Linux applications core if running (k)qemu

[Kostik Belousov]

On Sat, Sep 06, 2008 at 02:46:59PM +0400, Chagin Dmitry wrote:
> On Tue, Sep 02, 2008 at 03:56:33PM -0500, Sean C. Farley wrote:
> > On Sat, 30 Aug 2008, Chagin Dmitry wrote:
> > 
> > >On Fri, Aug 29, 2008 at 05:29:09PM -0500, Sean C. Farley wrote:
> > >>I am having trouble with kqemu.ko and linux.ko.  If I run qemu with
> > >>the following command, Linux applications (chroot, acroread, ls) will
> > >>start core dumping:
> > >>    qemu-system-x86_64 -m 512 \
> > >>    -drive file=/usr/QEMU/WinXP/c.img,if=ide,media=disk -boot c \
> > >>    -std-vga -parallel none -serial none -monitor stdio \
> > >>    -net nic,model=e1000 -net tap,ifname=tap0,script=no -localtime
> > >>
> > >>Loading kqemu.ko does not cause the problem, but the cores start a
> > >>little after WinXP starts running.  Unloading kqemu.ko does not help;
> > >>the cores still happen but more randomly.  I even tried unloading all
> > >>linux modules and reloading them without luck.  It takes a reboot.
> > >>
> > >>Packages:
> > >>qemu-devel-0.9.1s.20080620_1
> > >>kqemu-kmod-devel-1.4.0.p1
> > >>linux_base-f8-8_4
> > >>
> > >>sysctl:
> > >>compat.linux.osrelease: 2.6.16
> > >>
> > >>dmesg:
> > >>kqemu version 0x00010400
> > >>kqemu: KQEMU installed, max_locked_mem=1792492kB.
> > >>
> > >>System is 7-STABLE as of r181963 with or without the patch to fix RT
> > >>signals from Chagin.
> > >
> > >Interestingly... Sean, can you provide ktrace/kdump log of coring
> > >apps?  thnx!
> > 
> > Here they are (good and bad):
> > http://www.farley.org/freebsd/tmp/linuxulator_vs_kqemu/
> > 
> > The good trace is after the bad trace.  I just kept running ktrace
> > /compat/linux/bin/date over and over until I got a good trace.  Before
> > loading kqemu and running qemu, there were no core dumps.  Also, I
> > compared two bad traces and they were basically the same except for PID
> > and a couple of addresses (still very close in value).
> > 
> 
> Most likely it is a tls problem again, some days ago kib@ has made MFC
> r182684, probably it will help..

I doubt it. This seems to be an ingenious kqemu bug. As far as I remember,
it tries to use GDT/LDT. This probably has unwanted interaction with
PCB_GS32BIT.
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