PHYS(2) System Calls Manual PHYS(2)NAME
phys - allow a process to access physical addresses (2BSD)
phys(segreg, size, physaddr)
unsigned int segreg, size, physaddr;
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 physaddrx64 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(7, 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.
[EPERM] The process's effective user ID is not the super-user.
[EINVAL] Segreg is less than 0 or greater than 7.
[EINVAL] Size is less than 0 or greater than 128.
PDP-11 segmentation hardware
On systems with ENABLE/34(tm) memory mapping boards, phys cannot be used to map in the I/O page.
This system call is very dangerous. It is not considered a permanent part of the system.
Phys is unique to the PDP-11 and 2BSD; its use is discouraged.
3rd Berkeley Distribution January 22, 1987 PHYS(2)
Check Out this Related Man Page
MEM(4) Kernel Interfaces Manual MEM(4)NAME
mem, kmem - main memory
major device number(s):
minor device encoding:
mem: 0; kmem: 1; null: 2
Mem is a special file that is an image of the main memory of the computer. It may be used, for example, to examine (and even to patch) the
Byte addresses in mem are interpreted as physical memory addresses. References to non-existent locations cause errors to be returned.
The file kmem is the same as mem except that kernel virtual memory rather than physical memory is accessed. Only kernel virtual addresses
that are mapped to memory are allowed. Examining and patching device registers is likely to lead to unexpected results when read-only or
write-only bits are present.
On PDP-11s, the I/O page begins at location 0160000 of kmem and the per-process data segment for the current process begins at 0140000 and
is USIZE clicks (64 bytes each) long.
/dev/MAKEDEV script to create special files
/dev/MAKEDEV.local script to localize special files
On PDP-11's, specifying an odd kernel or user address, or an odd transfer count is [generally] slower than using all even parameters.
On machines with ENABLE/34(tm) memory mapping boards the I/O page can be accessed only through kmem.
3rd Berkeley Distribution January 28, 1988 MEM(4)
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