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.