[PATCH v2 3/3] integer-wrap: Force full rebuild when .scl file changes

[Kees Cook <kees@kernel.org>]

Since the integer wrapping sanitizer's behavior depends on its
associated .scl file, we must force a full rebuild if the file changes.
Universally include a synthetic header file that is rebuilt when the
.scl file changes, via compiler-version.h, since using "-include ..." is
not possible in the case of having compiler flags removed via
"filter-out" (which would remove all instances of "-include").

Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nicolas.schier@linux.dev>
Cc: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: <linux-kbuild@vger.kernel.org>
Cc: <kasan-dev@googlegroups.com>
Cc: <linux-hardening@vger.kernel.org>
---
 include/linux/compiler-version.h | 3 +++
 scripts/Makefile.ubsan           | 1 +
 scripts/basic/Makefile           | 9 +++++++++
 3 files changed, 13 insertions(+)

diff --git a/include/linux/compiler-version.h b/include/linux/compiler-version.h
index 05d555320a0f..9d6b1890ffc7 100644
--- a/include/linux/compiler-version.h
+++ b/include/linux/compiler-version.h
@@ -19,3 +19,6 @@
 #ifdef RANDSTRUCT
 #include "randstruct_hash.h"
 #endif
+#ifdef INTEGER_WRAP
+#include "integer-wrap.h"
+#endif
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index 9e35198edbf0..653f7117819c 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -15,6 +15,7 @@ ubsan-cflags-$(CONFIG_UBSAN_TRAP)		+= $(call cc-option,-fsanitize-trap=undefined
 export CFLAGS_UBSAN := $(ubsan-cflags-y)
 
 ubsan-integer-wrap-cflags-$(CONFIG_UBSAN_INTEGER_WRAP)     +=	\
+	-DINTEGER_WRAP						\
 	-fsanitize-undefined-ignore-overflow-pattern=all	\
 	-fsanitize=signed-integer-overflow			\
 	-fsanitize=unsigned-integer-overflow			\
diff --git a/scripts/basic/Makefile b/scripts/basic/Makefile
index 31637ce4dc5c..04f5620a3f8b 100644
--- a/scripts/basic/Makefile
+++ b/scripts/basic/Makefile
@@ -15,3 +15,12 @@ $(obj)/randstruct_hash.h $(obj)/randstruct.seed: $(gen-randstruct-seed) FORCE
 	$(call if_changed,create_randstruct_seed)
 
 always-$(CONFIG_RANDSTRUCT) += randstruct.seed randstruct_hash.h
+
+# integer-wrap: if the .scl file changes, we need to do a full rebuild.
+quiet_cmd_integer_wrap_updated = UPDATE  $@
+      cmd_integer_wrap_updated = echo '/* $^ */' > $(obj)/integer-wrap.h
+
+$(obj)/integer-wrap.h: $(srctree)/scripts/integer-wrap-ignore.scl FORCE
+	$(call if_changed,integer_wrap_updated)
+
+always-$(CONFIG_UBSAN_INTEGER_WRAP) += integer-wrap.h
-- 
2.34.1