ioperm - set port input/output permissions
Standard C library (libc, -lc)
#include <sys/io.h>
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 to indicate the error.
Invalid values for from or num.
(on PowerPC) This call is not supported.
Out of memory.
The calling thread has insufficient privilege.
glibc has an ioperm() prototype both in
<sys/io.h> and in <sys/perm.h>. Avoid the
latter, it is available on i386 only.
Linux.
Before Linux 2.4, permissions were not inherited by a child created by fork(2).
The /proc/ioports file shows the I/O ports that are
currently allocated on the system.
iopl(2), outb(2), capabilities(7)