Lost in Shared Memory with Module

My first try to use shared memory inside a module show many conflict
within header /sys/shm.h
So I changed the header for /linux/shm.h. But the shared memory function
has a sys_  prefix:
shmat is changed for sys_shmat. Unfortunatly there is a problem here:
the sys_shmat need a fourth parameter.
--->    asmlinkage int sys_shmat (int shmid, char *shmaddr, int shmflg,
unsigned long *addr);
and there is not man page about sys_shmat that explain the usage of the
addr parameter.

Is it the right way to share memory between module and application ?
Where can I found example of it ?


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