drivers/usb/mon/mon_text.c

   1 /*
   2  * The USB Monitor, inspired by Dave Harding's USBMon.
   3  *
   4  * This is a text format reader.
   5  */
   6
   7 #include <linux/kernel.h>
   8 #include <linux/list.h>
   9 #include <linux/usb.h>
  10 #include <linux/slab.h>
  11 #include <linux/sched/signal.h>
  12 #include <linux/time.h>
  13 #include <linux/ktime.h>
  14 #include <linux/export.h>
  15 #include <linux/mutex.h>
  16 #include <linux/debugfs.h>
  17 #include <linux/scatterlist.h>
  18 #include <linux/uaccess.h>
  19
  20 #include "usb_mon.h"
  21
  22 /*
  23  * No, we do not want arbitrarily long data strings.
  24  * Use the binary interface if you want to capture bulk data!
  25  */
  26 #define DATA_MAX  32
  27
  28 /*
  29  * Defined by USB 2.0 clause 9.3, table 9.2.
  30  */
  31 #define SETUP_MAX  8
  32
  33 /*
  34  * This limit exists to prevent OOMs when the user process stops reading.
  35  * If usbmon were available to unprivileged processes, it might be open
  36  * to a local DoS. But we have to keep to root in order to prevent
  37  * password sniffing from HID devices.
  38  */
  39 #define EVENT_MAX  (4*PAGE_SIZE / sizeof(struct mon_event_text))
  40
  41 /*
  42  * Potentially unlimited number; we limit it for similar allocations.
  43  * The usbfs limits this to 128, but we're not quite as generous.
  44  */
  45 #define ISODESC_MAX   5
  46
  47 #define PRINTF_DFL  250   /* with 5 ISOs segs */
  48
  49 struct mon_iso_desc {
  50         int status;
  51         unsigned int offset;
  52         unsigned int length;    /* Unsigned here, signed in URB. Historic. */
  53 };
  54
  55 struct mon_event_text {
  56         struct list_head e_link;
  57         int type;               /* submit, complete, etc. */
  58         unsigned long id;       /* From pointer, most of the time */
  59         unsigned int tstamp;
  60         int busnum;
  61         char devnum;
  62         char epnum;
  63         char is_in;
  64         char xfertype;
  65         int length;             /* Depends on type: xfer length or act length */
  66         int status;
  67         int interval;
  68         int start_frame;
  69         int error_count;
  70         char setup_flag;
  71         char data_flag;
  72         int numdesc;            /* Full number */
  73         struct mon_iso_desc isodesc[ISODESC_MAX];
  74         unsigned char setup[SETUP_MAX];
  75         unsigned char data[DATA_MAX];
  76 };
  77
  78 #define SLAB_NAME_SZ  30
  79 struct mon_reader_text {
  80         struct kmem_cache *e_slab;
  81         int nevents;
  82         struct list_head e_list;
  83         struct mon_reader r;    /* In C, parent class can be placed anywhere */
  84
  85         wait_queue_head_t wait;
  86         int printf_size;
  87         char *printf_buf;
  88         struct mutex printf_lock;
  89
  90         char slab_name[SLAB_NAME_SZ];
  91 };
  92
  93 static struct dentry *mon_dir;          /* Usually /sys/kernel/debug/usbmon */
  94
  95 static void mon_text_ctor(void *);
  96
  97 struct mon_text_ptr {
  98         int cnt, limit;
  99         char *pbuf;
 100 };
 101
 102 static struct mon_event_text *
 103     mon_text_read_wait(struct mon_reader_text *rp, struct file *file);
 104 static void mon_text_read_head_t(struct mon_reader_text *rp,
 105         struct mon_text_ptr *p, const struct mon_event_text *ep);
 106 static void mon_text_read_head_u(struct mon_reader_text *rp,
 107         struct mon_text_ptr *p, const struct mon_event_text *ep);
 108 static void mon_text_read_statset(struct mon_reader_text *rp,
 109         struct mon_text_ptr *p, const struct mon_event_text *ep);
 110 static void mon_text_read_intstat(struct mon_reader_text *rp,
 111         struct mon_text_ptr *p, const struct mon_event_text *ep);
 112 static void mon_text_read_isostat(struct mon_reader_text *rp,
 113         struct mon_text_ptr *p, const struct mon_event_text *ep);
 114 static void mon_text_read_isodesc(struct mon_reader_text *rp,
 115         struct mon_text_ptr *p, const struct mon_event_text *ep);
 116 static void mon_text_read_data(struct mon_reader_text *rp,
 117     struct mon_text_ptr *p, const struct mon_event_text *ep);
 118
 119 /*
 120  * mon_text_submit
 121  * mon_text_complete
 122  *
 123  * May be called from an interrupt.
 124  *
 125  * This is called with the whole mon_bus locked, so no additional lock.
 126  */
 127
 128 static inline char mon_text_get_setup(struct mon_event_text *ep,
 129     struct urb *urb, char ev_type, struct mon_bus *mbus)
 130 {
 131
 132         if (ep->xfertype != USB_ENDPOINT_XFER_CONTROL || ev_type != 'S')
 133                 return '-';
 134
 135         if (urb->setup_packet == NULL)
 136                 return 'Z';     /* '0' would be not as pretty. */
 137
 138         memcpy(ep->setup, urb->setup_packet, SETUP_MAX);
 139         return 0;
 140 }
 141
 142 static inline char mon_text_get_data(struct mon_event_text *ep, struct urb *urb,
 143     int len, char ev_type, struct mon_bus *mbus)
 144 {
 145         void *src;
 146
 147         if (len <= 0)
 148                 return 'L';
 149         if (len >= DATA_MAX)
 150                 len = DATA_MAX;
 151
 152         if (ep->is_in) {
 153                 if (ev_type != 'C')
 154                         return '<';
 155         } else {
 156                 if (ev_type != 'S')
 157                         return '>';
 158         }
 159
 160         if (urb->num_sgs == 0) {
 161                 src = urb->transfer_buffer;
 162                 if (src == NULL)
 163                         return 'Z';     /* '0' would be not as pretty. */
 164         } else {
 165                 struct scatterlist *sg = urb->sg;
 166
 167                 if (PageHighMem(sg_page(sg)))
 168                         return 'D';
 169
 170                 /* For the text interface we copy only the first sg buffer */
 171                 len = min_t(int, sg->length, len);
 172                 src = sg_virt(sg);
 173         }
 174
 175         memcpy(ep->data, src, len);
 176         return 0;
 177 }
 178
 179 static inline unsigned int mon_get_timestamp(void)
 180 {
 181         struct timespec64 now;
 182         unsigned int stamp;
 183
 184         ktime_get_ts64(&now);
 185         stamp = now.tv_sec & 0xFFF;  /* 2^32 = 4294967296. Limit to 4096s. */
 186         stamp = stamp * USEC_PER_SEC + now.tv_nsec / NSEC_PER_USEC;
 187         return stamp;
 188 }
 189
 190 static void mon_text_event(struct mon_reader_text *rp, struct urb *urb,
 191     char ev_type, int status)
 192 {
 193         struct mon_event_text *ep;
 194         unsigned int stamp;
 195         struct usb_iso_packet_descriptor *fp;
 196         struct mon_iso_desc *dp;
 197         int i, ndesc;
 198
 199         stamp = mon_get_timestamp();
 200
 201         if (rp->nevents >= EVENT_MAX ||
 202             (ep = kmem_cache_alloc(rp->e_slab, GFP_ATOMIC)) == NULL) {
 203                 rp->r.m_bus->cnt_text_lost++;
 204                 return;
 205         }
 206
 207         ep->type = ev_type;
 208         ep->id = (unsigned long) urb;
 209         ep->busnum = urb->dev->bus->busnum;
 210         ep->devnum = urb->dev->devnum;
 211         ep->epnum = usb_endpoint_num(&urb->ep->desc);
 212         ep->xfertype = usb_endpoint_type(&urb->ep->desc);
 213         ep->is_in = usb_urb_dir_in(urb);
 214         ep->tstamp = stamp;
 215         ep->length = (ev_type == 'S') ?
 216             urb->transfer_buffer_length : urb->actual_length;
 217         /* Collecting status makes debugging sense for submits, too */
 218         ep->status = status;
 219
 220         if (ep->xfertype == USB_ENDPOINT_XFER_INT) {
 221                 ep->interval = urb->interval;
 222         } else if (ep->xfertype == USB_ENDPOINT_XFER_ISOC) {
 223                 ep->interval = urb->interval;
 224                 ep->start_frame = urb->start_frame;
 225                 ep->error_count = urb->error_count;
 226         }
 227         ep->numdesc = urb->number_of_packets;
 228         if (ep->xfertype == USB_ENDPOINT_XFER_ISOC &&
 229                         urb->number_of_packets > 0) {
 230                 if ((ndesc = urb->number_of_packets) > ISODESC_MAX)
 231                         ndesc = ISODESC_MAX;
 232                 fp = urb->iso_frame_desc;
 233                 dp = ep->isodesc;
 234                 for (i = 0; i < ndesc; i++) {
 235                         dp->status = fp->status;
 236                         dp->offset = fp->offset;
 237                         dp->length = (ev_type == 'S') ?
 238                             fp->length : fp->actual_length;
 239                         fp++;
 240                         dp++;
 241                 }
 242                 /* Wasteful, but simple to understand: ISO 'C' is sparse. */
 243                 if (ev_type == 'C')
 244                         ep->length = urb->transfer_buffer_length;
 245         }
 246
 247         ep->setup_flag = mon_text_get_setup(ep, urb, ev_type, rp->r.m_bus);
 248         ep->data_flag = mon_text_get_data(ep, urb, ep->length, ev_type,
 249                         rp->r.m_bus);
 250
 251         rp->nevents++;
 252         list_add_tail(&ep->e_link, &rp->e_list);
 253         wake_up(&rp->wait);
 254 }
 255
 256 static void mon_text_submit(void *data, struct urb *urb)
 257 {
 258         struct mon_reader_text *rp = data;
 259         mon_text_event(rp, urb, 'S', -EINPROGRESS);
 260 }
 261
 262 static void mon_text_complete(void *data, struct urb *urb, int status)
 263 {
 264         struct mon_reader_text *rp = data;
 265         mon_text_event(rp, urb, 'C', status);
 266 }
 267
 268 static void mon_text_error(void *data, struct urb *urb, int error)
 269 {
 270         struct mon_reader_text *rp = data;
 271         struct mon_event_text *ep;
 272
 273         if (rp->nevents >= EVENT_MAX ||
 274             (ep = kmem_cache_alloc(rp->e_slab, GFP_ATOMIC)) == NULL) {
 275                 rp->r.m_bus->cnt_text_lost++;
 276                 return;
 277         }
 278
 279         ep->type = 'E';
 280         ep->id = (unsigned long) urb;
 281         ep->busnum = urb->dev->bus->busnum;
 282         ep->devnum = urb->dev->devnum;
 283         ep->epnum = usb_endpoint_num(&urb->ep->desc);
 284         ep->xfertype = usb_endpoint_type(&urb->ep->desc);
 285         ep->is_in = usb_urb_dir_in(urb);
 286         ep->tstamp = mon_get_timestamp();
 287         ep->length = 0;
 288         ep->status = error;
 289
 290         ep->setup_flag = '-';
 291         ep->data_flag = 'E';
 292
 293         rp->nevents++;
 294         list_add_tail(&ep->e_link, &rp->e_list);
 295         wake_up(&rp->wait);
 296 }
 297
 298 /*
 299  * Fetch next event from the circular buffer.
 300  */
 301 static struct mon_event_text *mon_text_fetch(struct mon_reader_text *rp,
 302     struct mon_bus *mbus)
 303 {
 304         struct list_head *p;
 305         unsigned long flags;
 306
 307         spin_lock_irqsave(&mbus->lock, flags);
 308         if (list_empty(&rp->e_list)) {
 309                 spin_unlock_irqrestore(&mbus->lock, flags);
 310                 return NULL;
 311         }
 312         p = rp->e_list.next;
 313         list_del(p);
 314         --rp->nevents;
 315         spin_unlock_irqrestore(&mbus->lock, flags);
 316         return list_entry(p, struct mon_event_text, e_link);
 317 }
 318
 319 /*
 320  */
 321 static int mon_text_open(struct inode *inode, struct file *file)
 322 {
 323         struct mon_bus *mbus;
 324         struct mon_reader_text *rp;
 325         int rc;
 326
 327         mutex_lock(&mon_lock);
 328         mbus = inode->i_private;
 329
 330         rp = kzalloc(sizeof(struct mon_reader_text), GFP_KERNEL);
 331         if (rp == NULL) {
 332                 rc = -ENOMEM;
 333                 goto err_alloc;
 334         }
 335         INIT_LIST_HEAD(&rp->e_list);
 336         init_waitqueue_head(&rp->wait);
 337         mutex_init(&rp->printf_lock);
 338
 339         rp->printf_size = PRINTF_DFL;
 340         rp->printf_buf = kmalloc(rp->printf_size, GFP_KERNEL);
 341         if (rp->printf_buf == NULL) {
 342                 rc = -ENOMEM;
 343                 goto err_alloc_pr;
 344         }
 345
 346         rp->r.m_bus = mbus;
 347         rp->r.r_data = rp;
 348         rp->r.rnf_submit = mon_text_submit;
 349         rp->r.rnf_error = mon_text_error;
 350         rp->r.rnf_complete = mon_text_complete;
 351
 352         snprintf(rp->slab_name, SLAB_NAME_SZ, "mon_text_%p", rp);
 353         rp->e_slab = kmem_cache_create(rp->slab_name,
 354             sizeof(struct mon_event_text), sizeof(long), 0,
 355             mon_text_ctor);
 356         if (rp->e_slab == NULL) {
 357                 rc = -ENOMEM;
 358                 goto err_slab;
 359         }
 360
 361         mon_reader_add(mbus, &rp->r);
 362
 363         file->private_data = rp;
 364         mutex_unlock(&mon_lock);
 365         return 0;
 366
 367 // err_busy:
 368 //      kmem_cache_destroy(rp->e_slab);
 369 err_slab:
 370         kfree(rp->printf_buf);
 371 err_alloc_pr:
 372         kfree(rp);
 373 err_alloc:
 374         mutex_unlock(&mon_lock);
 375         return rc;
 376 }
 377
 378 /*
 379  * For simplicity, we read one record in one system call and throw out
 380  * what does not fit. This means that the following does not work:
 381  *   dd if=/dbg/usbmon/0t bs=10
 382  * Also, we do not allow seeks and do not bother advancing the offset.
 383  */
 384 static ssize_t mon_text_read_t(struct file *file, char __user *buf,
 385                                 size_t nbytes, loff_t *ppos)
 386 {
 387         struct mon_reader_text *rp = file->private_data;
 388         struct mon_event_text *ep;
 389         struct mon_text_ptr ptr;
 390
 391         ep = mon_text_read_wait(rp, file);
 392         if (IS_ERR(ep))
 393                 return PTR_ERR(ep);
 394         mutex_lock(&rp->printf_lock);
 395         ptr.cnt = 0;
 396         ptr.pbuf = rp->printf_buf;
 397         ptr.limit = rp->printf_size;
 398
 399         mon_text_read_head_t(rp, &ptr, ep);
 400         mon_text_read_statset(rp, &ptr, ep);
 401         ptr.cnt += snprintf(ptr.pbuf + ptr.cnt, ptr.limit - ptr.cnt,
 402             " %d", ep->length);
 403         mon_text_read_data(rp, &ptr, ep);
 404
 405         if (copy_to_user(buf, rp->printf_buf, ptr.cnt))
 406                 ptr.cnt = -EFAULT;
 407         mutex_unlock(&rp->printf_lock);
 408         kmem_cache_free(rp->e_slab, ep);
 409         return ptr.cnt;
 410 }
 411
 412 static ssize_t mon_text_read_u(struct file *file, char __user *buf,
 413                                 size_t nbytes, loff_t *ppos)
 414 {
 415         struct mon_reader_text *rp = file->private_data;
 416         struct mon_event_text *ep;
 417         struct mon_text_ptr ptr;
 418
 419         ep = mon_text_read_wait(rp, file);
 420         if (IS_ERR(ep))
 421                 return PTR_ERR(ep);
 422         mutex_lock(&rp->printf_lock);
 423         ptr.cnt = 0;
 424         ptr.pbuf = rp->printf_buf;
 425         ptr.limit = rp->printf_size;
 426
 427         mon_text_read_head_u(rp, &ptr, ep);
 428         if (ep->type == 'E') {
 429                 mon_text_read_statset(rp, &ptr, ep);
 430         } else if (ep->xfertype == USB_ENDPOINT_XFER_ISOC) {
 431                 mon_text_read_isostat(rp, &ptr, ep);
 432                 mon_text_read_isodesc(rp, &ptr, ep);
 433         } else if (ep->xfertype == USB_ENDPOINT_XFER_INT) {
 434                 mon_text_read_intstat(rp, &ptr, ep);
 435         } else {
 436                 mon_text_read_statset(rp, &ptr, ep);
 437         }
 438         ptr.cnt += snprintf(ptr.pbuf + ptr.cnt, ptr.limit - ptr.cnt,
 439             " %d", ep->length);
 440         mon_text_read_data(rp, &ptr, ep);
 441
 442         if (copy_to_user(buf, rp->printf_buf, ptr.cnt))
 443                 ptr.cnt = -EFAULT;
 444         mutex_unlock(&rp->printf_lock);
 445         kmem_cache_free(rp->e_slab, ep);
 446         return ptr.cnt;
 447 }
 448
 449 static struct mon_event_text *mon_text_read_wait(struct mon_reader_text *rp,
 450     struct file *file)
 451 {
 452         struct mon_bus *mbus = rp->r.m_bus;
 453         DECLARE_WAITQUEUE(waita, current);
 454         struct mon_event_text *ep;
 455
 456         add_wait_queue(&rp->wait, &waita);
 457         set_current_state(TASK_INTERRUPTIBLE);
 458         while ((ep = mon_text_fetch(rp, mbus)) == NULL) {
 459                 if (file->f_flags & O_NONBLOCK) {
 460                         set_current_state(TASK_RUNNING);
 461                         remove_wait_queue(&rp->wait, &waita);
 462                         return ERR_PTR(-EWOULDBLOCK);
 463                 }
 464                 /*
 465                  * We do not count nwaiters, because ->release is supposed
 466                  * to be called when all openers are gone only.
 467                  */
 468                 schedule();
 469                 if (signal_pending(current)) {
 470                         remove_wait_queue(&rp->wait, &waita);
 471                         return ERR_PTR(-EINTR);
 472                 }
 473                 set_current_state(TASK_INTERRUPTIBLE);
 474         }
 475         set_current_state(TASK_RUNNING);
 476         remove_wait_queue(&rp->wait, &waita);
 477         return ep;
 478 }
 479
 480 static void mon_text_read_head_t(struct mon_reader_text *rp,
 481         struct mon_text_ptr *p, const struct mon_event_text *ep)
 482 {
 483         char udir, utype;
 484
 485         udir = (ep->is_in ? 'i' : 'o');
 486         switch (ep->xfertype) {
 487         case USB_ENDPOINT_XFER_ISOC:    utype = 'Z'; break;
 488         case USB_ENDPOINT_XFER_INT:     utype = 'I'; break;
 489         case USB_ENDPOINT_XFER_CONTROL: utype = 'C'; break;
 490         default: /* PIPE_BULK */  utype = 'B';
 491         }
 492         p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 493             "%lx %u %c %c%c:%03u:%02u",
 494             ep->id, ep->tstamp, ep->type,
 495             utype, udir, ep->devnum, ep->epnum);
 496 }
 497
 498 static void mon_text_read_head_u(struct mon_reader_text *rp,
 499         struct mon_text_ptr *p, const struct mon_event_text *ep)
 500 {
 501         char udir, utype;
 502
 503         udir = (ep->is_in ? 'i' : 'o');
 504         switch (ep->xfertype) {
 505         case USB_ENDPOINT_XFER_ISOC:    utype = 'Z'; break;
 506         case USB_ENDPOINT_XFER_INT:     utype = 'I'; break;
 507         case USB_ENDPOINT_XFER_CONTROL: utype = 'C'; break;
 508         default: /* PIPE_BULK */  utype = 'B';
 509         }
 510         p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 511             "%lx %u %c %c%c:%d:%03u:%u",
 512             ep->id, ep->tstamp, ep->type,
 513             utype, udir, ep->busnum, ep->devnum, ep->epnum);
 514 }
 515
 516 static void mon_text_read_statset(struct mon_reader_text *rp,
 517         struct mon_text_ptr *p, const struct mon_event_text *ep)
 518 {
 519
 520         if (ep->setup_flag == 0) {   /* Setup packet is present and captured */
 521                 p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 522                     " s %02x %02x %04x %04x %04x",
 523                     ep->setup[0],
 524                     ep->setup[1],
 525                     (ep->setup[3] << 8) | ep->setup[2],
 526                     (ep->setup[5] << 8) | ep->setup[4],
 527                     (ep->setup[7] << 8) | ep->setup[6]);
 528         } else if (ep->setup_flag != '-') { /* Unable to capture setup packet */
 529                 p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 530                     " %c __ __ ____ ____ ____", ep->setup_flag);
 531         } else {                     /* No setup for this kind of URB */
 532                 p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 533                     " %d", ep->status);
 534         }
 535 }
 536
 537 static void mon_text_read_intstat(struct mon_reader_text *rp,
 538         struct mon_text_ptr *p, const struct mon_event_text *ep)
 539 {
 540         p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 541             " %d:%d", ep->status, ep->interval);
 542 }
 543
 544 static void mon_text_read_isostat(struct mon_reader_text *rp,
 545         struct mon_text_ptr *p, const struct mon_event_text *ep)
 546 {
 547         if (ep->type == 'S') {
 548                 p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 549                     " %d:%d:%d", ep->status, ep->interval, ep->start_frame);
 550         } else {
 551                 p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 552                     " %d:%d:%d:%d",
 553                     ep->status, ep->interval, ep->start_frame, ep->error_count);
 554         }
 555 }
 556
 557 static void mon_text_read_isodesc(struct mon_reader_text *rp,
 558         struct mon_text_ptr *p, const struct mon_event_text *ep)
 559 {
 560         int ndesc;      /* Display this many */
 561         int i;
 562         const struct mon_iso_desc *dp;
 563
 564         p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 565             " %d", ep->numdesc);
 566         ndesc = ep->numdesc;
 567         if (ndesc > ISODESC_MAX)
 568                 ndesc = ISODESC_MAX;
 569         if (ndesc < 0)
 570                 ndesc = 0;
 571         dp = ep->isodesc;
 572         for (i = 0; i < ndesc; i++) {
 573                 p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 574                     " %d:%u:%u", dp->status, dp->offset, dp->length);
 575                 dp++;
 576         }
 577 }
 578
 579 static void mon_text_read_data(struct mon_reader_text *rp,
 580     struct mon_text_ptr *p, const struct mon_event_text *ep)
 581 {
 582         int data_len, i;
 583
 584         if ((data_len = ep->length) > 0) {
 585                 if (ep->data_flag == 0) {
 586                         p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 587                             " =");
 588                         if (data_len >= DATA_MAX)
 589                                 data_len = DATA_MAX;
 590                         for (i = 0; i < data_len; i++) {
 591                                 if (i % 4 == 0) {
 592                                         p->cnt += snprintf(p->pbuf + p->cnt,
 593                                             p->limit - p->cnt,
 594                                             " ");
 595                                 }
 596                                 p->cnt += snprintf(p->pbuf + p->cnt,
 597                                     p->limit - p->cnt,
 598                                     "%02x", ep->data[i]);
 599                         }
 600                         p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 601                             "\n");
 602                 } else {
 603                         p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt,
 604                             " %c\n", ep->data_flag);
 605                 }
 606         } else {
 607                 p->cnt += snprintf(p->pbuf + p->cnt, p->limit - p->cnt, "\n");
 608         }
 609 }
 610
 611 static int mon_text_release(struct inode *inode, struct file *file)
 612 {
 613         struct mon_reader_text *rp = file->private_data;
 614         struct mon_bus *mbus;
 615         /* unsigned long flags; */
 616         struct list_head *p;
 617         struct mon_event_text *ep;
 618
 619         mutex_lock(&mon_lock);
 620         mbus = inode->i_private;
 621
 622         if (mbus->nreaders <= 0) {
 623                 printk(KERN_ERR TAG ": consistency error on close\n");
 624                 mutex_unlock(&mon_lock);
 625                 return 0;
 626         }
 627         mon_reader_del(mbus, &rp->r);
 628
 629         /*
 630          * In theory, e_list is protected by mbus->lock. However,
 631          * after mon_reader_del has finished, the following is the case:
 632          *  - we are not on reader list anymore, so new events won't be added;
 633          *  - whole mbus may be dropped if it was orphaned.
 634          * So, we better not touch mbus.
 635          */
 636         /* spin_lock_irqsave(&mbus->lock, flags); */
 637         while (!list_empty(&rp->e_list)) {
 638                 p = rp->e_list.next;
 639                 ep = list_entry(p, struct mon_event_text, e_link);
 640                 list_del(p);
 641                 --rp->nevents;
 642                 kmem_cache_free(rp->e_slab, ep);
 643         }
 644         /* spin_unlock_irqrestore(&mbus->lock, flags); */
 645
 646         kmem_cache_destroy(rp->e_slab);
 647         kfree(rp->printf_buf);
 648         kfree(rp);
 649
 650         mutex_unlock(&mon_lock);
 651         return 0;
 652 }
 653
 654 static const struct file_operations mon_fops_text_t = {
 655         .owner =        THIS_MODULE,
 656         .open =         mon_text_open,
 657         .llseek =       no_llseek,
 658         .read =         mon_text_read_t,
 659         .release =      mon_text_release,
 660 };
 661
 662 static const struct file_operations mon_fops_text_u = {
 663         .owner =        THIS_MODULE,
 664         .open =         mon_text_open,
 665         .llseek =       no_llseek,
 666         .read =         mon_text_read_u,
 667         .release =      mon_text_release,
 668 };
 669
 670 int mon_text_add(struct mon_bus *mbus, const struct usb_bus *ubus)
 671 {
 672         struct dentry *d;
 673         enum { NAMESZ = 10 };
 674         char name[NAMESZ];
 675         int busnum = ubus? ubus->busnum: 0;
 676         int rc;
 677
 678         if (mon_dir == NULL)
 679                 return 0;
 680
 681         if (ubus != NULL) {
 682                 rc = snprintf(name, NAMESZ, "%dt", busnum);
 683                 if (rc <= 0 || rc >= NAMESZ)
 684                         goto err_print_t;
 685                 d = debugfs_create_file(name, 0600, mon_dir, mbus,
 686                                                              &mon_fops_text_t);
 687                 if (d == NULL)
 688                         goto err_create_t;
 689                 mbus->dent_t = d;
 690         }
 691
 692         rc = snprintf(name, NAMESZ, "%du", busnum);
 693         if (rc <= 0 || rc >= NAMESZ)
 694                 goto err_print_u;
 695         d = debugfs_create_file(name, 0600, mon_dir, mbus, &mon_fops_text_u);
 696         if (d == NULL)
 697                 goto err_create_u;
 698         mbus->dent_u = d;
 699
 700         rc = snprintf(name, NAMESZ, "%ds", busnum);
 701         if (rc <= 0 || rc >= NAMESZ)
 702                 goto err_print_s;
 703         d = debugfs_create_file(name, 0600, mon_dir, mbus, &mon_fops_stat);
 704         if (d == NULL)
 705                 goto err_create_s;
 706         mbus->dent_s = d;
 707
 708         return 1;
 709
 710 err_create_s:
 711 err_print_s:
 712         debugfs_remove(mbus->dent_u);
 713         mbus->dent_u = NULL;
 714 err_create_u:
 715 err_print_u:
 716         if (ubus != NULL) {
 717                 debugfs_remove(mbus->dent_t);
 718                 mbus->dent_t = NULL;
 719         }
 720 err_create_t:
 721 err_print_t:
 722         return 0;
 723 }
 724
 725 void mon_text_del(struct mon_bus *mbus)
 726 {
 727         debugfs_remove(mbus->dent_u);
 728         if (mbus->dent_t != NULL)
 729                 debugfs_remove(mbus->dent_t);
 730         debugfs_remove(mbus->dent_s);
 731 }
 732
 733 /*
 734  * Slab interface: constructor.
 735  */
 736 static void mon_text_ctor(void *mem)
 737 {
 738         /*
 739          * Nothing to initialize. No, really!
 740          * So, we fill it with garbage to emulate a reused object.
 741          */
 742         memset(mem, 0xe5, sizeof(struct mon_event_text));
 743 }
 744
 745 int __init mon_text_init(void)
 746 {
 747         struct dentry *mondir;
 748
 749         mondir = debugfs_create_dir("usbmon", usb_debug_root);
 750         if (IS_ERR(mondir)) {
 751                 /* debugfs not available, but we can use usbmon without it */
 752                 return 0;
 753         }
 754         if (mondir == NULL) {
 755                 printk(KERN_NOTICE TAG ": unable to create usbmon directory\n");
 756                 return -ENOMEM;
 757         }
 758         mon_dir = mondir;
 759         return 0;
 760 }
 761
 762 void mon_text_exit(void)
 763 {
 764         debugfs_remove(mon_dir);
 765 }