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Lu" Cc: Richard Earnshaw , GNU C Library , Richard Earnshaw Subject: Re: [PATCH v3 2/8] elf: Add a tunable to control use of tagged memory Message-ID: <20201126172056.GQ20578@arm.com> References: <26b8b11e-919a-b6e0-ff5f-51e724faffb2@foss.arm.com> <8ddb9604-5a6d-a656-0585-57a1b26c39f6@gotplt.org> <87e8b15f-8c86-4b2c-a5e4-3e70631ea505@gotplt.org> <23a8ad00-a376-48ae-cc6a-2684261146a1@foss.arm.com> <6173c59d-ee67-9499-ac61-c2dd37b56c67@foss.arm.com> <3b69bc46-df40-f9ad-b76b-b69483b0934c@foss.arm.com> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Originating-IP: [217.140.106.54] X-ClientProxiedBy: LO4P123CA0038.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:152::7) To PR3PR08MB5564.eurprd08.prod.outlook.com (2603:10a6:102:87::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from arm.com (217.140.106.54) by LO4P123CA0038.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:152::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3611.20 via Frontend Transport; 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DIR:OUT; SFP:1101; X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Nov 2020 17:21:07.1589 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 36a92960-13a0-49fb-f97e-08d8922fa92a X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d; Ip=[63.35.35.123]; Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: AM5EUR03FT004.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB7PR08MB3338 X-Spam-Status: No, score=-8.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, MSGID_FROM_MTA_HEADER, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_PASS, SPF_PASS, TXREP, UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 26 Nov 2020 17:21:12 -0000 The 11/26/2020 08:51, H.J. Lu via Libc-alpha wrote: > On Thu, Nov 26, 2020 at 8:28 AM Richard Earnshaw > wrote: > > On 26/11/2020 15:50, H.J. Lu wrote: > > > I think we need to address binary marking first before adding MTE to > > > glibc. > > > > Sorry, I disagree. While this is a debugging tool there's no need for > > binary marking. > > > > Once we have a clearer understanding of what's needed there, we can work > > out how best to do the marking. > > If the only goal is to have a malloc with memory tag, you should enable > memory tag in an out-of-tree malloc implementation. It should be sufficient. out-of-tree malloc implementation cannot reliably enable mte: it cannot guarantee that it can initialize mte before the process becomes multi-threaded or that it can execute code in all threads before allocated memory is accessed there, so mte checks can be off for some threads. so the mte on/off setting has to be in glibc for now (out-of-tree implementation is possible, but it won't be reliable in all cases).