For init process, pid is 1, and some other processes, when use pmap to show their mmapped file, results show like this:
0000000000000000 0K r-x-- /sbin/init
0000000000000000 0K r---- /sbin/init
0000000000000000 0K rw--- /sbin/init
0000000000000000 0K ----- [ stack ]
0000000000000000 0K rw--- [ stack ]
0000000000000000 0K r-x-- /lib/libc-2.12.2.so
0000000000000000 0K ----- /lib/libc-2.12.2.so
0000000000000000 0K r---- /lib/libc-2.12.2.so
0000000000000000 0K rw--- /lib/libc-2.12.2.so
0000000000000000 0K rw--- [ stack ]
0000000000000000 0K r-x-- /lib/ld-2.12.2.so
0000000000000000 0K rw--- [ stack ]
0000000000000000 0K rw--- [ stack ]
0000000000000000 0K r-x-- [ stack ]
0000000000000000 0K rw--- /lib/ld-2.12.2.so
0000000000000000 0K rw--- [ stack ]
0000000000000000 0K rw--- [ stack ]
ffffffffff600000 4K r---- [ anon ]
total 4K
why this happens? all virtual address except last one start from zero and size is zero.