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 superuser. 

DIAGNOSTICS

Phys will fail and the segmentation registers be unaffected if:

[EINVAL] Segreg is less than 0 or greater than 7. 

[EINVAL] Size is less than 0 or greater than 128. 

[EINVAL] An attempt was made to map a segment which was already mapped by some method other than by phys. 

[EPERM] The process’s effective user ID is not the superuser. 

RESTRICTIONS

This system call is obviously very machine dependent and very dangerous.  This system call is not considered a permanent part of the system. 

SEE ALSO

PDP-11 segmentation hardware

ASSEMBLER

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