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'. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> --- This is a workaround for now. We can revisit this when a need arises to copy more kernel code into the stub, by which time we could put in a more elaborate fix, or decide to no longer care about 'older' versions of objcopy. Since this fixes an ARM specific issue and only affects ARM specific Makefile variables, I am happy for this to go on top of the arm-soc patch that enables CONFIG_EFI for ARM's multi_v7_defconfig (queued for v4.9), given that we have no other changes queued in linux-efi that should conflict with this patch. Matt, any concerns? drivers/firmware/efi/libstub/Makefile | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index c06945160a41..5e23e2d305e7 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -11,7 +11,7 @@ cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2 \ -mno-mmx -mno-sse cflags-$(CONFIG_ARM64) := $(subst -pg,,$(KBUILD_CFLAGS)) -cflags-$(CONFIG_ARM) := $(subst -pg,,$(KBUILD_CFLAGS)) \ +cflags-$(CONFIG_ARM) := $(subst -pg,,$(KBUILD_CFLAGS)) -g0 \ -fno-builtin -fpic -mno-single-pic-base cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt @@ -79,5 +79,6 @@ quiet_cmd_stubcopy = STUBCPY $@ # decompressor. So move our .data to .data.efistub, which is preserved # explicitly by the decompressor linker script. # -STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub +STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ + -R ___ksymtab+sort -R ___kcrctab+sort STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
