kbuild: move vmlinux.o link to scripts/Makefile.vmlinux_o

JIRA: https://issues.redhat.com/browse/RHEL-2773
Conflicts:
	scripts/link-vmlinux.sh
	- cs-9 is missing upstream commit 7375cbc ("kbuild: stop
	  merging *.symversions") and related modpost enhancements.
	  That said, cs-9 doesn't support CONFIG_LTO_CLANG, so it's only
	  deadcode either way.  Remove it from this file and push it off
	  to a future merge conflict resolution should lto/clang become
	  a requirement.

commit 5d45950
Author: Masahiro Yamada <masahiroy@kernel.org>
Date:   Sun May 29 00:47:03 2022 +0900

    kbuild: move vmlinux.o link to scripts/Makefile.vmlinux_o

    This is a preparation for moving the objtool rule in the next commit.

    Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
    Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>

Author: joe-lawrence

scripts/Makefile.vmlinux_o

@@ -0,0 +1,61 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+PHONY := __default
+__default: vmlinux.o
+
+include include/config/auto.conf
+include $(srctree)/scripts/Kbuild.include
+
+# Generate a linker script to ensure correct ordering of initcalls for Clang LTO
+# ---------------------------------------------------------------------------
+
+quiet_cmd_gen_initcalls_lds = GEN     $@
+      cmd_gen_initcalls_lds = \
+	$(PYTHON3) $(srctree)/scripts/jobserver-exec \
+	$(PERL) $(real-prereqs) > $@
+
+.tmp_initcalls.lds: $(srctree)/scripts/generate_initcall_order.pl \
+		$(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS) FORCE
+	$(call if_changed,gen_initcalls_lds)
+
+targets := .tmp_initcalls.lds
+
+ifdef CONFIG_LTO_CLANG
+initcalls-lds := .tmp_initcalls.lds
+endif
+
+# Link of vmlinux.o used for section mismatch analysis
+# ---------------------------------------------------------------------------
+
+quiet_cmd_ld_vmlinux.o = LD      $@
+      cmd_ld_vmlinux.o = \
+	$(LD) ${KBUILD_LDFLAGS} -r -o $@ \
+	$(addprefix -T , $(initcalls-lds)) \
+	--whole-archive $(KBUILD_VMLINUX_OBJS) --no-whole-archive \
+	--start-group $(KBUILD_VMLINUX_LIBS) --end-group \
+
+define rule_ld_vmlinux.o
+	$(call cmd_and_savecmd,ld_vmlinux.o)
+endef
+
+vmlinux.o: $(initcalls-lds) $(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS) FORCE
+	$(call if_changed_rule,ld_vmlinux.o)
+
+targets += vmlinux.o
+
+# Add FORCE to the prequisites of a target to force it to be always rebuilt.
+# ---------------------------------------------------------------------------
+
+PHONY += FORCE
+FORCE:
+
+# Read all saved command lines and dependencies for the $(targets) we
+# may be building above, using $(if_changed{,_dep}). As an
+# optimization, we don't need to read them if the target does not
+# exist, we will rebuild anyway in that case.
+
+existing-targets := $(wildcard $(sort $(targets)))
+
+-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
+
+.PHONY: $(PHONY)

scripts/link-vmlinux.sh

@@ -52,64 +52,6 @@ info()
 	printf "  %-7s %s\n" "${1}" "${2}"
 }
 
-# Generate a linker script to ensure correct ordering of initcalls.
-gen_initcalls()
-{
-	info GEN .tmp_initcalls.lds
-
-	${PYTHON3} ${srctree}/scripts/jobserver-exec		\
-	${PERL} ${srctree}/scripts/generate_initcall_order.pl	\
-		${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}	\
-		> .tmp_initcalls.lds
-}
-
-# If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
-# .tmp_symversions.lds
-gen_symversions()
-{
-	info GEN .tmp_symversions.lds
-	rm -f .tmp_symversions.lds
-
-	for o in ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}; do
-		if [ -f ${o}.symversions ]; then
-			cat ${o}.symversions >> .tmp_symversions.lds
-		fi
-	done
-}
-
-# Link of vmlinux.o used for section mismatch analysis
-# ${1} output file
-modpost_link()
-{
-	local objects
-	local lds=""
-
-	objects="--whole-archive				\
-		${KBUILD_VMLINUX_OBJS}				\
-		--no-whole-archive				\
-		--start-group					\
-		${KBUILD_VMLINUX_LIBS}				\
-		--end-group"
-
-	if is_enabled CONFIG_LTO_CLANG; then
-		gen_initcalls
-		lds="-T .tmp_initcalls.lds"
-
-		if is_enabled CONFIG_MODVERSIONS; then
-			gen_symversions
-			lds="${lds} -T .tmp_symversions.lds"
-		fi
-
-		# This might take a while, so indicate that we're doing
-		# an LTO link
-		info LTO ${1}
-	else
-		info LD ${1}
-	fi
-
-	${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${lds} ${objects}
-}
-
 objtool_link()
 {
 	local objtoolcmd;
@@ -399,7 +341,7 @@ fi;
 ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init need-builtin=1
 
 #link vmlinux.o
-modpost_link vmlinux.o
+${MAKE} -f "${srctree}/scripts/Makefile.vmlinux_o"
 objtool_link vmlinux.o
 
 # modpost vmlinux.o to check for section mismatches