[PATCH v2 2/7] ubsan: Move cc-option tests into Kconfig

[Kees Cook <keescook@chromium.org>]

Instead of doing if/endif blocks with cc-option calls in the UBSAN
Makefile, move all the tests into Kconfig and use the Makefile to
collect the results.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/lkml/CAHk-=wjPasyJrDuwDnpHJS2TuQfExwe=px-SzLeN8GFMAQJPmQ@mail.gmail.com/
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 lib/Kconfig.ubsan      | 61 +++++++++++++++++++++++++++++++++++++++---
 scripts/Makefile.ubsan | 45 +++++++++++--------------------
 2 files changed, 73 insertions(+), 33 deletions(-)

diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index d8d4d6557b80..05147112b355 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -36,10 +36,17 @@ config UBSAN_KCOV_BROKEN
 	  See https://bugs.llvm.org/show_bug.cgi?id=45831 for the status
 	  in newer releases.
 
+config CC_HAS_UBSAN_BOUNDS
+	def_bool $(cc-option,-fsanitize=bounds)
+
+config CC_HAS_UBSAN_ARRAY_BOUNDS
+	def_bool $(cc-option,-fsanitize=array-bounds)
+
 config UBSAN_BOUNDS
 	bool "Perform array index bounds checking"
 	default UBSAN
 	depends on !UBSAN_KCOV_BROKEN
+	depends on CC_HAS_UBSAN_ARRAY_BOUNDS || CC_HAS_UBSAN_BOUNDS
 	help
 	  This option enables detection of directly indexed out of bounds
 	  array accesses, where the array size is known at compile time.
@@ -47,15 +54,30 @@ config UBSAN_BOUNDS
 	  to the {str,mem}*cpy() family of functions (that is addressed
 	  by CONFIG_FORTIFY_SOURCE).
 
+config UBSAN_ONLY_BOUNDS
+	def_bool CC_HAS_UBSAN_BOUNDS && !CC_HAS_UBSAN_ARRAY_BOUNDS
+	depends on UBSAN_BOUNDS
+	help
+	  This is a weird case: Clang's -fsanitize=bounds includes
+	  -fsanitize=local-bounds, but it's trapping-only, so for
+	  Clang, we must use -fsanitize=array-bounds when we want
+	  traditional array bounds checking enabled. For GCC, we
+	  want -fsanitize=bounds.
+
+config UBSAN_ARRAY_BOUNDS
+	def_bool CC_HAS_UBSAN_ARRAY_BOUNDS
+	depends on UBSAN_BOUNDS
+
 config UBSAN_LOCAL_BOUNDS
 	bool "Perform array local bounds checking"
 	depends on UBSAN_TRAP
-	depends on CC_IS_CLANG
 	depends on !UBSAN_KCOV_BROKEN
+	depends on $(cc-option,-fsanitize=local-bounds)
 	help
 	  This option enables -fsanitize=local-bounds which traps when an
-	  exception/error is detected. Therefore, it should be enabled only
-	  if trapping is expected.
+	  exception/error is detected. Therefore, it may only be enabled
+	  with CONFIG_UBSAN_TRAP.
+
 	  Enabling this option detects errors due to accesses through a
 	  pointer that is derived from an object of a statically-known size,
 	  where an added offset (which may not be known statically) is
@@ -69,6 +91,38 @@ config UBSAN_MISC
 	  own Kconfig options. Disable this if you only want to have
 	  individually selected checks.
 
+config UBSAN_SHIFT
+	def_bool UBSAN_MISC
+	depends on $(cc-option,-fsanitize=shift)
+
+config UBSAN_DIV_ZERO
+	def_bool UBSAN_MISC
+	depends on $(cc-option,-fsanitize=integer-divide-by-zero)
+
+config UBSAN_UNREACHABLE
+	def_bool UBSAN_MISC
+	depends on $(cc-option,-fsanitize=unreachable)
+
+config UBSAN_SIGNED_OVERFLOW
+	def_bool UBSAN_MISC
+	depends on $(cc-option,-fsanitize=signed-integer-overflow)
+
+config UBSAN_UNSIGNED_OVERFLOW
+	def_bool UBSAN_MISC
+	depends on $(cc-option,-fsanitize=unsigned-integer-overflow)
+
+config UBSAN_OBJECT_SIZE
+	def_bool UBSAN_MISC
+	depends on $(cc-option,-fsanitize=object-size)
+
+config UBSAN_BOOL
+	def_bool UBSAN_MISC
+	depends on $(cc-option,-fsanitize=bool)
+
+config UBSAN_ENUM
+	def_bool UBSAN_MISC
+	depends on $(cc-option,-fsanitize=enum)
+
 config UBSAN_SANITIZE_ALL
 	bool "Enable instrumentation for the entire kernel"
 	depends on ARCH_HAS_UBSAN_SANITIZE_ALL
@@ -85,6 +139,7 @@ config UBSAN_ALIGNMENT
 	bool "Enable checks for pointers alignment"
 	default !HAVE_EFFICIENT_UNALIGNED_ACCESS
 	depends on !UBSAN_TRAP
+	depends on $(cc-option,-fsanitize=alignment)
 	help
 	  This option enables the check of unaligned memory accesses.
 	  Enabling this option on architectures that support unaligned
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index c18fecc53605..0e53a93e8f15 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -1,33 +1,18 @@
 # SPDX-License-Identifier: GPL-2.0
 
-export CFLAGS_UBSAN :=
+# Enable available and selected UBSAN features.
+ubsan-cflags-$(CONFIG_UBSAN_ALIGNMENT)		+= -fsanitize=alignment
+ubsan-cflags-$(CONFIG_UBSAN_ONLY_BOUNDS)	+= -fsanitize=bounds
+ubsan-cflags-$(CONFIG_UBSAN_ARRAY_BOUNDS)	+= -fsanitize=array-bounds
+ubsan-cflags-$(CONFIG_UBSAN_LOCAL_BOUNDS)	+= -fsanitize=local-bounds
+ubsan-cflags-$(CONFIG_UBSAN_SHIFT)		+= -fsanitize=shift
+ubsan-cflags-$(CONFIG_UBSAN_DIV_ZERO)		+= -fsanitize=integer-divide-by-zero
+ubsan-cflags-$(CONFIG_UBSAN_UNREACHABLE)	+= -fsanitize=unreachable
+ubsan-cflags-$(CONFIG_UBSAN_SIGNED_OVERFLOW)	+= -fsanitize=signed-integer-overflow
+ubsan-cflags-$(CONFIG_UBSAN_UNSIGNED_OVERFLOW)	+= -fsanitize=unsigned-integer-overflow
+ubsan-cflags-$(CONFIG_UBSAN_OBJECT_SIZE)	+= -fsanitize=object-size
+ubsan-cflags-$(CONFIG_UBSAN_BOOL)		+= -fsanitize=bool
+ubsan-cflags-$(CONFIG_UBSAN_ENUM)		+= -fsanitize=enum
+ubsan-cflags-$(CONFIG_UBSAN_TRAP)		+= -fsanitize-undefined-trap-on-error
 
-ifdef CONFIG_UBSAN_ALIGNMENT
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
-endif
-
-ifdef CONFIG_UBSAN_BOUNDS
-      ifdef CONFIG_CC_IS_CLANG
-            CFLAGS_UBSAN += -fsanitize=array-bounds
-      else
-            CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
-      endif
-endif
-
-ifdef CONFIG_UBSAN_LOCAL_BOUNDS
-      CFLAGS_UBSAN += -fsanitize=local-bounds
-endif
-
-ifdef CONFIG_UBSAN_MISC
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=shift)
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=integer-divide-by-zero)
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=unreachable)
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=signed-integer-overflow)
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=object-size)
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=bool)
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=enum)
-endif
-
-ifdef CONFIG_UBSAN_TRAP
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize-undefined-trap-on-error)
-endif
+export CFLAGS_UBSAN := $(ubsan-cflags-y)
-- 
2.25.1