da_monitor.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Copyright (C) 2019-2022 Red Hat, Inc. Daniel Bristot de Oliveira <[email protected]>
 *
 * Deterministic automata (DA) monitor functions, to be used together
 * 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/monitor_synthesis.rst
 */

#ifndef _RV_DA_MONITOR_H
#define _RV_DA_MONITOR_H

#include <rv/automata.h>
#include <linux/rv.h>
#include <linux/stringify.h>
#include <linux/bug.h>
#include <linux/sched.h>

static struct rv_monitor rv_this;

static void react(enum states curr_state, enum events event)
{
	rv_react(&rv_this,
		 "rv: monitor %s does not allow event %s on state %s\n",
		 __stringify(MONITOR_NAME),
		 model_get_event_name(event),
		 model_get_state_name(curr_state));
}

/*
 * da_monitor_reset - reset a monitor and setting it to init state
 */
static inline void da_monitor_reset(struct da_monitor *da_mon)
{
	da_mon->monitoring = 0;
	da_mon->curr_state = model_get_initial_state();
}

/*
 * da_monitor_start - start monitoring
 *
 * The monitor will ignore all events until monitoring is set to true. This
 * function needs to be called to tell the monitor to start monitoring.
 */
static inline void da_monitor_start(struct da_monitor *da_mon)
{
	da_mon->curr_state = model_get_initial_state();
	da_mon->monitoring = 1;
}

/*
 * da_monitoring - returns true if the monitor is processing events
 */
static inline bool da_monitoring(struct da_monitor *da_mon)
{
	return da_mon->monitoring;
}

/*
 * da_monitor_enabled - checks if the monitor is enabled
 */
static inline bool da_monitor_enabled(void)
{
	/* global switch */
	if (unlikely(!rv_monitoring_on()))
		return 0;

	/* monitor enabled */
	if (unlikely(!rv_this.enabled))
		return 0;

	return 1;
}

/*
 * da_monitor_handling_event - checks if the monitor is ready to handle events
 */
static inline bool da_monitor_handling_event(struct da_monitor *da_mon)
{
	if (!da_monitor_enabled())
		return 0;

	/* monitor is actually monitoring */
	if (unlikely(!da_monitoring(da_mon)))
		return 0;

	return 1;
}

#if RV_MON_TYPE == RV_MON_GLOBAL || RV_MON_TYPE == RV_MON_PER_CPU
/*
 * Event handler for implicit monitors. Implicit monitor is the one which the
 * handler does not need to specify which da_monitor to manipulate. Examples
 * of implicit monitor are the per_cpu or the global ones.
 *
 * Retry in case there is a race between getting and setting the next state,
 * warn and reset the monitor if it runs out of retries. The monitor should be
 * able to handle various orders.
 */

static inline bool da_event(struct da_monitor *da_mon, enum events event)
{
	enum states curr_state, next_state;

	curr_state = READ_ONCE(da_mon->curr_state);
	for (int i = 0; i < MAX_DA_RETRY_RACING_EVENTS; i++) {
		next_state = model_get_next_state(curr_state, event);
		if (next_state == INVALID_STATE) {
			react(curr_state, event);
			CONCATENATE(trace_error_, MONITOR_NAME)(
				    model_get_state_name(curr_state),
				    model_get_event_name(event));
			return false;
		}
		if (likely(try_cmpxchg(&da_mon->curr_state, &curr_state, next_state))) {
			CONCATENATE(trace_event_, MONITOR_NAME)(
				    model_get_state_name(curr_state),
				    model_get_event_name(event),
				    model_get_state_name(next_state),
				    model_is_final_state(next_state));
			return true;
		}
	}

	trace_rv_retries_error(__stringify(MONITOR_NAME), model_get_event_name(event));
	pr_warn("rv: " __stringify(MAX_DA_RETRY_RACING_EVENTS)
		" retries reached for event %s, resetting monitor %s",
		model_get_event_name(event), __stringify(MONITOR_NAME));
	return false;
}

#elif RV_MON_TYPE == RV_MON_PER_TASK
/*
 * Event handler for per_task monitors.
 *
 * Retry in case there is a race between getting and setting the next state,
 * warn and reset the monitor if it runs out of retries. The monitor should be
 * able to handle various orders.
 */

static inline bool da_event(struct da_monitor *da_mon, struct task_struct *tsk,
			    enum events event)
{
	enum states curr_state, next_state;

	curr_state = READ_ONCE(da_mon->curr_state);
	for (int i = 0; i < MAX_DA_RETRY_RACING_EVENTS; i++) {
		next_state = model_get_next_state(curr_state, event);
		if (next_state == INVALID_STATE) {
			react(curr_state, event);
			CONCATENATE(trace_error_, MONITOR_NAME)(tsk->pid,
				    model_get_state_name(curr_state),
				    model_get_event_name(event));
			return false;
		}
		if (likely(try_cmpxchg(&da_mon->curr_state, &curr_state, next_state))) {
			CONCATENATE(trace_event_, MONITOR_NAME)(tsk->pid,
				    model_get_state_name(curr_state),
				    model_get_event_name(event),
				    model_get_state_name(next_state),
				    model_is_final_state(next_state));
			return true;
		}
	}

	trace_rv_retries_error(__stringify(MONITOR_NAME), model_get_event_name(event));
	pr_warn("rv: " __stringify(MAX_DA_RETRY_RACING_EVENTS)
		" retries reached for event %s, resetting monitor %s",
		model_get_event_name(event), __stringify(MONITOR_NAME));
	return false;
}
#endif /* RV_MON_TYPE */

#if RV_MON_TYPE == RV_MON_GLOBAL
/*
 * Functions to define, init and get a global monitor.
 */

/*
 * global monitor (a single variable)
 */
static struct da_monitor da_mon_this;

/*
 * da_get_monitor - return the global monitor address
 */
static struct da_monitor *da_get_monitor(void)
{
	return &da_mon_this;
}

/*
 * da_monitor_reset_all - reset the single monitor
 */
static void da_monitor_reset_all(void)
{
	da_monitor_reset(da_get_monitor());
}

/*
 * da_monitor_init - initialize a monitor
 */
static inline int da_monitor_init(void)
{
	da_monitor_reset_all();
	return 0;
}

/*
 * da_monitor_destroy - destroy the monitor
 */
static inline void da_monitor_destroy(void) { }

#elif RV_MON_TYPE == RV_MON_PER_CPU
/*
 * Functions to define, init and get a per-cpu monitor.
 */

/*
 * per-cpu monitor variables
 */
static DEFINE_PER_CPU(struct da_monitor, da_mon_this);

/*
 * da_get_monitor - return current CPU monitor address
 */
static struct da_monitor *da_get_monitor(void)
{
	return this_cpu_ptr(&da_mon_this);
}

/*
 * da_monitor_reset_all - reset all CPUs' monitor
 */
static void da_monitor_reset_all(void)
{
	struct da_monitor *da_mon;
	int cpu;

	for_each_cpu(cpu, cpu_online_mask) {
		da_mon = per_cpu_ptr(&da_mon_this, cpu);
		da_monitor_reset(da_mon);
	}
}

/*
 * da_monitor_init - initialize all CPUs' monitor
 */
static inline int da_monitor_init(void)
{
	da_monitor_reset_all();
	return 0;
}

/*
 * da_monitor_destroy - destroy the monitor
 */
static inline void da_monitor_destroy(void) { }

#elif RV_MON_TYPE == RV_MON_PER_TASK
/*
 * Functions to define, init and get a per-task monitor.
 */

/*
 * The per-task monitor is stored a vector in the task struct. This variable
 * stores the position on the vector reserved for this monitor.
 */
static int task_mon_slot = RV_PER_TASK_MONITOR_INIT;

/*
 * da_get_monitor - return the monitor in the allocated slot for tsk
 */
static inline struct da_monitor *da_get_monitor(struct task_struct *tsk)
{
	return &tsk->rv[task_mon_slot].da_mon;
}

static void da_monitor_reset_all(void)
{
	struct task_struct *g, *p;
	int cpu;

	read_lock(&tasklist_lock);
	for_each_process_thread(g, p)
		da_monitor_reset(da_get_monitor(p));
	for_each_present_cpu(cpu)
		da_monitor_reset(da_get_monitor(idle_task(cpu)));
	read_unlock(&tasklist_lock);
}

/*
 * da_monitor_init - initialize the per-task monitor
 *
 * Try to allocate a slot in the task's vector of monitors. If there
 * is an available slot, use it and reset all task's monitor.
 */
static int da_monitor_init(void)
{
	int slot;

	slot = rv_get_task_monitor_slot();
	if (slot < 0 || slot >= RV_PER_TASK_MONITOR_INIT)
		return slot;

	task_mon_slot = slot;

	da_monitor_reset_all();
	return 0;
}

/*
 * da_monitor_destroy - return the allocated slot
 */
static inline void da_monitor_destroy(void)
{
	if (task_mon_slot == RV_PER_TASK_MONITOR_INIT) {
		WARN_ONCE(1, "Disabling a disabled monitor: " __stringify(MONITOR_NAME));
		return;
	}
	rv_put_task_monitor_slot(task_mon_slot);
	task_mon_slot = RV_PER_TASK_MONITOR_INIT;
}
#endif /* RV_MON_TYPE */

#if RV_MON_TYPE == RV_MON_GLOBAL || RV_MON_TYPE == RV_MON_PER_CPU
/*
 * Handle event for implicit monitor: da_get_monitor() will figure out
 * the monitor.
 */

static inline void __da_handle_event(struct da_monitor *da_mon,
				     enum events event)
{
	bool retval;

	retval = da_event(da_mon, event);
	if (!retval)
		da_monitor_reset(da_mon);
}

/*
 * da_handle_event - handle an event
 */
static inline void da_handle_event(enum events event)
{
	struct da_monitor *da_mon = da_get_monitor();
	bool retval;

	retval = da_monitor_handling_event(da_mon);
	if (!retval)
		return;

	__da_handle_event(da_mon, event);
}

/*
 * da_handle_start_event - start monitoring or handle event
 *
 * This function is used to notify the monitor that the system is returning
 * to the initial state, so the monitor can start monitoring in the next event.
 * Thus:
 *
 * If the monitor already started, handle the event.
 * If the monitor did not start yet, start the monitor but skip the event.
 */
static inline bool da_handle_start_event(enum events event)
{
	struct da_monitor *da_mon;

	if (!da_monitor_enabled())
		return 0;

	da_mon = da_get_monitor();

	if (unlikely(!da_monitoring(da_mon))) {
		da_monitor_start(da_mon);
		return 0;
	}

	__da_handle_event(da_mon, event);

	return 1;
}

/*
 * da_handle_start_run_event - start monitoring and handle event
 *
 * This function is used to notify the monitor that the system is in the
 * initial state, so the monitor can start monitoring and handling event.
 */
static inline bool da_handle_start_run_event(enum events event)
{
	struct da_monitor *da_mon;

	if (!da_monitor_enabled())
		return 0;

	da_mon = da_get_monitor();

	if (unlikely(!da_monitoring(da_mon)))
		da_monitor_start(da_mon);

	__da_handle_event(da_mon, event);

	return 1;
}

#elif RV_MON_TYPE == RV_MON_PER_TASK
/*
 * Handle event for per task.
 */

static inline void __da_handle_event(struct da_monitor *da_mon,
				     struct task_struct *tsk, enum events event)
{
	bool retval;

	retval = da_event(da_mon, tsk, event);
	if (!retval)
		da_monitor_reset(da_mon);
}

/*
 * da_handle_event - handle an event
 */
static inline void da_handle_event(struct task_struct *tsk, enum events event)
{
	struct da_monitor *da_mon = da_get_monitor(tsk);
	bool retval;

	retval = da_monitor_handling_event(da_mon);
	if (!retval)
		return;

	__da_handle_event(da_mon, tsk, event);
}

/*
 * da_handle_start_event - start monitoring or handle event
 *
 * This function is used to notify the monitor that the system is returning
 * to the initial state, so the monitor can start monitoring in the next event.
 * Thus:
 *
 * If the monitor already started, handle the event.
 * If the monitor did not start yet, start the monitor but skip the event.
 */
static inline bool da_handle_start_event(struct task_struct *tsk,
					 enum events event)
{
	struct da_monitor *da_mon;

	if (!da_monitor_enabled())
		return 0;

	da_mon = da_get_monitor(tsk);

	if (unlikely(!da_monitoring(da_mon))) {
		da_monitor_start(da_mon);
		return 0;
	}

	__da_handle_event(da_mon, tsk, event);

	return 1;
}

/*
 * da_handle_start_run_event - start monitoring and handle event
 *
 * This function is used to notify the monitor that the system is in the
 * initial state, so the monitor can start monitoring and handling event.
 */
static inline bool da_handle_start_run_event(struct task_struct *tsk,
					     enum events event)
{
	struct da_monitor *da_mon;

	if (!da_monitor_enabled())
		return 0;

	da_mon = da_get_monitor(tsk);

	if (unlikely(!da_monitoring(da_mon)))
		da_monitor_start(da_mon);

	__da_handle_event(da_mon, tsk, event);

	return 1;
}
#endif /* RV_MON_TYPE */

#endif