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IOPERM(2)                  Linux Programmer's Manual                 IOPERM(2)
NAME
       ioperm - set port input/output permissions
SYNOPSIS
       #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 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 dis-
       abled.  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 architec-
       tures 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 thread has insufficient privilege.
CONFORMING TO
       ioperm() is Linux-specific and should not be used in programs  intended
       to be portable.
NOTES
       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.
SEE ALSO
       iopl(2), outb(2), capabilities(7)
COLOPHON
       This page is part of release 4.15 of the Linux  man-pages  project.   A
       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.
Linux                             2017-09-15                         IOPERM(2)