[plug] NBD issues

[Craig Ringer]

> Eww.. thats a nasty stack trace..
> Highlight the whole thing with gpm, fire up ksymoops and paste it into 
> that, that may provide some insight as to where it's going pear shaped.

This look about right? I've just used netcat to send the files from 
/proc across, then decoded it on my main machine. ksymoops is whining 
about the modules info being empty, but there were no modules loaded so 
it _should_ be empty. As such, the default (wrong) modules dir should be 
OK because it's not /using/ any modules - right?

This was triggered by an 'nbd-client -d /dev/nbd/0' after attaching NBD 
earlier. Nothing was /done/ on the NBD inbetween. It seems to be totally 
reproduceable, too.

So - think it's worth a bug report?

[craig at albert ksymoops-2.4.9]$ ./ksymoops -k /tmp/kdebug/ksyms -l 
/tmp/kdebug/modules -m ~/build/embed/l
.21/System.map < /tmp/kdebug/oops
ksymoops 2.4.9 on i686 2.4.21.  Options used
      -V (default)
      -k /tmp/kdebug/ksyms (specified)
      -l /tmp/kdebug/modules (specified)
      -o /lib/modules/2.4.21/ (default)
      -m /home/craig/build/embed/linux-2.4.21/System.map (specified)

No modules in ksyms, skipping objects
Warning (read_lsmod): no symbols in lsmod, is /tmp/kdebug/modules a 
valid lsmod file?
Unable to handle kernel NULL pointer dereference at virtual address 00000008
c0193b4b
*pde = 00000000
Oops: 0000
CPU:    0
EIP:    0010:[<c0193b4b>]    Not tainted
Using defaults from ksymoops -t elf32-i386 -a i386
EFLAGS: 00010282
eax: 00000000   ebx: c0311fb0   ecx: 00000001   edx: c1ef2000
esi: c0311f90   edi: 00000001   ebp: 00000004   esp: c1ee7f18
ds: 0018   es: 0018   ss: 0018
Process nbd-client (pid: 85, stackpage=c1ee7000)
Stack: c0262249 00000000 c191c4ac 00000001 00000000 00000000 00030002 
00000000
        00000000 00000000 00000000 00000000 00000000 00000000 00000000 
00000000
        00000000 00000000 00000000 00000000 00000000 00000000 00000000 
00000000
Call Trace:    [<c01379df>] [<c013e251>] [<c0108967>]
Code: 8b 50 08 6a 03 50 ff 52 28 c7 46 0c 00 00 00 00 83 c4 0c 89


 >>EIP; c0193b4b <nbd_ioctl+18f/424>   <=====

 >>ebx; c0311fb0 <nbd_dev+50/1800>
 >>esi; c0311f90 <nbd_dev+30/1800>

Trace; c01379df <blkdev_ioctl+2b/30>
Trace; c013e251 <sys_ioctl+81/174>
Trace; c0108967 <system_call+33/38>

Code;  c0193b4b <nbd_ioctl+18f/424>
00000000 <_EIP>:
Code;  c0193b4b <nbd_ioctl+18f/424>   <=====
    0:   8b 50 08                  mov    0x8(%eax),%edx   <=====
Code;  c0193b4e <nbd_ioctl+192/424>
    3:   6a 03                     push   $0x3
Code;  c0193b50 <nbd_ioctl+194/424>
    5:   50                        push   %eax
Code;  c0193b51 <nbd_ioctl+195/424>
    6:   ff 52 28                  call   *0x28(%edx)
Code;  c0193b54 <nbd_ioctl+198/424>
    9:   c7 46 0c 00 00 00 00      movl   $0x0,0xc(%esi)
Code;  c0193b5b <nbd_ioctl+19f/424>
   10:   83 c4 0c                  add    $0xc,%esp
Code;  c0193b5e <nbd_ioctl+1a2/424>
   13:   89 00                     mov    %eax,(%eax)

1 warning issued.  Results may not be reliable.

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