From owner-freebsd-arch@FreeBSD.ORG Wed Jul 23 11:11:26 2008 Return-Path: Delivered-To: freebsd-arch@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 8C86E106566B for ; Wed, 23 Jul 2008 11:11:26 +0000 (UTC) (envelope-from brde@optusnet.com.au) Received: from fallbackmx10.syd.optusnet.com.au (fallbackmx10.syd.optusnet.com.au [211.29.132.251]) by mx1.freebsd.org (Postfix) with ESMTP id 6AABB8FC15 for ; Wed, 23 Jul 2008 11:11:25 +0000 (UTC) (envelope-from brde@optusnet.com.au) Received: from mail05.syd.optusnet.com.au (mail05.syd.optusnet.com.au [211.29.132.186]) by fallbackmx10.syd.optusnet.com.au (8.13.1/8.13.1) with ESMTP id m6MHRNu0005863 for ; Wed, 23 Jul 2008 03:27:23 +1000 Received: from c220-239-252-11.carlnfd3.nsw.optusnet.com.au (c220-239-252-11.carlnfd3.nsw.optusnet.com.au [220.239.252.11]) by mail05.syd.optusnet.com.au (8.13.1/8.13.1) with ESMTP id m6MHRJRH032634 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 23 Jul 2008 03:27:20 +1000 Date: Wed, 23 Jul 2008 03:27:19 +1000 (EST) From: Bruce Evans X-X-Sender: bde@delplex.bde.org To: Bruce Evans In-Reply-To: <20080723025519.F18257@delplex.bde.org> Message-ID: <20080723032109.W18257@delplex.bde.org> References: <34889018-8358-46AC-897E-32767FB84E14@mac.com> <200807211049.47579.jhb@freebsd.org> <20080721214104.GF76659@elvis.mu.org> <20080723025519.F18257@delplex.bde.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: Alfred Perlstein , Marcel Moolenaar , freebsd-arch@FreeBSD.org Subject: Re: RFC: cross-libkvm/libthread_db/proc_service X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 23 Jul 2008 11:11:26 -0000 On Wed, 23 Jul 2008, Bruce Evans wrote: > On Mon, 21 Jul 2008, Alfred Perlstein wrote: > >> Isn't it a bit strange to export 64bit pointers to 32 bit userspace? > > Only for pointers in kernel objects, and I think the proposed change > doesn't touch that. > > kvm_read() doesn't use pointers for kernel addresses. It uses unsigned > longs. But even uintmax_t is not enough in general, since the application > uintmax_t might be too small to represent a kernel pointer. The type > used shouldn't be fixed-width, but typedefed in an MD way like vm_offset_t. > vm_offset_t gives the correct integral type to use for (mapped) kernel > addresses and related compat_fewer_bit[s] type[s] are needed in userland. > It would probably be too hard to support the general case which requires > the compat types to be arrays or structs. Bah, I forgot the original mail which already says to use an integral type named psaddr_t, and that, unfortunately, this seems to need being 64 bits even on pure 32-bit systems in case you want to run an (not quite pure) 32-bit application in compat32 mode on 64-bit system without recompiling. If psaddr_t is 32-bits on i386 but 64-bits on amd64, then pure 32-bit i386 applications won't run in compat32 mode on amd64, though (not quite pure) 32-bit applications compiled on amd64 will. I don't like putting 64-bit knowledge in 32-bit applications but I often compile on i386 and run on amd64. Bruce