NAME

       ioperm - set port input/output permissions

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <sys/io.h>

       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
       disabled.  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 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 to indicate the error.

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.

VERSIONS

       glibc  has  an  ioperm()  prototype  both  in  <sys/io.h>  and  in <sys/perm.h>.  Avoid the latter, it is
       available on i386 only.

STANDARDS

       Linux.

HISTORY

       Before Linux 2.4, permissions were not inherited by a child created by fork(2).

NOTES

       The /proc/ioports file shows the I/O ports that are currently allocated on the system.

SEE ALSO

       iopl(2), outb(2), capabilities(7)