// SPDX-License-Identifier: GPL-2.0
/*
 * The USB Monitor, inspired by Dave Harding's USBMon.
 *
 * This is a binary format reader.
 *
 * Copyright (C) 2006 Paolo Abeni (paolo.abeni@email.it)
 * Copyright (C) 2006,2007 Pete Zaitcev (zaitcev@redhat.com)
 */

#include <linux/kernel.h>
#include <linux/sched/signal.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/export.h>
#include <linux/usb.h>
#include <linux/poll.h>
#include <linux/compat.h>
#include <linux/mm.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <linux/time64.h>

#include <linux/uaccess.h>

#include "usb_mon.h"

/*
 * Defined by USB 2.0 clause 9.3, table 9.2.
 */
#define SETUP_LEN  8

/* ioctl macros */
#define MON_IOC_MAGIC 0x92

#define MON_IOCQ_URB_LEN _IO(MON_IOC_MAGIC, 1)
/* #2 used to be MON_IOCX_URB, removed before it got into Linus tree */
#define MON_IOCG_STATS _IOR(MON_IOC_MAGIC, 3, struct mon_bin_stats)
#define MON_IOCT_RING_SIZE _IO(MON_IOC_MAGIC, 4)
#define MON_IOCQ_RING_SIZE _IO(MON_IOC_MAGIC, 5)
#define MON_IOCX_GET   _IOW(MON_IOC_MAGIC, 6, struct mon_bin_get)
#define MON_IOCX_MFETCH _IOWR(MON_IOC_MAGIC, 7, struct mon_bin_mfetch)
#define MON_IOCH_MFLUSH _IO(MON_IOC_MAGIC, 8)
/* #9 was MON_IOCT_SETAPI */
#define MON_IOCX_GETX   _IOW(MON_IOC_MAGIC, 10, struct mon_bin_get)

#ifdef CONFIG_COMPAT
#define MON_IOCX_GET32 _IOW(MON_IOC_MAGIC, 6, struct mon_bin_get32)
#define MON_IOCX_MFETCH32 _IOWR(MON_IOC_MAGIC, 7, struct mon_bin_mfetch32)
#define MON_IOCX_GETX32   _IOW(MON_IOC_MAGIC, 10, struct mon_bin_get32)
#endif

/*
 * Some architectures have enormous basic pages (16KB for ia64, 64KB for ppc).
 * But it's all right. Just use a simple way to make sure the chunk is never
 * smaller than a page.
 *
 * N.B. An application does not know our chunk size.
 *
 * Woops, get_zeroed_page() returns a single page. I guess we're stuck with
 * page-sized chunks for the time being.
 */
#define CHUNK_SIZE   PAGE_SIZE
#define CHUNK_ALIGN(x)   (((x)+CHUNK_SIZE-1) & ~(CHUNK_SIZE-1))

/*
 * The magic limit was calculated so that it allows the monitoring
 * application to pick data once in two ticks. This way, another application,
 * which presumably drives the bus, gets to hog CPU, yet we collect our data.
 * If HZ is 100, a 480 mbit/s bus drives 614 KB every jiffy. USB has an
 * enormous overhead built into the bus protocol, so we need about 1000 KB.
 *
 * This is still too much for most cases, where we just snoop a few
 * descriptor fetches for enumeration. So, the default is a "reasonable"
 * amount for systems with HZ=250 and incomplete bus saturation.
 *
 * XXX What about multi-megabyte URBs which take minutes to transfer?
 */
#define BUFF_MAX  CHUNK_ALIGN(1200*1024)
#define BUFF_DFL   CHUNK_ALIGN(300*1024)
#define BUFF_MIN     CHUNK_ALIGN(8*1024)

/*
 * The per-event API header (2 per URB).
 *
 * This structure is seen in userland as defined by the documentation.
 */
struct mon_bin_hdr {
        u64 id;                 /* URB ID - from submission to callback */
        unsigned char type;     /* Same as in text API; extensible. */
        unsigned char xfer_type;        /* ISO, Intr, Control, Bulk */
        unsigned char epnum;    /* Endpoint number and transfer direction */
        unsigned char devnum;   /* Device address */
        unsigned short busnum;  /* Bus number */
        char flag_setup;
        char flag_data;
        s64 ts_sec;             /* ktime_get_real_ts64 */
        s32 ts_usec;            /* ktime_get_real_ts64 */
        int status;
        unsigned int len_urb;   /* Length of data (submitted or actual) */
        unsigned int len_cap;   /* Delivered length */
        union {
                unsigned char setup[SETUP_LEN]; /* Only for Control S-type */
                struct iso_rec {
                        int error_count;
                        int numdesc;
                } iso;
        } s;
        int interval;
        int start_frame;
        unsigned int xfer_flags;
        unsigned int ndesc;     /* Actual number of ISO descriptors */
};

/*
 * ISO vector, packed into the head of data stream.
 * This has to take 16 bytes to make sure that the end of buffer
 * wrap is not happening in the middle of a descriptor.
 */
struct mon_bin_isodesc {
        int          iso_status;
        unsigned int iso_off;
        unsigned int iso_len;
        u32 _pad;
};

/* per file statistic */
struct mon_bin_stats {
        u32 queued;
        u32 dropped;
};

struct mon_bin_get {
        struct mon_bin_hdr __user *hdr; /* Can be 48 bytes or 64. */
        void __user *data;
        size_t alloc;           /* Length of data (can be zero) */
};

struct mon_bin_mfetch {
        u32 __user *offvec;     /* Vector of events fetched */
        u32 nfetch;             /* Number of events to fetch (out: fetched) */
        u32 nflush;             /* Number of events to flush */
};

#ifdef CONFIG_COMPAT
struct mon_bin_get32 {
        u32 hdr32;
        u32 data32;
        u32 alloc32;
};

struct mon_bin_mfetch32 {
        u32 offvec32;
        u32 nfetch32;
        u32 nflush32;
};
#endif

/* Having these two values same prevents wrapping of the mon_bin_hdr */
#define PKT_ALIGN   64
#define PKT_SIZE    64

#define PKT_SZ_API0 48  /* API 0 (2.6.20) size */
#define PKT_SZ_API1 64  /* API 1 size: extra fields */

#define ISODESC_MAX   128       /* Same number as usbfs allows, 2048 bytes. */

/* max number of USB bus supported */
#define MON_BIN_MAX_MINOR 128

/*
 * The buffer: map of used pages.
 */
struct mon_pgmap {
        struct page *pg;
        unsigned char *ptr;     /* XXX just use page_to_virt everywhere? */
};

/*
 * This gets associated with an open file struct.
 */
struct mon_reader_bin {
        /* The buffer: one per open. */
        spinlock_t b_lock;              /* Protect b_cnt, b_in */
        unsigned int b_size;            /* Current size of the buffer - bytes */
        unsigned int b_cnt;             /* Bytes used */
        unsigned int b_in, b_out;       /* Offsets into buffer - bytes */
        unsigned int b_read;            /* Amount of read data in curr. pkt. */
        struct mon_pgmap *b_vec;        /* The map array */
        wait_queue_head_t b_wait;       /* Wait for data here */

        struct mutex fetch_lock;        /* Protect b_read, b_out */
        int mmap_active;

        /* A list of these is needed for "bus 0". Some time later. */
        struct mon_reader r;

        /* Stats */
        unsigned int cnt_lost;
};

static inline struct mon_bin_hdr *MON_OFF2HDR(const struct mon_reader_bin *rp,
    unsigned int offset)
{
        return (struct mon_bin_hdr *)
            (rp->b_vec[offset / CHUNK_SIZE].ptr + offset % CHUNK_SIZE);
}

#define MON_RING_EMPTY(rp)      ((rp)->b_cnt == 0)

static unsigned char xfer_to_pipe[4] = {
        PIPE_CONTROL, PIPE_ISOCHRONOUS, PIPE_BULK, PIPE_INTERRUPT
};

static struct class *mon_bin_class;
static dev_t mon_bin_dev0;
static struct cdev mon_bin_cdev;

static void mon_buff_area_fill(const struct mon_reader_bin *rp,
    unsigned int offset, unsigned int size);
static int mon_bin_wait_event(struct file *file, struct mon_reader_bin *rp);
static int mon_alloc_buff(struct mon_pgmap *map, int npages);
static void mon_free_buff(struct mon_pgmap *map, int npages);

/*
 * This is a "chunked memcpy". It does not manipulate any counters.
 */
static unsigned int mon_copy_to_buff(const struct mon_reader_bin *this,
    unsigned int off, const unsigned char *from, unsigned int length)
{
        unsigned int step_len;
        unsigned char *buf;
        unsigned int in_page;

        while (length) {
                /*
                 * Determine step_len.
                 */
                step_len = length;
                in_page = CHUNK_SIZE - (off & (CHUNK_SIZE-1));
                if (in_page < step_len)
                        step_len = in_page;

                /*
                 * Copy data and advance pointers.
                 */
                buf = this->b_vec[off / CHUNK_SIZE].ptr + off % CHUNK_SIZE;
                memcpy(buf, from, step_len);
                if ((off += step_len) >= this->b_size) off = 0;
                from += step_len;
                length -= step_len;
        }
        return off;
}

/*
 * This is a little worse than the above because it's "chunked copy_to_user".
 * The return value is an error code, not an offset.
 */
static int copy_from_buf(const struct mon_reader_bin *this, unsigned int off,
    char __user *to, int length)
{
        unsigned int step_len;
        unsigned char *buf;
        unsigned int in_page;

        while (length) {
                /*
                 * Determine step_len.
                 */
                step_len = length;
                in_page = CHUNK_SIZE - (off & (CHUNK_SIZE-1));
                if (in_page < step_len)
                        step_len = in_page;

                /*
                 * Copy data and advance pointers.
                 */
                buf = this->b_vec[off / CHUNK_SIZE].ptr + off % CHUNK_SIZE;
                if (copy_to_user(to, buf, step_len))
                        return -EINVAL;
                if ((off += step_len) >= this->b_size) off = 0;
                to += step_len;
                length -= step_len;
        }
        return 0;
}

/*
 * Allocate an (aligned) area in the buffer.
 * This is called under b_lock.
 * Returns ~0 on failure.
 */
static unsigned int mon_buff_area_alloc(struct mon_reader_bin *rp,
    unsigned int size)
{
        unsigned int offset;

        size = (size + PKT_ALIGN-1) & ~(PKT_ALIGN-1);
        if (rp->b_cnt + size > rp->b_size)
                return ~0;
        offset = rp->b_in;
        rp->b_cnt += size;
        if ((rp->b_in += size) >= rp->b_size)
                rp->b_in -= rp->b_size;
        return offset;
}

/*
 * This is the same thing as mon_buff_area_alloc, only it does not allow
 * buffers to wrap. This is needed by applications which pass references
 * into mmap-ed buffers up their stacks (libpcap can do that).
 *
 * Currently, we always have the header stuck with the data, although
 * it is not strictly speaking necessary.
 *
 * When a buffer would wrap, we place a filler packet to mark the space.
 */
static unsigned int mon_buff_area_alloc_contiguous(struct mon_reader_bin *rp,
    unsigned int size)
{
        unsigned int offset;
        unsigned int fill_size;

        size = (size + PKT_ALIGN-1) & ~(PKT_ALIGN-1);
        if (rp->b_cnt + size > rp->b_size)
                return ~0;
        if (rp->b_in + size > rp->b_size) {
                /*
                 * This would wrap. Find if we still have space after
                 * skipping to the end of the buffer. If we do, place
                 * a filler packet and allocate a new packet.
                 */
                fill_size = rp->b_size - rp->b_in;
                if (rp->b_cnt + size + fill_size > rp->b_size)
                        return ~0;
                mon_buff_area_fill(rp, rp->b_in, fill_size);

                offset = 0;
                rp->b_in = size;
                rp->b_cnt += size + fill_size;
        } else if (rp->b_in + size == rp->b_size) {
                offset = rp->b_in;
                rp->b_in = 0;
                rp->b_cnt += size;
        } else {
                offset = rp->b_in;
                rp->b_in += size;
                rp->b_cnt += size;
        }
        return offset;
}

/*
 * Return a few (kilo-)bytes to the head of the buffer.
 * This is used if a data fetch fails.
 */
static void mon_buff_area_shrink(struct mon_reader_bin *rp, unsigned int size)
{

        /* size &= ~(PKT_ALIGN-1);  -- we're called with aligned size */
        rp->b_cnt -= size;
        if (rp->b_in < size)
                rp->b_in += rp->b_size;
        rp->b_in -= size;
}

/*
 * This has to be called under both b_lock and fetch_lock, because
 * it accesses both b_cnt and b_out.
 */
static void mon_buff_area_free(struct mon_reader_bin *rp, unsigned int size)
{

        size = (size + PKT_ALIGN-1) & ~(PKT_ALIGN-1);
        rp->b_cnt -= size;
        if ((rp->b_out += size) >= rp->b_size)
                rp->b_out -= rp->b_size;
}

static void mon_buff_area_fill(const struct mon_reader_bin *rp,
    unsigned int offset, unsigned int size)
{
        struct mon_bin_hdr *ep;

        ep = MON_OFF2HDR(rp, offset);
        memset(ep, 0, PKT_SIZE);
        ep->type = '@';
        ep->len_cap = size - PKT_SIZE;
}

static inline char mon_bin_get_setup(unsigned char *setupb,
    const struct urb *urb, char ev_type)
{

        if (urb->setup_packet == NULL)
                return 'Z';
        memcpy(setupb, urb->setup_packet, SETUP_LEN);
        return 0;
}

static unsigned int mon_bin_get_data(const struct mon_reader_bin *rp,
    unsigned int offset, struct urb *urb, unsigned int length,
    char *flag)
{
        int i;
        struct scatterlist *sg;
        unsigned int this_len;

        *flag = 0;
        if (urb->num_sgs == 0) {
                if (urb->transfer_buffer == NULL) {
                        *flag = 'Z';
                        return length;
                }
                mon_copy_to_buff(rp, offset, urb->transfer_buffer, length);
                length = 0;

        } else {
                /* If IOMMU coalescing occurred, we cannot trust sg_page */
                if (urb->transfer_flags & URB_DMA_SG_COMBINED) {
                        *flag = 'D';
                        return length;
                }

                /* Copy up to the first non-addressable segment */
                for_each_sg(urb->sg, sg, urb->num_sgs, i) {
                        if (length == 0 || PageHighMem(sg_page(sg)))
                                break;
                        this_len = min_t(unsigned int, sg->length, length);
                        offset = mon_copy_to_buff(rp, offset, sg_virt(sg),
                                        this_len);
                        length -= this_len;
                }
                if (i == 0)
                        *flag = 'D';
        }

        return length;
}

/*
 * This is the look-ahead pass in case of 'C Zi', when actual_length cannot
 * be used to determine the length of the whole contiguous buffer.
 */
static unsigned int mon_bin_collate_isodesc(const struct mon_reader_bin *rp,
    struct urb *urb, unsigned int ndesc)
{
        struct usb_iso_packet_descriptor *fp;
        unsigned int length;

        length = 0;
        fp = urb->iso_frame_desc;
        while (ndesc-- != 0) {
                if (fp->actual_length != 0) {
                        if (fp->offset + fp->actual_length > length)
                                length = fp->offset + fp->actual_length;
                }
                fp++;
        }
        return length;
}

static void mon_bin_get_isodesc(const struct mon_reader_bin *rp,
    unsigned int offset, struct urb *urb, char ev_type, unsigned int ndesc)
{
        struct mon_bin_isodesc *dp;
        struct usb_iso_packet_descriptor *fp;

        fp = urb->iso_frame_desc;
        while (ndesc-- != 0) {
                dp = (struct mon_bin_isodesc *)
                    (rp->b_vec[offset / CHUNK_SIZE].ptr + offset % CHUNK_SIZE);
                dp->iso_status = fp->status;
                dp->iso_off = fp->offset;
                dp->iso_len = (ev_type == 'S') ? fp->length : fp->actual_length;
                dp->_pad = 0;
                if ((offset += sizeof(struct mon_bin_isodesc)) >= rp->b_size)
                        offset = 0;
                fp++;
        }
}

static void mon_bin_event(struct mon_reader_bin *rp, struct urb *urb,
    char ev_type, int status)
{
        const struct usb_endpoint_descriptor *epd = &urb->ep->desc;
        struct timespec64 ts;
        unsigned long flags;
        unsigned int urb_length;
        unsigned int offset;
        unsigned int length;
        unsigned int delta;
        unsigned int ndesc, lendesc;
        unsigned char dir;
        struct mon_bin_hdr *ep;
        char data_tag = 0;

        ktime_get_real_ts64(&ts);

        spin_lock_irqsave(&rp->b_lock, flags);

        /*
         * Find the maximum allowable length, then allocate space.
         */
        urb_length = (ev_type == 'S') ?
            urb->transfer_buffer_length : urb->actual_length;
        length = urb_length;

        if (usb_endpoint_xfer_isoc(epd)) {
                if (urb->number_of_packets < 0) {
                        ndesc = 0;
                } else if (urb->number_of_packets >= ISODESC_MAX) {
                        ndesc = ISODESC_MAX;
                } else {
                        ndesc = urb->number_of_packets;
                }
                if (ev_type == 'C' && usb_urb_dir_in(urb))
                        length = mon_bin_collate_isodesc(rp, urb, ndesc);
        } else {
                ndesc = 0;
        }
        lendesc = ndesc*sizeof(struct mon_bin_isodesc);

        /* not an issue unless there's a subtle bug in a HCD somewhere */
        if (length >= urb->transfer_buffer_length)
                length = urb->transfer_buffer_length;

        if (length >= rp->b_size/5)
                length = rp->b_size/5;

        if (usb_urb_dir_in(urb)) {
                if (ev_type == 'S') {
                        length = 0;
                        data_tag = '<';
                }
                /* Cannot rely on endpoint number in case of control ep.0 */
                dir = USB_DIR_IN;
        } else {
                if (ev_type == 'C') {
                        length = 0;
                        data_tag = '>';
                }
                dir = 0;
        }

        if (rp->mmap_active) {
                offset = mon_buff_area_alloc_contiguous(rp,
                                                 length + PKT_SIZE + lendesc);
        } else {
                offset = mon_buff_area_alloc(rp, length + PKT_SIZE + lendesc);
        }
        if (offset == ~0) {
                rp->cnt_lost++;
                spin_unlock_irqrestore(&rp->b_lock, flags);
                return;
        }

        ep = MON_OFF2HDR(rp, offset);
        if ((offset += PKT_SIZE) >= rp->b_size) offset = 0;

        /*
         * Fill the allocated area.
         */
        memset(ep, 0, PKT_SIZE);
        ep->type = ev_type;
        ep->xfer_type = xfer_to_pipe[usb_endpoint_type(epd)];
        ep->epnum = dir | usb_endpoint_num(epd);
        ep->devnum = urb->dev->devnum;
        ep->busnum = urb->dev->bus->busnum;
        ep->id = (unsigned long) urb;
        ep->ts_sec = ts.tv_sec;
        ep->ts_usec = ts.tv_nsec / NSEC_PER_USEC;
        ep->status = status;
        ep->len_urb = urb_length;
        ep->len_cap = length + lendesc;
        ep->xfer_flags = urb->transfer_flags;

        if (usb_endpoint_xfer_int(epd)) {
                ep->interval = urb->interval;
        } else if (usb_endpoint_xfer_isoc(epd)) {
                ep->interval = urb->interval;
                ep->start_frame = urb->start_frame;
                ep->s.iso.error_count = urb->error_count;
                ep->s.iso.numdesc = urb->number_of_packets;
        }

        if (usb_endpoint_xfer_control(epd) && ev_type == 'S') {
                ep->flag_setup = mon_bin_get_setup(ep->s.setup, urb, ev_type);
        } else {
                ep->flag_setup = '-';
        }

        if (ndesc != 0) {
                ep->ndesc = ndesc;
                mon_bin_get_isodesc(rp, offset, urb, ev_type, ndesc);
                if ((offset += lendesc) >= rp->b_size)
                        offset -= rp->b_size;
        }

        if (length != 0) {
                length = mon_bin_get_data(rp, offset, urb, length,
                                &ep->flag_data);
                if (length > 0) {
                        delta = (ep->len_cap + PKT_ALIGN-1) & ~(PKT_ALIGN-1);
                        ep->len_cap -= length;
                        delta -= (ep->len_cap + PKT_ALIGN-1) & ~(PKT_ALIGN-1);
                        mon_buff_area_shrink(rp, delta);
                }
        } else {
                ep->flag_data = data_tag;
        }

        spin_unlock_irqrestore(&rp->b_lock, flags);

        wake_up(&rp->b_wait);
}

static void mon_bin_submit(void *data, struct urb *urb)
{
        struct mon_reader_bin *rp = data;
        mon_bin_event(rp, urb, 'S', -EINPROGRESS);
}

static void mon_bin_complete(void *data, struct urb *urb, int status)
{
        struct mon_reader_bin *rp = data;
        mon_bin_event(rp, urb, 'C', status);
}

static void mon_bin_error(void *data, struct urb *urb, int error)
{
        struct mon_reader_bin *rp = data;
        struct timespec64 ts;
        unsigned long flags;
        unsigned int offset;
        struct mon_bin_hdr *ep;

        ktime_get_real_ts64(&ts);

        spin_lock_irqsave(&rp->b_lock, flags);

        offset = mon_buff_area_alloc(rp, PKT_SIZE);
        if (offset == ~0) {
                /* Not incrementing cnt_lost. Just because. */
                spin_unlock_irqrestore(&rp->b_lock, flags);
                return;
        }

        ep = MON_OFF2HDR(rp, offset);

        memset(ep, 0, PKT_SIZE);
        ep->type = 'E';
        ep->xfer_type = xfer_to_pipe[usb_endpoint_type(&urb->ep->desc)];
        ep->epnum = usb_urb_dir_in(urb) ? USB_DIR_IN : 0;
        ep->epnum |= usb_endpoint_num(&urb->ep->desc);
        ep->devnum = urb->dev->devnum;
        ep->busnum = urb->dev->bus->busnum;
        ep->id = (unsigned long) urb;
        ep->ts_sec = ts.tv_sec;
        ep->ts_usec = ts.tv_nsec / NSEC_PER_USEC;
        ep->status = error;

        ep->flag_setup = '-';
        ep->flag_data = 'E';

        spin_unlock_irqrestore(&rp->b_lock, flags);

        wake_up(&rp->b_wait);
}

static int mon_bin_open(struct inode *inode, struct file *file)
{
        struct mon_bus *mbus;
        struct mon_reader_bin *rp;
        size_t size;
        int rc;

        mutex_lock(&mon_lock);
        mbus = mon_bus_lookup(iminor(inode));
        if (mbus == NULL) {
                mutex_unlock(&mon_lock);
                return -ENODEV;
        }
        if (mbus != &mon_bus0 && mbus->u_bus == NULL) {
                printk(KERN_ERR TAG ": consistency error on open\n");
                mutex_unlock(&mon_lock);
                return -ENODEV;
        }

        rp = kzalloc(sizeof(struct mon_reader_bin), GFP_KERNEL);
        if (rp == NULL) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        spin_lock_init(&rp->b_lock);
        init_waitqueue_head(&rp->b_wait);
        mutex_init(&rp->fetch_lock);
        rp->b_size = BUFF_DFL;

        size = sizeof(struct mon_pgmap) * (rp->b_size/CHUNK_SIZE);
        if ((rp->b_vec = kzalloc(size, GFP_KERNEL)) == NULL) {
                rc = -ENOMEM;
                goto err_allocvec;
        }

        if ((rc = mon_alloc_buff(rp->b_vec, rp->b_size/CHUNK_SIZE)) < 0)
                goto err_allocbuff;

        rp->r.m_bus = mbus;
        rp->r.r_data = rp;
        rp->r.rnf_submit = mon_bin_submit;
        rp->r.rnf_error = mon_bin_error;
        rp->r.rnf_complete = mon_bin_complete;

        mon_reader_add(mbus, &rp->r);

        file->private_data = rp;
        mutex_unlock(&mon_lock);
        return 0;

err_allocbuff:
        kfree(rp->b_vec);
err_allocvec:
        kfree(rp);
err_alloc:
        mutex_unlock(&mon_lock);
        return rc;
}

/*
 * Extract an event from buffer and copy it to user space.
 * Wait if there is no event ready.
 * Returns zero or error.
 */
static int mon_bin_get_event(struct file *file, struct mon_reader_bin *rp,
    struct mon_bin_hdr __user *hdr, unsigned int hdrbytes,
    void __user *data, unsigned int nbytes)
{
        unsigned long flags;
        struct mon_bin_hdr *ep;
        size_t step_len;
        unsigned int offset;
        int rc;

        mutex_lock(&rp->fetch_lock);

        if ((rc = mon_bin_wait_event(file, rp)) < 0) {
                mutex_unlock(&rp->fetch_lock);
                return rc;
        }

        ep = MON_OFF2HDR(rp, rp->b_out);

        if (copy_to_user(hdr, ep, hdrbytes)) {
                mutex_unlock(&rp->fetch_lock);
                return -EFAULT;
        }

        step_len = min(ep->len_cap, nbytes);
        if ((offset = rp->b_out + PKT_SIZE) >= rp->b_size) offset = 0;

        if (copy_from_buf(rp, offset, data, step_len)) {
                mutex_unlock(&rp->fetch_lock);
                return -EFAULT;
        }

        spin_lock_irqsave(&rp->b_lock, flags);
        mon_buff_area_free(rp, PKT_SIZE + ep->len_cap);
        spin_unlock_irqrestore(&rp->b_lock, flags);
        rp->b_read = 0;

        mutex_unlock(&rp->fetch_lock);
        return 0;
}

static int mon_bin_release(struct inode *inode, struct file *file)
{
        struct mon_reader_bin *rp = file->private_data;
        struct mon_bus* mbus = rp->r.m_bus;

        mutex_lock(&mon_lock);

        if (mbus->nreaders <= 0) {
                printk(KERN_ERR TAG ": consistency error on close\n");
                mutex_unlock(&mon_lock);
                return 0;
        }
        mon_reader_del(mbus, &rp->r);

        mon_free_buff(rp->b_vec, rp->b_size/CHUNK_SIZE);
        kfree(rp->b_vec);
        kfree(rp);

        mutex_unlock(&mon_lock);
        return 0;
}

static ssize_t mon_bin_read(struct file *file, char __user *buf,
    size_t nbytes, loff_t *ppos)
{
        struct mon_reader_bin *rp = file->private_data;
        unsigned int hdrbytes = PKT_SZ_API0;
        unsigned long flags;
        struct mon_bin_hdr *ep;
        unsigned int offset;
        size_t step_len;
        char *ptr;
        ssize_t done = 0;
        int rc;

        mutex_lock(&rp->fetch_lock);

        if ((rc = mon_bin_wait_event(file, rp)) < 0) {
                mutex_unlock(&rp->fetch_lock);
                return rc;
        }

        ep = MON_OFF2HDR(rp, rp->b_out);

        if (rp->b_read < hdrbytes) {
                step_len = min(nbytes, (size_t)(hdrbytes - rp->b_read));
                ptr = ((char *)ep) + rp->b_read;
                if (step_len && copy_to_user(buf, ptr, step_len)) {
                        mutex_unlock(&rp->fetch_lock);
                        return -EFAULT;
                }
                nbytes -= step_len;
                buf += step_len;
                rp->b_read += step_len;
                done += step_len;
        }

        if (rp->b_read >= hdrbytes) {
                step_len = ep->len_cap;
                step_len -= rp->b_read - hdrbytes;
                if (step_len > nbytes)
                        step_len = nbytes;
                offset = rp->b_out + PKT_SIZE;
                offset += rp->b_read - hdrbytes;
                if (offset >= rp->b_size)
                        offset -= rp->b_size;
                if (copy_from_buf(rp, offset, buf, step_len)) {
                        mutex_unlock(&rp->fetch_lock);
                        return -EFAULT;
                }
                nbytes -= step_len;
                buf += step_len;
                rp->b_read += step_len;
                done += step_len;
        }

        /*
         * Check if whole packet was read, and if so, jump to the next one.
         */
        if (rp->b_read >= hdrbytes + ep->len_cap) {
                spin_lock_irqsave(&rp->b_lock, flags);
                mon_buff_area_free(rp, PKT_SIZE + ep->len_cap);
                spin_unlock_irqrestore(&rp->b_lock, flags);
                rp->b_read = 0;
        }

        mutex_unlock(&rp->fetch_lock);
        return done;
}

/*
 * Remove at most nevents from chunked buffer.
 * Returns the number of removed events.
 */
static int mon_bin_flush(struct mon_reader_bin *rp, unsigned nevents)
{
        unsigned long flags;
        struct mon_bin_hdr *ep;
        int i;

        mutex_lock(&rp->fetch_lock);
        spin_lock_irqsave(&rp->b_lock, flags);
        for (i = 0; i < nevents; ++i) {
                if (MON_RING_EMPTY(rp))
                        break;

                ep = MON_OFF2HDR(rp, rp->b_out);
                mon_buff_area_free(rp, PKT_SIZE + ep->len_cap);
        }
        spin_unlock_irqrestore(&rp->b_lock, flags);
        rp->b_read = 0;
        mutex_unlock(&rp->fetch_lock);
        return i;
}

/*
 * Fetch at most max event offsets into the buffer and put them into vec.
 * The events are usually freed later with mon_bin_flush.
 * Return the effective number of events fetched.
 */
static int mon_bin_fetch(struct file *file, struct mon_reader_bin *rp,
    u32 __user *vec, unsigned int max)
{
        unsigned int cur_out;
        unsigned int bytes, avail;
        unsigned int size;
        unsigned int nevents;
        struct mon_bin_hdr *ep;
        unsigned long flags;
        int rc;

        mutex_lock(&rp->fetch_lock);

        if ((rc = mon_bin_wait_event(file, rp)) < 0) {
                mutex_unlock(&rp->fetch_lock);
                return rc;
        }

        spin_lock_irqsave(&rp->b_lock, flags);
        avail = rp->b_cnt;
        spin_unlock_irqrestore(&rp->b_lock, flags);

        cur_out = rp->b_out;
        nevents = 0;
        bytes = 0;
        while (bytes < avail) {
                if (nevents >= max)
                        break;

                ep = MON_OFF2HDR(rp, cur_out);
                if (put_user(cur_out, &vec[nevents])) {
                        mutex_unlock(&rp->fetch_lock);
                        return -EFAULT;
                }

                nevents++;
                size = ep->len_cap + PKT_SIZE;
                size = (size + PKT_ALIGN-1) & ~(PKT_ALIGN-1);
                if ((cur_out += size) >= rp->b_size)
                        cur_out -= rp->b_size;
                bytes += size;
        }

        mutex_unlock(&rp->fetch_lock);
        return nevents;
}

/*
 * Count events. This is almost the same as the above mon_bin_fetch,
 * only we do not store offsets into user vector, and we have no limit.
 */
static int mon_bin_queued(struct mon_reader_bin *rp)
{
        unsigned int cur_out;
        unsigned int bytes, avail;
        unsigned int size;
        unsigned int nevents;
        struct mon_bin_hdr *ep;
        unsigned long flags;

        mutex_lock(&rp->fetch_lock);

        spin_lock_irqsave(&rp->b_lock, flags);
        avail = rp->b_cnt;
        spin_unlock_irqrestore(&rp->b_lock, flags);

        cur_out = rp->b_out;
        nevents = 0;
        bytes = 0;
        while (bytes < avail) {
                ep = MON_OFF2HDR(rp, cur_out);

                nevents++;
                size = ep->len_cap + PKT_SIZE;
                size = (size + PKT_ALIGN-1) & ~(PKT_ALIGN-1);
                if ((cur_out += size) >= rp->b_size)
                        cur_out -= rp->b_size;
                bytes += size;
        }

        mutex_unlock(&rp->fetch_lock);
        return nevents;
}

/*
 */
static long mon_bin_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct mon_reader_bin *rp = file->private_data;
        // struct mon_bus* mbus = rp->r.m_bus;
        int ret = 0;
        struct mon_bin_hdr *ep;
        unsigned long flags;

        switch (cmd) {

        case MON_IOCQ_URB_LEN:
                /*
                 * N.B. This only returns the size of data, without the header.
                 */
                spin_lock_irqsave(&rp->b_lock, flags);
                if (!MON_RING_EMPTY(rp)) {
                        ep = MON_OFF2HDR(rp, rp->b_out);

                        ret = ep->len_cap;
                }
                spin_unlock_irqrestore(&rp->b_lock, flags);
                break;

        case MON_IOCQ_RING_SIZE:
                mutex_lock(&rp->fetch_lock);
                ret = rp->b_size;
                mutex_unlock(&rp->fetch_lock);
                break;

        case MON_IOCT_RING_SIZE:
                /*
                 * Changing the buffer size will flush it's contents; the new
                 * buffer is allocated before releasing the old one to be sure
                 * the device will stay functional also in case of memory
                 * pressure.
                 */
                {
                int size;
                struct mon_pgmap *vec;

                if (arg < BUFF_MIN || arg > BUFF_MAX)
                        return -EINVAL;

                size = CHUNK_ALIGN(arg);
                vec = kcalloc(size / CHUNK_SIZE, sizeof(struct mon_pgmap),
                              GFP_KERNEL);
                if (vec == NULL) {
                        ret = -ENOMEM;
                        break;
                }

                ret = mon_alloc_buff(vec, size/CHUNK_SIZE);
                if (ret < 0) {
                        kfree(vec);
                        break;
                }

                mutex_lock(&rp->fetch_lock);
                spin_lock_irqsave(&rp->b_lock, flags);
                mon_free_buff(rp->b_vec, rp->b_size/CHUNK_SIZE);
                kfree(rp->b_vec);
                rp->b_vec  = vec;
                rp->b_size = size;
                rp->b_read = rp->b_in = rp->b_out = rp->b_cnt = 0;
                rp->cnt_lost = 0;
                spin_unlock_irqrestore(&rp->b_lock, flags);
                mutex_unlock(&rp->fetch_lock);
                }
                break;

        case MON_IOCH_MFLUSH:
                ret = mon_bin_flush(rp, arg);
                break;

        case MON_IOCX_GET:
        case MON_IOCX_GETX:
                {
                struct mon_bin_get getb;

                if (copy_from_user(&getb, (void __user *)arg,
                                            sizeof(struct mon_bin_get)))
                        return -EFAULT;

                if (getb.alloc > 0x10000000)    /* Want to cast to u32 */
                        return -EINVAL;
                ret = mon_bin_get_event(file, rp, getb.hdr,
                    (cmd == MON_IOCX_GET)? PKT_SZ_API0: PKT_SZ_API1,
                    getb.data, (unsigned int)getb.alloc);
                }
                break;

        case MON_IOCX_MFETCH:
                {
                struct mon_bin_mfetch mfetch;
                struct mon_bin_mfetch __user *uptr;

                uptr = (struct mon_bin_mfetch __user *)arg;

                if (copy_from_user(&mfetch, uptr, sizeof(mfetch)))
                        return -EFAULT;

                if (mfetch.nflush) {
                        ret = mon_bin_flush(rp, mfetch.nflush);
                        if (ret < 0)
                                return ret;
                        if (put_user(ret, &uptr->nflush))
                                return -EFAULT;
                }
                ret = mon_bin_fetch(file, rp, mfetch.offvec, mfetch.nfetch);
                if (ret < 0)
                        return ret;
                if (put_user(ret, &uptr->nfetch))
                        return -EFAULT;
                ret = 0;
                }
                break;

        case MON_IOCG_STATS: {
                struct mon_bin_stats __user *sp;
                unsigned int nevents;
                unsigned int ndropped;

                spin_lock_irqsave(&rp->b_lock, flags);
                ndropped = rp->cnt_lost;
                rp->cnt_lost = 0;
                spin_unlock_irqrestore(&rp->b_lock, flags);
                nevents = mon_bin_queued(rp);

                sp = (struct mon_bin_stats __user *)arg;
                if (put_user(ndropped, &sp->dropped))
                        return -EFAULT;
                if (put_user(nevents, &sp->queued))
                        return -EFAULT;

                }
                break;

        default:
                return -ENOTTY;
        }

        return ret;
}

#ifdef CONFIG_COMPAT
static long mon_bin_compat_ioctl(struct file *file,
    unsigned int cmd, unsigned long arg)
{
        struct mon_reader_bin *rp = file->private_data;
        int ret;

        switch (cmd) {

        case MON_IOCX_GET32:
        case MON_IOCX_GETX32:
                {
                struct mon_bin_get32 getb;

                if (copy_from_user(&getb, (void __user *)arg,
                                            sizeof(struct mon_bin_get32)))
                        return -EFAULT;

                ret = mon_bin_get_event(file, rp, compat_ptr(getb.hdr32),
                    (cmd == MON_IOCX_GET32)? PKT_SZ_API0: PKT_SZ_API1,
                    compat_ptr(getb.data32), getb.alloc32);
                if (ret < 0)
                        return ret;
                }
                return 0;

        case MON_IOCX_MFETCH32:
                {
                struct mon_bin_mfetch32 mfetch;
                struct mon_bin_mfetch32 __user *uptr;

                uptr = (struct mon_bin_mfetch32 __user *) compat_ptr(arg);

                if (copy_from_user(&mfetch, uptr, sizeof(mfetch)))
                        return -EFAULT;

                if (mfetch.nflush32) {
                        ret = mon_bin_flush(rp, mfetch.nflush32);
                        if (ret < 0)
                                return ret;
                        if (put_user(ret, &uptr->nflush32))
                                return -EFAULT;
                }
                ret = mon_bin_fetch(file, rp, compat_ptr(mfetch.offvec32),
                    mfetch.nfetch32);
                if (ret < 0)
                        return ret;
                if (put_user(ret, &uptr->nfetch32))
                        return -EFAULT;
                }
                return 0;

        case MON_IOCG_STATS:
                return mon_bin_ioctl(file, cmd, (unsigned long) compat_ptr(arg));

        case MON_IOCQ_URB_LEN:
        case MON_IOCQ_RING_SIZE:
        case MON_IOCT_RING_SIZE:
        case MON_IOCH_MFLUSH:
                return mon_bin_ioctl(file, cmd, arg);

        default:
                ;
        }
        return -ENOTTY;
}
#endif /* CONFIG_COMPAT */

static __poll_t
mon_bin_poll(struct file *file, struct poll_table_struct *wait)
{
        struct mon_reader_bin *rp = file->private_data;
        __poll_t mask = 0;
        unsigned long flags;

        if (file->f_mode & FMODE_READ)
                poll_wait(file, &rp->b_wait, wait);

        spin_lock_irqsave(&rp->b_lock, flags);
        if (!MON_RING_EMPTY(rp))
                mask |= EPOLLIN | EPOLLRDNORM;    /* readable */
        spin_unlock_irqrestore(&rp->b_lock, flags);
        return mask;
}

/*
 * open and close: just keep track of how many times the device is
 * mapped, to use the proper memory allocation function.
 */
static void mon_bin_vma_open(struct vm_area_struct *vma)
{
        struct mon_reader_bin *rp = vma->vm_private_data;
        rp->mmap_active++;
}

static void mon_bin_vma_close(struct vm_area_struct *vma)
{
        struct mon_reader_bin *rp = vma->vm_private_data;
        rp->mmap_active--;
}

/*
 * Map ring pages to user space.
 */
static vm_fault_t mon_bin_vma_fault(struct vm_fault *vmf)
{
        struct mon_reader_bin *rp = vmf->vma->vm_private_data;
        unsigned long offset, chunk_idx;
        struct page *pageptr;

        mutex_lock(&rp->fetch_lock);
        offset = vmf->pgoff << PAGE_SHIFT;
        if (offset >= rp->b_size) {
                mutex_unlock(&rp->fetch_lock);
                return VM_FAULT_SIGBUS;
        }
        chunk_idx = offset / CHUNK_SIZE;
        pageptr = rp->b_vec[chunk_idx].pg;
        get_page(pageptr);
        mutex_unlock(&rp->fetch_lock);
        vmf->page = pageptr;
        return 0;
}

static const struct vm_operations_struct mon_bin_vm_ops = {
        .open =     mon_bin_vma_open,
        .close =    mon_bin_vma_close,
        .fault =    mon_bin_vma_fault,
};

static int mon_bin_mmap(struct file *filp, struct vm_area_struct *vma)
{
        /* don't do anything here: "fault" will set up page table entries */
        vma->vm_ops = &mon_bin_vm_ops;
        vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
        vma->vm_private_data = filp->private_data;
        mon_bin_vma_open(vma);
        return 0;
}

static const struct file_operations mon_fops_binary = {
        .owner =        THIS_MODULE,
        .open =         mon_bin_open,
        .llseek =       no_llseek,
        .read =         mon_bin_read,
        /* .write =     mon_text_write, */
        .poll =         mon_bin_poll,
        .unlocked_ioctl = mon_bin_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = mon_bin_compat_ioctl,
#endif
        .release =      mon_bin_release,
        .mmap =         mon_bin_mmap,
};

static int mon_bin_wait_event(struct file *file, struct mon_reader_bin *rp)
{
        DECLARE_WAITQUEUE(waita, current);
        unsigned long flags;

        add_wait_queue(&rp->b_wait, &waita);
        set_current_state(TASK_INTERRUPTIBLE);

        spin_lock_irqsave(&rp->b_lock, flags);
        while (MON_RING_EMPTY(rp)) {
                spin_unlock_irqrestore(&rp->b_lock, flags);

                if (file->f_flags & O_NONBLOCK) {
                        set_current_state(TASK_RUNNING);
                        remove_wait_queue(&rp->b_wait, &waita);
                        return -EWOULDBLOCK; /* Same as EAGAIN in Linux */
                }
                schedule();
                if (signal_pending(current)) {
                        remove_wait_queue(&rp->b_wait, &waita);
                        return -EINTR;
                }
                set_current_state(TASK_INTERRUPTIBLE);

                spin_lock_irqsave(&rp->b_lock, flags);
        }
        spin_unlock_irqrestore(&rp->b_lock, flags);

        set_current_state(TASK_RUNNING);
        remove_wait_queue(&rp->b_wait, &waita);
        return 0;
}

static int mon_alloc_buff(struct mon_pgmap *map, int npages)
{
        int n;
        unsigned long vaddr;

        for (n = 0; n < npages; n++) {
                vaddr = get_zeroed_page(GFP_KERNEL);
                if (vaddr == 0) {
                        while (n-- != 0)
                                free_page((unsigned long) map[n].ptr);
                        return -ENOMEM;
                }
                map[n].ptr = (unsigned char *) vaddr;
                map[n].pg = virt_to_page((void *) vaddr);
        }
        return 0;
}

static void mon_free_buff(struct mon_pgmap *map, int npages)
{
        int n;

        for (n = 0; n < npages; n++)
                free_page((unsigned long) map[n].ptr);
}

int mon_bin_add(struct mon_bus *mbus, const struct usb_bus *ubus)
{
        struct device *dev;
        unsigned minor = ubus? ubus->busnum: 0;

        if (minor >= MON_BIN_MAX_MINOR)
                return 0;

        dev = device_create(mon_bin_class, ubus ? ubus->controller : NULL,
                            MKDEV(MAJOR(mon_bin_dev0), minor), NULL,
                            "usbmon%d", minor);
        if (IS_ERR(dev))
                return 0;

        mbus->classdev = dev;
        return 1;
}

void mon_bin_del(struct mon_bus *mbus)
{
        device_destroy(mon_bin_class, mbus->classdev->devt);
}

int __init mon_bin_init(void)
{
        int rc;

        mon_bin_class = class_create(THIS_MODULE, "usbmon");
        if (IS_ERR(mon_bin_class)) {
                rc = PTR_ERR(mon_bin_class);
                goto err_class;
        }

        rc = alloc_chrdev_region(&mon_bin_dev0, 0, MON_BIN_MAX_MINOR, "usbmon");
        if (rc < 0)
                goto err_dev;

        cdev_init(&mon_bin_cdev, &mon_fops_binary);
        mon_bin_cdev.owner = THIS_MODULE;

        rc = cdev_add(&mon_bin_cdev, mon_bin_dev0, MON_BIN_MAX_MINOR);
        if (rc < 0)
                goto err_add;

        return 0;

err_add:
        unregister_chrdev_region(mon_bin_dev0, MON_BIN_MAX_MINOR);
err_dev:
        class_destroy(mon_bin_class);
err_class:
        return rc;
}

void mon_bin_exit(void)
{
        cdev_del(&mon_bin_cdev);
        unregister_chrdev_region(mon_bin_dev0, MON_BIN_MAX_MINOR);
        class_destroy(mon_bin_class);
}