From patchwork Mon Jul 25 20:11:22 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Bristot de Oliveira X-Patchwork-Id: 12928362 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26199CCA48A for ; Mon, 25 Jul 2022 20:13:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236861AbiGYUNR (ORCPT ); Mon, 25 Jul 2022 16:13:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45076 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236845AbiGYUMs (ORCPT ); Mon, 25 Jul 2022 16:12:48 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 959E2220D5; Mon, 25 Jul 2022 13:12:41 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 327546114C; Mon, 25 Jul 2022 20:12:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0FE46C385A2; Mon, 25 Jul 2022 20:12:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658779960; bh=SiKAfcK1PLJNKE6AM2WSYxQBh8UVxnM60QtN2Z1WFCo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YVSNiUG8K+p5Uh0oCEJv8lT0dhZZEle8YhOFfxa2UjfTwAVSbzhZAzdHBDA4nRk2z 0FI5mfquDbeH4jWBtSFejTII14WphZMVH/lII67AMl9NDRjK/A8iwmLyy7z6tmaNiR xxXvv/MNVZz+4GATIKa7I+ziAlJDunDnvjleU9WSADHW2LKhuKYbEr0lteDiDgL1jg 22o0w86G5fMeL3rHNKXvQjDYgAGaEZ0RoP1q/40Ssk6lfA7CAYxMnIAqQbMJXi4YB8 xmUF+UPMda+DHFAjtC2hE5WCFQKFzfiYFdhPdEMFlQEW5XMTX6hlLJLdeUbDKZvyCt 4FlsbcPGGjtpw== From: Daniel Bristot de Oliveira To: Steven Rostedt Cc: Daniel Bristot de Oliveira , Wim Van Sebroeck , Guenter Roeck , Jonathan Corbet , Ingo Molnar , Thomas Gleixner , Peter Zijlstra , Will Deacon , Catalin Marinas , Marco Elver , Dmitry Vyukov , "Paul E. McKenney" , Shuah Khan , Gabriele Paoloni , Juri Lelli , Clark Williams , Tao Zhou , Randy Dunlap , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-devel@vger.kernel.org Subject: [PATCH V7 10/16] Documentation/rv: Add deterministic automata monitor synthesis documentation Date: Mon, 25 Jul 2022 22:11:22 +0200 Message-Id: X-Mailer: git-send-email 2.35.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org Add the da_monitor_synthesis.rst introduces some concepts behind the Deterministic Automata (DA) monitor synthesis and interface. Cc: Wim Van Sebroeck Cc: Guenter Roeck Cc: Jonathan Corbet Cc: Steven Rostedt Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Will Deacon Cc: Catalin Marinas Cc: Marco Elver Cc: Dmitry Vyukov Cc: "Paul E. McKenney" Cc: Shuah Khan Cc: Gabriele Paoloni Cc: Juri Lelli Cc: Clark Williams Cc: Tao Zhou Cc: Randy Dunlap Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-trace-devel@vger.kernel.org Signed-off-by: Daniel Bristot de Oliveira --- .../trace/rv/da_monitor_synthesis.rst | 147 ++++++++++++++++++ Documentation/trace/rv/index.rst | 1 + include/rv/da_monitor.h | 3 + tools/verification/dot2/dot2k | 3 + tools/verification/dot2/dot2k.py | 3 + 5 files changed, 157 insertions(+) create mode 100644 Documentation/trace/rv/da_monitor_synthesis.rst diff --git a/Documentation/trace/rv/da_monitor_synthesis.rst b/Documentation/trace/rv/da_monitor_synthesis.rst new file mode 100644 index 000000000000..0dbdcd1e62b9 --- /dev/null +++ b/Documentation/trace/rv/da_monitor_synthesis.rst @@ -0,0 +1,147 @@ +Deterministic Automata Monitor Synthesis +======================================== + +The starting point for the application of runtime verification (RV) technics +is the *specification* or *modeling* of the desired (or undesired) behavior +of the system under scrutiny. + +The formal representation needs to be then *synthesized* into a *monitor* +that can then be used in the analysis of the trace of the system. The +*monitor* connects to the system via an *instrumentation* that converts +the events from the *system* to the events of the *specification*. + + +In Linux terms, the runtime verification monitors are encapsulated inside +the *RV monitor* abstraction. The RV monitor includes a set of instances +of the monitor (per-cpu monitor, per-task monitor, and so on), the helper +functions that glue the monitor to the system reference model, and the +trace output as a reaction to event parsing and exceptions, as depicted +below:: + + Linux +----- RV Monitor ----------------------------------+ Formal + Realm | | Realm + +-------------------+ +----------------+ +-----------------+ + | Linux kernel | | Monitor | | Reference | + | Tracing | -> | Instance(s) | <- | Model | + | (instrumentation) | | (verification) | | (specification) | + +-------------------+ +----------------+ +-----------------+ + | | | + | V | + | +----------+ | + | | Reaction | | + | +--+--+--+-+ | + | | | | | + | | | +-> trace output ? | + +------------------------|--|----------------------+ + | +----> panic ? + +-------> + +DA monitor synthesis +-------------------- + +The synthesis of automata-based models into the Linux *RV monitor* abstraction +is automated by the dot2k tool and the rv/da_monitor.h header file that +contains a set of macros that automatically generate the monitor's code. + +dot2k +----- + +The dot2k utility leverages dot2c by converting an automaton model in +the DOT format into the C representation [1] and creating the skeleton of +a kernel monitor in C. + +For example, it is possible to transform the wip.dot model present in +[1] into a per-cpu monitor with the following command:: + + $ dot2k -d wip.dot -t per_cpu + +This will create a directory named wip/ with the following files: + +- wip.h: the wip model in C +- wip.c: the RV monitor + +The wip.c file contains the monitor declaration and the starting point for +the system instrumentation. + +Monitor macros +-------------- + +The rv/da_monitor.h enables automatic code generation for the *Monitor +Instance(s)* using C macros. + +The benefits of the usage of macro for monitor synthesis are 3-fold as it: + +- Reduces the code duplication; +- Facilitates the bug fix/improvement; +- Avoids the case of developers changing the core of the monitor code + to manipulate the model in a (let's say) non-standard way. + +This initial implementation presents three different types of monitor instances: + +- ``#define DECLARE_DA_MON_GLOBAL(name, type)`` +- ``#define DECLARE_DA_MON_PER_CPU(name, type)`` +- ``#define DECLARE_DA_MON_PER_TASK(name, type)`` + +The first declares the functions for a global deterministic automata monitor, +the second for monitors with per-cpu instances, and the third with per-task +instances. + +In all cases, the 'name' argument is a string that identifies the monitor, and +the 'type' argument is the data type used by dot2k on the representation of +the model in C. + +For example, the wip model with two states and three events can be +stored in an 'unsigned char' type. Considering that the preemption control +is a per-cpu behavior, the monitor declaration in the 'wip.c' file is:: + + DECLARE_DA_MON_PER_CPU(wip, unsigned char); + +The monitor is executed by sending events to be processed via the functions +presented below:: + + da_handle_event_$(MONITOR_NAME)($(event from event enum)); + da_handle_start_event_$(MONITOR_NAME)($(event from event enum)); + da_handle_start_run_event_$(MONITOR_NAME)($(event from event enum)); + +The function ``da_handle_event_$(MONITOR_NAME)()`` is the regular case where +the event will be processed if the monitor is processing events. + +When a monitor is enabled, it is placed in the initial state of the automata. +However, the monitor does not know if the system is in the *initial state*. + +The ``da_handle_start_event_$(MONITOR_NAME)()`` function is used to notify the +monitor that the system is returning to the initial state, so the monitor can +start monitoring the next event. + +The ``da_handle_start_run_event_$(MONITOR_NAME)()`` function is used to notify +the monitor that the system is known to be in the initial state, so the +monitor can start monitoring and monitor the current event. + +Using the wip model as example, the events "preempt_disable" and +"sched_waking" should be sent to monitor, respectively, via [2]:: + + da_handle_event_wip(preempt_disable_wip); + da_handle_event_wip(sched_waking_wip); + +While the event "preempt_enabled" will use:: + + da_handle_start_event_wip(preempt_enable_wip); + +To notify the monitor that the system will be returning to the initial state, +so the system and the monitor should be in sync. + +Final remarks +------------- + +With the monitor synthesis in place using the rv/da_monitor.h and +dot2k, the developer's work should be limited to the instrumentation +of the system, increasing the confidence in the overall approach. + +[1] For details about deterministic automata format and the translation +from one representation to another, see:: + + Documentation/trace/rv/deterministic_automata.rst + +[2] dot2k appends the monitor's name suffix to the events enums to +avoid conflicting variables when exporting the global vmlinux.h +use by BPF programs. diff --git a/Documentation/trace/rv/index.rst b/Documentation/trace/rv/index.rst index 013a41a410cf..46d47f33052c 100644 --- a/Documentation/trace/rv/index.rst +++ b/Documentation/trace/rv/index.rst @@ -8,3 +8,4 @@ Runtime Verification runtime-verification.rst deterministic_automata.rst + da_monitor_synthesis.rst diff --git a/include/rv/da_monitor.h b/include/rv/da_monitor.h index e14dad3ec4a8..f543efa0ed75 100644 --- a/include/rv/da_monitor.h +++ b/include/rv/da_monitor.h @@ -6,6 +6,9 @@ * with automata models in C generated by the dot2k tool. * * The dot2k tool is available at tools/verification/dot2k/ + * + * For further information, see: + * Documentation/trace/rv/da_monitor_synthesis.rst */ #include diff --git a/tools/verification/dot2/dot2k b/tools/verification/dot2/dot2k index 69106f4b7682..9dcd38abe20a 100644 --- a/tools/verification/dot2/dot2k +++ b/tools/verification/dot2/dot2k @@ -4,6 +4,9 @@ # Copyright (C) 2019-2022 Red Hat, Inc. Daniel Bristot de Oliveira # # dot2k: transform dot files into a monitor for the Linux kernel. +# +# For further information, see: +# Documentation/trace/rv/da_monitor_synthesis.rst if __name__ == '__main__': from dot2.dot2k import dot2k diff --git a/tools/verification/dot2/dot2k.py b/tools/verification/dot2/dot2k.py index 4eecd69c2568..2856e1ce1259 100644 --- a/tools/verification/dot2/dot2k.py +++ b/tools/verification/dot2/dot2k.py @@ -4,6 +4,9 @@ # Copyright (C) 2019-2022 Red Hat, Inc. Daniel Bristot de Oliveira # # dot2k: transform dot files into a monitor for the Linux kernel. +# +# For further information, see: +# Documentation/trace/rv/da_monitor_synthesis.rst from dot2.dot2c import Dot2c import platform