[PATCH v3 12/12] kbuild: split out *.mod out of {single,multi}-used-m rules

From: Masahiro Yamada
Date: Wed Jul 17 2019 - 02:19:09 EST


Currently, *.mod is created as a side-effect of obj-m.

Split out *.mod as a dedicated build rule, which allows to unify
the %.c -> %.o rule, and remove the single-used-m rule.

This also makes the incremental build of allmodconfig faster because
it saves $(NM) invocation when there is no change in the module.

Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
---

Changes in v3: None
Changes in v2: None

scripts/Makefile.build | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 9f37f203882f..0d434d0afc0b 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -67,8 +67,10 @@ ifeq ($(CONFIG_MODULES)$(need-modorder),y1)
modorder-target := $(obj)/modules.order
endif

+mod-targets := $(patsubst %.o, %.mod, $(obj-m))
+
__build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y)) \
- $(if $(KBUILD_MODULES),$(obj-m) $(modorder-target)) \
+ $(if $(KBUILD_MODULES),$(obj-m) $(mod-targets) $(modorder-target)) \
$(subdir-ym) $(always)
@:

@@ -261,7 +263,7 @@ endef

# List module undefined symbols (or empty line if not enabled)
ifdef CONFIG_TRIM_UNUSED_KSYMS
-cmd_undef_syms = $(NM) $@ | sed -n 's/^ *U //p' | xargs echo
+cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | xargs echo
else
cmd_undef_syms = echo
endif
@@ -271,11 +273,15 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
$(call cmd,force_checksrc)
$(call if_changed_rule,cc_o_c)

-$(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_dep) FORCE
- $(call cmd,force_checksrc)
- $(call if_changed_rule,cc_o_c)
- @{ echo $@; \
- $(cmd_undef_syms); } > $(patsubst %.o,%.mod,$@)
+cmd_mod = { \
+ echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \
+ $(cmd_undef_syms); \
+ } > $@
+
+$(obj)/%.mod: $(obj)/%.o FORCE
+ $(call if_changed,mod)
+
+targets += $(mod-targets)

quiet_cmd_cc_lst_c = MKLST $@
cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
@@ -456,8 +462,6 @@ quiet_cmd_link_multi-m = LD [M] $@

$(multi-used-m): FORCE
$(call if_changed,link_multi-m)
- @{ echo $(filter %.o,$^); \
- $(cmd_undef_syms); } > $(patsubst %.o,%.mod,$@)
$(call multi_depend, $(multi-used-m), .o, -objs -y -m)

targets += $(multi-used-m)
--
2.17.1