svatophys(9r) [osf1 man page]

svatophys(9r)															     svatophys(9r)

NAME

       svatophys - General: Converts a system virtual address to a physical address

SYNOPSIS

       kern_return_t svatophys(
	       vm_offset_t kern_addr,
	       vm_offset_t *phys_addr );

ARGUMENTS

       Specifies the kernel virtual address.  Specifies a pointer to the physical address to be filled in.

DESCRIPTION

       The  svatophys routine converts a system virtual address to the corresponding physical address. All address and data structure manipulation
       done within the kernel is performed using system virtual addresses.  Typically, system virtual addresses are a means  of  mapping  physical
       memory  and  I/O  space,  which often consists of device registers and DMA buffers. In contrast to this, devices are usually unaware of any
       virtual addressing and for this reason use physical addresses. You use the svatophys routine to perform this address translation.

       As an example of where you can use this address translation, a disk device driver can use DMA buffers to transfer blocks  of  data  to  the
       disk  (for  the case of a write operation). The data to be written to disk is present in system memory at a system virtual address known to
       the driver. To initiate the DMA operation, the disk driver can set up a command packet to specify a write operation to the underlying  disk
       controller  hardware.  This write command packet contains (among other things) the location of the DMA buffer as a physical address and the
       length of the buffer. Here, the driver calls the svatophys routine to translate the system virtual address of the DMA buffer to a  physical
       address in the command packet issued to the disk driver.

RETURN VALUES

       The  svatophys  routine returns the following: The address translation has been completed successfully.	Unable to perform address transla-
       tion. This value indicates that the address specified by the kern_addr argument is not a valid kernel or system virtual address.

																     svatophys(9r)

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 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.

SunOS 5.11							    18 Feb 2002 							   mem(7D)