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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Oct 2024 14:41:54.6164 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1e6a908f-355d-49be-a175-08dcf8f0ffc8 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: AM2PEPF0001C70E.eurprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: GV1PR08MB7779 On Wed, Oct 30, 2024 at 02:08:59PM +0000, Mark Brown wrote: > On Sat, Oct 05, 2024 at 11:31:27AM +0100, Mark Brown wrote: > > The kernel has recently added support for shadow stacks, currently > > x86 only using their CET feature but both arm64 and RISC-V have > > equivalent features (GCS and Zicfiss respectively), I am actively > > working on GCS[1]. With shadow stacks the hardware maintains an > > additional stack containing only the return addresses for branch > > instructions which is not generally writeable by userspace and ensures > > that any returns are to the recorded addresses. This provides some > > protection against ROP attacks and making it easier to collect call > > stacks. These shadow stacks are allocated in the address space of the > > userspace process. > > Does anyone have any thoughts on this? I reworked things to specify the > address for the shadow stack pointer rather than the extent of the stack > as Rick and Yuri suggested, otherwise the only change from the prior > version was rebasing onto the arm64 GCS support since that's queued in > -next. I think the only substantial question is picking the ABI for > specifying the shadow stack. I will need more time to review this as both my primary and shadow stacks are full with other work. At a glance, I cannot offer any informed opinion for choosing ABI atm. Apologies for the delay. Kind regards, Yury