linux-kernel - Re: arch/x86/mm/fault.o: warning: objtool: do_page

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Message-ID: <20200306142732.GA8590@lenoir>
Date:   Fri, 6 Mar 2020 15:27:33 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     kbuild test robot <lkp@...el.com>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: arch/x86/mm/fault.o: warning: objtool: do_page_fault()+0x4fb:
 unreachable instruction

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?

Thanks.