linux-kernel - Re: [kbuild-all] Re: arch/x86/mm/fault.o: warning: objtool: do_page

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Date:   Mon, 9 Mar 2020 16:37:24 +0800
From:   Rong Chen <rong.a.chen@...el.com>
To:     Frederic Weisbecker <frederic@...nel.org>,
        kbuild test robot <lkp@...el.com>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [kbuild-all] Re: arch/x86/mm/fault.o: warning: objtool:
 do_page_fault()+0x4fb: unreachable instruction



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@...el.com>
>>
>> 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