linux-kernel - Problems compiling with KCFLAGS="-frecord-gcc-switches"

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Date:   Fri, 29 Sep 2017 13:00:56 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Problems compiling with KCFLAGS="-frecord-gcc-switches"

Hi Josh,

when trying to compile an image with KCFLAGS="-frecord-gcc-switches",
I get the folllowing build warning/error.

make allmodconfig
KCFLAGS="-frecord-gcc-switches" make arch/x86/kvm/emulate.o
./tools/objtool/objtool check --no-unreachable "arch/x86/kvm/emulate.o"

arch/x86/kvm/emulate.o: warning:
	objtool: .GCC.command.line+0x0: special: can't find new instruction

Building a full image aborts with:

WARNING: arch/x86/kvm/kvm.o(__ex_table+0x4c): Section mismatch in reference
	from the (unknown reference) (unknown)
	to the variable .GCC.command.line:kvm_fastop_exception
FATAL: The relocation at __ex_table+0x4c references
section ".GCC.command.line" which is not executable, IOW
the kernel will fault if it ever tries to
jump to it.  Something is seriously wrong
and should be fixed.
make[2]: *** [arch/x86/kvm/kvm.o] Error 1

Any idea what might cause this problem ?

Thanks,
Guenter