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IOPERM(2)                  Linux Programmer's Manual                 IOPERM(2)

       ioperm - set port input/output permissions

       #include <unistd.h> /* for libc5 */
       #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 process for num bytes starting from port address
       from to the value turn_on.  If turn_on is non-zero, the calling process must be privileged (CAP_SYS_RAWIO).

       Only the first 0x3ff I/O ports can be specified in this manner.  For more ports, the iopl(2) system  call  must
       be used.

       Permissions  are  not  inherited  by the child created by fork(2).  Permissions are preserved across execve(2);
       this is useful for giving port access permissions to non-privileged 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 process has insufficient privilege.

       ioperm() is Linux-specific and should not be used in programs intended to be portable.

       Libc5  treats it as a system call and has a prototype in <unistd.h>.  Glibc1 does not have a prototype.  Glibc2
       has a prototype both in <sys/io.h> and in <sys/perm.h>.  Avoid the latter, it is available on i386 only.

       iopl(2), capabilities(7)

       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at

Linux                             2007-06-15                         IOPERM(2)