PHYS(2) (PDP11) 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
segreg×8K bytes. This address range is mapped into physical
address physadr×64 bytes. Only the first size×64 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 specified segreg is already used for
other than a previous call to phys.
BUGS
This system call is obviously very machine dependent and
very dangerous. This system call is not considered a perma-
nent part of the system.
ASSEMBLER
(phys = 52.)
sys phys; segreg; size; physadr