Você precisa ser root ou o usuário do qual o processo pertence para usar esse comando. Tente isso:
$ sudo pmap -d 23440
Por exemplo
$ sudo pmap -d 1457
1457: /usr/sbin/httpd
Address Kbytes Mode Offset Device Mapping
00007ff9f23bf000 76 r-x-- 0000000000000000 0fd:00000 zip.so
00007ff9f23d2000 2044 ----- 0000000000013000 0fd:00000 zip.so
00007ff9f25d1000 8 rw--- 0000000000012000 0fd:00000 zip.so
00007ff9f25d3000 12 r-x-- 0000000000000000 0fd:00000 libgpg-error.so.0.5.0
00007ff9f25d6000 2044 ----- 0000000000003000 0fd:00000 libgpg-error.so.0.5.0
00007ff9f27d5000 4 rw--- 0000000000002000 0fd:00000 libgpg-error.so.0.5.0
...
...
00007fff70db1000 84 rw--- 0000000000000000 000:00000 [ stack ]
00007fff70dff000 4 r-x-- 0000000000000000 000:00000 [ anon ]
ffffffffff600000 4 r-x-- 0000000000000000 000:00000 [ anon ]
mapped: 290336K writeable/private: 6288K shared: 580K