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kbuild: unify two modpost invocations

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Currently, modpost is executed twice; first for vmlinux, second
for modules.

This commit merges them.

Current build flow
==================

  1) build obj-y and obj-m objects
    2) link vmlinux.o
      3) modpost for vmlinux
        4) link vmlinux
          5) modpost for modules
            6) link modules (*.ko)

The build steps 1) through 6) are serialized, that is, modules are
built after vmlinux. You do not get benefits of parallel builds when
scripts/link-vmlinux.sh is being run.

New build flow
==============

  1) build obj-y and obj-m objects
    2) link vmlinux.o
      3) modpost for vmlinux and modules
        4a) link vmlinux
        4b) link modules (*.ko)

In the new build flow, modpost is invoked just once.

vmlinux and modules are built in parallel. One exception is
CONFIG_DEBUG_INFO_BTF_MODULES=y, where modules depend on vmlinux.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
This commit is contained in:
Masahiro Yamada 2022-09-25 03:19:13 +09:00
parent 9c5a0ac3c3
commit f73edc8951
4 changed files with 54 additions and 76 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

32
Makefile
View file

@ -1150,7 +1150,7 @@ cmd_link-vmlinux = \
$(CONFIG_SHELL) $< "$(LD)" "$(KBUILD_LDFLAGS)" "$(LDFLAGS_vmlinux)"; \
$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
vmlinux: scripts/link-vmlinux.sh vmlinux.o $(KBUILD_LDS) FORCE
vmlinux: scripts/link-vmlinux.sh vmlinux.o $(KBUILD_LDS) modpost FORCE
+$(call if_changed_dep,link-vmlinux)
targets := vmlinux
@ -1426,7 +1426,13 @@ endif
# Build modules
#
modules: $(if $(KBUILD_BUILTIN),vmlinux) modules_prepare
# *.ko are usually independent of vmlinux, but CONFIG_DEBUG_INFOBTF_MODULES
# is an exception.
ifdef CONFIG_DEBUG_INFO_BTF_MODULES
modules: vmlinux
endif
modules: modules_prepare
# Target to prepare building external modules
modules_prepare: prepare
@ -1739,8 +1745,12 @@ ifdef CONFIG_MODULES
$(MODORDER): $(build-dir)
@:
modules: modules_check
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
# KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
# This is solely useful to speed up test compiles.
modules: modpost
ifneq ($(KBUILD_MODPOST_NOFINAL),1)
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modfinal
endif
PHONY += modules_check
modules_check: $(MODORDER)
@ -1771,6 +1781,11 @@ KBUILD_MODULES :=
endif # CONFIG_MODULES
PHONY += modpost
modpost: $(if $(single-build),, $(if $(KBUILD_BUILTIN), vmlinux.o)) \
$(if $(KBUILD_MODULES), modules_check)
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
# Single targets
# ---------------------------------------------------------------------------
# To build individual files in subdirectories, you can do like this:
@ -1790,16 +1805,19 @@ single-ko := $(sort $(filter %.ko, $(MAKECMDGOALS)))
single-no-ko := $(filter-out $(single-ko), $(MAKECMDGOALS)) \
$(foreach x, o mod, $(patsubst %.ko, %.$x, $(single-ko)))
$(single-ko): single_modpost
$(single-ko): single_modules
@:
$(single-no-ko): $(build-dir)
@:
# Remove MODORDER when done because it is not the real one.
PHONY += single_modpost
single_modpost: $(single-no-ko) modules_prepare
PHONY += single_modules
single_modules: $(single-no-ko) modules_prepare
$(Q){ $(foreach m, $(single-ko), echo $(extmod_prefix)$m;) } > $(MODORDER)
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
ifneq ($(KBUILD_MODPOST_NOFINAL),1)
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modfinal
endif
$(Q)rm -f $(MODORDER)
single-goals := $(addprefix $(build-dir)/, $(single-no-ko))

2
scripts/Makefile.modfinal
View file

@ -55,7 +55,7 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \
printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
# Re-generate module BTFs if either module's .ko or vmlinux changed
$(modules): %.ko: %.o %.mod.o scripts/module.lds $(if $(KBUILD_BUILTIN),vmlinux) FORCE
$(modules): %.ko: %.o %.mod.o scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(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))

93
scripts/Makefile.modpost
View file

@ -32,9 +32,6 @@
# Step 4 is solely used to allow module versioning in external modules,
# where the CRC of each module is retrieved from the Module.symvers file.
# KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
# This is solely useful to speed up test compiles
PHONY := __modpost
__modpost:
@ -45,24 +42,23 @@ MODPOST = scripts/mod/modpost \
$(if $(CONFIG_MODVERSIONS),-m) \
$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \
$(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E) \
$(if $(KBUILD_NSDEPS),-d $(MODULES_NSDEPS)) \
$(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-N) \
-o $@
ifdef MODPOST_VMLINUX
# 'make -i -k' ignores compile errors, and builds as many modules as possible.
ifneq ($(findstring i,$(filter-out --%,$(MAKEFLAGS))),)
MODPOST += -n
endif
quiet_cmd_modpost = MODPOST $@
cmd_modpost = $(MODPOST) $<
vmlinux.symvers: vmlinux.o
$(call cmd,modpost)
__modpost: vmlinux.symvers
ifeq ($(KBUILD_EXTMOD),)
# Generate the list of in-tree objects in vmlinux
# ---------------------------------------------------------------------------
# This is used to retrieve symbol versions generated by genksyms.
ifdef CONFIG_MODVERSIONS
vmlinux.symvers: .vmlinux.objs
vmlinux.symvers Module.symvers: .vmlinux.objs
endif
# Ignore libgcc.a
@ -83,24 +79,12 @@ targets += .vmlinux.objs
.vmlinux.objs: $(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS) FORCE
$(call if_changed,vmlinux_objs)
else
ifeq ($(KBUILD_EXTMOD),)
input-symdump := vmlinux.symvers
output-symdump := modules-only.symvers
quiet_cmd_cat = GEN $@
cmd_cat = cat $(real-prereqs) > $@
ifneq ($(wildcard vmlinux.symvers),)
__modpost: Module.symvers
Module.symvers: vmlinux.symvers modules-only.symvers FORCE
$(call if_changed,cat)
targets += Module.symvers
vmlinux.o-if-present := $(wildcard vmlinux.o)
output-symdump := vmlinux.symvers
ifdef KBUILD_MODULES
output-symdump := $(if $(vmlinux.o-if-present), Module.symvers, modules-only.symvers)
missing-input := $(filter-out $(vmlinux.o-if-present),vmlinux.o)
endif
else
@ -112,56 +96,35 @@ src := $(obj)
# Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
include $(or $(wildcard $(src)/Kbuild), $(src)/Makefile)
# modpost option for external modules
MODPOST += -e
input-symdump := Module.symvers $(KBUILD_EXTRA_SYMBOLS)
module.symvers-if-present := $(wildcard Module.symvers)
output-symdump := $(KBUILD_EXTMOD)/Module.symvers
missing-input := $(filter-out $(module.symvers-if-present), Module.symvers)
endif
MODPOST += -e $(addprefix -i ,$(module.symvers-if-present) $(KBUILD_EXTRA_SYMBOLS))
existing-input-symdump := $(wildcard $(input-symdump))
endif # ($(KBUILD_EXTMOD),)
# modpost options for modules (both in-kernel and external)
MODPOST += \
$(addprefix -i ,$(existing-input-symdump)) \
$(if $(KBUILD_NSDEPS),-d $(MODULES_NSDEPS)) \
$(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-N)
# 'make -i -k' ignores compile errors, and builds as many modules as possible.
ifneq ($(findstring i,$(filter-out --%,$(MAKEFLAGS))),)
MODPOST += -n
endif
# Clear VPATH to not search for *.symvers in $(srctree). Check only $(objtree).
VPATH :=
$(input-symdump):
@echo >&2 'WARNING: Symbol version dump "$@" is missing.'
@echo >&2 ' Modules may not have dependencies or modversions.'
@echo >&2 ' You may get many unresolved symbol warnings.'
# KBUILD_MODPOST_WARN can be set to avoid error out in case of undefined symbols
ifneq ($(KBUILD_MODPOST_WARN)$(filter-out $(existing-input-symdump), $(input-symdump)),)
ifneq ($(KBUILD_MODPOST_WARN)$(missing-input),)
MODPOST += -w
endif
modorder-if-needed := $(if $(KBUILD_MODULES), $(MODORDER))
# 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$$/o/' $< | $(MODPOST) -T -
$(output-symdump): $(MODORDER) $(input-symdump) FORCE
$(call if_changed,modpost)
cmd_modpost = \
$(if $(missing-input), \
echo >&2 "WARNING: $(missing-input) is missing."; \
echo >&2 " Modules may not have dependencies or modversions."; \
echo >&2 " You may get many unresolved symbol warnings.";) \
sed 's/ko$$/o/' $(or $(modorder-if-needed), /dev/null) | $(MODPOST) $(vmlinux.o-if-present) -T -
targets += $(output-symdump)
$(output-symdump): $(modorder-if-needed) $(vmlinux.o-if-present) $(moudle.symvers-if-present) FORCE
$(call if_changed,modpost)
__modpost: $(output-symdump)
ifneq ($(KBUILD_MODPOST_NOFINAL),1)
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modfinal
endif
endif
PHONY += FORCE
FORCE:

3
scripts/link-vmlinux.sh
View file

@ -214,9 +214,6 @@ if [ "$1" = "clean" ]; then
exit 0
fi
# modpost vmlinux.o to check for section mismatches
${MAKE} -f "${srctree}/scripts/Makefile.modpost" MODPOST_VMLINUX=1
info MODINFO modules.builtin.modinfo
${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo
info GEN modules.builtin