/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Copyright (C) 2019-2022 Red Hat, Inc. Daniel Bristot de Oliveira <bristot@kernel.org>
 *
 * 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>

/*
 * Per-cpu variables require a unique name although static in some
 * configurations (e.g. CONFIG_DEBUG_FORCE_WEAK_PER_CPU or alpha modules).
 */
#define DA_MON_NAME CONCATENATE(da_mon_, MONITOR_NAME)

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_NAME;

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

/*
 * 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_NAME);

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

/*
 * 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_NAME, 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