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I386_GET_IOPERM(2) OpenBSD Programmer's Manual (i386) I386_GET_IOPERM(2)
i386_get_ioperm, i386_set_ioperm - manage i386 per-process I/O permission
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.
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.
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.
Intel, i386 Microprocessor Programmer's Reference Manual.
You can really hose your machine if you enable user-level I/O and write
to hardware ports without care.
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