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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.