MEM(4) | Device Drivers Manual (x86) | MEM(4)

# NAME

`mem`, `kmem` — memory files

# DESCRIPTION

The special file `/dev/mem` is an interface to the physical memory of the computer. Byte offsets in this file are interpreted as physical memory addresses. Reading and writing this file is equivalent to reading and writing memory itself. Only offsets within the bounds of `/dev/mem` are allowed.

Kernel virtual memory is accessed through the interface `/dev/kmem` in the same manner as `/dev/mem`. Only kernel virtual addresses that are currently mapped to memory are allowed.

On ISA the I/O memory space begins at physical address 0x000a0000 and runs to 0x00100000. The per-process data size for the current process is `UPAGES` long, and ends at virtual address 0xfe000000.

# FILES

/dev/mem
/dev/kmem

# HISTORY

The `mem`, `kmem` files appeared in Version 6 AT&T UNIX.

September 23, 2011 | NetBSD 11.99