kbuild: record needed exported symbols for modules (9895c03d) · Commits · 戴 / test

Kernel modules are partially linked object files with some undefined symbols that are expected to be matched with EXPORT_SYMBOL() entries from elsewhere. Each .tmp_versions/*.mod file currently contains two line of text separated by a newline character. The first line has the actual module file name while the second line has a list of object files constituting that module. Those files are parsed by modpost (scripts/mod/sumversion.c), scripts/Makefile.modpost, scripts/Makefile.modsign, etc. Only the modpost utility cares about the second line while the others retrieve only the first line. Therefore we can add a third line to record the list of undefined symbols aka required EXPORT_SYMBOL() entries for each module into that file without breaking anything. Like for the second line, symbols are separated by a blank and the list is terminated with a newline character. To avoid needless build overhead, the undefined symbols extraction is performed only when CONFIG_TRIM_UNUSED_KSYMS is selected. Signed-off-by:

Nicolas Pitre <nico@linaro.org> Acked-by:

Rusty Russell <rusty@rustcorp.com.au>

scripts/Makefile.build

+11 −2

Original line number	Diff line number	Diff line
		@@ -286,6 +286,13 @@ define rule_as_o_S
		mv -f $(dot-target).tmp $(dot-target).cmd
		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
		else
		cmd_undef_syms = echo
		endif

		# Built-in and composite module parts
		$(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
		$(call cmd,force_checksrc)
		@@ -296,7 +303,8 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
		$(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
		$(call cmd,force_checksrc)
		$(call if_changed_rule,cc_o_c)
		@{ echo $(@:.o=.ko); echo $@; } > $(MODVERDIR)/$(@F:.o=.mod)
		@{ echo $(@:.o=.ko); echo $@; \
		$(cmd_undef_syms); } > $(MODVERDIR)/$(@F:.o=.mod)

		quiet_cmd_cc_lst_c = MKLST $@
		cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
		@@ -426,7 +434,8 @@ $(call multi_depend, $(multi-used-y), .o, -objs -y)

		$(multi-used-m): FORCE
		$(call if_changed,link_multi-m)
		@{ echo $(@:.o=.ko); echo $(link_multi_deps); } > $(MODVERDIR)/$(@F:.o=.mod)
		@{ echo $(@:.o=.ko); echo $(link_multi_deps); \
		$(cmd_undef_syms); } > $(MODVERDIR)/$(@F:.o=.mod)
		$(call multi_depend, $(multi-used-m), .o, -objs -y -m)

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

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