Re: [kbuild-all] Re: arch/x86/mm/fault.o: warning: objtool: do_page_fault()+0x4fb: unreachable instruction

[Rong Chen]

On 3/6/20 10:27 PM, Frederic Weisbecker wrote:
> On Fri, Mar 06, 2020 at 06:48:47PM +0800, kbuild test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head:   9f65ed5fe41ce08ed1cb1f6a950f9ec694c142ad
> > commit: ee6352b2c47a24234398e06381edd93a8e965976 x86/context-tracking: Remove exception_enter/exit() from do_page_fault()
> > date:   8 weeks ago
> > config: x86_64-randconfig-a002-20200306 (attached as .config)
> > compiler: gcc-4.9 (Debian 4.9.2-10+deb8u1) 4.9.2
> > reproduce:
> >          git checkout ee6352b2c47a24234398e06381edd93a8e965976
> >          # save the attached .config to linux build tree
> >          make ARCH=x86_64
> >
> > If you fix the issue, kindly add following tag
> > Reported-by: kbuild test robot <lkp@xxxxxxxxx>
> >
> > All warnings (new ones prefixed by >>):
> >
> > > > arch/x86/mm/fault.o: warning: objtool: do_page_fault()+0x4fb: unreachable instruction
> I tried several versions of gcc and I can't reproduce the warning. Also looking
> at the code I fail to find an actual unreachable path. Do you still have the vmlinux around?

Hi Frederic,

Sorry for the inconvenience, we checked again and only found this issue 
on gcc-4.9.2,
and there's no issue on gcc-4.9.3 or other new versions.

Best Regards,
Rong Chen