NAME

       i386_vm86 — control vm86-related functions

LIBRARY

       Standard C Library (libc, -lc)

SYNOPSIS

       #include <sys/types.h>
       #include <machine/sysarch.h>
       #include <machine/vm86.h>

       int
       i386_vm86(int function, void *data);

DESCRIPTION

       The i386_vm86() system call is used to call various vm86 related functions.  The function argument can be
       one of the following values:

             VM86_INIT     This will initialize the kernel's vm86 parameter area for the process, and permit the
                           process to make vm86 calls.  The data argument points to the following structure:

                           struct vm86_init_args {
                                   int     debug;
                                   int     cpu_type;
                                   u_char  int_map[32];
                           };

                           The debug argument is used to turn on debugging code.  The cpu_type argument controls
                           the type of CPU being emulated, and is currently unimplemented.  The int_map argument
                           is  a bitmap which determines whether vm86 interrupts should be handled in vm86 mode,
                           or reflected back to the process.  If the Nth bit  is  set,  the  interrupt  will  be
                           reflected  to  the  process,  otherwise  it  will be dispatched by the vm86 interrupt
                           table.

             VM86_INTCALL  This allows calls to  be  made  to  vm86  interrupt  handlers  by  the  process.   It
                           effectively  simulates  an  INT  instruction.   data  should  point  to the following
                           structure:

                           struct vm86_intcall_args {
                                   int     intnum;
                                   struct  vm86frame vmf;
                           };

                           intnum specifies the operand of INT for the simulated call.  A  value  of  0x10,  for
                           example,  would  often  be used to call into the VGA BIOS.  vmf is used to initialize
                           CPU registers according to the calling convention for the interrupt handler.

             VM86_GET_VME  This is used to  retrieve  the  current  state  of  the  Pentium(r)  processor's  VME
                           (Virtual-8086  Mode  Extensions)  flag,  which  is  bit  0  of  CR4.   data should be
                           initialized to point to the following:

                           struct vm86_vme_args {
                                   int     state;                  /* status */
                           };

                           state will contain the state of the VME flag on return.

       vm86 mode is entered by calling sigreturn(2) with the correct machine context  for  vm86,  and  with  the
       PSL_VM bit set.  Control returns to the process upon delivery of a signal.

RETURN VALUES

       The  i386_vm86()  function  returns the value 0 if successful; otherwise the value -1 is returned and the
       global variable errno is set to indicate the error.

ERRORS

       The i386_vm86() system call will fail if:

       [EINVAL]           The kernel does not have vm86 support, or an invalid function was specified.

       [ENOMEM]           There is not enough memory to initialize the kernel data structures.

AUTHORS

       This man page was written by Jonathan Lemon, and updated by Bruce M Simpson.

Debian                                            July 27, 1998                                     I386_VM86(2)