4.9-stable review patch. If anyone has any objections, please let me know.
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From: Ard Biesheuvel ard.biesheuvel@linaro.org
commit 696204faa6e8a318320ebb49d9fa69bc8275644d upstream.
The build commands for the ARM and arm64 EFI stubs strip the .debug sections and other sections that may legally contain absolute relocations, in order to inspect the remaining sections for the presence of such relocations.
This leaves us without debugging symbols in the stub for no good reason, considering that these sections are omitted from the kernel binary anyway, and that these relocations are thus only consumed by users of the ELF binary, such as debuggers.
So move to 'strip' for performing the relocation check, and if it succeeds, invoke objcopy as before, but leaving the .debug sections in place. Note that these sections may refer to ksymtab/kcrctab contents, so leave those in place as well.
Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Matt Fleming matt@codeblueprint.co.uk Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/1485868902-20401-11-git-send-email-ard.biesheuvel@l... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/firmware/efi/libstub/Makefile | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-)
--- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -11,7 +11,7 @@ cflags-$(CONFIG_X86) += -m$(BITS) -D__K -mno-mmx -mno-sse
cflags-$(CONFIG_ARM64) := $(subst -pg,,$(KBUILD_CFLAGS)) -cflags-$(CONFIG_ARM) := $(subst -pg,,$(KBUILD_CFLAGS)) -g0 \ +cflags-$(CONFIG_ARM) := $(subst -pg,,$(KBUILD_CFLAGS)) \ -fno-builtin -fpic -mno-single-pic-base
cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt @@ -60,7 +60,7 @@ CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$ extra-$(CONFIG_EFI_ARMSTUB) := $(lib-y) lib-$(CONFIG_EFI_ARMSTUB) := $(patsubst %.o,%.stub.o,$(lib-y))
-STUBCOPY_FLAGS-y := -R .debug* -R *ksymtab* -R *kcrctab* +STUBCOPY_RM-y := -R *ksymtab* -R *kcrctab* STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ --prefix-symbols=__efistub_ STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS @@ -68,17 +68,25 @@ STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARC $(obj)/%.stub.o: $(obj)/%.o FORCE $(call if_changed,stubcopy)
+# +# Strip debug sections and some other sections that may legally contain +# absolute relocations, so that we can inspect the remaining sections for +# such relocations. If none are found, regenerate the output object, but +# this time, use objcopy and leave all sections in place. +# quiet_cmd_stubcopy = STUBCPY $@ - cmd_stubcopy = if $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@; then \ - $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y) \ - && (echo >&2 "$@: absolute symbol references not allowed in the EFI stub"; \ - rm -f $@; /bin/false); else /bin/false; fi + cmd_stubcopy = if $(STRIP) --strip-debug $(STUBCOPY_RM-y) -o $@ $<; \ + then if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); \ + then (echo >&2 "$@: absolute symbol references not allowed in the EFI stub"; \ + rm -f $@; /bin/false); \ + else $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@; fi \ + else /bin/false; fi
# # ARM discards the .data section because it disallows r/w data in the # decompressor. So move our .data to .data.efistub, which is preserved # explicitly by the decompressor linker script. # -STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ - -R ___ksymtab+sort -R ___kcrctab+sort +STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub +STUBCOPY_RM-$(CONFIG_ARM) += -R ___ksymtab+sort -R ___kcrctab+sort STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS