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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 nonzero, 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).  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 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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