I386_GET_IOPERM(2)

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

LIBRARY
libi386

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 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 super-user.

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.

RETURN VALUES
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
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 super-user, or the operation was not permitted at the current security level.

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).

SEE ALSO
i386_iopl(2)

REFERENCES
i386 Microprocessor Programmer's Reference Manual, Intel

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