man segment

I wrote that for a business unit at lucent that needed globally shared
segments for in memory databases.

     EXAMPLE
          Create a one megabyte segment at address 0x10000000:
               % bind '#g' /mnt/segment
               % mkdir /mnt/segment/example
               % echo 'va 0x10000000 0x100000' > /mnt/segment/example/ctl

          Put the string ``hi mom'' at the start of the segment:
               % echo -n hi mom > /mnt/segment/example/data

          Attach the segment to a process:
          {
               ulong va;

               va = segattach(0, "example", 0, 0);
          }

You'll have to make a kernel with devsegment in it.