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.
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