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bcopy(9f)

bcopy(9F)                      Kernel Functions                      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 an‐
       other. 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  as‐
       sumes  that  there will be no paging faults. If bcopy() attempts to ac‐
       cess 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 con‐
       text.

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 opera‐
       tion 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 in Oracle Solaris 11.4

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  se‐
       lected, the driver may corrupt the system in an unpredictable way.

Oracle Solaris 11.4               16 Jan 2006                        bcopy(9F)
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