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 v3:
- Rebased on 5.19
(rostedt's request were made on 1x1 meetings)
- Moved monitors to monitors/$name/ (Rostedt)
- Consolidate the tracepoints into a single include file in the default
directory (trave/events/rv.h) (Rostedt)
- The tracepoints now record the entire string to the buffer.
- Change the enable_monitors to disable monitors with ! (instead of -).
(Rostedt)
- Add a suffix to the state/events enums, to avoid conflict in the
vmlinux.h used by eBPF.
- The models are now placed in the $name.h (it used to store the
tracepoints, but they are now consolidated in a single file)
- dot2c and dot2k updated to the changes
- models re-generated with these new standards.
- user-space tools moved to an directory outside of tools/tracing as
other methods of verification/log sources are planned.
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
- dot2bpf
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 a 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 | 284 +++++++
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 | 38 +
include/linux/sched.h | 11 +
include/linux/watchdog.h | 7 +-
include/rv/automata.h | 49 ++
include/rv/da_monitor.h | 419 ++++++++++
include/rv/instrumentation.h | 23 +
include/rv/rv.h | 32 +
include/trace/events/rv.h | 153 ++++
include/trace/events/watchdog.h | 101 +++
kernel/fork.c | 14 +
kernel/trace/Kconfig | 2 +
kernel/trace/Makefile | 2 +
kernel/trace/rv/Kconfig | 84 ++
kernel/trace/rv/Makefile | 9 +
kernel/trace/rv/monitors/safe_wtd/safe_wtd.c | 300 +++++++
kernel/trace/rv/monitors/safe_wtd/safe_wtd.h | 84 ++
kernel/trace/rv/monitors/wip/wip.c | 110 +++
kernel/trace/rv/monitors/wip/wip.h | 38 +
kernel/trace/rv/monitors/wwnr/wwnr.c | 109 +++
kernel/trace/rv/monitors/wwnr/wwnr.h | 38 +
kernel/trace/rv/reactor_panic.c | 44 +
kernel/trace/rv/reactor_printk.c | 43 +
kernel/trace/rv/rv.c | 757 ++++++++++++++++++
kernel/trace/rv/rv.h | 54 ++
kernel/trace/rv/rv_reactors.c | 476 +++++++++++
kernel/trace/trace.c | 4 +
kernel/trace/trace.h | 2 +
tools/verification/dot2/Makefile | 26 +
tools/verification/dot2/automata.py | 179 +++++
tools/verification/dot2/dot2c | 30 +
tools/verification/dot2/dot2c.py | 244 ++++++
tools/verification/dot2/dot2k | 50 ++
tools/verification/dot2/dot2k.py | 177 ++++
.../dot2/dot2k_templates/main_global.c | 94 +++
.../dot2/dot2k_templates/main_per_cpu.c | 94 +++
.../dot2/dot2k_templates/main_per_task.c | 94 +++
tools/verification/safety_app/Makefile | 51 ++
tools/verification/safety_app/safety_app.c | 614 ++++++++++++++
46 files changed, 5691 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/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/monitors/safe_wtd/safe_wtd.c
create mode 100644 kernel/trace/rv/monitors/safe_wtd/safe_wtd.h
create mode 100644 kernel/trace/rv/monitors/wip/wip.c
create mode 100644 kernel/trace/rv/monitors/wip/wip.h
create mode 100644 kernel/trace/rv/monitors/wwnr/wwnr.c
create mode 100644 kernel/trace/rv/monitors/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 kernel/trace/rv/rv_reactors.c
create mode 100644 tools/verification/dot2/Makefile
create mode 100644 tools/verification/dot2/automata.py
create mode 100644 tools/verification/dot2/dot2c
create mode 100644 tools/verification/dot2/dot2c.py
create mode 100644 tools/verification/dot2/dot2k
create mode 100644 tools/verification/dot2/dot2k.py
create mode 100644 tools/verification/dot2/dot2k_templates/main_global.c
create mode 100644 tools/verification/dot2/dot2k_templates/main_per_cpu.c
create mode 100644 tools/verification/dot2/dot2k_templates/main_per_task.c
create mode 100644 tools/verification/safety_app/Makefile
create mode 100644 tools/verification/safety_app/safety_app.c
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2.35.1
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