NAME

mem, kmem − physical or virtual memory

SYNOPSIS

/dev/mem
/dev/kmem

DESCRIPTION

The file /dev/mem is a special file that is an image of the physical memory of the computer.  The file /dev/kmem is a special file that is an image of the kernel virtual memory of the computer.  Either may be used, for example, to examine, and even patch the system. 

Byte addresses in /dev/mem are interpreted as physical memory addresses.  Byte addresses in /dev/kmem are interpreted as kernel virtual memory addresses.  References to non-existent locations cause errors to be returned (see ERRORS below). 

The file /dev/kmem accesses up to 4GB of kernel virtual memory.  The file /dev/mem accesses physical memory; the size of the file is equal to the amount of physical memory in the computer.  This can be larger than 4GB; in which case, memory beyond 4GB can be accessed using a series of read(2) and write(2) commands or a combination of llseek(2) and read(2) and write(2). 

ERRORS

EFAULT Bad address.  This error can occur when trying to: write(2) a read-only location, read(2) a write-only location, or read(2) or write(2) a non-existent or unimplemented location. 

ENXIO This error results from attempting to mmap(2) a non-existent physical (mem) or virtual (kmem) memory address. 

FILES

/dev/mem File containing image of physical memory of computer. 

/dev/kmem File containing image of kernel virtual memory of computer. 

SEE ALSO

llseek(2), mmap(2), read(2), write(2)

NOTES

Some of /dev/kmem cannot be read because of write-only addresses or unequipped memory addresses. 

SunOS 5.5.1  —  Last change: 18 Mar 1994