[This needs to be a little re-worked and expanded upon, but I am waiting to see if the iBCS stuff makes any impact on it as I write other stuff.]
This section covers first the mechanisms provided by the 386 for handling system calls, and then shows how uses those mechanisms. This is not a reference to the individual system calls: There are very many of them, new ones are added occasionally, and they are documented in man pages that should be on your system.
[Ideally, this chapter should be part of another section, I think. Maybe, however, it should just be expanded. I think it belongs somewhere near the chapter on how to write a device driver, because it explains how to write a system call.]