process page map

[gary kong]

I am looking at the /proc/self/maps file. i find that for every shared
library there are 4 sections with different permission. what are the
reasons for this ? does that mean the same library is loaded 4 times ?
e.g.


7fb543e5d000-7fb54401a000 r-xp 00000000 08:01 6033115
  /lib/x86_64-linux-gnu/libc-2.17.so
7fb54401a000-7fb54421a000 ---p 001bd000 08:01 6033115
  /lib/x86_64-linux-gnu/libc-2.17.so
7fb54421a000-7fb54421e000 r--p 001bd000 08:01 6033115
  /lib/x86_64-linux-gnu/libc-2.17.so
7fb54421e000-7fb544220000 rw-p 001c1000 08:01 6033115
  /lib/x86_64-linux-gnu/libc-2.17.so
7fb544220000-7fb544225000 rw-p 00000000 00:00 0
7fb544225000-7fb54423a000 r-xp 00000000 08:01 6029447
  /lib/x86_64-linux-gnu/libgcc_s.so.1
7fb54423a000-7fb544439000 ---p 00015000 08:01 6029447
  /lib/x86_64-linux-gnu/libgcc_s.so.1
7fb544439000-7fb54443a000 r--p 00014000 08:01 6029447
  /lib/x86_64-linux-gnu/libgcc_s.so.1
7fb54443a000-7fb54443b000 rw-p 00015000 08:01 6029447
  /lib/x86_64-linux-gnu/libgcc_s.so.1
7fb54443b000-7fb54453e000 r-xp 00000000 08:01 6032973
  /lib/x86_64-linux-gnu/libm-2.17.so
7fb54453e000-7fb54473d000 ---p 00103000 08:01 6032973
  /lib/x86_64-linux-gnu/libm-2.17.so
7fb54473d000-7fb54473e000 r--p 00102000 08:01 6032973
  /lib/x86_64-linux-gnu/libm-2.17.so
7fb54473e000-7fb54473f000 rw-p 00103000 08:01 6032973
  /lib/x86_64-linux-gnu/libm-2.17.so

Gary