From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 61168 invoked by alias); 11 Sep 2017 08:58:03 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 61144 invoked by uid 89); 11 Sep 2017 08:58:02 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.1 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.2 spammy=interests, UD:jsp X-HELO: EUR02-AM5-obe.outbound.protection.outlook.com Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=Szabolcs.Nagy@arm.com; Message-ID: <59B65010.4020807@arm.com> Date: Mon, 11 Sep 2017 08:58:00 -0000 From: Szabolcs Nagy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 MIME-Version: 1.0 To: Florian Weimer , wangboshi CC: nd@arm.com, libc-alpha@sourceware.org Subject: Re: [RFC][PATCH] AArch64: use movz/movk instead of literal pools in start.S References: <877exalool.fsf@mid.deneb.enyo.de> In-Reply-To: <877exalool.fsf@mid.deneb.enyo.de> Content-Type: text/plain; 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XOM sets the code as executable and unreadable, so the >> access to any data, like literal pools, in the code section causes >> the fault with XOM. The compiler can disable literal pools for C >> source files, but not for assembly files, so I use movz/movk instead >> of literal pools in start.S for XOM. > > Isn't the main goal of XOM to make it more difficult for the > legitimate device owner to view running machine code? > > | Execute-only memory allows you to protect your intellectual property > | by preventing executable code being read by users. For example, you > | can place firmware in execute-only memory and load user code and > | drivers separately. Placing the firmware in execute-only memory > | prevents users from trivially reading the code. > > > > I don't think it's in the interests of the GNU projet to support such > a thing. > even if that's the main use of xom, there might be other uses and removing data from text might have other uses than xom (reduce rop gadget possibility?) so i don't think this should be a problem (the gnu project already supports gazillion features that can do harm).