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029223d301
Livepatch identifies a duplicate-named symbol by its position (sympos) among same-named kallsyms entries, which for vmlinux are counted in ascending address order in the final linked kernel. That order can't be reliably derived from vmlinux.o: the final link reorders sub-sections (.text.unlikely*, .data..*, etc). Bridge the gap with a new .klp.symid section which can be used to correlate symbols between vmlinux.o and vmlinux so that klp-diff can reliably determine the sympos. The table can't survive --gc-sections: keeping it alive would keep every duplicate-named symbol's section alive, so the reference kernel would stop matching the one which ships. klp-build rejects CONFIG_LD_DEAD_CODE_DATA_ELIMINATION instead. Nothing is lost today: x86_64 is the only HAVE_KLP_BUILD arch and doesn't select HAVE_LD_DEAD_CODE_DATA_ELIMINATION, arm64 and s390 have never selected it either, and on powerpc, it's still EXPERIMENTAL and disabled by every distro kernel. This is the build-time half of reliable vmlinux sympos computation; "objtool klp diff" will consume the table in a subsequent commit. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: live-patching@vger.kernel.org Link: https://patch.msgid.link/64d50f077b569f47883c015cdb7079edb068efe8.1785727106.git.jpoimboe@kernel.org
99 lines
3.0 KiB
Makefile
99 lines
3.0 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0-only
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PHONY := __default
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__default: vmlinux.o
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include include/config/auto.conf
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include $(srctree)/scripts/Kbuild.include
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# for objtool
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include $(srctree)/scripts/Makefile.lib
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# Generate a linker script to ensure correct ordering of initcalls for Clang LTO
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# ---------------------------------------------------------------------------
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quiet_cmd_gen_initcalls_lds = GEN $@
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cmd_gen_initcalls_lds = \
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$(PYTHON3) $(srctree)/scripts/jobserver-exec \
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$(PERL) $(real-prereqs) > $@
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.tmp_initcalls.lds: $(srctree)/scripts/generate_initcall_order.pl \
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vmlinux.a $(KBUILD_VMLINUX_LIBS) FORCE
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$(call if_changed,gen_initcalls_lds)
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targets := .tmp_initcalls.lds
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ifdef CONFIG_LTO_CLANG
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initcalls-lds := .tmp_initcalls.lds
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endif
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# objtool for vmlinux.o
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# ---------------------------------------------------------------------------
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#
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# For delay-objtool (IBT or LTO), objtool doesn't run on individual translation
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# units. Instead it runs on vmlinux.o.
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#
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# For !delay-objtool + CONFIG_NOINSTR_VALIDATION, it runs on both translation
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# units and vmlinux.o, with the latter only used for noinstr/unret validation.
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objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
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ifeq ($(delay-objtool),y)
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vmlinux-objtool-args-y += $(objtool-args-y)
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else
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vmlinux-objtool-args-$(CONFIG_OBJTOOL_WERROR) += --werror
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endif
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vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION) += --noinstr \
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$(if $(or $(CONFIG_MITIGATION_UNRET_ENTRY),$(CONFIG_MITIGATION_SRSO)), --unret)
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# Only used for builds initiated by klp-build
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vmlinux-objtool-args-$(if $(KLP_SYMIDS),y) += --klp-symids
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objtool-args = $(vmlinux-objtool-args-y) --link
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# Link of vmlinux.o used for section mismatch analysis
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# ---------------------------------------------------------------------------
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vmlinux-o-ld-args-$(CONFIG_BUILTIN_MODULE_RANGES) += -Map=$@.map
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quiet_cmd_ld_vmlinux.o = LD $@
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cmd_ld_vmlinux.o = \
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$(LD) ${KBUILD_LDFLAGS} -r -o $@ \
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$(vmlinux-o-ld-args-y) \
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$(addprefix -T , $(initcalls-lds)) \
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--whole-archive vmlinux.a --no-whole-archive \
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--start-group $(KBUILD_VMLINUX_LIBS) --end-group \
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$(cmd_objtool)
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cmd_check_function_names = $(srctree)/scripts/check-function-names.sh $@
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define rule_ld_vmlinux.o
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$(call cmd_and_savecmd,ld_vmlinux.o)
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$(call cmd,gen_objtooldep)
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$(call cmd,check_function_names)
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endef
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vmlinux.o: $(initcalls-lds) vmlinux.a $(KBUILD_VMLINUX_LIBS) FORCE
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$(call if_changed_rule,ld_vmlinux.o)
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targets += vmlinux.o
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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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