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 permanent part of the system. 

ASSEMBLER

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

7th Edition  —  PDP11