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From:   Marco Elver <elver@google.com>
Date:   Tue, 12 Jan 2021 21:44:35 +0100
Message-ID: <CANpmjNMu9zeNYEv8bpYo=uuvh8Atcbtf8JfeBQkXrBRj9DEtKw@mail.gmail.com>
Subject: Re: upstream build error (12)
To:     Nathan Chancellor <natechancellor@gmail.com>
Cc:     syzbot <syzbot+76880518931d755473cf@syzkaller.appspotmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Dmitry Vyukov <dvyukov@google.com>
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On Tue, 12 Jan 2021 at 21:32, Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Tue, Jan 12, 2021 at 12:40:58PM -0700, Nathan Chancellor wrote:
> > On Tue, Jan 12, 2021 at 11:20:27AM -0800, syzbot wrote:
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    e609571b Merge tag 'nfs-for-5.11-2' of git://git.linux-nfs..
> > > git tree:       upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=15965a00d00000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=6157970d0a91b812
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=76880518931d755473cf
> > > compiler:       clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+76880518931d755473cf@syzkaller.appspotmail.com
> > >
> > > clang-11: error: unable to execute command: Aborted (core dumped)
> > > clang-11: error: clang frontend command failed due to signal (use -v to see invocation)
> > >
> > > ---
> > > This report is generated by a bot. It may contain errors.
> > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > syzbot engineers can be reached at syzkaller@googlegroups.com.
> > >
> > > syzbot will keep track of this issue. See:
> > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> >
> > Would it be possible for clang-built-linux@googlegroups.com to be CC'd
> > when there is a build error and the compiler is clang? Especially if
> > clang is hitting an assertion.
>
> I cannot reproduce this with clang 11.0.1. I did a reverse bisect on
> LLVM and found commit 4b0aa5724fea ("Change the INLINEASM_BR MachineInstr
> to be a non-terminating instruction.") as the fix (which makes sense,
> that commit has direct kernel implications). It is probably worth
> upgrading syzkaller's clang to 11.0.1, where I have not seen any
> assertions across all of the configurations that I test.
>
> Ccing Dmitry and Marco directly.

I'll upgrade syzbot's clang 11. I think the version we use right now
was still a pre-release.

Thanks,
-- Marco