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mem (7)
  • mem (4) ( FreeBSD man: Специальные файлы /dev/* )
  • mem (4) ( Русские man: Специальные файлы /dev/* )
  • mem (4) ( Linux man: Специальные файлы /dev/* )
  • >> mem (7) ( Solaris man: Макропакеты и соглашения )
  •  

    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 special 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.


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    ERRORS
    FILES
    SEE ALSO
    WARNINGS


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