[PATCH v2 2/3] randstruct: Force full rebuild when seed changes

[Kees Cook]

While the randstruct GCC plugin was being rebuilt if the randstruct
seed changed, Clangs build did not notice the change. Include the hash
header directly so that it becomes a universal build dependency and full
rebuilds will happen if it changes.

Since we cannot use "-include ..." as the randstruct flags are removed
via "filter-out" (which would cause all instances of "-include" to be
removed), use the existing -DRANDSTRUCT to control the header inclusion
via include/linux/compiler-version.h. Universally add a -I for the
scripts/basic directory, where header exists. The UM build requires that
the -I be explicitly added.

Signed-off-by: Kees Cook <kees at kernel.org>
---
Cc: Masahiro Yamada <masahiroy at kernel.org>
Cc: Nathan Chancellor <nathan at kernel.org>
Cc: Nicolas Schier <nicolas.schier at linux.dev>
Cc: Petr Pavlu <petr.pavlu at suse.com>
Cc: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
Cc: <linux-kbuild at vger.kernel.org>
---
 Makefile                         |  1 +
 arch/um/Makefile                 |  1 +
 include/linux/compiler-version.h |  3 +++
 include/linux/vermagic.h         |  1 -
 scripts/basic/Makefile           | 11 ++++++-----
 5 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index 5aa9ee52a765..cef652227843 100644
--- a/Makefile
+++ b/Makefile
@@ -567,6 +567,7 @@ LINUXINCLUDE    := \
 		-I$(objtree)/arch/$(SRCARCH)/include/generated \
 		-I$(srctree)/include \
 		-I$(objtree)/include \
+		-I$(objtree)/scripts/basic \
 		$(USERINCLUDE)
 
 KBUILD_AFLAGS   := -D__ASSEMBLY__ -fno-PIE
diff --git a/arch/um/Makefile b/arch/um/Makefile
index 8cc0f22ebefa..38f6024e75d7 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -73,6 +73,7 @@ USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -I%,,$(KBUILD_CFLAGS))) \
 		-D_FILE_OFFSET_BITS=64 -idirafter $(srctree)/include \
 		-idirafter $(objtree)/include -D__KERNEL__ -D__UM_HOST__ \
 		-I$(objtree)/scripts/gcc-plugins \
+		-I$(objtree)/scripts/basic \
 		-include $(srctree)/include/linux/compiler-version.h \
 		-include $(srctree)/include/linux/kconfig.h
 
diff --git a/include/linux/compiler-version.h b/include/linux/compiler-version.h
index 08943df04ebb..05d555320a0f 100644
--- a/include/linux/compiler-version.h
+++ b/include/linux/compiler-version.h
@@ -16,3 +16,6 @@
 #ifdef GCC_PLUGINS_ENABLED
 #include "gcc-plugins-deps.h"
 #endif
+#ifdef RANDSTRUCT
+#include "randstruct_hash.h"
+#endif
diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h
index 939ceabcaf06..335c360d4f9b 100644
--- a/include/linux/vermagic.h
+++ b/include/linux/vermagic.h
@@ -33,7 +33,6 @@
 #define MODULE_VERMAGIC_MODVERSIONS ""
 #endif
 #ifdef RANDSTRUCT
-#include <generated/randstruct_hash.h>
 #define MODULE_RANDSTRUCT "RANDSTRUCT_" RANDSTRUCT_HASHED_SEED
 #else
 #define MODULE_RANDSTRUCT
diff --git a/scripts/basic/Makefile b/scripts/basic/Makefile
index dd289a6725ac..31637ce4dc5c 100644
--- a/scripts/basic/Makefile
+++ b/scripts/basic/Makefile
@@ -8,9 +8,10 @@ hostprogs-always-y	+= fixdep
 # before running a Clang kernel build.
 gen-randstruct-seed	:= $(srctree)/scripts/gen-randstruct-seed.sh
 quiet_cmd_create_randstruct_seed = GENSEED $@
-cmd_create_randstruct_seed = \
-	$(CONFIG_SHELL) $(gen-randstruct-seed) \
-		$@ $(objtree)/include/generated/randstruct_hash.h
-$(obj)/randstruct.seed: $(gen-randstruct-seed) FORCE
+      cmd_create_randstruct_seed = $(CONFIG_SHELL) $(gen-randstruct-seed) \
+		$(obj)/randstruct.seed $(obj)/randstruct_hash.h
+
+$(obj)/randstruct_hash.h $(obj)/randstruct.seed: $(gen-randstruct-seed) FORCE
 	$(call if_changed,create_randstruct_seed)
-always-$(CONFIG_RANDSTRUCT) += randstruct.seed
+
+always-$(CONFIG_RANDSTRUCT) += randstruct.seed randstruct_hash.h
-- 
2.34.1