MMAP(2)                 COMMAND REFERENCE                 MMAP(2)



NAME
     mmap - map pages of memory

SYNOPSIS
     #include <sys/types.h>
     #include <sys/mman.h>

     mmap(pid, fromaddr, toaddr, len, prot, share)
     int pid;
     caddrt fromaddr, toaddr;
     uint len, prot, share;

DESCRIPTION
     The mapping routine mmap allows a process to access areas of
     other processes through its own address space.  It causes
     the calling process' pages starting at toaddr and continuing
     for len bytes to map onto the process with id pid, starting
     at the object's pages fromaddr.

     If pid is M_SELF, an area of the process is mapped to
     itself.  If pid is M_PHYS, an area of the process is mapped
     to physical memory (in which case share is ignored).  If pid
     is M_ZFILL, an area of the process is made "zero-fill-on-
     demand" (in which case fromaddr and share are ignored).

     mmap has been enhanced for UTek 4301, 432X and 433X
     workstations with the ability to read and write into VME
     address space. share and prot are ignored. The user address
     range can cross a 16Mbyte boundary, but the VME memory range
     cannot. Following is a list of the pids:

          M_VMEEXT  A32  extended
          M_VMESTD  A24  standard
          M_VMESHORT     A16  short
          M_VME          an alias for M_VMEEXT

     If the parameter share is true, both mappings will share the
     same memory.  Otherwise, a private copy of the area is made,
     and changes through one mapping are not visible through the
     other.

          PRIVATE     make a private copy for the new mapping
          SHARED      share the area between the mappings

     The parameter prot specifies the accessibility of the pages
     through the new mapping.  Read and write access may be given
     on the basis of processes of the same user, same process
     group, same group, and world.  A process may also protect
     its pages against itself.  The protection for a page is
     specified by or'ing together the following values:





Printed 4/12/89                                                 1

MMAP(2)                 COMMAND REFERENCE                 MMAP(2)



          M_R_SELF    read, process
          M_W_SELF    write, process
          M_R_USER    read, user
          M_W_USER    write, user
          M_R_PGROUP  read, process group
          M_W_PGROUP  write, process group
          M_R_GROUP   read, group
          M_W_GROUP   write, group
          M_R_WORLD   read, world
          M_W_WORLD   write, world

     Note that the protection is associated with the mapping, and
     not with the actual memory.

     If the process must change the protection of a mapping, it
     may map the area to itself, with the new protection.  Doing
     this with share cleared will disassociate the area with all
     other mappings.

     The terms "zero-fill-on-demand" and "provide-on-demand" used
     above refer to the handling of pages in mappings which have
     no initial contents.  UTek does not allocate physical memory
     or swap space to such a page until the first reference
     (demand) for that page.  If M_ZFILL is selected, the page is
     filled with zeros before the first reference is satisfied.
     This provides a standard initial value for data regions,
     which is expected by some software.

     The toaddr, fromaddr and len parameters must be multiples of
     the system cluster size (found using the getpagesize(2)
     call).

DIAGNOSTICS
     Mmap will fail when one of the following occurs:

     [EINVAL]     An address is not on a cluster boundary or len
                  is not positive.

     [EMCOLLIDE]  Portions of the new area are already mapped.

     [EMRANGE]    An area is outside the possible user's address
                  space or includes part of the uarea.

     [EACCES]     The required permissions (for reading and/or
                  writing) are denied for the named file or area
                  of a process.

     [ESRCH]      No process can be found corresponding to the
                  specified pid.

     [EPERM]      The area of the object to be mapped is
                  protected against the desired operation.



Printed 4/12/89                                                 2

MMAP(2)                 COMMAND REFERENCE                 MMAP(2)



RETURN VALUE
     Upon successful completion, a value of 0 is returned.
     Otherwise, a value of -1 is returned and errno is set to
     indicate the error.

SEE ALSO
     getpagesize(2), mremap(2), and munmap(2).
















































Printed 4/12/89                                                 3

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