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

Kees Cook kees at kernel.org
Fri May 2 15:54:14 PDT 2025


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




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