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linux/scripts/Makefile.vmlinux
Nathan Chancellor b0f2942a16 kbuild: Use '--strip-unneeded-symbol' for removing module device table symbols 
After commit 5ab23c7923 ("modpost: Create modalias for builtin
modules"), relocatable RISC-V kernels with CONFIG_KASAN=y start failing
when attempting to strip the module device table symbols:

  riscv64-linux-objcopy: not stripping symbol `__mod_device_table__kmod_irq_starfive_jh8100_intc__of__starfive_intc_irqchip_match_table' because it is named in a relocation
  make[4]: *** [scripts/Makefile.vmlinux:97: vmlinux] Error 1

The relocation appears to come from .LASANLOC5 in .data.rel.local:

  $ llvm-objdump --disassemble-symbols=.LASANLOC5 --disassemble-all -r drivers/irqchip/irq-starfive-jh8100-intc.o

  drivers/irqchip/irq-starfive-jh8100-intc.o:   file format elf64-littleriscv

  Disassembly of section .data.rel.local:

  0000000000000180 <.LASANLOC5>:
  ...
       1d0: 0000          unimp
                  00000000000001d0:  R_RISCV_64   __mod_device_table__kmod_irq_starfive_jh8100_intc__of__starfive_intc_irqchip_match_table
  ...

This section appears to come from GCC for including additional
information about global variables that may be protected by KASAN.

There appears to be no way to opt out of the generation of these symbols
through either a flag or attribute. Attempting to remove '.LASANLOC*'
with '--strip-symbol' results in the same error as above because these
symbols may refer to (thus have relocation between) each other.

Avoid this build breakage by switching to '--strip-unneeded-symbol' for
removing __mod_device_table__ symbols, as it will only remove the symbol
when there is no relocation pointing to it. While this may result in a
little more bloat in the symbol table in certain configurations, it is
not as bad as outright build failures.

Fixes: 5ab23c7923 ("modpost: Create modalias for builtin modules")
Reported-by: Charles Mirabile <cmirabil@redhat.com>
Closes: https://lore.kernel.org/20251007011637.2512413-1-cmirabil@redhat.com/
Suggested-by: Alexey Gladkov <legion@kernel.org>
Tested-by: Nicolas Schier <nsc@kernel.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
2025-10-10 14:50:35 -07:00

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# SPDX-License-Identifier: GPL-2.0-only
PHONY := __default
__default: vmlinux
include include/config/auto.conf
include $(srctree)/scripts/Kbuild.include
include $(srctree)/scripts/Makefile.lib
targets :=
%.o: %.c FORCE
$(call if_changed_rule,cc_o_c)
%.o: %.S FORCE
$(call if_changed_rule,as_o_S)
# Built-in dtb
# ---------------------------------------------------------------------------
quiet_cmd_wrap_dtbs = WRAP $@
cmd_wrap_dtbs = { \
echo '\#include <asm-generic/vmlinux.lds.h>'; \
echo '.section .dtb.init.rodata,"a"'; \
while read dtb; do \
symbase=__dtb_$$(basename -s .dtb "$${dtb}" | tr - _); \
echo '.balign STRUCT_ALIGNMENT'; \
echo ".global $${symbase}_begin"; \
echo "$${symbase}_begin:"; \
echo '.incbin "'$$dtb'" '; \
echo ".global $${symbase}_end"; \
echo "$${symbase}_end:"; \
done < $<; \
} > $@
.builtin-dtbs.S: .builtin-dtbs-list FORCE
$(call if_changed,wrap_dtbs)
quiet_cmd_gen_dtbs_list = GEN $@
cmd_gen_dtbs_list = \
$(if $(CONFIG_BUILTIN_DTB_NAME), echo "arch/$(SRCARCH)/boot/dts/$(CONFIG_BUILTIN_DTB_NAME).dtb",:) > $@
.builtin-dtbs-list: arch/$(SRCARCH)/boot/dts/dtbs-list FORCE
$(call if_changed,$(if $(CONFIG_BUILTIN_DTB_ALL),copy,gen_dtbs_list))
targets += .builtin-dtbs-list
ifdef CONFIG_GENERIC_BUILTIN_DTB
targets += .builtin-dtbs.S .builtin-dtbs.o
vmlinux.unstripped: .builtin-dtbs.o
endif
# vmlinux.unstripped
# ---------------------------------------------------------------------------
ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
vmlinux.unstripped: arch/$(SRCARCH)/tools/vmlinux.arch.o
arch/$(SRCARCH)/tools/vmlinux.arch.o: vmlinux.o FORCE
$(Q)$(MAKE) $(build)=arch/$(SRCARCH)/tools $@
endif
ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
# Final link of vmlinux with optional arch pass after final link
cmd_link_vmlinux = \
$< "$(LD)" "$(KBUILD_LDFLAGS)" "$(LDFLAGS_vmlinux)" "$@"; \
$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
targets += vmlinux.unstripped .vmlinux.export.o
vmlinux.unstripped: scripts/link-vmlinux.sh vmlinux.o .vmlinux.export.o $(KBUILD_LDS) FORCE
+$(call if_changed_dep,link_vmlinux)
ifdef CONFIG_DEBUG_INFO_BTF
vmlinux.unstripped: $(RESOLVE_BTFIDS)
endif
ifdef CONFIG_BUILDTIME_TABLE_SORT
vmlinux.unstripped: scripts/sorttable
endif
# vmlinux
# ---------------------------------------------------------------------------
remove-section-y := .modinfo
remove-section-$(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS) += '.rel*' '!.rel*.dyn'
# for compatibility with binutils < 2.32
# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=c12d9fa2afe7abcbe407a00e15719e1a1350c2a7
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) $@
targets += vmlinux
vmlinux: vmlinux.unstripped FORCE
$(call if_changed,strip_relocs)
# modules.builtin.modinfo
# ---------------------------------------------------------------------------
OBJCOPYFLAGS_modules.builtin.modinfo := -j .modinfo -O binary
targets += modules.builtin.modinfo
modules.builtin.modinfo: vmlinux.unstripped FORCE
$(call if_changed,objcopy)
# modules.builtin
# ---------------------------------------------------------------------------
__default: modules.builtin
# The second line aids cases where multiple modules share the same object.
quiet_cmd_modules_builtin = GEN $@
cmd_modules_builtin = \
tr '\0' '\n' < $< | \
sed -n 's/^[[:alnum:]:_]*\.file=//p' | \
tr ' ' '\n' | uniq | sed -e 's:^:kernel/:' -e 's/$$/.ko/' > $@
targets += modules.builtin
modules.builtin: modules.builtin.modinfo FORCE
$(call if_changed,modules_builtin)
# modules.builtin.ranges
# ---------------------------------------------------------------------------
ifdef CONFIG_BUILTIN_MODULE_RANGES
__default: modules.builtin.ranges
quiet_cmd_modules_builtin_ranges = GEN $@
cmd_modules_builtin_ranges = gawk -f $(real-prereqs) > $@
targets += modules.builtin.ranges
modules.builtin.ranges: $(srctree)/scripts/generate_builtin_ranges.awk \
modules.builtin vmlinux.map vmlinux.o.map FORCE
$(call if_changed,modules_builtin_ranges)
vmlinux.map: vmlinux.unstripped
@:
endif
# Add FORCE to the prerequisites of a target to force it to be always rebuilt.
# ---------------------------------------------------------------------------
PHONY += FORCE
FORCE:
# Read all saved command lines and dependencies for the $(targets) we
# may be building above, using $(if_changed{,_dep}). As an
# optimization, we don't need to read them if the target does not
# exist, we will rebuild anyway in that case.
existing-targets := $(wildcard $(sort $(targets)))
-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
.PHONY: $(PHONY)
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