qemu-system-sparc64: entering the debugger

[Mark Cave-Ayland]

Hi all,

I've finally got some time to start looking at this again, so I'm trying
to experiment a little with ddb:


FreeBSD/sparc64 bootstrap loader, Revision 1.0
(mca at freebsd, Thu Sep 24 00:27:19 BST 2015)
bootpath="/pci at 1fe,0/pci-ata at 5/ide1 at 8200/cdrom at 0:a"
Loading /boot/defaults/loader.conf
/boot/kernel/kernel data=0xd893c0+0x20ffd8 syms=[0x8+0xdc578+0x8+0xcb349]
\
Hit [Enter] to boot immediately, or any other key for command prompt.
Booting [/boot/kernel/kernel] in 9 seconds...

Type '?' for a list of commands, 'help' for more detailed help.
OK boot -d
Booting...
jumping to kernel entry at 0xc00b0000.
GDB: no debug ports present
KDB: debugger backends: ddb
KDB: current backend: ddb
KDB: enter: Boot flags requested debugger
[ thread pid 0 tid 0 ]
Stopped at      0xc0630b00
db> bt
Tracing pid 0 tid 0 td 0xc0e3fb50
(null)() at 0xc09d0fc4
(null)() at 0xc00b001c
FreeBSD/sparc64 bootstrap loader, Revision 1.0
(mca at freebsd, Thu Sep 24 00:27:19 BST 2015)
bootpath="/pci at 1fe,0/pci-ata at 5/ide1 at 8200/cdrom at 0:a"
Loading /boot/defaults/loader.conf
/boot/kernel/kernel data=0xd893c0+0x20ffd8 syms=[0x8+0xdc578+0x8+0xcb349]
\
Hit [Enter] to boot immediately, or any other key for command prompt.
Booting [/boot/kernel/kernel] in 9 seconds...

Type '?' for a list of commands, 'help' for more detailed help.
OK boot -d
Booting...
jumping to kernel entry at 0xc00b0000.
GDB: no debug ports present
KDB: debugger backends: ddb
KDB: current backend: ddb
KDB: enter: Boot flags requested debugger
[ thread pid 0 tid 0 ]
Stopped at      0xc0630b00
db> ps/m
  pid  ppid  pgrp   uid   state   wmesg         wchan        cmd
    0     0     0     0KDB: reentering
KDB: stack backtrace:
 (null)() at 0xc063105c
(null)() at 0xc09e193c
(null)() at 0xc00b1078
(null)() at 0xc011bb1c
KDB: reentering
KDB: stack backtrace:
(null)() at 0xc063105c
(null)() at 0xc09e193c
(null)() at 0xc00b1078
(null)() at 0xc011a050
KDB: reentering
KDB: stack backtrace:
(null)() at 0xc063105c
(null)() at 0xc09e193c
(null)() at 0xc00b1078
(null)() at 0xc011a050

..etc..

So it looks like something has already gone wrong simply trying to dump
the process map. Fortunately the number of QEMU translation blocks
between the output of the "ps/m" header and the "KDB reentering" is
quite small so I've uploaded it to
https://www.ilande.co.uk/tmp/qemu/freebsd-tb.txt.

Can anyone have a quick look at the link above and give me an idea as to
roughly what the code is doing here?


Many thanks,

Mark.