1mem(7D)                             Devices                            mem(7D)
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NAME

6       mem, kmem, allkmem - physical or virtual memory access
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SYNOPSIS

9       /dev/mem
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12       /dev/kmem
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15       /dev/allkmem
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DESCRIPTION

19       The  file /dev/mem is a special file that provides access to the physi‐
20       cal memory of the computer.
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23       The file /dev/kmem is a special file that provides access to  the  vir‐
24       tual  address  space  of  the operating system kernel, excluding memory
25       that is associated with an I/O device.
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28       The file /dev/allkmem is a special file that  provides  access  to  the
29       virtual  address space of the operating system kernel, including memory
30       that is associated with an I/O  device.   You  can  use  any  of  these
31       devices to examine and modify the system.
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34       Byte   addresses   in  /dev/mem  are  interpreted  as  physical  memory
35       addresses. Byte addresses in /dev/kmem and /dev/allkmem are interpreted
36       as kernel virtual memory addresses. A reference to a non-existent loca‐
37       tion returns an error. See ERRORS for more information.
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40       The file /dev/mem accesses physical memory; the size  of  the  file  is
41       equal  to  the amount of physical memory in the computer. This size may
42       be larger than 4GB on a system running the  32-bit  operating  environ‐
43       ment.  In this case, you can access memory beyond 4GB using a series of
44       read(2) and write(2) calls, a pread64() or pwrite64() call, or a combi‐
45       nation of llseek(2) and read(2) or write(2).
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ERRORS

48       EFAULT    Occurs  when  trying to  write(2) a read-only location (allk‐
49                 mem), read(2) a write-only location (allkmem), or read(2)  or
50                 write(2) a non-existent or unimplemented location (mem, kmem,
51                 allkmem).
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54       EIO       Occurs when trying to read(2) or write(2) a  memory  location
55                 that  is  associated  with  an I/O device using the /dev/kmem
56                 special file.
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59       ENXIO     Results from attempting to mmap(2)  a  non-existent  physical
60                 (mem) or virtual (kmem, allkmem) memory address.
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FILES

64       /dev/mem        Provides access to the computer's physical memory.
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67       /dev/kmem       Provides  access  to  the  virtual address space of the
68                       operating system kernel, excluding memory that is asso‐
69                       ciated with an I/O device.
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72       /dev/allkmem    Provides  access  to  the  virtual address space of the
73                       operating system kernel, including memory that is asso‐
74                       ciated with an I/O device.
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SEE ALSO

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

81       Using  these devices to modify (that is, write to) the address space of
82       a live running operating system or to modify the state of      a  hard‐
83       ware  device is extremely dangerous and may result in a system panic if
84       kernel data structures are damaged or if device state is changed.
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88SunOS 5.11                        18 Feb 2002                          mem(7D)