[PATCH 11/11] kbuild: split out *.mod out of {single,multi}-used-m rules

From: Masahiro Yamada
Date: Tue Jul 09 2019 - 00:26:13 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>
---

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

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index f34f941c3b9b..00bd3bc1d6ba 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -69,8 +69,10 @@ modorder-target := $(obj)/modules.order
endif
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)
@:

@@ -268,7 +270,7 @@ 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
@@ -278,11 +280,15 @@ $(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 $< && \
@@ -463,8 +469,6 @@ cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^) $(cmd_secanalysis

$(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