Merge tag 'kbuild-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Add -s option (strict mode) to merge_config.sh to make it fail when
   any symbol is redefined.

 - Show a warning if a different compiler is used for building external
   modules.

 - Infer --target from ARCH for CC=clang to let you cross-compile the
   kernel without CROSS_COMPILE.

 - Make the integrated assembler default (LLVM_IAS=1) for CC=clang.

 - Add <linux/stdarg.h> to the kernel source instead of borrowing
   <stdarg.h> from the compiler.

 - Add Nick Desaulniers as a Kbuild reviewer.

 - Drop stale cc-option tests.

 - Fix the combination of CONFIG_TRIM_UNUSED_KSYMS and CONFIG_LTO_CLANG
   to handle symbols in inline assembly.

 - Show a warning if 'FORCE' is missing for if_changed rules.

 - Various cleanups

* tag 'kbuild-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (39 commits)
  kbuild: redo fake deps at include/ksym/*.h
  kbuild: clean up objtool_args slightly
  modpost: get the *.mod file path more simply
  checkkconfigsymbols.py: Fix the '--ignore' option
  kbuild: merge vmlinux_link() between ARCH=um and other architectures
  kbuild: do not remove 'linux' link in scripts/link-vmlinux.sh
  kbuild: merge vmlinux_link() between the ordinary link and Clang LTO
  kbuild: remove stale *.symversions
  kbuild: remove unused quiet_cmd_update_lto_symversions
  gen_compile_commands: extract compiler command from a series of commands
  x86: remove cc-option-yn test for -mtune=
  arc: replace cc-option-yn uses with cc-option
  s390: replace cc-option-yn uses with cc-option
  ia64: move core-y in arch/ia64/Makefile to arch/ia64/Kbuild
  sparc: move the install rule to arch/sparc/Makefile
  security: remove unneeded subdir-$(CONFIG_...)
  kbuild: sh: remove unused install script
  kbuild: Fix 'no symbols' warning when CONFIG_TRIM_UNUSD_KSYMS=y
  kbuild: Switch to 'f' variants of integrated assembler flag
  kbuild: Shuffle blank line to improve comment meaning
  ...

1 files changed, 10 insertions, 3 deletions

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index f247e691562d..cdec22088423 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -57,6 +57,7 @@ kecho := $($(quiet)kecho)
 # - If the content differ the new file is used
 # - If they are equal no change, and no timestamp update
 define filechk
+	$(check-FORCE)
 	$(Q)set -e;						\
 	mkdir -p $(dir $@);					\
 	trap "rm -f $(dot-target).tmp" EXIT;			\
@@ -130,13 +131,19 @@ make-cmd = $(call escsq,$(subst $(pound),$$(pound),$(subst $$,$$$$,$(cmd_$(1))))
 # PHONY targets skipped in both cases.
 newer-prereqs = $(filter-out $(PHONY),$?)
 
+# It is a typical mistake to forget the FORCE prerequisite. Check it here so
+# no more breakage will slip in.
+check-FORCE = $(if $(filter FORCE, $^),,$(warning FORCE prerequisite is missing))
+
+if-changed-cond = $(newer-prereqs)$(cmd-check)$(check-FORCE)
+
 # Execute command if command has changed or prerequisite(s) are updated.
-if_changed = $(if $(newer-prereqs)$(cmd-check),                              \
+if_changed = $(if $(if-changed-cond),                                        \
 	$(cmd);                                                              \
 	printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
 
 # Execute the command and also postprocess generated .d dependencies file.
-if_changed_dep = $(if $(newer-prereqs)$(cmd-check),$(cmd_and_fixdep),@:)
+if_changed_dep = $(if $(if-changed-cond),$(cmd_and_fixdep),@:)
 
 cmd_and_fixdep =                                                             \
 	$(cmd);                                                              \
@@ -146,7 +153,7 @@ cmd_and_fixdep =                                                             \
 # Usage: $(call if_changed_rule,foo)
 # Will check if $(cmd_foo) or any of the prerequisites changed,
 # and if so will execute $(rule_foo).
-if_changed_rule = $(if $(newer-prereqs)$(cmd-check),$(rule_$(1)),@:)
+if_changed_rule = $(if $(if-changed-cond),$(rule_$(1)),@:)
 
 ###
 # why - tell why a target got built