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X86_64_IOPL(2)           System Calls Manual (x86_64)           X86_64_IOPL(2)

NAME
     x86_64_iopl - change the x86_64 I/O privilege level

LIBRARY
     x86_64 Architecture Library (libx86_64, -lx86_64)

SYNOPSIS
     #include <sys/types.h>
     #include <machine/sysarch.h>

     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.

NetBSD 10.99                     July 3, 2002                     NetBSD 10.99