From owner-freebsd-arch@FreeBSD.ORG Thu Aug 12 20:01:33 2010 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 A6F5F106566C for ; Thu, 12 Aug 2010 20:01:33 +0000 (UTC) (envelope-from mdf356@gmail.com) Received: from mail-ey0-f182.google.com (mail-ey0-f182.google.com [209.85.215.182]) by mx1.freebsd.org (Postfix) with ESMTP id 33C318FC19 for ; Thu, 12 Aug 2010 20:01:32 +0000 (UTC) Received: by eyh6 with SMTP id 6so1100132eyh.13 for ; Thu, 12 Aug 2010 13:01:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:sender:received :in-reply-to:references:date:x-google-sender-auth:message-id:subject :from:to:content-type:content-transfer-encoding; bh=zFuvjoa05Lcq6HTMsoEBMqPXxZSoAxhb7yZ5vSGE9L8=; b=HbMBxIRBzUcWkH3XegbBQ8jJkW+K/RSvKdoyWAODABC3yDA7un66+PoiR1bwqsaV0i yI63Iic2OoRpQCUqW4WlrAdeUwdNId82abMKw9bb4KTGrujx23ExlwjyGhbJcrFeAn9y dZOF3vtyeoZFrVufNjGOzMf7+WE4HBTK5E3gg= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type :content-transfer-encoding; b=FAgO0wHmFZ63vrLvdNA6/oVglm9pGIrIXH9cu6DaxEXNDj2ltJDhQPf1meJfpURjWi GwJpULIXvqDUcB//nMtdqucz8FmQ0CdSQkFygxUNvAebXM7KBFCKjAgFWtClYijvRmNb bdWjuPXXR+yO4a1l2tKwpVj8PROFKKPzxPeGs= MIME-Version: 1.0 Received: by 10.213.62.206 with SMTP id y14mr7812539ebh.34.1281643291996; Thu, 12 Aug 2010 13:01:31 -0700 (PDT) Sender: mdf356@gmail.com Received: by 10.213.10.196 with HTTP; Thu, 12 Aug 2010 13:01:31 -0700 (PDT) In-Reply-To: <20100812195654.GB2978@hoeg.nl> References: <20100812195654.GB2978@hoeg.nl> Date: Thu, 12 Aug 2010 13:01:31 -0700 X-Google-Sender-Auth: jVu9EdlK9dudTtfTsN3NsMkTMzU Message-ID: From: mdf@FreeBSD.org To: Ed Schouten , freebsd-arch@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: Subject: Re: RFC: replace vm_offset_t with uintptr_t and vm_size_t with size_t 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: Thu, 12 Aug 2010 20:01:33 -0000 On Thu, Aug 12, 2010 at 12:56 PM, Ed Schouten wrote: > Hi Matthew, > > * mdf@FreeBSD.org wrote: >> Looking over the arch-specific definitions, using uintptr_t and size_t >> would not affect the actual width of these sizes. =A0However, it would >> simplify e.g. conformant printf(9) statements, since there is an >> approved specifier for size_t and, while there isn't one for >> uintptr_t, ptrdiff_t is pretty close (Bruce, is there a better >> specifier)? > > Not that I know any architecture we support which does this, but what > happens if userspace has a larger address space than kernelspace? Say, > we ever have some kind of architecture with a 32-bit kernel running > 64-bit userspace applications. True, in that instance 32-bit types wouldn't work. However, there is a *lot* of vm work needed to support 64 bit apps on a 32-bit kernel, and I really doubt there will be any investment in this for any of the 32-bit architectures. We had such a setup on AIX until the 32-bit kernel was killed, to support applications that needed more than 4GB before IBM was ready to do the 64-bit kernel project. Such a setup requires running on 64-bit hardware, and for whatever reason choosing to use the 32-bit kernel. I also can't think of any compelling reason to use a 32-bit kernel when a 64-bit one is available. Thanks, matthew