From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 11385 invoked by alias); 16 Oct 2015 15:28:38 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 11373 invoked by uid 89); 16 Oct 2015 15:28:37 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.2 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail-wi0-f171.google.com Received: from mail-wi0-f171.google.com (HELO mail-wi0-f171.google.com) (209.85.212.171) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Fri, 16 Oct 2015 15:28:36 +0000 Received: by wicll6 with SMTP id ll6so15433970wic.0 for ; Fri, 16 Oct 2015 08:28:33 -0700 (PDT) X-Received: by 10.194.91.193 with SMTP id cg1mr20162048wjb.88.1445009313681; Fri, 16 Oct 2015 08:28:33 -0700 (PDT) Received: from [192.168.10.165] (94-39-171-91.adsl-ull.clienti.tiscali.it. [94.39.171.91]) by smtp.googlemail.com with ESMTPSA id bv2sm23131385wjc.11.2015.10.16.08.28.32 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Oct 2015 08:28:32 -0700 (PDT) Subject: Re: [PATCH 5/9] i386: Add address spaces for fs/gs segments To: Richard Henderson , gcc-patches@gcc.gnu.org, Avi Kivity References: <1444280375-20866-1-git-send-email-rth@redhat.com> <1444280375-20866-6-git-send-email-rth@redhat.com> From: Paolo Bonzini X-Enigmail-Draft-Status: N1110 Message-ID: <5621179F.5070303@gnu.org> Date: Fri, 16 Oct 2015 15:29:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <1444280375-20866-6-git-send-email-rth@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit X-SW-Source: 2015-10/txt/msg01616.txt.bz2 On 08/10/2015 06:59, Richard Henderson wrote: > +/* Address space support. > + > + This is not "far pointers" in the 16-bit sense, but an easy way > + to use %fs and %gs segment prefixes. Therefore: > + > + (a) All address spaces have the same modes, > + (b) All address spaces have the same addresss forms, > + (c) While %fs and %gs are technically subsets of the generic > + address space, they are probably not subsets of each other. > + (d) Since we have no access to the segment base register values > + without resorting to a system call, we cannot convert a > + non-default address space to a default address space. > + Therefore we do not claim %fs or %gs are subsets of generic. rdfsbase and rdgsbase are potentially accessible to userspace too, so I think %fs or %gs should be considered subsets of generic. Paolo > + Therefore, we need not override any of the address space hooks. */