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I386_GET_IOPERM(2)    OpenBSD Programmer's Manual (i386)    I386_GET_IOPERM(2)

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

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

     int
     i386_get_ioperm(u_long *iomap);

     int
     i386_set_ioperm(u_long *iomap);

DESCRIPTION
     i386_get_ioperm() copies the current I/O permission bitmap into the memo-
     ry 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 deliv-
     ery 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
     Upon successful completion, i386_get_ioperm() and i386_set_ioperm() re-
     turn 0.  Otherwise, a value of -1 is returned and the global variable
     errno is set to indicate the error.

ERRORS
     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
     i386_iopl(2)

     Intel, i386 Microprocessor Programmer's Reference Manual.

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

BUGS
     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 3.8                    October 14, 1995                              1