From owner-freebsd-hackers Sun Jul 26 15:32:11 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id PAA19748 for freebsd-hackers-outgoing; Sun, 26 Jul 1998 15:32:11 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from implode.root.com (implode.root.com [198.145.90.17]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id PAA19711 for ; Sun, 26 Jul 1998 15:32:05 -0700 (PDT) (envelope-from root@implode.root.com) Received: from implode.root.com (localhost [127.0.0.1]) by implode.root.com (8.8.5/8.8.5) with ESMTP id PAA16544; Sun, 26 Jul 1998 15:29:15 -0700 (PDT) Message-Id: <199807262229.PAA16544@implode.root.com> To: zhihuizhang cc: hackers Subject: Re: APTDpde question (pmap) In-reply-to: Your message of "Sun, 26 Jul 1998 16:27:43 EDT." From: David Greenman Reply-To: dg@root.com Date: Sun, 26 Jul 1998 15:29:15 -0700 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG >In pmap.c module, we set PTDPTDI entry of the page directory page to point >to itself. So PTDpde and PTmap works well. However, I do not find a >similar setting of APTDTDI (=1023) in pmap.c. My question is how APTDpde >and the alternate address space it's supposed to relate to (APTmap) are >used. (has something to do with pmap copy?) The alternate page table map is used when the kernel wants to access the page tables of a non-current process. The page directory of the target process is mapped at PTD offset 1023, which causes the target process's page tables to become accessable in the final 4MB of the current address space. -DG David Greenman Co-founder/Principal Architect, The FreeBSD Project To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message