b0dddf6c14
When building the ARM kernel with CONFIG_EFI=y, the following build error may occur when using a less recent version of binutils (2.23 or older): STUBCPY drivers/firmware/efi/libstub/lib-sort.stub.o 00000000 R_ARM_ABS32 sort 00000004 R_ARM_ABS32 __ksymtab_strings drivers/firmware/efi/libstub/lib-sort.stub.o: absolute symbol references not allowed in the EFI stub (and when building with debug symbols, the list above is much longer, and contains all the internal references between the .debug sections and the actual code) This issue is caused by the fact that objcopy v2.23 or earlier does not support wildcards in its -R and -j options, which means the following line from the Makefile: STUBCOPY_FLAGS-y := -R .debug* -R *ksymtab* -R *kcrctab* fails to take effect, leaving harmless absolute relocations in the binary that are indistinguishable from relocations that may cause crashes at runtime due to the fact that these relocations are resolved at link time using the virtual address of the kernel, which is always different from the address at which the EFI firmware loads and invokes the stub. So, as a workaround, disable debug symbols explicitly when building the stub for ARM, and strip the ksymtab and kcrctab symbols for the only exported symbol we currently reuse in the stub, which is 'sort'. Tested-by: Jon Hunter <jonathanh@nvidia.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/1476805991-7160-2-git-send-email-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
85 lines
3.4 KiB
Makefile
85 lines
3.4 KiB
Makefile
#
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# The stub may be linked into the kernel proper or into a separate boot binary,
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# but in either case, it executes before the kernel does (with MMU disabled) so
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# things like ftrace and stack-protector are likely to cause trouble if left
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# enabled, even if doing so doesn't break the build.
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#
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cflags-$(CONFIG_X86_32) := -march=i386
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cflags-$(CONFIG_X86_64) := -mcmodel=small
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cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2 \
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-fPIC -fno-strict-aliasing -mno-red-zone \
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-mno-mmx -mno-sse
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cflags-$(CONFIG_ARM64) := $(subst -pg,,$(KBUILD_CFLAGS))
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cflags-$(CONFIG_ARM) := $(subst -pg,,$(KBUILD_CFLAGS)) -g0 \
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-fno-builtin -fpic -mno-single-pic-base
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cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt
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KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \
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$(call cc-option,-ffreestanding) \
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$(call cc-option,-fno-stack-protector)
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GCOV_PROFILE := n
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KASAN_SANITIZE := n
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UBSAN_SANITIZE := n
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OBJECT_FILES_NON_STANDARD := y
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# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
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KCOV_INSTRUMENT := n
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lib-y := efi-stub-helper.o gop.o
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# include the stub's generic dependencies from lib/ when building for ARM/arm64
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arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c
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$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
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$(call if_changed_rule,cc_o_c)
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lib-$(CONFIG_EFI_ARMSTUB) += arm-stub.o fdt.o string.o \
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$(patsubst %.c,lib-%.o,$(arm-deps))
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lib-$(CONFIG_ARM) += arm32-stub.o
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lib-$(CONFIG_ARM64) += arm64-stub.o random.o
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CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
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#
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# arm64 puts the stub in the kernel proper, which will unnecessarily retain all
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# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
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# So let's apply the __init annotations at the section level, by prefixing
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# the section names directly. This will ensure that even all the inline string
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# literals are covered.
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# The fact that the stub and the kernel proper are essentially the same binary
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# also means that we need to be extra careful to make sure that the stub does
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# not rely on any absolute symbol references, considering that the virtual
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# kernel mapping that the linker uses is not active yet when the stub is
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# executing. So build all C dependencies of the EFI stub into libstub, and do
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# a verification pass to see if any absolute relocations exist in any of the
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# object files.
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#
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extra-$(CONFIG_EFI_ARMSTUB) := $(lib-y)
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lib-$(CONFIG_EFI_ARMSTUB) := $(patsubst %.o,%.stub.o,$(lib-y))
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STUBCOPY_FLAGS-y := -R .debug* -R *ksymtab* -R *kcrctab*
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STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
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--prefix-symbols=__efistub_
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STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS
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$(obj)/%.stub.o: $(obj)/%.o FORCE
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$(call if_changed,stubcopy)
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quiet_cmd_stubcopy = STUBCPY $@
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cmd_stubcopy = if $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@; then \
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$(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y) \
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&& (echo >&2 "$@: absolute symbol references not allowed in the EFI stub"; \
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rm -f $@; /bin/false); else /bin/false; fi
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#
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# ARM discards the .data section because it disallows r/w data in the
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# decompressor. So move our .data to .data.efistub, which is preserved
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# explicitly by the decompressor linker script.
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#
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STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
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-R ___ksymtab+sort -R ___kcrctab+sort
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STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
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