// SPDX-License-Identifier: GPL-2.0
/*
 * Generic dynamic event control interface
 *
 * Copyright (C) 2018 Masami Hiramatsu <mhiramat@kernel.org>
 */

#include <linux/debugfs.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/tracefs.h>

#include "trace.h"
#include "trace_dynevent.h"

static DEFINE_MUTEX(dyn_event_ops_mutex);
static LIST_HEAD(dyn_event_ops_list);

int dyn_event_register(struct dyn_event_operations *ops)
{
        if (!ops || !ops->create || !ops->show || !ops->is_busy ||
            !ops->free || !ops->match)
                return -EINVAL;

        INIT_LIST_HEAD(&ops->list);
        mutex_lock(&dyn_event_ops_mutex);
        list_add_tail(&ops->list, &dyn_event_ops_list);
        mutex_unlock(&dyn_event_ops_mutex);
        return 0;
}

int dyn_event_release(int argc, char **argv, struct dyn_event_operations *type)
{
        struct dyn_event *pos, *n;
        char *system = NULL, *event, *p;
        int ret = -ENOENT;

        if (argv[0][0] == '-') {
                if (argv[0][1] != ':')
                        return -EINVAL;
                event = &argv[0][2];
        } else {
                event = strchr(argv[0], ':');
                if (!event)
                        return -EINVAL;
                event++;
        }

        p = strchr(event, '/');
        if (p) {
                system = event;
                event = p + 1;
                *p = '\0';
        }
        if (event[0] == '\0')
                return -EINVAL;

        mutex_lock(&event_mutex);
        for_each_dyn_event_safe(pos, n) {
                if (type && type != pos->ops)
                        continue;
                if (pos->ops->match(system, event, pos)) {
                        ret = pos->ops->free(pos);
                        break;
                }
        }
        mutex_unlock(&event_mutex);

        return ret;
}

static int create_dyn_event(int argc, char **argv)
{
        struct dyn_event_operations *ops;
        int ret = -ENODEV;

        if (argv[0][0] == '-' || argv[0][0] == '!')
                return dyn_event_release(argc, argv, NULL);

        mutex_lock(&dyn_event_ops_mutex);
        list_for_each_entry(ops, &dyn_event_ops_list, list) {
                ret = ops->create(argc, (const char **)argv);
                if (!ret || ret != -ECANCELED)
                        break;
        }
        mutex_unlock(&dyn_event_ops_mutex);
        if (ret == -ECANCELED)
                ret = -EINVAL;

        return ret;
}

/* Protected by event_mutex */
LIST_HEAD(dyn_event_list);

void *dyn_event_seq_start(struct seq_file *m, loff_t *pos)
{
        mutex_lock(&event_mutex);
        return seq_list_start(&dyn_event_list, *pos);
}

void *dyn_event_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
        return seq_list_next(v, &dyn_event_list, pos);
}

void dyn_event_seq_stop(struct seq_file *m, void *v)
{
        mutex_unlock(&event_mutex);
}

static int dyn_event_seq_show(struct seq_file *m, void *v)
{
        struct dyn_event *ev = v;

        if (ev && ev->ops)
                return ev->ops->show(m, ev);

        return 0;
}

static const struct seq_operations dyn_event_seq_op = {
        .start  = dyn_event_seq_start,
        .next   = dyn_event_seq_next,
        .stop   = dyn_event_seq_stop,
        .show   = dyn_event_seq_show
};

/*
 * dyn_events_release_all - Release all specific events
 * @type:       the dyn_event_operations * which filters releasing events
 *
 * This releases all events which ->ops matches @type. If @type is NULL,
 * all events are released.
 * Return -EBUSY if any of them are in use, and return other errors when
 * it failed to free the given event. Except for -EBUSY, event releasing
 * process will be aborted at that point and there may be some other
 * releasable events on the list.
 */
int dyn_events_release_all(struct dyn_event_operations *type)
{
        struct dyn_event *ev, *tmp;
        int ret = 0;

        mutex_lock(&event_mutex);
        for_each_dyn_event(ev) {
                if (type && ev->ops != type)
                        continue;
                if (ev->ops->is_busy(ev)) {
                        ret = -EBUSY;
                        goto out;
                }
        }
        for_each_dyn_event_safe(ev, tmp) {
                if (type && ev->ops != type)
                        continue;
                ret = ev->ops->free(ev);
                if (ret)
                        break;
        }
out:
        mutex_unlock(&event_mutex);

        return ret;
}

static int dyn_event_open(struct inode *inode, struct file *file)
{
        int ret;

        if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
                ret = dyn_events_release_all(NULL);
                if (ret < 0)
                        return ret;
        }

        return seq_open(file, &dyn_event_seq_op);
}

static ssize_t dyn_event_write(struct file *file, const char __user *buffer,
                                size_t count, loff_t *ppos)
{
        return trace_parse_run_command(file, buffer, count, ppos,
                                       create_dyn_event);
}

static const struct file_operations dynamic_events_ops = {
        .owner          = THIS_MODULE,
        .open           = dyn_event_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
        .write          = dyn_event_write,
};

/* Make a tracefs interface for controlling dynamic events */
static __init int init_dynamic_event(void)
{
        struct dentry *d_tracer;
        struct dentry *entry;

        d_tracer = tracing_init_dentry();
        if (IS_ERR(d_tracer))
                return 0;

        entry = tracefs_create_file("dynamic_events", 0644, d_tracer,
                                    NULL, &dynamic_events_ops);

        /* Event list interface */
        if (!entry)
                pr_warn("Could not create tracefs 'dynamic_events' entry\n");

        return 0;
}
fs_initcall(init_dynamic_event);