NAME    [Toc]    [Back]

     i386_get_ioperm, i386_set_ioperm - manage  i386  per-process
I/O permission
     bitmap

SYNOPSIS    [Toc]    [Back]

     #include <sys/types.h>
     #include <machine/sysarch.h>

     int
     i386_get_ioperm(u_long *iomap);

     int
     i386_set_ioperm(u_long *iomap);

DESCRIPTION    [Toc]    [Back]

     i386_get_ioperm()  copies  the current I/O permission bitmap
into the memory
 referenced by iomap.

     i386_set_ioperm() sets the I/O permission  bitmap  from  the
data pointed to
     by iomap.  This call is restricted to the superuser.

     The  permission  bitmap  contains 1024 bits in 32 longwords.
If bit n is
     clear in the bitmap, then access is granted to I/O  port  n.
If bit n is
     set  in the bitmap, then an attempt to access I/O port n results in delivery
 of a SIGBUS signal unless the process's  I/O  permission
level would
     grant I/O access.

     Note: Code using the i386_get_ioperm() and i386_set_ioperm()
functions
     must be compiled using -li386.

RETURN VALUES    [Toc]    [Back]

     Upon   successful    completion,    i386_get_ioperm()    and
i386_set_ioperm() return
 0.  Otherwise, a value of -1 is returned and the global
variable
     errno is set to indicate the error.

ERRORS    [Toc]    [Back]

     i386_get_ioperm() and i386_set_ioperm() will fail if:

     [EFAULT]  iomap points outside the process's  allocated  address space.

     [EPERM]   The caller was not the superuser.

SEE ALSO    [Toc]    [Back]

     i386_iopl(2)

     Intel, i386 Microprocessor Programmer's Reference Manual.

WARNING    [Toc]    [Back]

     You  can  really  hose your machine if you enable user-level
I/O and write
     to hardware ports without care.

BUGS    [Toc]    [Back]

     The bitmap should really cover 65536 bits, but  that's  just
too big for
     allocation  in  a  kernel  structure.  If you need access to
ports beyond
     1024, use i386_iopl(2).

OpenBSD     3.6                        October      14,      1995