bcopy(9F)						   Kernel Functions for Drivers 						 bcopy(9F)

NAME

       bcopy - copy data between address locations in the kernel

SYNOPSIS

       #include <sys/types.h>
       #include <sys/sunddi.h>

       void bcopy(const void *from, void *to, size_t bcount);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

PARAMETERS

       from	Source address from which the copy is made.

       to	Destination address to which copy is made.

       bcount	The number of bytes moved.

DESCRIPTION

       bcopy()	copies	bcount bytes from one kernel address to another.  If the input and output addresses overlap, the command executes, but the
       results may not be as expected.

       Note that bcopy() should never be used to move data in or out of a user buffer, because it has no provision for handling page  faults.  The
       user  address  space can be swapped out at any time, and bcopy() always assumes that there will be no paging faults. If bcopy() attempts to
       access the user buffer when it is swapped out, the system will panic. It is safe to use bcopy() to move data  within  kernel  space,  since
       kernel space is never swapped out.

CONTEXT

       bcopy() can be called from user or interrupt context.

EXAMPLES

       Example 1: Copying data between address locations in the kernel:

       An  I/O	request  is  made for data stored in a RAM disk. If the I/O operation is a read request, the data is copied from the RAM disk to a
       buffer (line 8).  If it is a write request, the data is copied from a buffer to the RAM disk (line 15). bcopy() is used since both the  RAM
       disk and the buffer are part of the kernel address space.

	1 #define RAMDNBLK 1000 	       /* blocks in the RAM disk */
	2 #define RAMDBSIZ 512		       /* bytes per block */
	3 char ramdblks[RAMDNBLK][RAMDBSIZ];   /* blocks forming RAM
					       /* disk
	       ...
	4
	5 if   (bp->b_flags & B_READ)	   /* if read request, copy data */
	6				   /* from RAM disk data block */
	7				   /* to system buffer */
	8	    bcopy(&ramdblks[bp->b_blkno][0], bp->b_un.b_addr,
	9		bp->b_bcount);
       10
       11 else				   /* else write request, */
       12				   /* copy data from a */
       13				   /* system buffer to RAM disk */
       14				   /* data block */
       15	    bcopy(bp->b_un.b_addr, &ramdblks[bp->b_blkno][0],
       16		bp->b_bcount);

SEE ALSO

       copyin(9F), copyout(9F)

       Writing Device Drivers

WARNINGS

       The   from  and	 to  addresses	must be within the kernel space.  No range checking is done.  If an address outside of the kernel space is
       selected, the driver may corrupt the system in an unpredictable way.

SunOS 5.10							   4 August 2003							 bcopy(9F)