help !why cannot i get core file?

[wang <constant9824@gmail.com>]

hi all
   i use fedora 7.debug a device based on arm + linux using gdb on
fedora and gdbserver on device.
[root@wang wang]# ulimit -a
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 2560
max locked memory       (kbytes, -l) 32
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 2560
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
[root@wang wang]#

[root@wang wang]# /usr/local/arm-linux/bin/arm-linux-gdb -q
(gdb) file /home/wang/master/master.exe
Reading symbols from /home/wang/master/master.exe...done.
(gdb) target remote 192.168.1.203:2323
Remote debugging using 192.168.1.203:2323
Cannot access memory at address 0x0
0x40001b80 in ?? ()
(gdb) c
Continuing.

Program received signal SIGSEGV, Segmentation fault.
Cannot access memory at address 0x5a4
0x40046ca4 in ?? ()
---------------------------------------------------------
(gdb) q
The program is running.  Exit anyway? (y or n) y
[root@wang wang]# ls core.*
ls: cannot access core.*: No such file or directory
[root@wang wang]#

or
---------------------------------------------------------
(gdb) list core.*
Can't find member of namespace, class, struct, or union named "core.*"
Hint: try 'core.*<TAB> or 'core.*<ESC-?>
(Note leading single quote.)
(gdb)

but now  i didnot get a core file and i donot know witch line the
error occured at.
and what the "Cannot access memory at address 0x5a40x40046ca4 in ?? ()"  mean?