mem(7d) [sunos man page]

mem(7D) 							      Devices								   mem(7D)

NAME

       mem, kmem, allkmem - physical or virtual memory access

SYNOPSIS

       /dev/mem

       /dev/kmem

       /dev/allkmem

DESCRIPTION

       The file /dev/mem is a special file that provides access to the physical memory of the computer.

       The  file  /dev/kmem  is  a special file that provides access to the virtual address space of the operating system kernel, excluding memory
       that is associated with an I/O device.

       The file /dev/allkmem is a special file that provides access to the virtual address space of the operating system kernel, including  memory
       that is associated with an I/O device.  You can use any of these devices to examine and modify the system.

       Byte  addresses	in  /dev/mem are interpreted as physical memory addresses. Byte addresses in /dev/kmem and /dev/allkmem are interpreted as
       kernel virtual memory addresses.  A reference to a non-existent location returns an error. See ERRORS for more information.

       The file /dev/mem accesses physical memory; the size of the file is equal to the amount of physical memory in the computer.  This size  may
       be  larger  than 4GB on a system running the 32-bit operating environment. In this case, you can access memory beyond 4GB using a series of
       read(2) and write(2) calls, a pread64() or pwrite64() call, or a combination of llseek(2) and read(2) or write(2).

ERRORS

       EFAULT	       Occurs when trying to  write(2) a read-only location (allkmem),	read(2) a write-only location  (allkmem),  or  read(2)	or
		       write(2) a non-existent or unimplemented location (mem, kmem, allkmem).

       EIO	       Occurs  when trying to read(2) or write(2) a memory location that is associated with an I/O device using the /dev/kmem spe-
		       cial file.

       ENXIO	       Results from attempting to mmap(2) a non-existent physical (mem) or virtual (kmem, allkmem) memory address.

FILES

       /dev/mem        Provides access to the computer's physical memory.

       /dev/kmem       Provides access to the virtual address space of the operating system kernel, excluding memory that is  associated  with	an
		       I/O device.

       /dev/allkmem    Provides  access  to  the virtual address space of the operating system kernel, including memory that is associated with an
		       I/O device.

SEE ALSO

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

WARNINGS

       Using these devices to modify (that is, write to) the address space of a live running operating system or to modify  the  state	of	 a
       hardware  device  is  extremely	dangerous  and	may  result  in a system panic if kernel data structures are damaged or if device state is
       changed.

SunOS 5.10							    18 Feb 2002 							   mem(7D)

Check Out this Related Man Page

MEM(4)                                                       Linux Programmer's Manual                                                      MEM(4)

NAME

       mem, kmem, port - system memory, kernel memory and system ports

DESCRIPTION

       /dev/mem is a character device file that is an image of the main memory of the computer.  It may be used, for example, to examine (and even
       patch) the system.

       Byte addresses in /dev/mem are interpreted as physical memory addresses.  References to nonexistent locations cause errors to be returned.

       Examining and patching is likely to lead to unexpected results when read-only or write-only bits are present.

       Since Linux 2.6.26, and depending on the architecture, the CONFIG_STRICT_DEVMEM kernel configuration option limits the areas which  can  be
       accessed through this file.  For example: on x86, RAM access is not allowed but accessing memory-mapped PCI regions is.

       It is typically created by:

           mknod -m 660 /dev/mem c 1 1
           chown root:kmem /dev/mem

       The  file  /dev/kmem  is  the same as /dev/mem, except that the kernel virtual memory rather than physical memory is accessed.  Since Linux
       2.6.26, this file is available only if the CONFIG_DEVKMEM kernel configuration option is enabled.

       It is typically created by:

           mknod -m 640 /dev/kmem c 1 2
           chown root:kmem /dev/kmem

       /dev/port is similar to /dev/mem, but the I/O ports are accessed.

       It is typically created by:

           mknod -m 660 /dev/port c 1 4
           chown root:kmem /dev/port

FILES

       /dev/mem
       /dev/kmem
       /dev/port

SEE ALSO

       chown(1), mknod(1), ioperm(2)

COLOPHON

       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Linux                                                               2015-01-02                                                              MEM(4)

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mem(7d) [sunos man page]

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