NAME    [Toc]    [Back]

     i386_vm86 -- control vm86-related functions

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

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

     int
     i386_vm86(int function, void *data);

DESCRIPTION    [Toc]    [Back]

     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    [Toc]    [Back]

     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    [Toc]    [Back]

     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    [Toc]    [Back]

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


FreeBSD 5.2.1			 July 27, 1998			 FreeBSD 5.2.1