From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- Documentation/virt/coco/tdx-guest.rst | 52 +++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 Documentation/virt/coco/tdx-guest.rst (limited to 'Documentation/virt/coco/tdx-guest.rst') diff --git a/Documentation/virt/coco/tdx-guest.rst b/Documentation/virt/coco/tdx-guest.rst new file mode 100644 index 000000000..46e316db6 --- /dev/null +++ b/Documentation/virt/coco/tdx-guest.rst @@ -0,0 +1,52 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================================================================== +TDX Guest API Documentation +=================================================================== + +1. General description +====================== + +The TDX guest driver exposes IOCTL interfaces via the /dev/tdx-guest misc +device to allow userspace to get certain TDX guest-specific details. + +2. API description +================== + +In this section, for each supported IOCTL, the following information is +provided along with a generic description. + +:Input parameters: Parameters passed to the IOCTL and related details. +:Output: Details about output data and return value (with details about + the non common error values). + +2.1 TDX_CMD_GET_REPORT0 +----------------------- + +:Input parameters: struct tdx_report_req +:Output: Upon successful execution, TDREPORT data is copied to + tdx_report_req.tdreport and return 0. Return -EINVAL for invalid + operands, -EIO on TDCALL failure or standard error number on other + common failures. + +The TDX_CMD_GET_REPORT0 IOCTL can be used by the attestation software to get +the TDREPORT0 (a.k.a. TDREPORT subtype 0) from the TDX module using +TDCALL[TDG.MR.REPORT]. + +A subtype index is added at the end of this IOCTL CMD to uniquely identify the +subtype-specific TDREPORT request. Although the subtype option is mentioned in +the TDX Module v1.0 specification, section titled "TDG.MR.REPORT", it is not +currently used, and it expects this value to be 0. So to keep the IOCTL +implementation simple, the subtype option was not included as part of the input +ABI. However, in the future, if the TDX Module supports more than one subtype, +a new IOCTL CMD will be created to handle it. To keep the IOCTL naming +consistent, a subtype index is added as part of the IOCTL CMD. + +Reference +--------- + +TDX reference material is collected here: + +https://www.intel.com/content/www/us/en/developer/articles/technical/intel-trust-domain-extensions.html + +The driver is based on TDX module specification v1.0 and TDX GHCI specification v1.0. -- cgit v1.3.1