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PHYS(2)                       System Calls Manual                      PHYS(2)



NAME
       phys - allow a process to access physical addresses

SYNOPSIS
       phys(segreg, size, physadr)

DESCRIPTION
       The  argument  segreg  specifies a process virtual (data-space) address
       range of 8K bytes starting at virtual address  segregx8K  bytes.   This
       address  range  is mapped into physical address physadrx64 bytes.  Only
       the first sizex64 bytes of this mapping is  addressable.   If  size  is
       zero,  any previous mapping of this virtual address range is nullified.
       For example, the call

            phys(6, 1, 0177775);

       will map virtual  addresses  0160000-0160077  into  physical  addresses
       017777500-017777577.   In  particular,  virtual  address 0160060 is the
       PDP-11 console located at physical address 017777560.

       This call may only be executed by the super-user.

SEE ALSO
       PDP-11 segmentation hardware

DIAGNOSTICS
       The function value zero is returned  if  the  physical  mapping  is  in
       effect.   The  value -1 is returned if not super-user, if segreg is not
       in the range 0-7, if size is not in the range 0-127, or if  the  speci-
       fied segreg is already used for other than a previous call to phys.

BUGS
       This  system  call is obviously very machine dependent and very danger-
       ous.  This system call is not considered a permanent part of  the  sys-
       tem.

ASSEMBLER
       (phys = 52.)
       sys phys; segreg; size; physadr



                                     PDP11                             PHYS(2)