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75b2f7e4c9
-flto* implies -ffunction-sections. With LTO enabled, ld.lld generates
multiple .text sections for purgatory.ro:
$ readelf -S purgatory.ro | grep " .text"
[ 1] .text PROGBITS 0000000000000000 00000040
[ 7] .text.purgatory PROGBITS 0000000000000000 000020e0
[ 9] .text.warn PROGBITS 0000000000000000 000021c0
[13] .text.sha256_upda PROGBITS 0000000000000000 000022f0
[15] .text.sha224_upda PROGBITS 0000000000000000 00002be0
[17] .text.sha256_fina PROGBITS 0000000000000000 00002bf0
[19] .text.sha224_fina PROGBITS 0000000000000000 00002cc0
This causes WARNING from kexec_purgatory_setup_sechdrs():
WARNING: CPU: 26 PID: 110894 at kernel/kexec_file.c:919
kexec_load_purgatory+0x37f/0x390
Fix this by disabling LTO for purgatory.
[ AFAICT, x86 is the only arch that supports LTO and purgatory. ]
We could also fix this with an explicit linker script to rejoin .text.*
sections back into .text. However, given the benefit of LTOing purgatory
is small, simply disable the production of more .text.* sections for now.
Fixes: b33fff07e3 ("x86, build: allow LTO to be selected")
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20230914170138.995606-1-song@kernel.org
91 lines
2.9 KiB
Makefile
91 lines
2.9 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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OBJECT_FILES_NON_STANDARD := y
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purgatory-y := purgatory.o stack.o setup-x86_$(BITS).o sha256.o entry64.o string.o
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targets += $(purgatory-y)
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PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
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$(obj)/string.o: $(srctree)/arch/x86/boot/compressed/string.c FORCE
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$(call if_changed_rule,cc_o_c)
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$(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE
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$(call if_changed_rule,cc_o_c)
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CFLAGS_sha256.o := -D__DISABLE_EXPORTS -D__NO_FORTIFY
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# When profile-guided optimization is enabled, llvm emits two different
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# overlapping text sections, which is not supported by kexec. Remove profile
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# optimization flags.
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KBUILD_CFLAGS := $(filter-out -fprofile-sample-use=% -fprofile-use=%,$(KBUILD_CFLAGS))
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# When LTO is enabled, llvm emits many text sections, which is not supported
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# by kexec. Remove -flto=* flags.
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KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO),$(KBUILD_CFLAGS))
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# When linking purgatory.ro with -r unresolved symbols are not checked,
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# also link a purgatory.chk binary without -r to check for unresolved symbols.
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PURGATORY_LDFLAGS := -e purgatory_start -z nodefaultlib
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LDFLAGS_purgatory.ro := -r $(PURGATORY_LDFLAGS)
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LDFLAGS_purgatory.chk := $(PURGATORY_LDFLAGS)
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targets += purgatory.ro purgatory.chk
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# Sanitizer, etc. runtimes are unavailable and cannot be linked here.
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GCOV_PROFILE := n
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KASAN_SANITIZE := n
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UBSAN_SANITIZE := n
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KCSAN_SANITIZE := n
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KMSAN_SANITIZE := n
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KCOV_INSTRUMENT := n
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# These are adjustments to the compiler flags used for objects that
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# make up the standalone purgatory.ro
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PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
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PURGATORY_CFLAGS := -mcmodel=large -ffreestanding -fno-zero-initialized-in-bss -g0
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PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING
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PURGATORY_CFLAGS += -fno-stack-protector
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# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
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# in turn leaves some undefined symbols like __fentry__ in purgatory and not
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# sure how to relocate those.
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ifdef CONFIG_FUNCTION_TRACER
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PURGATORY_CFLAGS_REMOVE += $(CC_FLAGS_FTRACE)
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endif
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ifdef CONFIG_STACKPROTECTOR
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PURGATORY_CFLAGS_REMOVE += -fstack-protector
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endif
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ifdef CONFIG_STACKPROTECTOR_STRONG
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PURGATORY_CFLAGS_REMOVE += -fstack-protector-strong
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endif
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ifdef CONFIG_RETPOLINE
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PURGATORY_CFLAGS_REMOVE += $(RETPOLINE_CFLAGS)
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endif
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ifdef CONFIG_CFI_CLANG
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PURGATORY_CFLAGS_REMOVE += $(CC_FLAGS_CFI)
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endif
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CFLAGS_REMOVE_purgatory.o += $(PURGATORY_CFLAGS_REMOVE)
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CFLAGS_purgatory.o += $(PURGATORY_CFLAGS)
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CFLAGS_REMOVE_sha256.o += $(PURGATORY_CFLAGS_REMOVE)
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CFLAGS_sha256.o += $(PURGATORY_CFLAGS)
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CFLAGS_REMOVE_string.o += $(PURGATORY_CFLAGS_REMOVE)
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CFLAGS_string.o += $(PURGATORY_CFLAGS)
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asflags-remove-y += $(foreach x, -g -gdwarf-4 -gdwarf-5, $(x) -Wa,$(x))
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$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
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$(call if_changed,ld)
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$(obj)/purgatory.chk: $(obj)/purgatory.ro FORCE
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$(call if_changed,ld)
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$(obj)/kexec-purgatory.o: $(obj)/purgatory.ro $(obj)/purgatory.chk
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obj-y += kexec-purgatory.o
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