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.