vga_safety_fork(3) start a parallel process to restore the console at a crash


#include <vga.h>

void vga_safety_fork(void (*shutdown_routine)(void))


Calling this at the start of a program results in a better chance of textmode being restored in case of a crash. However it has to raise the iopl level to 3 to work. This is a small security breach as it is inherited to any programs you fork of. However, some SVGA card drivers have to use iopl(3) anyway. If you use it call that function as the very first vga_ function. Call it right before vga_init (3). Note that vga_safety_fork() will already enter a graphicsmode. (For font and grafix state saving). Don't overestimate the power of this function. Your application will continue to run in background while a foreground application will restore a usable screen and graphics mode in case of a crash.

The forktest(6) demo shows the principal operation. (*shutdown_routine)() is called when the system crashes. However, realize that the call will take in a forked copy of your program, you'll not have access to any globals modified after the vga_safety_fork() call!


This manual page was edited by Michael Weller <[email protected]>. The exact source of the referenced function as well as of the original documentation is unknown.

It is very likely that both are at least to some extent are due to Harm Hanemaayer <[email protected]>.

Occasionally this might be wrong. I hereby asked to be excused by the original author and will happily accept any additions or corrections to this first version of the svgalib manual.