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



NAME
       ioperm - set port input/output permissions

SYNOPSIS
       #include <unistd.h> /* for libc5 */
       #include <sys/io.h> /* for glibc */

       int ioperm(unsigned long from, unsigned long num, int turn_on);

DESCRIPTION
       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 nonzero, 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  use-
       ful 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.

RETURN VALUE
       On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.

ERRORS
       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.

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

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

SEE ALSO
       iopl(2), capabilities(7)

COLOPHON
       This  page  is  part of release 3.25 of the Linux man-pages project.  A description of the project, and information about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                                                      2007-06-15                                                  IOPERM(2)