ioperm - set port input/output permissions
#include <sys/io.h> /* for glibc */
int ioperm(unsigned long from, unsigned long num,
int turn_on);
ioperm() sets the port access permission bits for the calling thread for
num bits starting from port address
from. If
turn_on is
nonzero, then permission for the specified bits is enabled; otherwise it is
disabled. If
turn_on is nonzero, the calling thread must be privileged
(
CAP_SYS_RAWIO).
Before Linux 2.6.8, only the first 0x3ff I/O ports could be specified in this
manner. For more ports, the
iopl(2) system call had to be used (with a
level argument of 3). Since Linux 2.6.8, 65,536 I/O ports can be
specified.
Permissions are inherited by the child created by
fork(2) (but see
NOTES). Permissions are preserved across
execve(2); this is useful for
giving port access permissions to unprivileged programs.
This call is mostly for the i386 architecture. On many other architectures it
does not exist or will always return an error.
On success, zero is returned. On error, -1 is returned, and
errno is set
appropriately.
- EINVAL
- Invalid values for from or num.
- EIO
- (on PowerPC) This call is not supported.
- ENOMEM
- Out of memory.
- EPERM
- The calling thread has insufficient privilege.
ioperm() is Linux-specific and should not be used in programs intended to
be portable.
The
/proc/ioports file shows the I/O ports that are currently allocated
on the system.
Before Linux 2.4, permissions were not inherited by a child created by
fork(2).
Glibc has an
ioperm() prototype both in
<sys/io.h> and in
<sys/perm.h>. Avoid the latter, it is available on i386 only.
iopl(2),
outb(2),
capabilities(7)