Date:   Mon, 17 Oct 2022 02:23:35 +0200
From:   Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>
To:     Thorsten Leemhuis <regressions@...mhuis.info>
Cc:     Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Denis Chancogne <denis.chancogne@...e.fr>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        LKML <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: Re: Bug 216581 - Kernel panic on /init as busybox symbolic link with
 xen efi

On Sun, Oct 16, 2022 at 01:08:53PM +0200, Thorsten Leemhuis wrote:
> Hi, this is your Linux kernel regression tracker speaking.
> 
> I noticed a regression report in bugzilla.kernel.org. As many (most?)
> kernel developer don't keep an eye on it, I decided to forward it by
> mail. Quoting from https://bugzilla.kernel.org/show_bug.cgi?id=216581 :
> 
> >  Denis Chancogne 2022-10-13 22:00:19 UTC
> > 
> > Created attachment 302995 [details]
> > /proc/cpuinfo, .config
> > 
> > Hi,
> > 
> > when I start Xen 4.15.3 in efi with kernel 5.18.19, all works well;
> > but since kernel 5.19, I have a kernel panic on my /init process as
> > busybox symbolic link inside initramfs.
> > 
> > This is the kernel log :
> > ...
> > [    6.265122] Run /init as init process
> > [    6.266027] traps: init[1] trap invalid opcode ip:5855d1 sp:7ffe5ceddeb0 error:0 in busybox[401000+1db000]
> > [    6.266553] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
> > [    6.267039] CPU: 3 PID: 1 Comm: init Tainted: G        W         5.19.0-dch #1
> > [    6.267522] Hardware name: Micro-Star International Co., Ltd. MS-7B84/B450M PRO-M2 (MS-7B84), BIOS 2.E0 06/12/2020
> > [    6.268010] Call Trace:
> > [    6.268495]  <TASK>
> > [    6.268974]  dump_stack_lvl+0x45/0x5e
> > [    6.269455]  panic+0x107/0x285
> > [    6.269923]  do_exit.cold+0x15/0x45
> > [    6.270389]  do_group_exit+0x28/0x90
> > [    6.270852]  get_signal+0x9f1/0xa40
> > [    6.271313]  arch_do_signal_or_restart+0x57/0x7b0
> > [    6.271771]  ? _raw_spin_unlock+0x10/0x30
> > [    6.272223]  ? finish_task_switch.isra.0+0x8e/0x270
> > [    6.272674]  ? __switch_to+0x186/0x400
> > [    6.273118]  exit_to_user_mode_prepare+0xc8/0x150
> > [    6.273564]  irqentry_exit_to_user_mode+0x5/0x20
> > [    6.274003]  asm_exc_invalid_op+0x16/0x20
> > [    6.274441] RIP: 0033:0x5855d1
> > [    6.274877] Code: f6 48 89 ef e8 90 79 03 00 48 c7 05 cd 2e 0c 00 01 00 00 00 48 89 2d 26 a2 0c 00 4c 8d 74 24 20 4c 8d 6c 24 40 4c 8d 64 24 18 <c5> f9 ef c0 48 b8 f6 75 ae 03 01 00 00 00 4c 8d 3d 8c 02 0a 00 c5
> > [    6.275776] RSP: 002b:00007ffe5ceddeb0 EFLAGS: 00010202
> > [    6.276221] RAX: 0000000000000000 RBX: 00000000004006c8 RCX: 0000000000000001
> > [    6.276670] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000648400
> > [    6.277116] RBP: 00000000009e0060 R08: 00007ffe5cfdf178 R09: 00000000effffef5
> > [    6.277561] R10: 0000000070000022 R11: 0000000000000032 R12: 00007ffe5ceddec8
> > [    6.278003] R13: 00007ffe5ceddef0 R14: 00007ffe5cedded0 R15: 000000006ffffeff
> > [    6.278442]  </TASK>
> > [    6.278903] Kernel Offset: disabled
> > 
> > I try to decode it :
> > 
> > All code
> > ========
> >    0:   f6 48 89 ef             testb  $0xef,-0x77(%rax)
> >    4:   e8 90 79 03 00          call   0x37999
> >    9:   48 c7 05 cd 2e 0c 00    movq   $0x1,0xc2ecd(%rip)        # 0xc2ee1
> >   10:   01 00 00 00 
> >   14:   48 89 2d 26 a2 0c 00    mov    %rbp,0xca226(%rip)        # 0xca241
> >   1b:   4c 8d 74 24 20          lea    0x20(%rsp),%r14
> >   20:   4c 8d 6c 24 40          lea    0x40(%rsp),%r13
> >   25:   4c 8d 64 24 18          lea    0x18(%rsp),%r12
> >   2a:*  c5 f9 ef c0             vpxor  %xmm0,%xmm0,%xmm0                <-- trapping instruction
> >   2e:   48 b8 f6 75 ae 03 01    movabs $0x103ae75f6,%rax
> >   35:   00 00 00 
> >   38:   4c 8d 3d 8c 02 0a 00    lea    0xa028c(%rip),%r15        # 0xa02cb
> >   3f:   c5                      .byte 0xc5
> > 
> > Code starting with the faulting instruction
> > ===========================================
> >    0:   c5 f9 ef c0             vpxor  %xmm0,%xmm0,%xmm0
> >    4:   48 b8 f6 75 ae 03 01    movabs $0x103ae75f6,%rax
> >    b:   00 00 00 
> >    e:   4c 8d 3d 8c 02 0a 00    lea    0xa028c(%rip),%r15        # 0xa02a1
> >   15:   c5                      .byte 0xc5
> > 
> > Regards,
> > Denis
> > PS:
> >    denis@...2 ~ $ gcc --version
> >    gcc (Gentoo 11.3.0 p4) 11.3.0
> 
> See the ticket for more details.

Thanks for forwarding.

This is already fixed on the Xen side: https://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=c3bd0b83ea5b7c0da6542687436042eeea1e7909
The commit is also in 4.15 branch already:
https://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=7923ea47e578bca30a6e45951a9da09e827ff028,
to be included in 4.15.4 rather soon.

> BTW, let me use this mail to also add the report to the list of tracked
> regressions to ensure it's doesn't fall through the cracks:
> 
> #regzbot introduced: v5.18..v5.19
> #regzbot ignore-activity
> 
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> 
> P.S.: As the Linux kernel's regression tracker I deal with a lot of
> reports and sometimes miss something important when writing mails like
> this. If that's the case here, don't hesitate to tell me in a public
> reply, it's in everyone's interest to set the public record straight.
> 

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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