[PATCH 1/4] ubsan: Move cc-option tests into Kconfig

[Kees Cook]

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@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/lkml/CAHk-=wjPasyJrDuwDnpHJS2TuQfExwe=px-SzLeN8GFMAQJPmQ@xxxxxxxxxxxxxx/
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 lib/Kconfig.ubsan      | 48 +++++++++++++++++++++++++++++++++++++++-
 scripts/Makefile.ubsan | 50 ++++++++++++++----------------------------
 2 files changed, 64 insertions(+), 34 deletions(-)

diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index 58f8d03d037b..c0b801871e0b 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.
@@ -47,11 +54,17 @@ config UBSAN_BOUNDS
 	  to the {str,mem}*cpy() family of functions (that is addressed
 	  by CONFIG_FORTIFY_SOURCE).
 
+config CC_ARG_UBSAN_BOUNDS
+	string
+	default "-fsanitize=array-bounds" if CC_HAS_UBSAN_ARRAY_BOUNDS
+	default "-fsanitize=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
@@ -69,6 +82,38 @@ 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
@@ -89,6 +134,7 @@ 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 9716dab06bc7..72862da47baf 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -1,37 +1,21 @@
 # SPDX-License-Identifier: GPL-2.0
 
-export CFLAGS_UBSAN :=
+# -fsanitize=* options makes GCC less smart than usual and
+# increases the number of 'maybe-uninitialized' false-positives.
+ubsan-cflags-$(CONFIG_UBSAN) += $(call cc-disable-warning, maybe-uninitialized)
 
-ifdef CONFIG_UBSAN_ALIGNMENT
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
-endif
+# Enable available and selected UBSAN features.
+ubsan-cflags-$(CONFIG_UBSAN_ALIGNMENT)		+= -fsanitize=alignment
+ubsan-cflags-$(CONFIG_UBSAN_BOUNDS)		+= $(CONFIG_CC_ARG_UBSAN_BOUNDS)
+ubsan-cflags-$(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_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
-
-      # -fsanitize=* options makes GCC less smart than usual and
-      # increase number of 'maybe-uninitialized false-positives
-      CFLAGS_UBSAN += $(call cc-option, -Wno-maybe-uninitialized)
+export CFLAGS_UBSAN := $(ubsan-cflags-y)
-- 
2.25.1