Over the last years, I've been exploring the possibility of verifying the Linux kernel behavior using Runtime Verification. Runtime Verification (RV) is a lightweight (yet rigorous) method that complements classical exhaustive verification techniques (such as model checking and theorem proving) with a more practical approach for complex systems. Instead of relying on a fine-grained model of a system (e.g., a re-implementation a instruction level), RV works by analyzing the trace of the system's actual execution, comparing it against a formal specification of the system behavior. The usage of deterministic automaton for RV is a well-established approach. In the specific case of the Linux kernel, you can check how to model complex behavior of the Linux kernel with this paper: DE OLIVEIRA, Daniel Bristot; CUCINOTTA, Tommaso; DE OLIVEIRA, Romulo Silva. *Efficient formal verification for the Linux kernel.* In: International Conference on Software Engineering and Formal Methods. Springer, Cham, 2019. p. 315-332. And how efficient is this approach here: DE OLIVEIRA, Daniel B.; DE OLIVEIRA, Romulo S.; CUCINOTTA, Tommaso. *A thread synchronization model for the PREEMPT_RT Linux kernel.* Journal of Systems Architecture, 2020, 107: 101729. tlrd: it is possible to model complex behaviors in a modular way, with an acceptable overhead (even for production systems). See this presentation at 2019's ELCE: https://www.youtube.com/watch?v=BfTuEHafNgg Here I am proposing a more practical approach for the usage of deterministic automata for runtime verification, and it includes: - An interface for controlling the verification; - A tool and set of headers that enables the automatic code generation of the RV monitor (Monitor Synthesis); - Sample monitors to evaluate the interface; - A sample monitor developed in the context of the Elisa Project demonstrating how to use RV in the context of safety-critical systems. Given that RV is a tracing consumer, the code is being placed inside the tracing subsystem (Steven and I have been talking about it for a while). Changes from v2: - Tons of checkpatch and kernel test robot - Moved files to better places - Adjusted watchdog tracepoints patch (Guenter Roeck) - Added pretimeout watchdog events (Peter Enderborg) - Used task struct to store per-task monitors (Peter Zijlstra) - Changed the instrumentation to use internal definition of tracepoint and check the callback signature (Steven Rostedt) - Used printk_deferred() and removed the comment about deadlocks (Shuah Khan/John Ogness) - Some simplifications: - Removed the safe watchdog nowayout for now (myself) - Removed export symbols for now (myself) Changes from V1: - rebased to the latest kernel; - code cleanup; - the watchdog dev monitor; - safety app; Things kept for a second moment (after this patchset): - Add a reactor tha enables the visualization of the visited states via KCOV (Marco Elver & Dmitry Vyukov) - Add a CRC method to check from user-space if the values exported by the monitor were not corrupted by any other kernel task (Gabriele Paoloni) - Export symbols for external modules Daniel Bristot de Oliveira (20): rv: Add Runtime Verification (RV) interface rv: Add runtime reactors interface rv/include: Add helper functions for deterministic automata rv/include: Add deterministic automata monitor definition via C macros rv/include: Add instrumentation helper functions tools/rv: Add dot2c tools/rv: Add dot2k rv/monitor: Add the wip monitor skeleton created by dot2k rv/monitor: wip instrumentation and Makefile/Kconfig entries rv/monitor: Add the wwnr monitor skeleton created by dot2k rv/monitor: wwnr instrumentation and Makefile/Kconfig entries rv/reactor: Add the printk reactor rv/reactor: Add the panic reactor Documentation/rv: Add a basic documentation Documentation/rv: Add deterministic automata monitor synthesis documentation Documentation/rv: Add deterministic automata instrumentation documentation watchdog/dev: Add tracepoints rv/monitor: Add safe watchdog monitor rv/safety_app: Add an safety_app sample Documentation/rv: Add watchdog-monitor documentation Documentation/trace/index.rst | 1 + .../trace/rv/da_monitor_instrumentation.rst | 223 ++++++ .../trace/rv/da_monitor_synthesis.rst | 286 +++++++ Documentation/trace/rv/index.rst | 9 + .../trace/rv/runtime-verification.rst | 233 ++++++ Documentation/trace/rv/watchdog-monitor.rst | 250 ++++++ drivers/watchdog/watchdog_dev.c | 43 +- drivers/watchdog/watchdog_pretimeout.c | 2 + include/linux/rv.h | 36 + include/linux/sched.h | 11 + include/linux/watchdog.h | 7 +- include/rv/automata.h | 49 ++ include/rv/da_monitor.h | 421 ++++++++++ include/rv/instrumentation.h | 23 + include/rv/rv.h | 32 + include/trace/events/watchdog.h | 101 +++ kernel/fork.c | 14 + kernel/trace/Kconfig | 2 + kernel/trace/Makefile | 2 + kernel/trace/rv/Kconfig | 68 ++ kernel/trace/rv/Makefile | 9 + kernel/trace/rv/monitor_safe_wtd/model.h | 84 ++ kernel/trace/rv/monitor_safe_wtd/safe_wtd.c | 302 +++++++ kernel/trace/rv/monitor_safe_wtd/safe_wtd.h | 64 ++ kernel/trace/rv/monitor_wip/model.h | 38 + kernel/trace/rv/monitor_wip/wip.c | 112 +++ kernel/trace/rv/monitor_wip/wip.h | 64 ++ kernel/trace/rv/monitor_wwnr/model.h | 38 + kernel/trace/rv/monitor_wwnr/wwnr.c | 110 +++ kernel/trace/rv/monitor_wwnr/wwnr.h | 70 ++ kernel/trace/rv/reactor_panic.c | 44 + kernel/trace/rv/reactor_printk.c | 43 + kernel/trace/rv/rv.c | 752 ++++++++++++++++++ kernel/trace/rv/rv.h | 54 ++ kernel/trace/trace.c | 4 + kernel/trace/trace.h | 2 + tools/tracing/rv/dot2/Makefile | 26 + tools/tracing/rv/dot2/automata.py | 179 +++++ tools/tracing/rv/dot2/dot2c | 30 + tools/tracing/rv/dot2/dot2c.py | 240 ++++++ tools/tracing/rv/dot2/dot2k | 46 ++ tools/tracing/rv/dot2/dot2k.py | 188 +++++ .../rv/dot2/dot2k_templates/main_global.c | 97 +++ .../rv/dot2/dot2k_templates/main_global.h | 64 ++ .../rv/dot2/dot2k_templates/main_per_cpu.c | 97 +++ .../rv/dot2/dot2k_templates/main_per_cpu.h | 64 ++ .../rv/dot2/dot2k_templates/main_per_task.c | 97 +++ .../rv/dot2/dot2k_templates/main_per_task.h | 70 ++ tools/tracing/rv/safety_app/Makefile | 51 ++ tools/tracing/rv/safety_app/safety_app.c | 645 +++++++++++++++ 50 files changed, 5487 insertions(+), 10 deletions(-) create mode 100644 Documentation/trace/rv/da_monitor_instrumentation.rst create mode 100644 Documentation/trace/rv/da_monitor_synthesis.rst create mode 100644 Documentation/trace/rv/index.rst create mode 100644 Documentation/trace/rv/runtime-verification.rst create mode 100644 Documentation/trace/rv/watchdog-monitor.rst create mode 100644 include/linux/rv.h create mode 100644 include/rv/automata.h create mode 100644 include/rv/da_monitor.h create mode 100644 include/rv/instrumentation.h create mode 100644 include/rv/rv.h create mode 100644 include/trace/events/watchdog.h create mode 100644 kernel/trace/rv/Kconfig create mode 100644 kernel/trace/rv/Makefile create mode 100644 kernel/trace/rv/monitor_safe_wtd/model.h create mode 100644 kernel/trace/rv/monitor_safe_wtd/safe_wtd.c create mode 100644 kernel/trace/rv/monitor_safe_wtd/safe_wtd.h create mode 100644 kernel/trace/rv/monitor_wip/model.h create mode 100644 kernel/trace/rv/monitor_wip/wip.c create mode 100644 kernel/trace/rv/monitor_wip/wip.h create mode 100644 kernel/trace/rv/monitor_wwnr/model.h create mode 100644 kernel/trace/rv/monitor_wwnr/wwnr.c create mode 100644 kernel/trace/rv/monitor_wwnr/wwnr.h create mode 100644 kernel/trace/rv/reactor_panic.c create mode 100644 kernel/trace/rv/reactor_printk.c create mode 100644 kernel/trace/rv/rv.c create mode 100644 kernel/trace/rv/rv.h create mode 100644 tools/tracing/rv/dot2/Makefile create mode 100644 tools/tracing/rv/dot2/automata.py create mode 100644 tools/tracing/rv/dot2/dot2c create mode 100644 tools/tracing/rv/dot2/dot2c.py create mode 100644 tools/tracing/rv/dot2/dot2k create mode 100644 tools/tracing/rv/dot2/dot2k.py create mode 100644 tools/tracing/rv/dot2/dot2k_templates/main_global.c create mode 100644 tools/tracing/rv/dot2/dot2k_templates/main_global.h create mode 100644 tools/tracing/rv/dot2/dot2k_templates/main_per_cpu.c create mode 100644 tools/tracing/rv/dot2/dot2k_templates/main_per_cpu.h create mode 100644 tools/tracing/rv/dot2/dot2k_templates/main_per_task.c create mode 100644 tools/tracing/rv/dot2/dot2k_templates/main_per_task.h create mode 100644 tools/tracing/rv/safety_app/Makefile create mode 100644 tools/tracing/rv/safety_app/safety_app.c -- 2.35.1
