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5fe4dd5966
Commit 3e86e4d74c ("kbuild: keep .modinfo section in vmlinux.unstripped")
placed MODULE_INFO() strings in the .modinfo section in vmlinux.unstripped,
however it left the section allocatable, so it gets assigned an address and
on arm64, arm and riscv, the section is tagged as PT_LOAD.
This is useless as the data is ultimately stripped anyway.
Doing this results in a lot of unnecessary work - each pass copies the
whole file, 450 MiB with relocations for an x86 allmodconfig build and 250
MiB for an arm64 allmodconfig build.
This adds ~0.7s on the serial tail of every build for arm64 and ~0.2s for
x86 (the tail is single-threaded work done after parallel work has
finished).
Nothing requires .modinfo to exist at an address, so mark the output
section (INFO) so that it's not allocated and use --dump-section to extract
it as -O only emits allocated sections.
The dump doesn't pick up the arch's OBJCOPYFLAGS any longer as they should
not impact the output of this section.
Image, bzImage, System.map and modules.builtin.modinfo are unchanged and
the stripped vmlinux differs only in its program headers.
The objcopy passes are on the serial tail of every build that links
vmlinux, no-op builds are unchanged.
Whole build, 128-thread Threadripper 9980X, best of N runs:
before after delta
-------------------------------
x86 defconfig, touch mm/vma.c, gcc 11.2s 11.1s -0.15s (-1%)
x86 defconfig, touch mm/vma.c, clang 11.3s 11.1s -0.19s (-2%)
x86 defconfig, clean, gcc 32.5s 32.3s -0.16s (-1%)
x86 defconfig, clean, clang 34.5s 34.2s -0.26s (-1%)
x86 allmodconfig, touch mm/vma.c, gcc 40.1s 39.7s -0.44s (-1%)
Assisted-by: LLM
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@fritz.com>
Link: https://patch.msgid.link/20260923-build-speedup-v4-1-73128809a4a4@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
160 lines
5.0 KiB
Makefile
160 lines
5.0 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0-only
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PHONY := __default
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__default: vmlinux
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include include/config/auto.conf
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include $(srctree)/scripts/Kbuild.include
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include $(srctree)/scripts/Makefile.lib
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targets :=
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%.o: %.c FORCE
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$(call if_changed_rule,cc_o_c)
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%.o: %.S FORCE
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$(call if_changed_rule,as_o_S)
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# Built-in dtb
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# ---------------------------------------------------------------------------
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quiet_cmd_wrap_dtbs = WRAP $@
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cmd_wrap_dtbs = { \
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echo '\#include <asm-generic/vmlinux.lds.h>'; \
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echo '.section .dtb.init.rodata,"a"'; \
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while read dtb; do \
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symbase=__dtb_$$(basename -s .dtb "$${dtb}" | tr - _); \
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echo '.balign STRUCT_ALIGNMENT'; \
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echo ".global $${symbase}_begin"; \
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echo "$${symbase}_begin:"; \
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echo '.incbin "'$$dtb'" '; \
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echo ".global $${symbase}_end"; \
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echo "$${symbase}_end:"; \
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done < $<; \
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} > $@
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.builtin-dtbs.S: .builtin-dtbs-list FORCE
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$(call if_changed,wrap_dtbs)
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quiet_cmd_gen_dtbs_list = GEN $@
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cmd_gen_dtbs_list = \
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$(if $(CONFIG_BUILTIN_DTB_NAME), echo "arch/$(SRCARCH)/boot/dts/$(CONFIG_BUILTIN_DTB_NAME).dtb",:) > $@
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.builtin-dtbs-list: arch/$(SRCARCH)/boot/dts/dtbs-list FORCE
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$(call if_changed,$(if $(CONFIG_BUILTIN_DTB_ALL),copy,gen_dtbs_list))
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targets += .builtin-dtbs-list
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ifdef CONFIG_GENERIC_BUILTIN_DTB
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targets += .builtin-dtbs.S .builtin-dtbs.o
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vmlinux.unstripped: .builtin-dtbs.o
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endif
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# vmlinux.unstripped
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# ---------------------------------------------------------------------------
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ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
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vmlinux.unstripped: arch/$(SRCARCH)/tools/vmlinux.arch.o
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arch/$(SRCARCH)/tools/vmlinux.arch.o: vmlinux.o FORCE
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$(Q)$(MAKE) $(build)=arch/$(SRCARCH)/tools $@
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endif
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ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
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# Final link of vmlinux with optional arch pass after final link
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cmd_link_vmlinux = \
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$< "$(LD)" "$(KBUILD_LDFLAGS)" "$(LDFLAGS_vmlinux)" "$@"; \
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$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
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targets += vmlinux.unstripped .vmlinux.export.o
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vmlinux.unstripped: scripts/link-vmlinux.sh vmlinux.o .vmlinux.export.o $(KBUILD_LDS) FORCE
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+$(call if_changed_dep,link_vmlinux)
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ifdef CONFIG_DEBUG_INFO_BTF
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vmlinux.unstripped: $(RESOLVE_BTFIDS) $(srctree)/scripts/gen-btf.sh
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endif
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ifdef CONFIG_BUILDTIME_TABLE_SORT
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vmlinux.unstripped: scripts/sorttable
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endif
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# vmlinux
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# ---------------------------------------------------------------------------
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remove-section-y := .modinfo
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remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel*' '!.rel*.dyn'
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# for compatibility with binutils < 2.32
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# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=c12d9fa2afe7abcbe407a00e15719e1a1350c2a7
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remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel.*'
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remove-symbols := -w --strip-unneeded-symbol='__mod_device_table__*'
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quiet_cmd_strip_relocs = OBJCOPY $@
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cmd_strip_relocs = $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) $(remove-symbols) $< $@
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targets += vmlinux
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vmlinux: vmlinux.unstripped FORCE
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$(call if_changed,strip_relocs)
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# modules.builtin.modinfo
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# ---------------------------------------------------------------------------
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quiet_cmd_modules_builtin_modinfo = GEN $@
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cmd_modules_builtin_modinfo = $(OBJCOPY) -O binary -j .modinfo --dump-section .modinfo=$@ $< /dev/null
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targets += modules.builtin.modinfo
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modules.builtin.modinfo: vmlinux.unstripped FORCE
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$(call if_changed,modules_builtin_modinfo)
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# modules.builtin
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# ---------------------------------------------------------------------------
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__default: modules.builtin
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# The second line aids cases where multiple modules share the same object.
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quiet_cmd_modules_builtin = GEN $@
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cmd_modules_builtin = \
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tr '\0' '\n' < $< | \
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sed -n 's/^[[:alnum:]:_]*\.file=//p' | \
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tr ' ' '\n' | uniq | sed -e 's:^:kernel/:' -e 's/$$/.ko/' > $@
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targets += modules.builtin
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modules.builtin: modules.builtin.modinfo FORCE
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$(call if_changed,modules_builtin)
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# modules.builtin.ranges
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# ---------------------------------------------------------------------------
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ifdef CONFIG_BUILTIN_MODULE_RANGES
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__default: modules.builtin.ranges
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quiet_cmd_modules_builtin_ranges = GEN $@
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cmd_modules_builtin_ranges = gawk -f $(real-prereqs) > $@
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targets += modules.builtin.ranges
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modules.builtin.ranges: $(srctree)/scripts/generate_builtin_ranges.awk \
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modules.builtin vmlinux.map vmlinux.o.map FORCE
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$(call if_changed,modules_builtin_ranges)
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vmlinux.map: vmlinux.unstripped
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@:
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endif
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# Add FORCE to the prerequisites of a target to force it to be always rebuilt.
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# ---------------------------------------------------------------------------
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PHONY += FORCE
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FORCE:
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# Read all saved command lines and dependencies for the $(targets) we
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# may be building above, using $(if_changed{,_dep}). As an
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# optimization, we don't need to read them if the target does not
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# exist, we will rebuild anyway in that case.
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existing-targets := $(wildcard $(sort $(targets)))
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-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
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.PHONY: $(PHONY)
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