i386_vm86(2)

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 re

lated 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 unimplement

ed. The
int_map argument is a bitmap which de

termines 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 in

terrupt han

dlers 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 cor

rect machine
context for vm86, and with the PSL_VM bit set. Control re

turns 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.

BSD July 27, 1998

BSD