rv/include: Add helper functions for deterministic automata

Formally, a deterministic automaton, denoted by G, is defined as a
quintuple:

  G = { X, E, f, x_0, X_m }

where:
	- X is the set of states;
	- E is the finite set of events;
	- x_0 is the initial state;
	- X_m (subset of X) is the set of marked states.
	- f : X x E -> X $ is the transition function. It defines the
	  state transition in the occurrence of a event from E in
	  the state X. In the special case of deterministic automata,
	  the occurrence of the event in E in a state in X has a
	  deterministic next state from X.

An automaton can also be represented using a graphical format of
vertices (nodes) and edges. The open-source tool Graphviz can produce
this graphic format using the (textual) DOT language as the source code.

The dot2c tool presented in 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.

Translates a deterministic automaton in the DOT format into a C
source code representation that to be used for monitoring.

This header file implements helper functions to facilitate the usage
of the C output from dot2c/k for monitoring.

Link: https://lkml.kernel.org/r/563234f2bfa84b540f60cf9e39c2d9f0eea95a55.1659052063.git.bristot@kernel.org

Cc: Wim Van Sebroeck <wim@linux-watchdog.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Gabriele Paoloni <gpaoloni@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Tao Zhou <tao.zhou@linux.dev>
Cc: Randy Dunlap <rdunlap@infradead.org>
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 <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

include/rv/automata.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019-2022 Red Hat, Inc. Daniel Bristot de Oliveira  <bristot@kernel.org>
+ *
+ * Deterministic automata helper functions, to be used with the automata
+ * models in C generated by the dot2k tool.
+ */
+
+/*
+ * DECLARE_AUTOMATA_HELPERS - define a set of helper functions for automata
+ *
+ * Define a set of helper functions for automata. The 'name' argument is used
+ * as suffix for the functions and data. These functions will handle automaton
+ * with data type 'type'.
+ */
+#define DECLARE_AUTOMATA_HELPERS(name, type)					\
+										\
+/*										\
+ * model_get_state_name_##name - return the (string) name of the given state	\
+ */ 										\
+static char *model_get_state_name_##name(enum states_##name state)		\
+{										\
+	if ((state < 0) || (state >= state_max_##name))				\
+		return "INVALID";						\
+										\
+	return automaton_##name.state_names[state];				\
+}										\
+										\
+/*										\
+ * model_get_event_name_##name - return the (string) name of the given event	\
+ */										\
+static char *model_get_event_name_##name(enum events_##name event)		\
+{										\
+	if ((event < 0) || (event >= event_max_##name))				\
+		return "INVALID";						\
+										\
+	return automaton_##name.event_names[event];				\
+}										\
+										\
+/*										\
+ * model_get_initial_state_##name - return the automaton's initial state		\
+ */										\
+static inline type model_get_initial_state_##name(void)				\
+{										\
+	return automaton_##name.initial_state;					\
+}										\
+										\
+/*										\
+ * model_get_next_state_##name - process an automaton event occurrence		\
+ *										\
+ * Given the current state (curr_state) and the event (event), returns		\
+ * the next state, or INVALID_STATE in case of error.				\
+ */										\
+static inline type model_get_next_state_##name(enum states_##name curr_state,	\
+					       enum events_##name event)	\
+{										\
+	if ((curr_state < 0) || (curr_state >= state_max_##name))		\
+		return INVALID_STATE;						\
+										\
+	if ((event < 0) || (event >= event_max_##name))				\
+		return INVALID_STATE;						\
+										\
+	return automaton_##name.function[curr_state][event];			\
+}										\
+										\
+/*										\
+ * model_is_final_state_##name - check if the given state is a final state	\
+ */										\
+static inline bool model_is_final_state_##name(enum states_##name state)	\
+{										\
+	if ((state < 0) || (state >= state_max_##name))				\
+		return 0;							\
+										\
+	return automaton_##name.final_states[state];				\
+}