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
The
bcopy() function 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
The
bcopy() function can be called from user, interrupt, or kernel
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 DriversWARNINGS
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.
January 16, 2006
BCOPY(9F)