On Thu, 2018-01-18 at 11:41 -0800, Guenter Roeck wrote:
> 
> > Not sure, does your gcc have retpolines?  Give me your .o file and I can
> > diagnose it.
> > 
> Yes, it does, only it is the gcc from the Google toolchain which may
> generate different code than the upstream version.
> 
> I attached an affected object file. Please let me know if there is anything else
> I can do to help.
Disassembly of section .text.__x86.indirect_thunk:

0000000000000000 <__x86.indirect_thunk>:
   0:	e8 04 00 00 00       	callq  9 <__x86.indirect_thunk+0x9>
   5:	f3 90                	pause  
   7:	eb fc                	jmp    5 <__x86.indirect_thunk+0x5>
   9:	48 8d 64 24 08       	lea    0x8(%rsp),%rsp
   e:	c3                   	retq   

That has the old-style CET-incompatible retpoline in a COMDAT section
in the .o file. What compiler options are being used for that? The
kernel should only use retpoline if GCC supports both of
-mindirect-branch=thunk-extern and -mindirect-branch-register, and this
compiler is doing *neither* of those.