dgrp_mon_ops.c

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/*****************************************************************************
 *
 * Copyright 1999 Digi International (www.digi.com)
 *     James Puzzo <jamesp at digi dot com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED; without even the
 * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 */

/*
 *
 *  Filename:
 *
 *     dgrp_mon_ops.c
 *
 *  Description:
 *
 *     Handle the file operations required for the "monitor" devices.
 *     Includes those functions required to register the "mon" devices
 *     in "/proc".
 *
 *  Author:
 *
 *     James A. Puzzo
 *
 */

#include <linux/module.h>
#include <linux/tty.h>
#include <linux/sched.h>
#include <asm/unaligned.h>
#include <linux/proc_fs.h>
#include <linux/uaccess.h>

#include "dgrp_common.h"

/* File operation declarations */
static int dgrp_mon_open(struct inode *, struct file *);
static int dgrp_mon_release(struct inode *, struct file *);
static ssize_t dgrp_mon_read(struct file *, char __user *, size_t, loff_t *);
static long dgrp_mon_ioctl(struct file *file, unsigned int cmd,
               unsigned long arg);

static const struct file_operations mon_ops = {
    .owner   = THIS_MODULE,
    .read    = dgrp_mon_read,
    .unlocked_ioctl = dgrp_mon_ioctl,
    .open    = dgrp_mon_open,
    .release = dgrp_mon_release,
};

static struct inode_operations mon_inode_ops = {
    .permission = dgrp_inode_permission
};

void dgrp_register_mon_hook(struct proc_dir_entry *de)
{
    struct nd_struct *node = de->data;

    de->proc_iops = &mon_inode_ops;
    de->proc_fops = &mon_ops;
    node->nd_mon_de = de;
    sema_init(&node->nd_mon_semaphore, 1);
}

static int dgrp_mon_open(struct inode *inode, struct file *file)
{
    struct nd_struct *nd;
    struct proc_dir_entry *de;
    struct timeval tv;
    uint32_t time;
    u8 *buf;
    int rtn;

    rtn = try_module_get(THIS_MODULE);
    if (!rtn)
        return -ENXIO;

    rtn = 0;

    if (!capable(CAP_SYS_ADMIN)) {
        rtn = -EPERM;
        goto done;
    }

    /*
     *  Make sure that the "private_data" field hasn't already been used.
     */
    if (file->private_data) {
        rtn = -EINVAL;
        goto done;
    }

    /*
     *  Get the node pointer, and fail if it doesn't exist.
     */
    de = PDE(inode);
    if (!de) {
        rtn = -ENXIO;
        goto done;
    }

    nd = (struct nd_struct *)de->data;
    if (!nd) {
        rtn = -ENXIO;
        goto done;
    }

    file->private_data = (void *) nd;

    /*
     * Allocate the monitor buffer.
     */

    /*
     *  Grab the MON lock.
     */
    down(&nd->nd_mon_semaphore);

    if (nd->nd_mon_buf) {
        rtn = -EBUSY;
        goto done_up;
    }

    nd->nd_mon_buf = kmalloc(MON_MAX, GFP_KERNEL);

    if (!nd->nd_mon_buf) {
        rtn = -ENOMEM;
        goto done_up;
    }

    /*
     *  Enter an RPDUMP file header into the buffer.
     */

    buf = nd->nd_mon_buf;

    strcpy(buf, RPDUMP_MAGIC);
    buf += strlen(buf) + 1;

    do_gettimeofday(&tv);

    /*
     *  tv.tv_sec might be a 64 bit quantity.  Pare
     *  it down to 32 bits before attempting to encode
     *  it.
     */
    time = (uint32_t) (tv.tv_sec & 0xffffffff);

    put_unaligned_be32(time, buf);
    put_unaligned_be16(0, buf + 4);
    buf += 6;

    if (nd->nd_tx_module) {
        buf[0] = RPDUMP_CLIENT;
        put_unaligned_be32(0, buf + 1);
        put_unaligned_be16(1, buf + 5);
        buf[7] = 0xf0 + nd->nd_tx_module;
        buf += 8;
    }

    if (nd->nd_rx_module) {
        buf[0] = RPDUMP_SERVER;
        put_unaligned_be32(0, buf + 1);
        put_unaligned_be16(1, buf + 5);
        buf[7] = 0xf0 + nd->nd_rx_module;
        buf += 8;
    }

    nd->nd_mon_out = 0;
    nd->nd_mon_in  = buf - nd->nd_mon_buf;
    nd->nd_mon_lbolt = jiffies;

done_up:
    up(&nd->nd_mon_semaphore);

done:
    if (rtn)
        module_put(THIS_MODULE);
    return rtn;
}


static int dgrp_mon_release(struct inode *inode, struct file *file)
{
    struct nd_struct *nd;

    /*
     *  Get the node pointer, and quit if it doesn't exist.
     */
    nd = (struct nd_struct *)(file->private_data);
    if (!nd)
        goto done;

    /*
     *  Free the monitor buffer.
     */

    down(&nd->nd_mon_semaphore);

    kfree(nd->nd_mon_buf);
    nd->nd_mon_buf = NULL;
    nd->nd_mon_out = nd->nd_mon_in;

    /*
     *  Wakeup any thread waiting for buffer space.
     */

    if (nd->nd_mon_flag & MON_WAIT_SPACE) {
        nd->nd_mon_flag &= ~MON_WAIT_SPACE;
        wake_up_interruptible(&nd->nd_mon_wqueue);
    }

    up(&nd->nd_mon_semaphore);

    /*
     *  Make sure there is no thread in the middle of writing a packet.
     */
    down(&nd->nd_net_semaphore);
    up(&nd->nd_net_semaphore);

done:
    module_put(THIS_MODULE);
    file->private_data = NULL;
    return 0;
}

static ssize_t dgrp_mon_read(struct file *file, char __user *buf, size_t count,
                 loff_t *ppos)
{
    struct nd_struct *nd;
    int r;
    int offset = 0;
    int res = 0;
    ssize_t rtn;

    /*
     *  Get the node pointer, and quit if it doesn't exist.
     */
    nd = (struct nd_struct *)(file->private_data);
    if (!nd)
        return -ENXIO;

    /*
     *  Wait for some data to appear in the buffer.
     */

    down(&nd->nd_mon_semaphore);

    for (;;) {
        res = (nd->nd_mon_in - nd->nd_mon_out) & MON_MASK;

        if (res)
            break;

        nd->nd_mon_flag |= MON_WAIT_DATA;

        up(&nd->nd_mon_semaphore);

        /*
         * Go to sleep waiting until the condition becomes true.
         */
        rtn = wait_event_interruptible(nd->nd_mon_wqueue,
                           ((nd->nd_mon_flag & MON_WAIT_DATA) == 0));

        if (rtn)
            return rtn;

        down(&nd->nd_mon_semaphore);
    }

    /*
     *  Read whatever is there.
     */

    if (res > count)
        res = count;

    r = MON_MAX - nd->nd_mon_out;

    if (r <= res) {
        rtn = copy_to_user((void __user *)buf,
                   nd->nd_mon_buf + nd->nd_mon_out, r);
        if (rtn) {
            up(&nd->nd_mon_semaphore);
            return -EFAULT;
        }

        nd->nd_mon_out = 0;
        res -= r;
        offset = r;
    }

    rtn = copy_to_user((void __user *) buf + offset,
               nd->nd_mon_buf + nd->nd_mon_out, res);
    if (rtn) {
        up(&nd->nd_mon_semaphore);
        return -EFAULT;
    }

    nd->nd_mon_out += res;

    *ppos += res;

    up(&nd->nd_mon_semaphore);

    /*
     *  Wakeup any thread waiting for buffer space.
     */

    if (nd->nd_mon_flag & MON_WAIT_SPACE) {
        nd->nd_mon_flag &= ~MON_WAIT_SPACE;
        wake_up_interruptible(&nd->nd_mon_wqueue);
    }

    return res;
}

/*  ioctl is not valid on monitor device */
static long dgrp_mon_ioctl(struct file *file, unsigned int cmd,
               unsigned long arg)
{
    return -EINVAL;
}