// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2010-2018  B.A.T.M.A.N. contributors:
 *
 * Marek Lindner
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#include "log.h"
#include "main.h"

#include <linux/compiler.h>
#include <linux/debugfs.h>
#include <linux/errno.h>
#include <linux/eventpoll.h>
#include <linux/export.h>
#include <linux/fcntl.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/sched.h> /* for linux/wait.h */
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/stddef.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <linux/wait.h>
#include <stdarg.h>

#define BATADV_LOG_BUFF_MASK (batadv_log_buff_len - 1)

static const int batadv_log_buff_len = BATADV_LOG_BUF_LEN;

static char *batadv_log_char_addr(struct batadv_priv_debug_log *debug_log,
                                  size_t idx)
{
        return &debug_log->log_buff[idx & BATADV_LOG_BUFF_MASK];
}

static void batadv_emit_log_char(struct batadv_priv_debug_log *debug_log,
                                 char c)
{
        char *char_addr;

        char_addr = batadv_log_char_addr(debug_log, debug_log->log_end);
        *char_addr = c;
        debug_log->log_end++;

        if (debug_log->log_end - debug_log->log_start > batadv_log_buff_len)
                debug_log->log_start = debug_log->log_end - batadv_log_buff_len;
}

__printf(2, 3)
static int batadv_fdebug_log(struct batadv_priv_debug_log *debug_log,
                             const char *fmt, ...)
{
        va_list args;
        static char debug_log_buf[256];
        char *p;

        if (!debug_log)
                return 0;

        spin_lock_bh(&debug_log->lock);
        va_start(args, fmt);
        vscnprintf(debug_log_buf, sizeof(debug_log_buf), fmt, args);
        va_end(args);

        for (p = debug_log_buf; *p != 0; p++)
                batadv_emit_log_char(debug_log, *p);

        spin_unlock_bh(&debug_log->lock);

        wake_up(&debug_log->queue_wait);

        return 0;
}

/**
 * batadv_debug_log() - Add debug log entry
 * @bat_priv: the bat priv with all the soft interface information
 * @fmt: format string
 *
 * Return: 0 on success or negative error number in case of failure
 */
int batadv_debug_log(struct batadv_priv *bat_priv, const char *fmt, ...)
{
        va_list args;
        char tmp_log_buf[256];

        va_start(args, fmt);
        vscnprintf(tmp_log_buf, sizeof(tmp_log_buf), fmt, args);
        batadv_fdebug_log(bat_priv->debug_log, "[%10u] %s",
                          jiffies_to_msecs(jiffies), tmp_log_buf);
        va_end(args);

        return 0;
}

static int batadv_log_open(struct inode *inode, struct file *file)
{
        if (!try_module_get(THIS_MODULE))
                return -EBUSY;

        nonseekable_open(inode, file);
        file->private_data = inode->i_private;
        return 0;
}

static int batadv_log_release(struct inode *inode, struct file *file)
{
        module_put(THIS_MODULE);
        return 0;
}

static bool batadv_log_empty(struct batadv_priv_debug_log *debug_log)
{
        return !(debug_log->log_start - debug_log->log_end);
}

static ssize_t batadv_log_read(struct file *file, char __user *buf,
                               size_t count, loff_t *ppos)
{
        struct batadv_priv *bat_priv = file->private_data;
        struct batadv_priv_debug_log *debug_log = bat_priv->debug_log;
        int error, i = 0;
        char *char_addr;
        char c;

        if ((file->f_flags & O_NONBLOCK) && batadv_log_empty(debug_log))
                return -EAGAIN;

        if (!buf)
                return -EINVAL;

        if (count == 0)
                return 0;

        if (!access_ok(VERIFY_WRITE, buf, count))
                return -EFAULT;

        error = wait_event_interruptible(debug_log->queue_wait,
                                         (!batadv_log_empty(debug_log)));

        if (error)
                return error;

        spin_lock_bh(&debug_log->lock);

        while ((!error) && (i < count) &&
               (debug_log->log_start != debug_log->log_end)) {
                char_addr = batadv_log_char_addr(debug_log,
                                                 debug_log->log_start);
                c = *char_addr;

                debug_log->log_start++;

                spin_unlock_bh(&debug_log->lock);

                error = __put_user(c, buf);

                spin_lock_bh(&debug_log->lock);

                buf++;
                i++;
        }

        spin_unlock_bh(&debug_log->lock);

        if (!error)
                return i;

        return error;
}

static __poll_t batadv_log_poll(struct file *file, poll_table *wait)
{
        struct batadv_priv *bat_priv = file->private_data;
        struct batadv_priv_debug_log *debug_log = bat_priv->debug_log;

        poll_wait(file, &debug_log->queue_wait, wait);

        if (!batadv_log_empty(debug_log))
                return EPOLLIN | EPOLLRDNORM;

        return 0;
}

static const struct file_operations batadv_log_fops = {
        .open           = batadv_log_open,
        .release        = batadv_log_release,
        .read           = batadv_log_read,
        .poll           = batadv_log_poll,
        .llseek         = no_llseek,
};

/**
 * batadv_debug_log_setup() - Initialize debug log
 * @bat_priv: the bat priv with all the soft interface information
 *
 * Return: 0 on success or negative error number in case of failure
 */
int batadv_debug_log_setup(struct batadv_priv *bat_priv)
{
        struct dentry *d;

        if (!bat_priv->debug_dir)
                goto err;

        bat_priv->debug_log = kzalloc(sizeof(*bat_priv->debug_log), GFP_ATOMIC);
        if (!bat_priv->debug_log)
                goto err;

        spin_lock_init(&bat_priv->debug_log->lock);
        init_waitqueue_head(&bat_priv->debug_log->queue_wait);

        d = debugfs_create_file("log", 0400, bat_priv->debug_dir, bat_priv,
                                &batadv_log_fops);
        if (!d)
                goto err;

        return 0;

err:
        return -ENOMEM;
}

/**
 * batadv_debug_log_cleanup() - Destroy debug log
 * @bat_priv: the bat priv with all the soft interface information
 */
void batadv_debug_log_cleanup(struct batadv_priv *bat_priv)
{
        kfree(bat_priv->debug_log);
        bat_priv->debug_log = NULL;
}