From 5fe4dd59664105a9ea1a9468aa7391806b80364a Mon Sep 17 00:00:00 2001 From: "Lorenzo Stoakes (ARM)" Date: Wed, 23 Sep 2026 18:17:50 +0100 Subject: kbuild: do not allocate .modinfo in vmlinux Commit 3e86e4d74c04 ("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 Signed-off-by: Lorenzo Stoakes (ARM) Reviewed-by: Nicolas Schier Link: https://patch.msgid.link/20260923-build-speedup-v4-1-73128809a4a4@kernel.org Signed-off-by: Nathan Chancellor --- scripts/Makefile.vmlinux | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) (limited to 'scripts/Makefile.vmlinux') diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux index 6833b517cacb..95b523fe4f9e 100644 --- a/scripts/Makefile.vmlinux +++ b/scripts/Makefile.vmlinux @@ -89,11 +89,8 @@ remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel.*' remove-symbols := -w --strip-unneeded-symbol='__mod_device_table__*' -# To avoid warnings: "empty loadable segment detected at ..." from GNU objcopy, -# it is necessary to remove the PT_LOAD flag from the segment. quiet_cmd_strip_relocs = OBJCOPY $@ - cmd_strip_relocs = $(OBJCOPY) $(patsubst %,--set-section-flags %=noload,$(remove-section-y)) $< $@; \ - $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) $(remove-symbols) $@ + cmd_strip_relocs = $(OBJCOPY) $(addprefix --remove-section=,$(remove-section-y)) $(remove-symbols) $< $@ targets += vmlinux vmlinux: vmlinux.unstripped FORCE @@ -103,10 +100,7 @@ vmlinux: vmlinux.unstripped FORCE # --------------------------------------------------------------------------- quiet_cmd_modules_builtin_modinfo = GEN $@ - cmd_modules_builtin_modinfo = $(cmd_objcopy); \ - chmod -x $@ - -OBJCOPYFLAGS_modules.builtin.modinfo := -j .modinfo -O binary + cmd_modules_builtin_modinfo = $(OBJCOPY) -O binary -j .modinfo --dump-section .modinfo=$@ $< /dev/null targets += modules.builtin.modinfo modules.builtin.modinfo: vmlinux.unstripped FORCE -- cgit v1.2.3