problems debugging an uml skas kernel with gdb

[marco ghidinelli <marcogh@linux.it>]

hello, 

i've problems debugging a UML SKAS kernel.
the host is an x86 kernel 2.6.12-rc4-skas3-v9-pre4
the guest is a kernel 2.6.12-rc4.

GNU gdb 6.3.50.20050606-cvs,
gcc version 3.3.5 (Debian 1:3.3.5-8ubuntu2)

the problems are:

1) a pointer to a struct was not seen by the debugger:

example session:

Breakpoint 4, yoghi_init (sch=0x9d1b830, opt=0x9d1b400)
    at net/sched/sch_yoghi.c:235
235             printk(KERN_DEBUG "Yoghi 0.0.3 Initiaziled\n");
(gdb) n
Yoghi 0.0.3 Initiaziled
236             if(q != NULL)
(gdb) n
237                     printk(KERN_DEBUG "yoghi_init: q =
0x%x\n",(u32)q);
(gdb) n
yoghi_init: q = 0x9d1b480
238             return 0;
(gdb) p q
No symbol "q" in current context.

this is quite annoying but i can get my info in another way:
(gdb) p (struct yoghi_sched_data)*0x9d1b480

2) sometimes the debugger get lost:

Breakpoint 3, yoghi_bind (sch=0xa8bcf20, parent=0, classid=176934688)
    at net/sched/sch_yoghi.c:271
271             return yoghi_get(sch, classid);
(gdb) s
yoghi_get (sch=0x10003, classid=65539) at net/sched/sch_yoghi.c:257

note that sch was changed!!

and sometimes it get completly lost:

Breakpoint 1, yoghi_get (sch=0x10013, classid=65555)
    at net/sched/sch_yoghi.c:259
259             u32 band  = TC_H_MIN(classid);
(gdb) n
261             printk(KERN_DEBUG "yoghi_get: classid = %d ; band = %d ;
band2 = %d\n",classid,band,band2);
(gdb) p band
$8 = 19
(gdb) n
yoghi_get: classid = 65555 ; band = 19 ; band2 = 19
262             if (band -1 > q->bands)
(gdb) n
263                     return 0; /* means not found */
(gdb) n
265     }
(gdb) n
0x0a8846d2 in ?? ()
(gdb) bt
#0  0x0a8846d2 in ?? ()
#1  0x09d1b000 in ?? ()
#2  0x00010013 in ?? ()
#3  0x00010013 in ?? ()
#4  0x00000000 in ?? ()

bye!