Re: port-xen/53863: panic: xen_failsafe_handler called! while running 32-bit binary on 64-bit.

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

The following reply was made to PR port-xen/53863; it has been noted by GNATS.

From: Manuel Bouyer <bouyer%antioche.eu.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: port-xen-maintainer%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
        netbsd-bugs%netbsd.org@localhost
Subject: Re: port-xen/53863: panic: xen_failsafe_handler called! while
 running 32-bit binary on 64-bit.
Date: Sun, 13 Jan 2019 11:01:52 +0100

 On Sun, Jan 13, 2019 at 03:15:00AM +0000, marcotte%panix.com@localhost wrote:
 > NetBSD/xen 64-bit domU.
 > 
 > When running an old 32-bit perl binary which loads modules, I sometimes get this:
 > 
 >   panic: xen_failsafe_handler called!
 > 
 >   cpu0: Begin traceback...
 >   vpanic() at netbsd:vpanic+0x140
 >   snprintf() at netbsd:snprintf
 >   xpq_flush_queue() at netbsd:xpq_flush_queue
 >   failsafe_callback() at netbsd:failsafe_callback+0xa1
 >   x86_64_tls_switch() at netbsd:x86_64_tls_switch+0x8a
 >   cpu_switchto() at netbsd:cpu_switchto+0x88
 >   preempt() at netbsd:preempt+0x4d
 >   trap() at netbsd:trap+0x747
 >   --- trap (number 3) ---
 >   7f7fd860c36a:
 >   cpu0: End traceback...
 > 
 > The binary is an old 32-bit perl which when loading certain modules, changes the text section to read/write. By default this should fail in NetBSD-8 because of mprotect, but it shoudn't panic the kernel. Turning off mprotect allows the program to run, but it sometimes still panics the kernel on startup.
 > 
 > 
 > >How-To-Repeat:
 > I wasn't able to make a simple program to cause the panic, but I can reproduce it pretty reliably here.
 > 
 > >Fix:
 > Don't know what the fix is, but I tracked it down to this change:
 > 
 >   src/sys/arch/amd64/amd64/machdep.c
 >   1.255.6.1 -> 1.255.6.2
 > 
 > That's a pullup of version 1.267.
 > 
 > When I revert that, I no longer get the panic.
 
 Do you have anything relevant in xl dmesg on the dom0 ? booting with
 a xen-debug.gz kernel may be needed to get usefull information
 
 -- 
 Manuel Bouyer <bouyer%antioche.eu.org@localhost>
      NetBSD: 26 ans d'experience feront toujours la difference
 --