ubsan: move cc-option tests into Kconfig

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.

Link: https://lkml.kernel.org/r/20201203004437.389959-3-keescook@chromium.org
Link: https://lore.kernel.org/lkml/CAHk-=wjPasyJrDuwDnpHJS2TuQfExwe=px-SzLeN8GFMAQJPmQ@mail.gmail.com/
Signed-off-by: Kees Cook <keescook@chromium.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: George Popescu <georgepope@android.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Marco Elver <elver@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/Kconfig.ubsan

@@ -36,26 +36,48 @@ 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.
 	  Note that this does not protect array overflows via bad calls
 	  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

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)