Path: utzoo!censor!geac!alias!mark
From: mark@alias.uucp (Mark Andrews)
Newsgroups: comp.unix.wizards
Subject: Software extension to BSD PCB
Message-ID: <1990May30.190346.29652@alias.uucp>
Date: 30 May 90 19:03:46 GMT
Reply-To: mark@alias.UUCP (Mark Andrews)
Distribution: na
Organization: Alias Research Inc., Toronto, Canada
Lines: 34

In the Process Control block for VAX 4.[23]BSD, there is a software extension:

/*
 * Software pcb (extension)
 */
        int     pcb_szpt;       /* number of pages of user page table */
        int     pcb_cmap2;
        int     *pcb_sswap;
        int     pcb_sigc[5];


What are all these fields for? I realize that CMAP2 (pte in system page table)
is saved in the `pcb_cmap2' field of 1 pcb and restored from the pcb of another
process during a context switch, but why?

The BSD book mentions that the `pcb_cmap2' field is used when dealing with
segments, but does not go into any further detail.

Thanks,

Mark
------------------------------------------------------------------------------
	Mark Andrews
	Systems Programmer,
	Alias Research,
	Toronto, Canada
Phone:	(416)-362-9181
Mail box: mark%alias@csri.utoronto.ca

-- 
------------------------------------------------------------------------------
	Mark Andrews
	Systems Programmer,
	Alias Research,