How to interpret stacktrace

[domenico.dileo@unina.it]

When executing the command print_stack we get something like:

0xc0191730 : fget_light+0x0/0xb0 [kernel]
0xc04f4243 : kretprobe_trampoline+0x0/0x3d [kernel]
0xda64efa0

0xc019cfd9 : do_sys_poll+0x179/0x380 [kernel]
0xc019cfd9 : do_sys_poll+0x179/0x380 [kernel]
0xc04f4243 : kretprobe_trampoline+0x0/0x3d [kernel]

0xc018c880 : kmem_cache_alloc+0x0/0x110 [kernel]
0xc04f4243 : kretprobe_trampoline+0x0/0x3d [kernel]
0xc04f4243 : kretprobe_trampoline+0x0/0x3d [kernel]
0xdde8bdc8
0xddd06388

Firstly, what addresses 0xd... refer to?
I tried to find them among the kernel symbols with no success.
Sometimes I also have addresses like 0xc... that I can't find among symbols.

Secondly, Why do_sys_poll (similarly other functions) appear twice?
Thank you.