I386_VM86(2)						   BSD/i386 System Calls Manual 					      I386_VM86(2)

NAME

     i386_vm86 -- set virtual 8086 processor registers and mode

LIBRARY

     i386 Architecture Library (libi386, -li386)

SYNOPSIS

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

     int
     i386_vm86(struct vm86_struct *vmcp);

DESCRIPTION

     i386_vm86() will set the process into virtual 8086 mode using the registers and selectors specified by the context pointed to by vmcp.  The
     processor registers are set from vmcp->substr.regs, and the emulated processor type from vmcp->substr.ss_cpu_type.

     The kernel keeps a pointer to the context, and uses the tables stored at vmcp->int_byuser and vmcp->int21_byuser for fast virtual interrupt
     handling.	If the n th bit is clear in the first of these arrays, then the kernel may directly emulate the real-mode x86 INT n instruction
     handling.	If the n th bit is set, then the process is delivered a signal when an INT instruction is executed.

     Since MS-DOS puts many DOS functions onto interrupt 21, it is handled specially:  the k th bit in the vmcp->int21_byuser array is checked
     when INT 21 is requested and the ah register is k.

RETURN VALUES

     This routine does not normally return: 32-bit mode will be restored by the delivery of a signal to the process.  In case of an error in set-
     ting the VM86 mode, a value of -1 is returned and the global variable errno is set to indicate the error.

ERRORS

     i386_vm86() will fail if:

     [EFAULT]  The state at vmcp was not readable to the user process.

REFERENCES

     i386 Microprocessor Programmer's Reference Manual, Intel

BSD
								 February 20, 1996							       BSD