vm86(2) System Calls Manual vm86(2)

vm86old, vm86 - enter virtual 8086 mode

Standard C library (libc, -lc)

#include <sys/vm86.h>
int vm86old(struct vm86_struct *info);
int vm86(unsigned long fn, struct vm86plus_struct *v86);

The system call vm86() was introduced in Linux 0.97p2. In Linux 2.1.15 and 2.0.28, it was renamed to vm86old(), and a new vm86() was introduced. The definition of struct vm86_struct was changed in 1.1.8 and 1.1.9.

These calls cause the process to enter VM86 mode (virtual-8086 in Intel literature), and are used by dosemu.

VM86 mode is an emulation of real mode within a protected mode task.

On success, zero is returned. On error, -1 is returned, and errno is set to indicate the error.

This return value is specific to i386 and indicates a problem with getting user-space data.
This return value indicates the call is not implemented on the present architecture.
Saved kernel stack exists. (This is a kernel sanity check; the saved stack should exist only within vm86 mode itself.)

This call is specific to Linux on 32-bit Intel processors, and should not be used in programs intended to be portable.

2022-10-30 Linux man-pages 6.02