[PATCH v2 4/6] bootconfig: clean build-time tools/bootconfig from make clean

[Breno Leitao]

The previous patch builds tools/bootconfig during 'make prepare' to
render the embedded bootconfig cmdline, but nothing removes it on
'make clean', leaving the compiled tool and its objects behind.

Wire a bootconfig_clean hook into the top-level clean target so the
compiled tool and its objects are removed by make clean, matching the
prepare-wired tools/objtool and tools/bpf/resolve_btfids.

The hook runs tools/bootconfig's Makefile via $(MAKE), which the kernel
build invokes with -rR (MAKEFLAGS += -rR). -rR drops the built-in $(RM)
variable, so the existing "$(RM) -f ..." clean recipe would expand to a
bare "-f ..." and fail. Spell the recipe with a literal "rm -f" so it
keeps working both standalone and when invoked from Kbuild.

Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
---
 Makefile                  | 13 ++++++++++++-
 tools/bootconfig/Makefile |  2 +-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index e95992959f44..4f31222ff1d1 100644
--- a/Makefile
+++ b/Makefile
@@ -1574,6 +1574,17 @@ ifneq ($(wildcard $(objtool_O)),)
 	$(Q)$(MAKE) -sC $(abs_srctree)/tools/objtool O=$(objtool_O) srctree=$(abs_srctree) $(patsubst objtool_%,%,$@)
 endif
 
+PHONY += bootconfig_clean
+
+bootconfig_O = $(abspath $(objtree))/tools/bootconfig
+
+# tools/bootconfig is only built (via the prepare hook above) when
+# CONFIG_BOOT_CONFIG_EMBED_CMDLINE is set; skip its clean otherwise.
+bootconfig_clean:
+ifneq ($(wildcard $(bootconfig_O)),)
+	$(Q)$(MAKE) -sC $(srctree)/tools/bootconfig O=$(bootconfig_O) clean
+endif
+
 tools/: FORCE
 	$(Q)mkdir -p $(objtree)/tools
 	$(Q)$(MAKE) O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/
@@ -1743,7 +1754,7 @@ vmlinuxclean:
 	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/link-vmlinux.sh clean
 	$(Q)$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) clean)
 
-clean: archclean vmlinuxclean resolve_btfids_clean objtool_clean
+clean: archclean vmlinuxclean resolve_btfids_clean objtool_clean bootconfig_clean
 
 # mrproper - Delete all generated files, including .config
 #
diff --git a/tools/bootconfig/Makefile b/tools/bootconfig/Makefile
index aa75a7828685..86f1a4e64f04 100644
--- a/tools/bootconfig/Makefile
+++ b/tools/bootconfig/Makefile
@@ -31,4 +31,4 @@ install: $(ALL_PROGRAMS)
 	install $(OUTPUT)bootconfig $(DESTDIR)$(bindir)
 
 clean:
-	$(RM) -f $(OUTPUT)*.o $(ALL_PROGRAMS)
+	rm -f $(OUTPUT)*.o $(ALL_PROGRAMS)

-- 
2.53.0-Meta