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/trace/sys-t.rst | 62 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 Documentation/trace/sys-t.rst (limited to 'Documentation/trace/sys-t.rst') diff --git a/Documentation/trace/sys-t.rst b/Documentation/trace/sys-t.rst new file mode 100644 index 000000000..3d8eb9273 --- /dev/null +++ b/Documentation/trace/sys-t.rst @@ -0,0 +1,62 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================== +MIPI SyS-T over STP +=================== + +The MIPI SyS-T protocol driver can be used with STM class devices to +generate standardized trace stream. Aside from being a standard, it +provides better trace source identification and timestamp correlation. + +In order to use the MIPI SyS-T protocol driver with your STM device, +first, you'll need CONFIG_STM_PROTO_SYS_T. + +Now, you can select which protocol driver you want to use when you create +a policy for your STM device, by specifying it in the policy name: + +# mkdir /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/ + +In other words, the policy name format is extended like this: + + :. + +With Intel TH, therefore it can look like "0-sth:p_sys-t.my-policy". + +If the protocol name is omitted, the STM class will chose whichever +protocol driver was loaded first. + +You can also double check that everything is working as expected by + +# cat /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/protocol +p_sys-t + +Now, with the MIPI SyS-T protocol driver, each policy node in the +configfs gets a few additional attributes, which determine per-source +parameters specific to the protocol: + +# mkdir /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/default +# ls /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/default +channels +clocksync_interval +do_len +masters +ts_interval +uuid + +The most important one here is the "uuid", which determines the UUID +that will be used to tag all data coming from this source. It is +automatically generated when a new node is created, but it is likely +that you would want to change it. + +do_len switches on/off the additional "payload length" field in the +MIPI SyS-T message header. It is off by default as the STP already +marks message boundaries. + +ts_interval and clocksync_interval determine how much time in milliseconds +can pass before we need to include a protocol (not transport, aka STP) +timestamp in a message header or send a CLOCKSYNC packet, respectively. + +See Documentation/ABI/testing/configfs-stp-policy-p_sys-t for more +details. + +* [1] https://www.mipi.org/specifications/sys-t -- cgit v1.3.1