Copyright (c) 1993 Michael Haardt (email@example.com) Fri Apr 2 11:32:09 MET DST 1993 %%%LICENSE_START(GPLv2+_DOC_FULL) This is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU General Public License's references to "object code" and "executables" are to be interpreted as the output of any document formatt...
NAMEioperm - set port input/output permissions
SYNOPSIS#include <sys/io.h> /* for glibc */
int ioperm(unsigned long from, unsigned long num, int turn_on);
DESCRIPTIONioperm() 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 not inherited by the child created by fork(2); following a fork(2) the child must turn on those permissions that it needs. 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 VALUEOn success, zero is returned. On error, -1 is returned, and errno is set appropriately.
- Invalid values for from or num.
- (on PowerPC) This call is not supported.
- Out of memory.
- The calling thread has insufficient privilege.
CONFORMING TOioperm() is Linux-specific and should not be used in programs intended to be portable.
NOTESThe /proc/ioports file shows the I/O ports that are currently allocated on the system.
Glibc has an ioperm() prototype both in <sys/io.h> and in <sys/perm.h>. Avoid the latter, it is available on i386 only.