Re: objtool warnings in prerelease clang-9

[Josh Poimboeuf]

On Tue, Jul 02, 2019 at 11:58:27PM +0200, Thomas Gleixner wrote:
> platform-quirks.o:
> 
>         if (x86_platform.set_legacy_features)
>   74:   4c 8b 1d 00 00 00 00    mov    0x0(%rip),%r11        # 7b <x86_early_init_platform_quirks+0x7b>
>   7b:   4d 85 db                test   %r11,%r11
>   7e:   0f 85 00 00 00 00       jne    84 <x86_early_init_platform_quirks+0x84>
>                 x86_platform.set_legacy_features();
> }
>   84:   c3                      retq   
> 
> That jne jumps to __x86_indirect_thunk_r11, aka. ratpoutine.
> 
> No idea why objtool thinks that the instruction at 0x84 is not
> reachable. Josh?

That's a conditional tail call, which is something GCC never does.
Objtool doesn't understand that, so we'll need to fix it.

-- 
Josh