[PATCH v3 2/5] kasan/Makefile: Support LLVM style asan parameters.

[Paul Lawrence]

LLVM doesn't understand GCC-style paramters ("--param asan-foo=bar"),
thus we currently we don't use inline/globals/stack instrumentation
when building the kernel with clang.

Add support for LLVM-style parameters ("-mllvm -asan-foo=bar") to
enable all KASAN features.

Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
---
 scripts/Makefile.kasan | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index 1ce7115aa499..7c00be9216f4 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -10,10 +10,7 @@ KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
 
 CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
 
-CFLAGS_KASAN := $(call cc-option, -fsanitize=kernel-address \
-		-fasan-shadow-offset=$(KASAN_SHADOW_OFFSET) \
-		--param asan-stack=1 --param asan-globals=1 \
-		--param asan-instrumentation-with-call-threshold=$(call_threshold))
+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)
@@ -21,13 +18,23 @@ ifeq ($(call cc-option, $(CFLAGS_KASAN_MINIMAL) -Werror),)
             -fsanitize=kernel-address is not supported by compiler)
    endif
 else
-    ifeq ($(CFLAGS_KASAN),)
-        ifneq ($(CONFIG_COMPILE_TEST),y)
-            $(warning CONFIG_KASAN: compiler does not support all options.\
-                Trying minimal configuration)
-        endif
-        CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
-    endif
+   # -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 ("$(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)
+   endif
+
 endif
 
 CFLAGS_KASAN += $(call cc-option, -fsanitize-address-use-after-scope)
-- 
2.15.0.531.g2ccb3012c9-goog