// SPDX-License-Identifier: GPL-2.0
/*
 * Infrastructure for statistic tracing (histogram output).
 *
 * Copyright (C) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
 *
 * Based on the code from trace_branch.c which is
 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
 *
 */

#include <linux/security.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/rbtree.h>
#include <linux/tracefs.h>
#include "trace_stat.h"
#include "trace.h"


/*
 * List of stat red-black nodes from a tracer
 * We use a such tree to sort quickly the stat
 * entries from the tracer.
 */
struct stat_node {
        struct rb_node          node;
        void                    *stat;
};

/* A stat session is the stats output in one file */
struct stat_session {
        struct list_head        session_list;
        struct tracer_stat      *ts;
        struct rb_root          stat_root;
        struct mutex            stat_mutex;
        struct dentry           *file;
};

/* All of the sessions currently in use. Each stat file embed one session */
static LIST_HEAD(all_stat_sessions);
static DEFINE_MUTEX(all_stat_sessions_mutex);

/* The root directory for all stat files */
static struct dentry            *stat_dir;

static void __reset_stat_session(struct stat_session *session)
{
        struct stat_node *snode, *n;

        rbtree_postorder_for_each_entry_safe(snode, n, &session->stat_root, node) {
                if (session->ts->stat_release)
                        session->ts->stat_release(snode->stat);
                kfree(snode);
        }

        session->stat_root = RB_ROOT;
}

static void reset_stat_session(struct stat_session *session)
{
        mutex_lock(&session->stat_mutex);
        __reset_stat_session(session);
        mutex_unlock(&session->stat_mutex);
}

static void destroy_session(struct stat_session *session)
{
        tracefs_remove(session->file);
        __reset_stat_session(session);
        mutex_destroy(&session->stat_mutex);
        kfree(session);
}

static int insert_stat(struct rb_root *root, void *stat, cmp_func_t cmp)
{
        struct rb_node **new = &(root->rb_node), *parent = NULL;
        struct stat_node *data;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;
        data->stat = stat;

        /*
         * Figure out where to put new node
         * This is a descendent sorting
         */
        while (*new) {
                struct stat_node *this;
                int result;

                this = container_of(*new, struct stat_node, node);
                result = cmp(data->stat, this->stat);

                parent = *new;
                if (result >= 0)
                        new = &((*new)->rb_left);
                else
                        new = &((*new)->rb_right);
        }

        rb_link_node(&data->node, parent, new);
        rb_insert_color(&data->node, root);
        return 0;
}

/*
 * For tracers that don't provide a stat_cmp callback.
 * This one will force an insertion as right-most node
 * in the rbtree.
 */
static int dummy_cmp(const void *p1, const void *p2)
{
        return -1;
}

/*
 * Initialize the stat rbtree at each trace_stat file opening.
 * All of these copies and sorting are required on all opening
 * since the stats could have changed between two file sessions.
 */
static int stat_seq_init(struct stat_session *session)
{
        struct tracer_stat *ts = session->ts;
        struct rb_root *root = &session->stat_root;
        void *stat;
        int ret = 0;
        int i;

        mutex_lock(&session->stat_mutex);
        __reset_stat_session(session);

        if (!ts->stat_cmp)
                ts->stat_cmp = dummy_cmp;

        stat = ts->stat_start(ts);
        if (!stat)
                goto exit;

        ret = insert_stat(root, stat, ts->stat_cmp);
        if (ret)
                goto exit;

        /*
         * Iterate over the tracer stat entries and store them in an rbtree.
         */
        for (i = 1; ; i++) {
                stat = ts->stat_next(stat, i);

                /* End of insertion */
                if (!stat)
                        break;

                ret = insert_stat(root, stat, ts->stat_cmp);
                if (ret)
                        goto exit_free_rbtree;
        }

exit:
        mutex_unlock(&session->stat_mutex);
        return ret;

exit_free_rbtree:
        __reset_stat_session(session);
        mutex_unlock(&session->stat_mutex);
        return ret;
}


static void *stat_seq_start(struct seq_file *s, loff_t *pos)
{
        struct stat_session *session = s->private;
        struct rb_node *node;
        int n = *pos;
        int i;

        /* Prevent from tracer switch or rbtree modification */
        mutex_lock(&session->stat_mutex);

        /* If we are in the beginning of the file, print the headers */
        if (session->ts->stat_headers) {
                if (n == 0)
                        return SEQ_START_TOKEN;
                n--;
        }

        node = rb_first(&session->stat_root);
        for (i = 0; node && i < n; i++)
                node = rb_next(node);

        return node;
}

static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
{
        struct stat_session *session = s->private;
        struct rb_node *node = p;

        (*pos)++;

        if (p == SEQ_START_TOKEN)
                return rb_first(&session->stat_root);

        return rb_next(node);
}

static void stat_seq_stop(struct seq_file *s, void *p)
{
        struct stat_session *session = s->private;
        mutex_unlock(&session->stat_mutex);
}

static int stat_seq_show(struct seq_file *s, void *v)
{
        struct stat_session *session = s->private;
        struct stat_node *l = container_of(v, struct stat_node, node);

        if (v == SEQ_START_TOKEN)
                return session->ts->stat_headers(s);

        return session->ts->stat_show(s, l->stat);
}

static const struct seq_operations trace_stat_seq_ops = {
        .start          = stat_seq_start,
        .next           = stat_seq_next,
        .stop           = stat_seq_stop,
        .show           = stat_seq_show
};

/* The session stat is refilled and resorted at each stat file opening */
static int tracing_stat_open(struct inode *inode, struct file *file)
{
        int ret;
        struct seq_file *m;
        struct stat_session *session = inode->i_private;

        ret = security_locked_down(LOCKDOWN_TRACEFS);
        if (ret)
                return ret;

        ret = stat_seq_init(session);
        if (ret)
                return ret;

        ret = seq_open(file, &trace_stat_seq_ops);
        if (ret) {
                reset_stat_session(session);
                return ret;
        }

        m = file->private_data;
        m->private = session;
        return ret;
}

/*
 * Avoid consuming memory with our now useless rbtree.
 */
static int tracing_stat_release(struct inode *i, struct file *f)
{
        struct stat_session *session = i->i_private;

        reset_stat_session(session);

        return seq_release(i, f);
}

static const struct file_operations tracing_stat_fops = {
        .open           = tracing_stat_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = tracing_stat_release
};

static int tracing_stat_init(void)
{
        int ret;

        ret = tracing_init_dentry();
        if (ret)
                return -ENODEV;

        stat_dir = tracefs_create_dir("trace_stat", NULL);
        if (!stat_dir) {
                pr_warn("Could not create tracefs 'trace_stat' entry\n");
                return -ENOMEM;
        }
        return 0;
}

static int init_stat_file(struct stat_session *session)
{
        int ret;

        if (!stat_dir && (ret = tracing_stat_init()))
                return ret;

        session->file = tracefs_create_file(session->ts->name, 0644,
                                            stat_dir,
                                            session, &tracing_stat_fops);
        if (!session->file)
                return -ENOMEM;
        return 0;
}

int register_stat_tracer(struct tracer_stat *trace)
{
        struct stat_session *session, *node;
        int ret = -EINVAL;

        if (!trace)
                return -EINVAL;

        if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
                return -EINVAL;

        /* Already registered? */
        mutex_lock(&all_stat_sessions_mutex);
        list_for_each_entry(node, &all_stat_sessions, session_list) {
                if (node->ts == trace)
                        goto out;
        }

        ret = -ENOMEM;
        /* Init the session */
        session = kzalloc(sizeof(*session), GFP_KERNEL);
        if (!session)
                goto out;

        session->ts = trace;
        INIT_LIST_HEAD(&session->session_list);
        mutex_init(&session->stat_mutex);

        ret = init_stat_file(session);
        if (ret) {
                destroy_session(session);
                goto out;
        }

        ret = 0;
        /* Register */
        list_add_tail(&session->session_list, &all_stat_sessions);
 out:
        mutex_unlock(&all_stat_sessions_mutex);

        return ret;
}

void unregister_stat_tracer(struct tracer_stat *trace)
{
        struct stat_session *node, *tmp;

        mutex_lock(&all_stat_sessions_mutex);
        list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
                if (node->ts == trace) {
                        list_del(&node->session_list);
                        destroy_session(node);
                        break;
                }
        }
        mutex_unlock(&all_stat_sessions_mutex);
}