mon_main.c

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/*
 * The USB Monitor, inspired by Dave Harding's USBMon.
 *
 * mon_main.c: Main file, module initiation and exit, registrations, etc.
 *
 * Copyright (C) 2005 Pete Zaitcev ([email protected])
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/usb/hcd.h>
#include <linux/slab.h>
#include <linux/notifier.h>
#include <linux/mutex.h>

#include "usb_mon.h"


static void mon_stop(struct mon_bus *mbus);
static void mon_dissolve(struct mon_bus *mbus, struct usb_bus *ubus);
static void mon_bus_drop(struct kref *r);
static void mon_bus_init(struct usb_bus *ubus);

DEFINE_MUTEX(mon_lock);

struct mon_bus mon_bus0;        /* Pseudo bus meaning "all buses" */
static LIST_HEAD(mon_buses);        /* All buses we know: struct mon_bus */

/*
 * Link a reader into the bus.
 *
 * This must be called with mon_lock taken because of mbus->ref.
 */
void mon_reader_add(struct mon_bus *mbus, struct mon_reader *r)
{
    unsigned long flags;
    struct list_head *p;

    spin_lock_irqsave(&mbus->lock, flags);
    if (mbus->nreaders == 0) {
        if (mbus == &mon_bus0) {
            list_for_each (p, &mon_buses) {
                struct mon_bus *m1;
                m1 = list_entry(p, struct mon_bus, bus_link);
                m1->u_bus->monitored = 1;
            }
        } else {
            mbus->u_bus->monitored = 1;
        }
    }
    mbus->nreaders++;
    list_add_tail(&r->r_link, &mbus->r_list);
    spin_unlock_irqrestore(&mbus->lock, flags);

    kref_get(&mbus->ref);
}

/*
 * Unlink reader from the bus.
 *
 * This is called with mon_lock taken, so we can decrement mbus->ref.
 */
void mon_reader_del(struct mon_bus *mbus, struct mon_reader *r)
{
    unsigned long flags;

    spin_lock_irqsave(&mbus->lock, flags);
    list_del(&r->r_link);
    --mbus->nreaders;
    if (mbus->nreaders == 0)
        mon_stop(mbus);
    spin_unlock_irqrestore(&mbus->lock, flags);

    kref_put(&mbus->ref, mon_bus_drop);
}

/*
 */
static void mon_bus_submit(struct mon_bus *mbus, struct urb *urb)
{
    unsigned long flags;
    struct list_head *pos;
    struct mon_reader *r;

    spin_lock_irqsave(&mbus->lock, flags);
    mbus->cnt_events++;
    list_for_each (pos, &mbus->r_list) {
        r = list_entry(pos, struct mon_reader, r_link);
        r->rnf_submit(r->r_data, urb);
    }
    spin_unlock_irqrestore(&mbus->lock, flags);
}

static void mon_submit(struct usb_bus *ubus, struct urb *urb)
{
    struct mon_bus *mbus;

    if ((mbus = ubus->mon_bus) != NULL)
        mon_bus_submit(mbus, urb);
    mon_bus_submit(&mon_bus0, urb);
}

/*
 */
static void mon_bus_submit_error(struct mon_bus *mbus, struct urb *urb, int error)
{
    unsigned long flags;
    struct list_head *pos;
    struct mon_reader *r;

    spin_lock_irqsave(&mbus->lock, flags);
    mbus->cnt_events++;
    list_for_each (pos, &mbus->r_list) {
        r = list_entry(pos, struct mon_reader, r_link);
        r->rnf_error(r->r_data, urb, error);
    }
    spin_unlock_irqrestore(&mbus->lock, flags);
}

static void mon_submit_error(struct usb_bus *ubus, struct urb *urb, int error)
{
    struct mon_bus *mbus;

    if ((mbus = ubus->mon_bus) != NULL)
        mon_bus_submit_error(mbus, urb, error);
    mon_bus_submit_error(&mon_bus0, urb, error);
}

/*
 */
static void mon_bus_complete(struct mon_bus *mbus, struct urb *urb, int status)
{
    unsigned long flags;
    struct list_head *pos;
    struct mon_reader *r;

    spin_lock_irqsave(&mbus->lock, flags);
    mbus->cnt_events++;
    list_for_each (pos, &mbus->r_list) {
        r = list_entry(pos, struct mon_reader, r_link);
        r->rnf_complete(r->r_data, urb, status);
    }
    spin_unlock_irqrestore(&mbus->lock, flags);
}

static void mon_complete(struct usb_bus *ubus, struct urb *urb, int status)
{
    struct mon_bus *mbus;

    if ((mbus = ubus->mon_bus) != NULL)
        mon_bus_complete(mbus, urb, status);
    mon_bus_complete(&mon_bus0, urb, status);
}

/* int (*unlink_urb) (struct urb *urb, int status); */

/*
 * Stop monitoring.
 */
static void mon_stop(struct mon_bus *mbus)
{
    struct usb_bus *ubus;
    struct list_head *p;

    if (mbus == &mon_bus0) {
        list_for_each (p, &mon_buses) {
            mbus = list_entry(p, struct mon_bus, bus_link);
            /*
             * We do not change nreaders here, so rely on mon_lock.
             */
            if (mbus->nreaders == 0 && (ubus = mbus->u_bus) != NULL)
                ubus->monitored = 0;
        }
    } else {
        /*
         * A stop can be called for a dissolved mon_bus in case of
         * a reader staying across an rmmod foo_hcd, so test ->u_bus.
         */
        if (mon_bus0.nreaders == 0 && (ubus = mbus->u_bus) != NULL) {
            ubus->monitored = 0;
            mb();
        }
    }
}

/*
 * Add a USB bus (usually by a modprobe foo-hcd)
 *
 * This does not return an error code because the core cannot care less
 * if monitoring is not established.
 */
static void mon_bus_add(struct usb_bus *ubus)
{
    mon_bus_init(ubus);
    mutex_lock(&mon_lock);
    if (mon_bus0.nreaders != 0)
        ubus->monitored = 1;
    mutex_unlock(&mon_lock);
}

/*
 * Remove a USB bus (either from rmmod foo-hcd or from a hot-remove event).
 */
static void mon_bus_remove(struct usb_bus *ubus)
{
    struct mon_bus *mbus = ubus->mon_bus;

    mutex_lock(&mon_lock);
    list_del(&mbus->bus_link);
    if (mbus->text_inited)
        mon_text_del(mbus);
    if (mbus->bin_inited)
        mon_bin_del(mbus);

    mon_dissolve(mbus, ubus);
    kref_put(&mbus->ref, mon_bus_drop);
    mutex_unlock(&mon_lock);
}

static int mon_notify(struct notifier_block *self, unsigned long action,
              void *dev)
{
    switch (action) {
    case USB_BUS_ADD:
        mon_bus_add(dev);
        break;
    case USB_BUS_REMOVE:
        mon_bus_remove(dev);
    }
    return NOTIFY_OK;
}

static struct notifier_block mon_nb = {
    .notifier_call =    mon_notify,
};

/*
 * Ops
 */
static struct usb_mon_operations mon_ops_0 = {
    .urb_submit =   mon_submit,
    .urb_submit_error = mon_submit_error,
    .urb_complete = mon_complete,
};

/*
 * Tear usb_bus and mon_bus apart.
 */
static void mon_dissolve(struct mon_bus *mbus, struct usb_bus *ubus)
{

    if (ubus->monitored) {
        ubus->monitored = 0;
        mb();
    }

    ubus->mon_bus = NULL;
    mbus->u_bus = NULL;
    mb();

    /* We want synchronize_irq() here, but that needs an argument. */
}

/*
 */
static void mon_bus_drop(struct kref *r)
{
    struct mon_bus *mbus = container_of(r, struct mon_bus, ref);
    kfree(mbus);
}

/*
 * Initialize a bus for us:
 *  - allocate mon_bus
 *  - refcount USB bus struct
 *  - link
 */
static void mon_bus_init(struct usb_bus *ubus)
{
    struct mon_bus *mbus;

    if ((mbus = kzalloc(sizeof(struct mon_bus), GFP_KERNEL)) == NULL)
        goto err_alloc;
    kref_init(&mbus->ref);
    spin_lock_init(&mbus->lock);
    INIT_LIST_HEAD(&mbus->r_list);

    /*
     * We don't need to take a reference to ubus, because we receive
     * a notification if the bus is about to be removed.
     */
    mbus->u_bus = ubus;
    ubus->mon_bus = mbus;

    mbus->text_inited = mon_text_add(mbus, ubus);
    mbus->bin_inited = mon_bin_add(mbus, ubus);

    mutex_lock(&mon_lock);
    list_add_tail(&mbus->bus_link, &mon_buses);
    mutex_unlock(&mon_lock);
    return;

err_alloc:
    return;
}

static void mon_bus0_init(void)
{
    struct mon_bus *mbus = &mon_bus0;

    kref_init(&mbus->ref);
    spin_lock_init(&mbus->lock);
    INIT_LIST_HEAD(&mbus->r_list);

    mbus->text_inited = mon_text_add(mbus, NULL);
    mbus->bin_inited = mon_bin_add(mbus, NULL);
}

/*
 * Search a USB bus by number. Notice that USB bus numbers start from one,
 * which we may later use to identify "all" with zero.
 *
 * This function must be called with mon_lock held.
 *
 * This is obviously inefficient and may be revised in the future.
 */
struct mon_bus *mon_bus_lookup(unsigned int num)
{
    struct list_head *p;
    struct mon_bus *mbus;

    if (num == 0) {
        return &mon_bus0;
    }
    list_for_each (p, &mon_buses) {
        mbus = list_entry(p, struct mon_bus, bus_link);
        if (mbus->u_bus->busnum == num) {
            return mbus;
        }
    }
    return NULL;
}

static int __init mon_init(void)
{
    struct usb_bus *ubus;
    int rc;

    if ((rc = mon_text_init()) != 0)
        goto err_text;
    if ((rc = mon_bin_init()) != 0)
        goto err_bin;

    mon_bus0_init();

    if (usb_mon_register(&mon_ops_0) != 0) {
        printk(KERN_NOTICE TAG ": unable to register with the core\n");
        rc = -ENODEV;
        goto err_reg;
    }
    // MOD_INC_USE_COUNT(which_module?);

    mutex_lock(&usb_bus_list_lock);
    list_for_each_entry (ubus, &usb_bus_list, bus_list) {
        mon_bus_init(ubus);
    }
    usb_register_notify(&mon_nb);
    mutex_unlock(&usb_bus_list_lock);
    return 0;

err_reg:
    mon_bin_exit();
err_bin:
    mon_text_exit();
err_text:
    return rc;
}

static void __exit mon_exit(void)
{
    struct mon_bus *mbus;
    struct list_head *p;

    usb_unregister_notify(&mon_nb);
    usb_mon_deregister();

    mutex_lock(&mon_lock);

    while (!list_empty(&mon_buses)) {
        p = mon_buses.next;
        mbus = list_entry(p, struct mon_bus, bus_link);
        list_del(p);

        if (mbus->text_inited)
            mon_text_del(mbus);
        if (mbus->bin_inited)
            mon_bin_del(mbus);

        /*
         * This never happens, because the open/close paths in
         * file level maintain module use counters and so rmmod fails
         * before reaching here. However, better be safe...
         */
        if (mbus->nreaders) {
            printk(KERN_ERR TAG
                ": Outstanding opens (%d) on usb%d, leaking...\n",
                mbus->nreaders, mbus->u_bus->busnum);
            atomic_set(&mbus->ref.refcount, 2); /* Force leak */
        }

        mon_dissolve(mbus, mbus->u_bus);
        kref_put(&mbus->ref, mon_bus_drop);
    }

    mbus = &mon_bus0;
    if (mbus->text_inited)
        mon_text_del(mbus);
    if (mbus->bin_inited)
        mon_bin_del(mbus);

    mutex_unlock(&mon_lock);

    mon_text_exit();
    mon_bin_exit();
}

module_init(mon_init);
module_exit(mon_exit);

MODULE_LICENSE("GPL");