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Re: kern/49603: Single-stepping into syscall reboots -current/amd64 under qemu
The following reply was made to PR kern/49603; it has been noted by GNATS.
From: David Laight <david%l8s.co.uk@localhost>
Subject: Re: kern/49603: Single-stepping into syscall reboots -current/amd64 under qemu
Date: Mon, 26 Jan 2015 08:25:48 +0000
On Sun, Jan 25, 2015 at 01:55:01PM +0000, Andreas Gustafsson wrote:
> >Number: 49603
> >Category: kern
> >Synopsis: Single-stepping into syscall reboots -current/amd64 under qemu
> When debugging a userland process using gdb under NetBSD-current/amd64
> running in qemu virtual machine, single stepping into a system call
> causes an instant reboot. Root privileges are not required.
> I ran an automated binary search to find when the problem first
> appeard, and it pointed at src/sys/sys/ksyms.h 1.30, committed by
> christos on CVS date 2014.12.14.18.14.15.
That file looks unlikely.
Sounds more like a qemu bug to do with faulting on the system
call entry/exit instruction when 'single step' is enabled.
> The reboot is consistently reproducible under qemu, but I have not
> been able to reproduce it on physical hardware (tested on an AMD
> Athlon64). It also does not happen with the i386 port, only amd64.
> pkg_add py-anita
> anita interact http://nyftp.netbsd.org/pub/NetBSD-daily/HEAD/201501250540Z/amd64/
> (log in as root)
> gdb /bin/sync
> break sync
Which instructions are being stepped over?
Do you know if the syscall happens - ie is the
error on the syscall entry, syscall exit or the
David Laight: david%l8s.co.uk@localhost
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