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SubjectRe: [v8,02/12] objtool: Allow alternatives to be ignored
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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. [unhandled content-type:application/x-pkcs7-signature]
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