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/tools/rtla/rtla-timerlat.rst | 54 ++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 Documentation/tools/rtla/rtla-timerlat.rst (limited to 'Documentation/tools/rtla/rtla-timerlat.rst') diff --git a/Documentation/tools/rtla/rtla-timerlat.rst b/Documentation/tools/rtla/rtla-timerlat.rst new file mode 100644 index 000000000..63718c52a --- /dev/null +++ b/Documentation/tools/rtla/rtla-timerlat.rst @@ -0,0 +1,54 @@ +================ +rtla-timerlat +================ +------------------------------------------- +Measures the operating system timer latency +------------------------------------------- + +:Manual section: 1 + +SYNOPSIS +======== +**rtla timerlat** [*MODE*] ... + +DESCRIPTION +=========== + +.. include:: common_timerlat_description.txt + +The **rtla timerlat top** mode displays a summary of the periodic output +from the *timerlat* tracer. The **rtla timerlat hist** mode displays +a histogram of each tracer event occurrence. For further details, please +refer to the respective man page. + +MODES +===== +**top** + + Prints the summary from *timerlat* tracer. + +**hist** + + Prints a histogram of timerlat samples. + +If no *MODE* is given, the top mode is called, passing the arguments. + +OPTIONS +======= +**-h**, **--help** + + Display the help text. + +For other options, see the man page for the corresponding mode. + +SEE ALSO +======== +**rtla-timerlat-top**\(1), **rtla-timerlat-hist**\(1) + +`Timerlat tracer `__ + +AUTHOR +====== +Written by Daniel Bristot de Oliveira + +.. include:: common_appendix.txt -- cgit v1.3.1