• NAME
  
  ioperm - set port input/output permissions
• 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
  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) . Permissions 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 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 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
  
  This page is part of release 3.19 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

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