[PATCH] kbuild: introduce include/generated/global-rebuild.h
Masahiro Yamada
masahiroy at kernel.org
Sat May 3 01:41:43 PDT 2025
Sometimes we need to trigger a global rebuild of the kernel tree -
for instance, when any of the GCC plugins changes. [1]
This commit provides a simple mechanism to force a global rebuild
using a single header file.
The top-level Makefile creates include/generated/global-rebuild.h if
it does not exist, and this file is included by all kernel sources.
You can touch it in a build rule when a global rebuild is required.
The following is an example change to the GCC plugin build rule.
quiet_cmd_plugin_cxx_so_c = HOSTCXX $@
- cmd_plugin_cxx_so_c = $(HOSTCXX) $(plugin_cxxflags) $(plugin_ldflags) -o $@ $<
+ cmd_plugin_cxx_so_c = $(HOSTCXX) $(plugin_cxxflags) $(plugin_ldflags) -o $@ $<; touch include/generated/global-rebuild.h
Link: https://lore.kernel.org/linux-kbuild/CAK7LNATDbxc+3HQ6zoSk9t-Lkf4MSNmEUN6S5EqoVWnBQw_K6g@mail.gmail.com/T/#me069145443a17f0b464c13814424dbba0d970863 [1]
Cc: Kees Cook <kees at kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy at kernel.org>
---
Makefile | 9 ++++++++-
arch/um/Makefile | 3 ++-
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index 5aa9ee52a765..64811eebd549 100644
--- a/Makefile
+++ b/Makefile
@@ -558,7 +558,8 @@ USERINCLUDE := \
-I$(srctree)/include/uapi \
-I$(objtree)/include/generated/uapi \
-include $(srctree)/include/linux/compiler-version.h \
- -include $(srctree)/include/linux/kconfig.h
+ -include $(srctree)/include/linux/kconfig.h \
+ -include $(objtree)/include/generated/global-rebuild.h
# Use LINUXINCLUDE when you must reference the include/ directory.
# Needed to be compatible with the O= option
@@ -1257,6 +1258,11 @@ endif
include/config/kernel.release: FORCE
$(call filechk,kernel.release)
+filechk_empty = printf ''
+
+include/generated/global-rebuild.h: FORCE
+ $(call filechk,empty)
+
# Additional helpers built in scripts/
# Carefully list dependencies so we do not try to build scripts twice
# in parallel
@@ -1273,6 +1279,7 @@ scripts: scripts_basic scripts_dtc
PHONY += prepare archprepare
archprepare: outputmakefile archheaders archscripts scripts include/config/kernel.release \
+ include/generated/global-rebuild.h \
asm-generic $(version_h) include/generated/utsrelease.h \
include/generated/compile.h include/generated/autoconf.h \
include/generated/rustc_cfg remove-stale-files
diff --git a/arch/um/Makefile b/arch/um/Makefile
index 1d36a613aad8..f564a26c1364 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -73,7 +73,8 @@ 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__ \
-include $(srctree)/include/linux/compiler-version.h \
- -include $(srctree)/include/linux/kconfig.h
+ -include $(srctree)/include/linux/kconfig.h \
+ -include $(objtree)/include/generated/global-rebuild.h
#This will adjust *FLAGS accordingly to the platform.
include $(srctree)/$(ARCH_DIR)/Makefile-os-Linux
--
2.43.0
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