amd64_get_ioperm, amd64_set_ioperm - manage amd64 per-process I/O permission
amd64_get_ioperm() copies the current I/O permission bitmap
into the memory
referenced by iomap.
amd64_set_ioperm() sets the I/O permission bitmap from the
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
grant I/O access.
Note: Code using the amd64_get_ioperm() and
must be compiled using -lamd64.
Upon successful completion, amd64_get_ioperm() and
0. Otherwise, a value of -1 is returned and the global
errno is set to indicate the error.
amd64_get_ioperm() and amd64_set_ioperm() will fail if:
[EFAULT] iomap points outside the process's allocated address space.
[EPERM] The caller was not the superuser.
Intel, AMD64 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
1024, use amd64_iopl(2).
OpenBSD 3.6 October 14, 1995
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