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I386_VM86(2) System Calls Manual I386_VM86(2)


i386_vm86control vm86-related functions


Standard C Library (libc, -lc)


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

i386_vm86(int function, void *data);


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

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 bit is set, the interrupt will be reflected to the process, otherwise it will be dispatched by the vm86 interrupt table.

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.

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.


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.


The i386_vm86() system call will fail if:

The kernel does not have vm86 support, or an invalid function was specified.
There is not enough memory to initialize the kernel data structures.


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

July 27, 1998 Debian