| Message ID | 20210831074004.3195284-9-masahiroy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kbuild: second round of Clang LTO refactoring | expand |
On Tue, Aug 31, 2021 at 04:39:59PM +0900, Masahiro Yamada wrote: > When Clang LTO is enabled, additional intermediate files *.lto.o are > created because LLVM bitcode must be converted to ELF before modpost. > > For non-LTO builds: > > $(LD) $(LD) > objects ---> <modname>.o -----> <modname>.ko > | > <modname>.mod.o ---/ > > For Clang LTO builds: > > $(AR) $(LD) $(LD) > objects ---> <modname>.o ---> <modname>.lto.o -----> <modname>.ko > | > <modname>.mod.o --/ > > Since the Clang LTO introduction, Kbuild code is complicated due to > CONFIG_LTO_CLANG conditionals sprinkled everywhere. > > Another confusion for Clang LTO builds is, <modname>.o is an archive > that contains LLVM bitcode files. The suffix should be .a instead of .o > > To clean up the code, unify the build process of modules, as follows: > > $(AR) $(LD) $(LD) > objects ---> <modname>.a ---> <modname>.prelink.o -----> <modname>.ko > | > <modname>.mod.o ------/ > > Here, 'objects' are either ELF or LLVM bitcode. <modname>.a is an archive, > <modname>.prelink.o is ELF. This is a good diagram and helps me understand what's happening here. Do you think there's a place for it somewhere in the kbuild documentation? > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> My question about speed changes also applies to this, since there's now a new step for non-LTO builds. I think you said it wasn't a meaningful change in speed, but I think it'd be worth mentioning performance changes in this commit message. > --- > > scripts/Makefile.build | 100 +++++++++++++++++--------------------- > scripts/Makefile.lib | 11 ++--- > scripts/Makefile.modfinal | 4 +- > scripts/Makefile.modpost | 7 +-- > scripts/mod/modpost.c | 6 +-- > 5 files changed, 56 insertions(+), 72 deletions(-) > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build > index 3ad1b1227371..cdc09e9080ca 100644 > --- a/scripts/Makefile.build > +++ b/scripts/Makefile.build > @@ -88,9 +88,7 @@ endif > > targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m))) > > -ifdef CONFIG_LTO_CLANG > -targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m))) > -endif > +targets-for-modules += $(patsubst %.o, %.prelink.o, $(filter %.o, $(obj-m))) > > ifdef need-modorder > targets-for-modules += $(obj)/modules.order > @@ -243,9 +241,12 @@ endif # CONFIG_STACK_VALIDATION > > ifdef CONFIG_LTO_CLANG > > -# Skip objtool for LLVM bitcode > +# Skip objtool LLVM bitcode Nit: needless comment change? > $(obj)/%o: objtool-enabled := > > +# Run objtool now that we have compiled modules into native code > +$(obj)/%.prelink.o: objtool-enabled := y > + > else > > # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory > @@ -255,6 +256,8 @@ else > $(obj)/%o: objtool-enabled = $(if $(filter-out y%, \ > $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y) > > +$(obj)/%.prelink.o: objtool-enabled := > + > endif > > ifdef CONFIG_TRIM_UNUSED_KSYMS > @@ -287,32 +290,12 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE > $(call if_changed_rule,cc_o_c) > $(call cmd,force_checksrc) > > -ifdef CONFIG_LTO_CLANG > -# Module .o files may contain LLVM bitcode, compile them into native code > -# before ELF processing > -quiet_cmd_cc_lto_link_modules = LTO [M] $@ > -cmd_cc_lto_link_modules = \ > - $(LD) $(ld_flags) -r -o $@ \ > - $(shell [ -s $(@:.lto.o=.o.symversions) ] && \ > - echo -T $(@:.lto.o=.o.symversions)) \ > - --whole-archive $(filter-out FORCE,$^) \ > - $(cmd_objtool) > - > -# objtool was skipped for LLVM bitcode, run it now that we have compiled > -# modules into native code > -$(obj)/%.lto.o: objtool-enabled = y > -$(obj)/%.lto.o: part-of-module := y > - > -$(obj)/%.lto.o: $(obj)/%.o FORCE > - $(call if_changed,cc_lto_link_modules) > -endif > - > cmd_mod = { \ > echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \ > $(undefined_syms) echo; \ > } > $@ > > -$(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE > +$(obj)/%.mod: $(obj)/%.prelink.o FORCE > $(call if_changed,mod) > > quiet_cmd_cc_lst_c = MKLST $@ > @@ -416,17 +399,6 @@ $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler > $(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ; > $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ; > > -# combine symversions for later processing > -ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y) > - cmd_update_lto_symversions = \ > - rm -f $@.symversions \ > - $(foreach n, $(filter-out FORCE,$^), \ > - $(if $(shell test -s $(n).symversions && echo y), \ > - ; cat $(n).symversions >> $@.symversions)) > -else > - cmd_update_lto_symversions = echo >/dev/null > -endif > - > # > # Rule to compile a set of .o files into one .a file (without symbol table) > # > @@ -446,10 +418,10 @@ $(obj)/built-in.a: $(real-obj-y) FORCE > # modules.order unless contained modules are updated. > > cmd_modules_order = { $(foreach m, $(real-prereqs), \ > - $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.o,%.ko,$m));) :; } \ > + $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.a,%.ko,$m));) :; } \ > | $(AWK) '!x[$$0]++' - > $@ > > -$(obj)/modules.order: $(obj-m) FORCE > +$(obj)/modules.order: $(modules) FORCE > $(call if_changed,modules_order) > > # > @@ -458,26 +430,44 @@ $(obj)/modules.order: $(obj-m) FORCE > $(obj)/lib.a: $(lib-y) FORCE > $(call if_changed,ar) > > -# NOTE: > -# Do not replace $(filter %.o,^) with $(real-prereqs). When a single object > -# module is turned into a multi object module, $^ will contain header file > -# dependencies recorded in the .*.cmd file. > -ifdef CONFIG_LTO_CLANG > -quiet_cmd_link_multi-m = AR [M] $@ > -cmd_link_multi-m = \ > - $(cmd_update_lto_symversions); \ > - rm -f $@; \ > - $(AR) cDPrsT $@ $(filter %.o,$^) > -else > -quiet_cmd_link_multi-m = LD [M] $@ > - cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^) > +# > +# Rule to prelink modules > +# > + > +ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y) > + > +cmd_merge_symver = $(PERL) scripts/merge-symvers.pl -a $(AR) -o $@ $< > + > +$(obj)/%.prelink.symversions: $(obj)/%.a FORCE > + $(call if_changed,merge_symver) > + > +targets += $(patsubst %.a, %.prelink.symversions, $(modules)) > + > +$(obj)/%.prelink.o: ld_flags += --script=$(filter %.symversions,$^) > +module-symver = $(obj)/%.prelink.symversions > + > endif > > -$(multi-obj-m): FORCE > - $(call if_changed,link_multi-m) > -$(call multi_depend, $(multi-obj-m), .o, -objs -y -m) > +quiet_cmd_ld_o_a = LD [M] $@ > + cmd_ld_o_a = $(LD) $(ld_flags) -r -o $@ --whole-archive $< $(cmd_objtool) > + > +$(obj)/%.prelink.o: part-of-module := y > + > +$(obj)/%.prelink.o: $(obj)/%.a $(module-symver) FORCE > + $(call if_changed,ld_o_a) > + > +quiet_cmd_ar_module = AR [M] $@ > + cmd_ar_module = rm -f $@; $(AR) cDPrST $@ $(real-prereqs) > + > +$(modules-single): %.a: %.o FORCE > + $(call if_changed,ar_module) > + > +$(modules-multi): FORCE > + $(call if_changed,ar_module) > +$(call multi_depend, $(modules-multi), .a, -objs -y -m) > + > +targets += $(modules-single) $(modules-multi) > > -targets += $(multi-obj-m) > targets := $(filter-out $(PHONY), $(targets)) > > # Add intermediate targets: > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib > index 34c4c11c4bc1..5074922db82d 100644 > --- a/scripts/Makefile.lib > +++ b/scripts/Makefile.lib > @@ -106,6 +106,10 @@ multi-dtb-y := $(addprefix $(obj)/, $(multi-dtb-y)) > real-dtb-y := $(addprefix $(obj)/, $(real-dtb-y)) > subdir-ym := $(addprefix $(obj)/,$(subdir-ym)) > > +modules := $(patsubst %.o, %.a, $(obj-m)) > +modules-multi := $(sort $(patsubst %.o, %.a, $(multi-obj-m))) > +modules-single := $(sort $(filter-out $(modules-multi), $(filter %.a, $(modules)))) > + > # Finds the multi-part object the current object will be linked into. > # If the object belongs to two or more multi-part objects, list them all. > modname-multi = $(sort $(foreach m,$(multi-obj-ym),\ > @@ -225,13 +229,6 @@ dtc_cpp_flags = -Wp,-MMD,$(depfile).pre.tmp -nostdinc \ > $(addprefix -I,$(DTC_INCLUDE)) \ > -undef -D__DTS__ > > -ifeq ($(CONFIG_LTO_CLANG),y) > -# With CONFIG_LTO_CLANG, .o files in modules might be LLVM bitcode, so we > -# need to run LTO to compile them into native code (.lto.o) before further > -# processing. > -mod-prelink-ext := .lto > -endif > - > # Useful for describing the dependency of composite objects > # Usage: > # $(call multi_depend, multi_used_targets, suffix_to_remove, suffix_to_add) > diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal > index ff805777431c..1b6401f53662 100644 > --- a/scripts/Makefile.modfinal > +++ b/scripts/Makefile.modfinal > @@ -9,7 +9,7 @@ __modfinal: > include include/config/auto.conf > include $(srctree)/scripts/Kbuild.include > > -# for c_flags and mod-prelink-ext > +# for c_flags > include $(srctree)/scripts/Makefile.lib > > # find all modules listed in modules.order > @@ -55,7 +55,7 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \ > > > # Re-generate module BTFs if either module's .ko or vmlinux changed > -$(modules): %.ko: %$(mod-prelink-ext).o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE > +$(modules): %.ko: %.prelink.o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE > +$(call if_changed_except,ld_ko_o,vmlinux) > ifdef CONFIG_DEBUG_INFO_BTF_MODULES > +$(if $(newer-prereqs),$(call cmd,btf_ko)) > diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost > index eef56d629799..11883b31c615 100644 > --- a/scripts/Makefile.modpost > +++ b/scripts/Makefile.modpost > @@ -41,9 +41,6 @@ __modpost: > include include/config/auto.conf > include $(srctree)/scripts/Kbuild.include > > -# for mod-prelink-ext > -include $(srctree)/scripts/Makefile.lib > - > MODPOST = scripts/mod/modpost \ > $(if $(CONFIG_MODVERSIONS),-m) \ > $(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \ > @@ -128,9 +125,9 @@ endif > # Read out modules.order to pass in modpost. > # Otherwise, allmodconfig would fail with "Argument list too long". > quiet_cmd_modpost = MODPOST $@ > - cmd_modpost = sed 's/\.ko$$/$(mod-prelink-ext)\.o/' $< | $(MODPOST) -T - > + cmd_modpost = sed 's/ko$$/prelink.o/' $< | $(MODPOST) -T - > > -$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(mod-prelink-ext).o) FORCE > +$(output-symdump): $(MODORDER) $(input-symdump) $(modules:ko=prelink.o) FORCE > $(call if_changed,modpost) > > targets += $(output-symdump) > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > index a26139aa57fd..56cd9b7a5dd0 100644 > --- a/scripts/mod/modpost.c > +++ b/scripts/mod/modpost.c > @@ -2000,9 +2000,9 @@ static void read_symbols(const char *modname) > /* strip trailing .o */ > tmp = NOFAIL(strdup(modname)); > tmp[strlen(tmp) - 2] = '\0'; > - /* strip trailing .lto */ > - if (strends(tmp, ".lto")) > - tmp[strlen(tmp) - 4] = '\0'; > + /* strip trailing .prelink */ > + if (strends(tmp, ".prelink")) > + tmp[strlen(tmp) - 8] = '\0'; > mod = new_module(tmp); > free(tmp); > } > -- > 2.30.2 > Otherwise, looks good!
On Tue, Aug 31, 2021 at 12:40 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > When Clang LTO is enabled, additional intermediate files *.lto.o are > created because LLVM bitcode must be converted to ELF before modpost. > > For non-LTO builds: > > $(LD) $(LD) > objects ---> <modname>.o -----> <modname>.ko > | > <modname>.mod.o ---/ > > For Clang LTO builds: > > $(AR) $(LD) $(LD) > objects ---> <modname>.o ---> <modname>.lto.o -----> <modname>.ko > | > <modname>.mod.o --/ Is it worth modifying the diagram to note that objects in non-LTO builds are <objects>.o, while for LTO builds, they are <objects>.bc? If we're not using the .bc file suffix, can we? > > Since the Clang LTO introduction, Kbuild code is complicated due to > CONFIG_LTO_CLANG conditionals sprinkled everywhere. > > Another confusion for Clang LTO builds is, <modname>.o is an archive > that contains LLVM bitcode files. The suffix should be .a instead of .o > > To clean up the code, unify the build process of modules, as follows: > > $(AR) $(LD) $(LD) > objects ---> <modname>.a ---> <modname>.prelink.o -----> <modname>.ko > | > <modname>.mod.o ------/ And here, too. > > Here, 'objects' are either ELF or LLVM bitcode. <modname>.a is an archive, > <modname>.prelink.o is ELF. > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > --- > > scripts/Makefile.build | 100 +++++++++++++++++--------------------- > scripts/Makefile.lib | 11 ++--- > scripts/Makefile.modfinal | 4 +- > scripts/Makefile.modpost | 7 +-- > scripts/mod/modpost.c | 6 +-- > 5 files changed, 56 insertions(+), 72 deletions(-) > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build > index 3ad1b1227371..cdc09e9080ca 100644 > --- a/scripts/Makefile.build > +++ b/scripts/Makefile.build > @@ -88,9 +88,7 @@ endif > > targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m))) > > -ifdef CONFIG_LTO_CLANG > -targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m))) > -endif > +targets-for-modules += $(patsubst %.o, %.prelink.o, $(filter %.o, $(obj-m))) > > ifdef need-modorder > targets-for-modules += $(obj)/modules.order > @@ -243,9 +241,12 @@ endif # CONFIG_STACK_VALIDATION > > ifdef CONFIG_LTO_CLANG > > -# Skip objtool for LLVM bitcode > +# Skip objtool LLVM bitcode I agree with Kees here; drop this comment change. > $(obj)/%o: objtool-enabled := > > +# Run objtool now that we have compiled modules into native code > +$(obj)/%.prelink.o: objtool-enabled := y > + > else > > # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory > @@ -255,6 +256,8 @@ else > $(obj)/%o: objtool-enabled = $(if $(filter-out y%, \ > $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y) > > +$(obj)/%.prelink.o: objtool-enabled := Can we use the canonical .bc file suffix for LLVM bitcode, rather than .prelink.o? > + > endif > > ifdef CONFIG_TRIM_UNUSED_KSYMS > @@ -287,32 +290,12 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE > $(call if_changed_rule,cc_o_c) > $(call cmd,force_checksrc) > > -ifdef CONFIG_LTO_CLANG > -# Module .o files may contain LLVM bitcode, compile them into native code > -# before ELF processing > -quiet_cmd_cc_lto_link_modules = LTO [M] $@ > -cmd_cc_lto_link_modules = \ > - $(LD) $(ld_flags) -r -o $@ \ > - $(shell [ -s $(@:.lto.o=.o.symversions) ] && \ > - echo -T $(@:.lto.o=.o.symversions)) \ > - --whole-archive $(filter-out FORCE,$^) \ > - $(cmd_objtool) > - > -# objtool was skipped for LLVM bitcode, run it now that we have compiled > -# modules into native code > -$(obj)/%.lto.o: objtool-enabled = y > -$(obj)/%.lto.o: part-of-module := y > - > -$(obj)/%.lto.o: $(obj)/%.o FORCE > - $(call if_changed,cc_lto_link_modules) > -endif > - > cmd_mod = { \ > echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \ > $(undefined_syms) echo; \ > } > $@ > > -$(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE > +$(obj)/%.mod: $(obj)/%.prelink.o FORCE > $(call if_changed,mod) > > quiet_cmd_cc_lst_c = MKLST $@ > @@ -416,17 +399,6 @@ $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler > $(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ; > $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ; > > -# combine symversions for later processing > -ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y) > - cmd_update_lto_symversions = \ > - rm -f $@.symversions \ > - $(foreach n, $(filter-out FORCE,$^), \ > - $(if $(shell test -s $(n).symversions && echo y), \ > - ; cat $(n).symversions >> $@.symversions)) > -else > - cmd_update_lto_symversions = echo >/dev/null > -endif > - > # > # Rule to compile a set of .o files into one .a file (without symbol table) > # > @@ -446,10 +418,10 @@ $(obj)/built-in.a: $(real-obj-y) FORCE > # modules.order unless contained modules are updated. > > cmd_modules_order = { $(foreach m, $(real-prereqs), \ > - $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.o,%.ko,$m));) :; } \ > + $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.a,%.ko,$m));) :; } \ > | $(AWK) '!x[$$0]++' - > $@ > > -$(obj)/modules.order: $(obj-m) FORCE > +$(obj)/modules.order: $(modules) FORCE > $(call if_changed,modules_order) > > # > @@ -458,26 +430,44 @@ $(obj)/modules.order: $(obj-m) FORCE > $(obj)/lib.a: $(lib-y) FORCE > $(call if_changed,ar) > > -# NOTE: > -# Do not replace $(filter %.o,^) with $(real-prereqs). When a single object > -# module is turned into a multi object module, $^ will contain header file > -# dependencies recorded in the .*.cmd file. > -ifdef CONFIG_LTO_CLANG > -quiet_cmd_link_multi-m = AR [M] $@ > -cmd_link_multi-m = \ > - $(cmd_update_lto_symversions); \ > - rm -f $@; \ > - $(AR) cDPrsT $@ $(filter %.o,$^) > -else > -quiet_cmd_link_multi-m = LD [M] $@ > - cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^) > +# > +# Rule to prelink modules > +# > + > +ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y) > + > +cmd_merge_symver = $(PERL) scripts/merge-symvers.pl -a $(AR) -o $@ $< > + > +$(obj)/%.prelink.symversions: $(obj)/%.a FORCE > + $(call if_changed,merge_symver) > + > +targets += $(patsubst %.a, %.prelink.symversions, $(modules)) > + > +$(obj)/%.prelink.o: ld_flags += --script=$(filter %.symversions,$^) > +module-symver = $(obj)/%.prelink.symversions > + > endif > > -$(multi-obj-m): FORCE > - $(call if_changed,link_multi-m) > -$(call multi_depend, $(multi-obj-m), .o, -objs -y -m) > +quiet_cmd_ld_o_a = LD [M] $@ > + cmd_ld_o_a = $(LD) $(ld_flags) -r -o $@ --whole-archive $< $(cmd_objtool) > + > +$(obj)/%.prelink.o: part-of-module := y > + > +$(obj)/%.prelink.o: $(obj)/%.a $(module-symver) FORCE > + $(call if_changed,ld_o_a) > + > +quiet_cmd_ar_module = AR [M] $@ > + cmd_ar_module = rm -f $@; $(AR) cDPrST $@ $(real-prereqs) > + > +$(modules-single): %.a: %.o FORCE > + $(call if_changed,ar_module) > + > +$(modules-multi): FORCE > + $(call if_changed,ar_module) > +$(call multi_depend, $(modules-multi), .a, -objs -y -m) > + > +targets += $(modules-single) $(modules-multi) > > -targets += $(multi-obj-m) > targets := $(filter-out $(PHONY), $(targets)) > > # Add intermediate targets: > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib > index 34c4c11c4bc1..5074922db82d 100644 > --- a/scripts/Makefile.lib > +++ b/scripts/Makefile.lib > @@ -106,6 +106,10 @@ multi-dtb-y := $(addprefix $(obj)/, $(multi-dtb-y)) > real-dtb-y := $(addprefix $(obj)/, $(real-dtb-y)) > subdir-ym := $(addprefix $(obj)/,$(subdir-ym)) > > +modules := $(patsubst %.o, %.a, $(obj-m)) > +modules-multi := $(sort $(patsubst %.o, %.a, $(multi-obj-m))) > +modules-single := $(sort $(filter-out $(modules-multi), $(filter %.a, $(modules)))) > + > # Finds the multi-part object the current object will be linked into. > # If the object belongs to two or more multi-part objects, list them all. > modname-multi = $(sort $(foreach m,$(multi-obj-ym),\ > @@ -225,13 +229,6 @@ dtc_cpp_flags = -Wp,-MMD,$(depfile).pre.tmp -nostdinc \ > $(addprefix -I,$(DTC_INCLUDE)) \ > -undef -D__DTS__ > > -ifeq ($(CONFIG_LTO_CLANG),y) > -# With CONFIG_LTO_CLANG, .o files in modules might be LLVM bitcode, so we > -# need to run LTO to compile them into native code (.lto.o) before further > -# processing. > -mod-prelink-ext := .lto > -endif > - > # Useful for describing the dependency of composite objects > # Usage: > # $(call multi_depend, multi_used_targets, suffix_to_remove, suffix_to_add) > diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal > index ff805777431c..1b6401f53662 100644 > --- a/scripts/Makefile.modfinal > +++ b/scripts/Makefile.modfinal > @@ -9,7 +9,7 @@ __modfinal: > include include/config/auto.conf > include $(srctree)/scripts/Kbuild.include > > -# for c_flags and mod-prelink-ext > +# for c_flags > include $(srctree)/scripts/Makefile.lib > > # find all modules listed in modules.order > @@ -55,7 +55,7 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \ > > > # Re-generate module BTFs if either module's .ko or vmlinux changed > -$(modules): %.ko: %$(mod-prelink-ext).o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE > +$(modules): %.ko: %.prelink.o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE > +$(call if_changed_except,ld_ko_o,vmlinux) > ifdef CONFIG_DEBUG_INFO_BTF_MODULES > +$(if $(newer-prereqs),$(call cmd,btf_ko)) > diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost > index eef56d629799..11883b31c615 100644 > --- a/scripts/Makefile.modpost > +++ b/scripts/Makefile.modpost > @@ -41,9 +41,6 @@ __modpost: > include include/config/auto.conf > include $(srctree)/scripts/Kbuild.include > > -# for mod-prelink-ext > -include $(srctree)/scripts/Makefile.lib > - > MODPOST = scripts/mod/modpost \ > $(if $(CONFIG_MODVERSIONS),-m) \ > $(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \ > @@ -128,9 +125,9 @@ endif > # Read out modules.order to pass in modpost. > # Otherwise, allmodconfig would fail with "Argument list too long". > quiet_cmd_modpost = MODPOST $@ > - cmd_modpost = sed 's/\.ko$$/$(mod-prelink-ext)\.o/' $< | $(MODPOST) -T - > + cmd_modpost = sed 's/ko$$/prelink.o/' $< | $(MODPOST) -T - > > -$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(mod-prelink-ext).o) FORCE > +$(output-symdump): $(MODORDER) $(input-symdump) $(modules:ko=prelink.o) FORCE > $(call if_changed,modpost) > > targets += $(output-symdump) > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > index a26139aa57fd..56cd9b7a5dd0 100644 > --- a/scripts/mod/modpost.c > +++ b/scripts/mod/modpost.c > @@ -2000,9 +2000,9 @@ static void read_symbols(const char *modname) > /* strip trailing .o */ > tmp = NOFAIL(strdup(modname)); > tmp[strlen(tmp) - 2] = '\0'; > - /* strip trailing .lto */ > - if (strends(tmp, ".lto")) > - tmp[strlen(tmp) - 4] = '\0'; > + /* strip trailing .prelink */ > + if (strends(tmp, ".prelink")) > + tmp[strlen(tmp) - 8] = '\0'; > mod = new_module(tmp); > free(tmp); > } > -- > 2.30.2 >
diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 3ad1b1227371..cdc09e9080ca 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -88,9 +88,7 @@ endif targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m))) -ifdef CONFIG_LTO_CLANG -targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m))) -endif +targets-for-modules += $(patsubst %.o, %.prelink.o, $(filter %.o, $(obj-m))) ifdef need-modorder targets-for-modules += $(obj)/modules.order @@ -243,9 +241,12 @@ endif # CONFIG_STACK_VALIDATION ifdef CONFIG_LTO_CLANG -# Skip objtool for LLVM bitcode +# Skip objtool LLVM bitcode $(obj)/%o: objtool-enabled := +# Run objtool now that we have compiled modules into native code +$(obj)/%.prelink.o: objtool-enabled := y + else # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory @@ -255,6 +256,8 @@ else $(obj)/%o: objtool-enabled = $(if $(filter-out y%, \ $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y) +$(obj)/%.prelink.o: objtool-enabled := + endif ifdef CONFIG_TRIM_UNUSED_KSYMS @@ -287,32 +290,12 @@ $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE $(call if_changed_rule,cc_o_c) $(call cmd,force_checksrc) -ifdef CONFIG_LTO_CLANG -# Module .o files may contain LLVM bitcode, compile them into native code -# before ELF processing -quiet_cmd_cc_lto_link_modules = LTO [M] $@ -cmd_cc_lto_link_modules = \ - $(LD) $(ld_flags) -r -o $@ \ - $(shell [ -s $(@:.lto.o=.o.symversions) ] && \ - echo -T $(@:.lto.o=.o.symversions)) \ - --whole-archive $(filter-out FORCE,$^) \ - $(cmd_objtool) - -# objtool was skipped for LLVM bitcode, run it now that we have compiled -# modules into native code -$(obj)/%.lto.o: objtool-enabled = y -$(obj)/%.lto.o: part-of-module := y - -$(obj)/%.lto.o: $(obj)/%.o FORCE - $(call if_changed,cc_lto_link_modules) -endif - cmd_mod = { \ echo $(if $($*-objs)$($*-y)$($*-m), $(addprefix $(obj)/, $($*-objs) $($*-y) $($*-m)), $(@:.mod=.o)); \ $(undefined_syms) echo; \ } > $@ -$(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE +$(obj)/%.mod: $(obj)/%.prelink.o FORCE $(call if_changed,mod) quiet_cmd_cc_lst_c = MKLST $@ @@ -416,17 +399,6 @@ $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler $(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ; $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ; -# combine symversions for later processing -ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y) - cmd_update_lto_symversions = \ - rm -f $@.symversions \ - $(foreach n, $(filter-out FORCE,$^), \ - $(if $(shell test -s $(n).symversions && echo y), \ - ; cat $(n).symversions >> $@.symversions)) -else - cmd_update_lto_symversions = echo >/dev/null -endif - # # Rule to compile a set of .o files into one .a file (without symbol table) # @@ -446,10 +418,10 @@ $(obj)/built-in.a: $(real-obj-y) FORCE # modules.order unless contained modules are updated. cmd_modules_order = { $(foreach m, $(real-prereqs), \ - $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.o,%.ko,$m));) :; } \ + $(if $(filter %/modules.order, $m), cat $m, echo $(patsubst %.a,%.ko,$m));) :; } \ | $(AWK) '!x[$$0]++' - > $@ -$(obj)/modules.order: $(obj-m) FORCE +$(obj)/modules.order: $(modules) FORCE $(call if_changed,modules_order) # @@ -458,26 +430,44 @@ $(obj)/modules.order: $(obj-m) FORCE $(obj)/lib.a: $(lib-y) FORCE $(call if_changed,ar) -# NOTE: -# Do not replace $(filter %.o,^) with $(real-prereqs). When a single object -# module is turned into a multi object module, $^ will contain header file -# dependencies recorded in the .*.cmd file. -ifdef CONFIG_LTO_CLANG -quiet_cmd_link_multi-m = AR [M] $@ -cmd_link_multi-m = \ - $(cmd_update_lto_symversions); \ - rm -f $@; \ - $(AR) cDPrsT $@ $(filter %.o,$^) -else -quiet_cmd_link_multi-m = LD [M] $@ - cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^) +# +# Rule to prelink modules +# + +ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y) + +cmd_merge_symver = $(PERL) scripts/merge-symvers.pl -a $(AR) -o $@ $< + +$(obj)/%.prelink.symversions: $(obj)/%.a FORCE + $(call if_changed,merge_symver) + +targets += $(patsubst %.a, %.prelink.symversions, $(modules)) + +$(obj)/%.prelink.o: ld_flags += --script=$(filter %.symversions,$^) +module-symver = $(obj)/%.prelink.symversions + endif -$(multi-obj-m): FORCE - $(call if_changed,link_multi-m) -$(call multi_depend, $(multi-obj-m), .o, -objs -y -m) +quiet_cmd_ld_o_a = LD [M] $@ + cmd_ld_o_a = $(LD) $(ld_flags) -r -o $@ --whole-archive $< $(cmd_objtool) + +$(obj)/%.prelink.o: part-of-module := y + +$(obj)/%.prelink.o: $(obj)/%.a $(module-symver) FORCE + $(call if_changed,ld_o_a) + +quiet_cmd_ar_module = AR [M] $@ + cmd_ar_module = rm -f $@; $(AR) cDPrST $@ $(real-prereqs) + +$(modules-single): %.a: %.o FORCE + $(call if_changed,ar_module) + +$(modules-multi): FORCE + $(call if_changed,ar_module) +$(call multi_depend, $(modules-multi), .a, -objs -y -m) + +targets += $(modules-single) $(modules-multi) -targets += $(multi-obj-m) targets := $(filter-out $(PHONY), $(targets)) # Add intermediate targets: diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 34c4c11c4bc1..5074922db82d 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -106,6 +106,10 @@ multi-dtb-y := $(addprefix $(obj)/, $(multi-dtb-y)) real-dtb-y := $(addprefix $(obj)/, $(real-dtb-y)) subdir-ym := $(addprefix $(obj)/,$(subdir-ym)) +modules := $(patsubst %.o, %.a, $(obj-m)) +modules-multi := $(sort $(patsubst %.o, %.a, $(multi-obj-m))) +modules-single := $(sort $(filter-out $(modules-multi), $(filter %.a, $(modules)))) + # Finds the multi-part object the current object will be linked into. # If the object belongs to two or more multi-part objects, list them all. modname-multi = $(sort $(foreach m,$(multi-obj-ym),\ @@ -225,13 +229,6 @@ dtc_cpp_flags = -Wp,-MMD,$(depfile).pre.tmp -nostdinc \ $(addprefix -I,$(DTC_INCLUDE)) \ -undef -D__DTS__ -ifeq ($(CONFIG_LTO_CLANG),y) -# With CONFIG_LTO_CLANG, .o files in modules might be LLVM bitcode, so we -# need to run LTO to compile them into native code (.lto.o) before further -# processing. -mod-prelink-ext := .lto -endif - # Useful for describing the dependency of composite objects # Usage: # $(call multi_depend, multi_used_targets, suffix_to_remove, suffix_to_add) diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal index ff805777431c..1b6401f53662 100644 --- a/scripts/Makefile.modfinal +++ b/scripts/Makefile.modfinal @@ -9,7 +9,7 @@ __modfinal: include include/config/auto.conf include $(srctree)/scripts/Kbuild.include -# for c_flags and mod-prelink-ext +# for c_flags include $(srctree)/scripts/Makefile.lib # find all modules listed in modules.order @@ -55,7 +55,7 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \ # Re-generate module BTFs if either module's .ko or vmlinux changed -$(modules): %.ko: %$(mod-prelink-ext).o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE +$(modules): %.ko: %.prelink.o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE +$(call if_changed_except,ld_ko_o,vmlinux) ifdef CONFIG_DEBUG_INFO_BTF_MODULES +$(if $(newer-prereqs),$(call cmd,btf_ko)) diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index eef56d629799..11883b31c615 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -41,9 +41,6 @@ __modpost: include include/config/auto.conf include $(srctree)/scripts/Kbuild.include -# for mod-prelink-ext -include $(srctree)/scripts/Makefile.lib - MODPOST = scripts/mod/modpost \ $(if $(CONFIG_MODVERSIONS),-m) \ $(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \ @@ -128,9 +125,9 @@ endif # Read out modules.order to pass in modpost. # Otherwise, allmodconfig would fail with "Argument list too long". quiet_cmd_modpost = MODPOST $@ - cmd_modpost = sed 's/\.ko$$/$(mod-prelink-ext)\.o/' $< | $(MODPOST) -T - + cmd_modpost = sed 's/ko$$/prelink.o/' $< | $(MODPOST) -T - -$(output-symdump): $(MODORDER) $(input-symdump) $(modules:.ko=$(mod-prelink-ext).o) FORCE +$(output-symdump): $(MODORDER) $(input-symdump) $(modules:ko=prelink.o) FORCE $(call if_changed,modpost) targets += $(output-symdump) diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index a26139aa57fd..56cd9b7a5dd0 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -2000,9 +2000,9 @@ static void read_symbols(const char *modname) /* strip trailing .o */ tmp = NOFAIL(strdup(modname)); tmp[strlen(tmp) - 2] = '\0'; - /* strip trailing .lto */ - if (strends(tmp, ".lto")) - tmp[strlen(tmp) - 4] = '\0'; + /* strip trailing .prelink */ + if (strends(tmp, ".prelink")) + tmp[strlen(tmp) - 8] = '\0'; mod = new_module(tmp); free(tmp); }
When Clang LTO is enabled, additional intermediate files *.lto.o are created because LLVM bitcode must be converted to ELF before modpost. For non-LTO builds: $(LD) $(LD) objects ---> <modname>.o -----> <modname>.ko | <modname>.mod.o ---/ For Clang LTO builds: $(AR) $(LD) $(LD) objects ---> <modname>.o ---> <modname>.lto.o -----> <modname>.ko | <modname>.mod.o --/ Since the Clang LTO introduction, Kbuild code is complicated due to CONFIG_LTO_CLANG conditionals sprinkled everywhere. Another confusion for Clang LTO builds is, <modname>.o is an archive that contains LLVM bitcode files. The suffix should be .a instead of .o To clean up the code, unify the build process of modules, as follows: $(AR) $(LD) $(LD) objects ---> <modname>.a ---> <modname>.prelink.o -----> <modname>.ko | <modname>.mod.o ------/ Here, 'objects' are either ELF or LLVM bitcode. <modname>.a is an archive, <modname>.prelink.o is ELF. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- scripts/Makefile.build | 100 +++++++++++++++++--------------------- scripts/Makefile.lib | 11 ++--- scripts/Makefile.modfinal | 4 +- scripts/Makefile.modpost | 7 +-- scripts/mod/modpost.c | 6 +-- 5 files changed, 56 insertions(+), 72 deletions(-)