[PATCH] livepatch: fixup klp-convert tool integration

[Konstantin Khlebnikov <khlebnikov@yandex-team.ru>]

I've found some minor problems, this patch fixes:

* save cmd_ld_ko_o into .module.cmd, if_changed_rule doesn't do that
* fix bashisms for debian where /bin/sh is a symlink to /bin/dash
* rename rule_link_module to rule_ld_ko_o, otherwise arg-check inside
  if_changed_rule compares cmd_link_module and cmd_ld_ko_o
* use HOSTLOADLIBES_$module instead of HOSTLDFLAGS: -lelf must be at the end
* check modinfo -F livepatch only if CONFIG_LIVEPATCH is true

I think "modinfo -F" could be replaced with explicit mark in makefile,
for example: LIVEPATCH_module.ko := y (like KASAN_SANITIZE_obj.o := n).

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
 scripts/Kbuild.include     |    4 +++-
 scripts/Makefile.modpost   |   24 +++++++++++-------------
 scripts/livepatch/Makefile |    2 +-
 3 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 179219845dfc..e299fde3423b 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -247,6 +247,8 @@ endif
 # (needed for the shell)
 make-cmd = $(call escsq,$(subst \#,\\\#,$(subst $$,$$$$,$(cmd_$(1)))))
 
+save-cmd = printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd
+
 # Find any prerequisites that is newer than target or that does not exist.
 # PHONY targets skipped in both cases.
 any-prereq = $(filter-out $(PHONY),$?) $(filter-out $(PHONY) $(wildcard $^),$^)
@@ -256,7 +258,7 @@ any-prereq = $(filter-out $(PHONY),$?) $(filter-out $(PHONY) $(wildcard $^),$^)
 if_changed = $(if $(strip $(any-prereq) $(arg-check)),                       \
 	@set -e;                                                             \
 	$(echo-cmd) $(cmd_$(1));                                             \
-	printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
+	$(save-cmd), @:)
 
 # Execute the command and also postprocess generated .d dependencies file.
 if_changed_dep = $(if $(strip $(any-prereq) $(arg-check) ),                  \
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 916dd347e8f6..5d149d0b05c2 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -123,24 +123,22 @@ quiet_cmd_ld_ko_o = LD [M]  $@
 	$(LD) -r $(LDFLAGS)                                             \
                  $(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE)             \
                  -o $@ $(filter-out FORCE,$^) ;                         \
-	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true) ;
+	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
 
-ifdef CONFIG_LIVEPATCH
 KLP_CONVERT = scripts/livepatch/klp-convert
-      cmd_klp_convert =							\
-	if [[ -n "`modinfo -F livepatch $@`" ]]; then			\
-		mv $@ $(@:.ko=.klp.o);					\
-		$(KLP_CONVERT) $(@:.ko=.klp.o) $@;			\
-	fi ;
-endif
-
-define rule_link_module
-	$(call echo-cmd,ld_ko_o) $(cmd_ld_ko_o)				\
-	$(cmd_klp_convert)
+quiet_cmd_klp_convert = LIVEPATCH $@
+      cmd_klp_convert = mv $@ $(@:.ko=.klp.o); $(KLP_CONVERT) $(@:.ko=.klp.o) $@
+
+define rule_ld_ko_o
+       $(call echo-cmd,ld_ko_o) $(cmd_ld_ko_o) ;                        \
+       $(call save-cmd,ld_ko_o) ;                                       \
+       $(if $(CONFIG_LIVEPATCH),                                        \
+         if [ -n "`modinfo -F livepatch $@`" ] ; then                   \
+           $(call echo-cmd,klp_convert) $(cmd_klp_convert) ; fi)
 endef
 
 $(modules): %.ko :%.o %.mod.o FORCE
-	+$(call if_changed_rule,link_module)
+	+$(call if_changed_rule,ld_ko_o)
 
 targets += $(modules)
 
diff --git a/scripts/livepatch/Makefile b/scripts/livepatch/Makefile
index 221829bb34c7..bd5c1ae553ab 100644
--- a/scripts/livepatch/Makefile
+++ b/scripts/livepatch/Makefile
@@ -4,4 +4,4 @@ always			:= $(hostprogs-y)
 klp-convert-objs	:= klp-convert.o elf.o
 
 HOSTCFLAGS		:= -g -I$(INSTALL_HDR_PATH)/include -Wall
-HOSTLDFLAGS		:= -lelf
+HOSTLOADLIBES_klp-convert	:= -lelf