>

Author: xairy

scripts/Makefile.kasan

@@ -44,7 +44,8 @@ else
 endif
 
 CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
-		-mllvm -hwasan-instrument-stack=0 \
+		-mllvm -hwasan-instrument-stack=$(CONFIG_KASAN_STACK) \
+		-mllvm -hwasan-use-short-granules=0 \
 		$(instrumentation_flags)
 
 endif # CONFIG_KASAN_SW_TAGS