July 3, 2002 X86_64_IOPL 2 x86_64

### NAME

x86_64_iopl - change the x86_64 I/O privilege level

### LIBRARY

### SYNOPSIS

```int` x86_64_iopl(```int iopl`)

### DESCRIPTION

x86_64_iopl(``) sets the x86_64 I/O privilege level to the value specified by iopl. This call is restricted to the super-user.

### RETURN VALUES

Upon successful completion, x86_64_iopl(``) returns 0. Otherwise, a value of -1 is returned and the global variable errno is set to indicate the error.

### ERRORS

x86_64_iopl(``) will fail if:

[```EPERM`]
  The caller was not the super-user, or the operation was not permitted at the current security level.

### WARNING

You can really hose your machine if you enable user-level I/O and write to hardware ports without care.