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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?xxPUtHx/Cvyb9mA41850yieTFEM/C8PtZoqfuXBIsTq+NHas+X2cHKE/l12D?= =?us-ascii?Q?YkRTjjOUqt6pXhCOoQ6RsSR3oBsb4YHONZmUSqabQ97t3+I0V3CbvEqFXDdY?= =?us-ascii?Q?HBWxJBucCl5Bml/3hD9plMiiErontpsKZQUkYR18hdHLeoYwg0vnUz50edhI?= =?us-ascii?Q?9jDrb/EQGztKfBfWjMySYgdMkI0UaL3fmlUxYEJXQHytvbNYOL+MuDeTov4D?= =?us-ascii?Q?+ys68+eF8K9uoIOX4KbVhwkWcWDdPsbouqbIcLZwAyIjKeLyZ/NRQXs4TiuE?= =?us-ascii?Q?GH6j42pENwjDc9NOTFcAH2lMrnhgsk/iPJeRno+nR6pX2bFfXTajtIny8U9a?= =?us-ascii?Q?Rj2+d1Bi7QLj0o+9Be/555oCJxiCAea2j4zYOPc1nSl6nhaWbgWPnrWkQJVz?= =?us-ascii?Q?sVyNOO/P3u8uoo5EgSajXCZFnVIenU652NNI2BLme8vYR6zYOWndUvwbbDv2?= =?us-ascii?Q?VQeuCBc4yt2xJpvxUqL0QMMNbjna3MnYHk+Wy/VsmGEsJC3Mj8IqIkSKjjPb?= =?us-ascii?Q?D8n21IixxujdcdGiSKEuNqYvXj++F6bEJrs9EpZDNLq24YSegxiiQhnEWtlN?= =?us-ascii?Q?fMdt470oxwMQtAnDlyOgyFJmHePy3X/Y1mjQJN00wsrdZlqaSAxfVh3Ej49Z?= =?us-ascii?Q?ufdqZ9MtF5ivFZh3G0s4veaQ8BqgfYbgTm4msL2DrV+C0qi98fZ04JrQWi5q?= =?us-ascii?Q?w7QJ3Ll2+WgoqtcUwASxhN2p9SnUj9y9zyQqZFqkQNxc1/C44W/xyNxFdxsp?= =?us-ascii?Q?2QFVlvxGEp2x6Fdcss4JsWEMXrXkAj3oubcjqa/uDo8nGNmkmQN/3yYAPvQ9?= =?us-ascii?Q?5Rp7t9EKv2Jjv2f3Ug/GM3O4HZrMjOi7l7ElkgQcX7OC5LQ09rlr1wnOEmvp?= =?us-ascii?Q?trx3NioPMsyzR9Z+cBt7dVvtwf8TuIirJ/xVOBqyfRYxI+f9fjZbYxGo+ZmS?= =?us-ascii?Q?HhzRadeS6EnAE+RwMig5vNRTRzo/e0UUixx1WqxqB3Um0nthIR46RApKAsjY?= =?us-ascii?Q?+nh/Dl/k/VaB9S91/SRsXIcqEFGOKN3DZ2Iou4GlZPoF8IIo2y6o+aB/LJpT?= =?us-ascii?Q?rmeEkcqOnHTY19wnURfG0N90/wRAY1VLIAWGlzMb0jFY29MnpiMSr5T7XjNG?= =?us-ascii?Q?qOLM/gsRHesJP2zd2sJHU7CSRkAIMmKnoVupU+9EqO9AXEqlicyDBzZQHYWg?= =?us-ascii?Q?Y4hVGP5eFF7oPw/D8kDF0nNXXNWTgA2jfo5sTLWQ4fO0MaobYxxIPjsJkYgP?= =?us-ascii?Q?6C3WY4BD76pLrmVXzBw9YgSloRQnPY4IQ4Ak7C6S+7JXEXNH40zA8gaaVOO5?= =?us-ascii?Q?Bz4it0ly7J2tvrEs0VpZl5AGmZzqq4EmvjWb/gMiBgKAEU3UBQs5JJaJ/zVN?= =?us-ascii?Q?8anaSVmSXiyWiHSYCXkcNC6OFpMbT3s35F9BKwLQS4rX0LjRN19Pm935NnTz?= =?us-ascii?Q?6a8v8rV/ewckbLU3avtH97ghV74sUDAaG8zWD0on0HUodBsdG9YRr1oWmE+W?= =?us-ascii?Q?pzy8KOE04GhZI0kOK0gZfHKOVaxqoup+WVmPx7kaH5fdi8u2IBgiG0xHuwma?= =?us-ascii?Q?Su4cTstiNpr4Cx5o39kq/E5mzWN7us2CwI9lDgumj5vkbwW6RQ45GSg71O7y?= =?us-ascii?Q?rg=3D=3D?= X-OriginatorOrg: memverge.com X-MS-Exchange-CrossTenant-Network-Message-Id: 8699717f-7a11-4564-a8f1-08daffcda7c0 X-MS-Exchange-CrossTenant-AuthSource: BN6PR17MB3121.namprd17.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Jan 2023 18:46:37.6021 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 5c90cb59-37e7-4c81-9c07-00473d5fb682 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: z9zgQnR7GCz4Dd91bLy5ojZUXmzNLOmZcUcqLoqFw+/005VpYleOLzjyi3qA1HFJUK55l6jTdOEqvHwEnZfcElvkaa0T8LQWnJVVVGZ5GtQ= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR17MB6892 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 26, 2023 at 07:30:19PM +0100, Oleg Nesterov wrote: > On 01/26, Andrei Vagin wrote: > > > > On Thu, Jan 26, 2023 at 7:07 AM Oleg Nesterov wrote: > > > > > > IIUC, PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH is needed to run the injected > > > code, and this also needs to change the state of the traced process. If > > > the tracer (CRIU) dies while the tracee runs this code, I guess the tracee > > > will have other problems? > > > > Our injected code can reheal itself if something goes wrong. The hack > > here is that we inject > > the code with a signal frame and it calls rt_segreturn to resume the process. > > What will happen if CRIU dies and clears ->ptrace right before > syscall_user_dispatch() checks PT_SUSPEND_SYSCALL_USER_DISPATCH ? > > How the tracee will react to SIGSYS with unexpected .si_syscall ? > > > I don't expect that > > the syscall user dispatch > > is used by many applications, > > Agreed, so the case when CRIU will need to do the additional > PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG twice to disable and then re-enable > syscall_user_dispatch is unlikely. > > > so I don't strongly insist on > > PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH. > > I too won't argue too much. but so far I do not feel there is enough > justification for this feature ... > > Oleg. > I'm not married to the idea, just want to make sure I have the tools needed to make checkpoint work. The option seems like the easiest way given the exclusion area issue. One idea is to overwrite a portion of the exclusion area, but this obviously can increase the complexity of the checkpoint process. Another idea is to disable/enable SUD via get/set, but this produces potential detach issues. @Andrei i'm happy to take this to IRC or somewhere else out of band to discuss the checkpoint specifics, if that would be preferable and you are interested.