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CTRY:IE; LANG:en; SCL:1; SRV:; IPV:CAL; SFV:NSPM; H:64aa7808-outbound-1.mta.getcheckrecipient.com; PTR:ec2-63-35-35-123.eu-west-1.compute.amazonaws.com; CAT:NONE; SFS:(4636009)(396003)(346002)(39860400002)(136003)(376002)(36840700001)(46966006)(81166007)(356005)(1076003)(36860700001)(8886007)(7696005)(26005)(47076005)(2906002)(186003)(82310400003)(33656002)(36756003)(86362001)(55016002)(336012)(44832011)(82740400003)(316002)(956004)(2616005)(8936002)(5660300002)(70206006)(70586007)(110136005)(8676002)(478600001); DIR:OUT; SFP:1101; X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Aug 2021 12:33:08.4759 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b1885b89-010f-41eb-1f51-08d9617b2b62 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: VE1EUR03FT012.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0801MB1898 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: , From: Szabolcs Nagy via Libc-alpha Reply-To: Szabolcs Nagy Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org Sender: "Libc-alpha" The 08/12/2021 13:01, Szabolcs Nagy via Libc-alpha wrote: > The 08/12/2021 10:36, Florian Weimer wrote: > > I still don't see a way how we can split tag address bits used by the > > implementation (glibc, sanitizers) and the application. ... > so one approach is to just disallow user tags, only sanitizer > and similar tools can tag (and i think hwasan can coordinate > with glibc via less formal api/abi that we can change later) to expand on this: i think we should just focus on the hwasan use-case. there may be other use-cases for tagged addresses, but we need more experience before we can design a generic api. hwasan can just poke at implementation internals and have target specific logic for now. allowing application code to use the tag bits can break c semantics and compiler assumptions too easily. and we should not require hwasan to use libc apis to work with tagged addresses, that would slow it down. so i think we don't need the tagged address representation related apis. we may need something __hwasan_init can call to set up os support. on aarch64 that's a prctl now, but a libc api would allow us to disable hwasan from glibc (e.g. if there are elf markings for incompatible dsos), i don't know if that makes sense (does hwasan have a fall back if there is no os support?).