BUG - (suspected) - ORC unwinder with elfutils-0.174 causes ld failure during make

From: John Lumby
Date: Fri Sep 21 2018 - 11:56:25 EST


.config has CONFIG_UNWINDER_ORC=y

elfutils version 0.174 (latest)

make of the kernel source fails with errors such as this
arch/x86/kvm/../../../virt/kvm/kvm_main.o: file not recognized: file
format not recognized
emitted by ld

ld is from latest binutils version 2.31
gcc is version 7.3

Found in kernel kver 4.17.10 and also in latest 4.19-rc4

problem is caused by this transformation directed from the Makefile

./tools/objtool/objtool orc generate --module --no-fp
--retpoline "arch/x86/kvm/../../../virt/kvm/kvm_main.o";

make succeeds when CONFIG_UNWINDER_ORC is not set

Cheers, John Lumby