remote kernel gdb: break, continue: fatal trap 12

[Marco Molteni]

Hi,

I am playing around with remote gdb on a -current cvsupped 2 days ago.
In gdb I set a breakpoint on ums_open (USB mouse driver, as a module),
in the console I execute cat /dev/ums0, the breakpoint triggers, in gdb
I issue a continue and I get a Fatal trap 12: page fault while in kernel mode,
as detailed below.

Any ideas why?

thanks
marco


(gdb) tr0
(gdb) getsyms
[..]

(gdb) b ums_open
Breakpoint 1 at 0xc072eedf: file /home/usr.src/sys/modules/ums/../../dev/usb/ums.c, line 594.
(gdb) c

=================
cat /dev/ums0
=================

[New Thread 100057]
[Switching to Thread 100057]

Breakpoint 1, ums_open (dev=0xc064ef6c, flag=0x1, fmt=0x2000, p=0xc10242c0) at
/home/usr.src/sys/modules/ums/../../dev/usb/ums.c:594
(gdb) c

Program received signal SIGSEGV, Segmentation fault.
cdevsw_rel (csw=0x0) at /home/usr.src/sys/kern/kern_conf.c:124
/home/usr.src/sys/kern/kern_conf.c:124:3280:beg:0xc0489e14




Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0x48
fault code              = supervisor write, page not present
instruction pointer     = 0x8:0xc0489e14
stack pointer           = 0x10:0xcbf6e9c0
frame pointer           = 0x10:0xcbf6e9c4
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 559 (cat)

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