man i386_vm86 (2): control vm86-related functions

LIBRARY

Lb libc

SYNOPSIS

In sys/types.h In machine/sysarch.h In machine/vm86.h Ft int Fn i386_vm86 int function void *data

DESCRIPTION

The Fn i386_vm86 system call is used to call various vm86 related functions. The Fa 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 Fa data argument points to the following structure:

struct vm86_init_args {
        int     debug;
        int     cpu_type;
        u_char  int_map[32];
};

The Fa debug argument is used to turn on debugging code. The Fa cpu_type argument controls the type of CPU being emulated, and is currently unimplemented. The Fa 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. Fa data should point to the following structure:

struct vm86_intcall_args {
        int     intnum;
        struct  vm86frame vmf;
};

Fa 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. Fa 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. Fa data should be initialized to point to the following:

struct vm86_vme_args {
        int     state;                  /* status */
};

Fa 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

Rv -std i386_vm86

ERRORS

The Fn i386_vm86 system call will fail if:

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

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