ioperm


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   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).  Permis-
       sions 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 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 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 prototype 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
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