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kbuild: record needed exported symbols for modules

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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>
This commit is contained in:
Nicolas Pitre 2016-01-21 17:07:24 -05:00
parent f55532a0c0
commit 9895c03d48
1 changed files with 11 additions and 2 deletions
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13
scripts/Makefile.build
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@ -286,6 +286,13 @@ define rule_as_o_S
mv -f $(dot-target).tmp $(dot-target).cmd mv -f $(dot-target).tmp $(dot-target).cmd
endef 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 # Built-in and composite module parts
$(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
$(call cmd,force_checksrc) $(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 $(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
$(call cmd,force_checksrc) $(call cmd,force_checksrc)
$(call if_changed_rule,cc_o_c) $(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 $@ quiet_cmd_cc_lst_c = MKLST $@
cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \ 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 $(multi-used-m): FORCE
$(call if_changed,link_multi-m) $(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) $(call multi_depend, $(multi-used-m), .o, -objs -y -m)
targets += $(multi-used-y) $(multi-used-m) targets += $(multi-used-y) $(multi-used-m)