[PATCH 2/2] kbuild: rust: Enable KASAN support

[Matthew Maurer]

Rust supports KASAN via LLVM, but prior to this patch, the flags aren't
set properly.

Suggested-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Signed-off-by: Matthew Maurer <mmaurer@xxxxxxxxxx>
---
 scripts/Makefile.kasan | 46 +++++++++++++++++++++++++++++++++++++++++-
 scripts/Makefile.lib   |  3 +++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index 390658a2d5b7..84572c473e23 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -12,6 +12,7 @@ endif
 KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
 
 cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))
+rustc-param = $(call rustc-option, -Cllvm-args=-$(1),)
 
 ifdef CONFIG_KASAN_STACK
 	stack_enable := 1
@@ -28,6 +29,7 @@ else
 endif
 
 CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
+RUSTFLAGS_KASAN_MINIMAL := -Zsanitizer=kernel-address -Zsanitizer-recover=kernel-address
 
 # -fasan-shadow-offset fails without -fsanitize
 CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
@@ -36,13 +38,36 @@ CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
 			-mllvm -asan-mapping-offset=$(KASAN_SHADOW_OFFSET)))
 
 ifeq ($(strip $(CFLAGS_KASAN_SHADOW)),)
+	KASAN_SHADOW_SUPPORTED := n
+else
+	KASAN_SHADOW_SUPPORTED := y
+endif
+
+ifdef CONFIG_RUST
+	RUSTFLAGS_KASAN_SHADOW := $(call rustc-option $(RUSTFLAGS_KASAN_MINIMAL) \
+				  -Cllvm-args=-asan-mapping-offset=$(KASAN_SHADOW_OFFSET))
+	ifeq ($(strip $(RUSTFLAGS_KASAN_SHADOW)),)
+		KASAN_SHADOW_SUPPORTED := n
+	endif
+endif
+
+ifeq ($(KASAN_SHADOW_SUPPORTED),y)
 	CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
+	ifdef CONFIG_RUST
+		RUSTFLAGS_KASAN := $(RUSTFLAGS_KASAN_MINIMAL)
+	endif
 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-instrument-allocas=1)
+	ifdef CONFIG_RUST
+		RUSTFLAGS_KASAN := $(RUSTFLAGS_KASAN_SHADOW) \
+		 $(call rustc-param,asan-globals=1) \
+		 $(call rustc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
+		 $(call rustc-param,asan-instrument-allocas=1)
+	endif
 endif
 
 CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))
@@ -52,6 +77,11 @@ CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))
 # memintrinsics won't be checked by KASAN on GENERIC_ENTRY architectures.
 CFLAGS_KASAN += $(call cc-param,asan-kernel-mem-intrinsic-prefix=1)
 
+ifdef CONFIG_RUST
+	RUSTFLAGS_KASAN += $(call rustc-param,asan-stack=$(stack_enable))
+	RUSTFLAGS_KASAN += $(call rustc-param,asan-kernel-mem-intrinsic-prefix=1)
+endif
+
 endif # CONFIG_KASAN_GENERIC
 
 ifdef CONFIG_KASAN_SW_TAGS
@@ -73,6 +103,20 @@ ifeq ($(call clang-min-version, 150000)$(call gcc-min-version, 130000),y)
 CFLAGS_KASAN += $(call cc-param,hwasan-kernel-mem-intrinsic-prefix=1)
 endif
 
+ifdef CONFIG_RUST
+	ifdef CONFIG_KASAN_INLINE
+		rust_instrumentation_flags := $(call rustc-param,hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET))
+	else
+		rust_instrumentation_flags := $(call rustc-param,hwasan-instrument-with-calls=1)
+	endif
+	RUSTFLAGS_KASAN := -Zsanitizer=kernel-hwaddress -Zsanitizer-recover=kernel-hwaddress \
+			   $(call rustc-param,hwasan-instrument-stack=$(stack_enable)) \
+			   $(call rustc-param,hwasan-use-short-granules=0) \
+			   $(call rustc-param,hwasan-inline-all-checks=0) \
+			   $(call rustc-param,hwasan-kernel-mem-intrinsic-prefix=1) \
+			   $(instrumentation_flags)
+endif
+
 endif # CONFIG_KASAN_SW_TAGS
 
-export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE
+export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE RUSTFLAGS_KASAN
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 9f06f6aaf7fc..4a58636705e0 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -167,6 +167,9 @@ ifneq ($(CONFIG_KASAN_HW_TAGS),y)
 _c_flags += $(if $(patsubst n%,, \
 		$(KASAN_SANITIZE_$(target-stem).o)$(KASAN_SANITIZE)$(is-kernel-object)), \
 		$(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE))
+_rust_flags += $(if $(patsubst n%,, \
+		$(KASAN_SANITIZE_$(target-stem).o)$(KASAN_SANITIZE)$(is-kernel-object)), \
+		$(RUSTFLAGS_KASAN))
 endif
 endif
 
-- 
2.46.0.rc1.232.g9752f9e123-goog