drivers/dma-buf/sw_sync.c

   1 /*
   2  * Sync File validation framework
   3  *
   4  * Copyright (C) 2012 Google, Inc.
   5  *
   6  * This software is licensed under the terms of the GNU General Public
   7  * License version 2, as published by the Free Software Foundation, and
   8  * may be copied, distributed, and modified under those terms.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  */
  16
  17 #include <linux/file.h>
  18 #include <linux/fs.h>
  19 #include <linux/uaccess.h>
  20 #include <linux/slab.h>
  21 #include <linux/sync_file.h>
  22
  23 #include "sync_debug.h"
  24
  25 #define CREATE_TRACE_POINTS
  26 #include "sync_trace.h"
  27
  28 /*
  29  * SW SYNC validation framework
  30  *
  31  * A sync object driver that uses a 32bit counter to coordinate
  32  * synchronization.  Useful when there is no hardware primitive backing
  33  * the synchronization.
  34  *
  35  * To start the framework just open:
  36  *
  37  * <debugfs>/sync/sw_sync
  38  *
  39  * That will create a sync timeline, all fences created under this timeline
  40  * file descriptor will belong to the this timeline.
  41  *
  42  * The 'sw_sync' file can be opened many times as to create different
  43  * timelines.
  44  *
  45  * Fences can be created with SW_SYNC_IOC_CREATE_FENCE ioctl with struct
  46  * sw_sync_create_fence_data as parameter.
  47  *
  48  * To increment the timeline counter, SW_SYNC_IOC_INC ioctl should be used
  49  * with the increment as u32. This will update the last signaled value
  50  * from the timeline and signal any fence that has a seqno smaller or equal
  51  * to it.
  52  *
  53  * struct sw_sync_create_fence_data
  54  * @value:      the seqno to initialise the fence with
  55  * @name:       the name of the new sync point
  56  * @fence:      return the fd of the new sync_file with the created fence
  57  */
  58 struct sw_sync_create_fence_data {
  59         __u32   value;
  60         char    name[32];
  61         __s32   fence; /* fd of new fence */
  62 };
  63
  64 #define SW_SYNC_IOC_MAGIC       'W'
  65
  66 #define SW_SYNC_IOC_CREATE_FENCE        _IOWR(SW_SYNC_IOC_MAGIC, 0,\
  67                 struct sw_sync_create_fence_data)
  68
  69 #define SW_SYNC_IOC_INC                 _IOW(SW_SYNC_IOC_MAGIC, 1, __u32)
  70
  71 static const struct dma_fence_ops timeline_fence_ops;
  72
  73 static inline struct sync_pt *dma_fence_to_sync_pt(struct dma_fence *fence)
  74 {
  75         if (fence->ops != &timeline_fence_ops)
  76                 return NULL;
  77         return container_of(fence, struct sync_pt, base);
  78 }
  79
  80 /**
  81  * sync_timeline_create() - creates a sync object
  82  * @name:       sync_timeline name
  83  *
  84  * Creates a new sync_timeline. Returns the sync_timeline object or NULL in
  85  * case of error.
  86  */
  87 static struct sync_timeline *sync_timeline_create(const char *name)
  88 {
  89         struct sync_timeline *obj;
  90
  91         obj = kzalloc(sizeof(*obj), GFP_KERNEL);
  92         if (!obj)
  93                 return NULL;
  94
  95         kref_init(&obj->kref);
  96         obj->context = dma_fence_context_alloc(1);
  97         strlcpy(obj->name, name, sizeof(obj->name));
  98
  99         obj->pt_tree = RB_ROOT;
 100         INIT_LIST_HEAD(&obj->pt_list);
 101         spin_lock_init(&obj->lock);
 102
 103         sync_timeline_debug_add(obj);
 104
 105         return obj;
 106 }
 107
 108 static void sync_timeline_free(struct kref *kref)
 109 {
 110         struct sync_timeline *obj =
 111                 container_of(kref, struct sync_timeline, kref);
 112
 113         sync_timeline_debug_remove(obj);
 114
 115         kfree(obj);
 116 }
 117
 118 static void sync_timeline_get(struct sync_timeline *obj)
 119 {
 120         kref_get(&obj->kref);
 121 }
 122
 123 static void sync_timeline_put(struct sync_timeline *obj)
 124 {
 125         kref_put(&obj->kref, sync_timeline_free);
 126 }
 127
 128 static const char *timeline_fence_get_driver_name(struct dma_fence *fence)
 129 {
 130         return "sw_sync";
 131 }
 132
 133 static const char *timeline_fence_get_timeline_name(struct dma_fence *fence)
 134 {
 135         struct sync_timeline *parent = dma_fence_parent(fence);
 136
 137         return parent->name;
 138 }
 139
 140 static void timeline_fence_release(struct dma_fence *fence)
 141 {
 142         struct sync_pt *pt = dma_fence_to_sync_pt(fence);
 143         struct sync_timeline *parent = dma_fence_parent(fence);
 144
 145         if (!list_empty(&pt->link)) {
 146                 unsigned long flags;
 147
 148                 spin_lock_irqsave(fence->lock, flags);
 149                 if (!list_empty(&pt->link)) {
 150                         list_del(&pt->link);
 151                         rb_erase(&pt->node, &parent->pt_tree);
 152                 }
 153                 spin_unlock_irqrestore(fence->lock, flags);
 154         }
 155
 156         sync_timeline_put(parent);
 157         dma_fence_free(fence);
 158 }
 159
 160 static bool timeline_fence_signaled(struct dma_fence *fence)
 161 {
 162         struct sync_timeline *parent = dma_fence_parent(fence);
 163
 164         return !__dma_fence_is_later(fence->seqno, parent->value);
 165 }
 166
 167 static bool timeline_fence_enable_signaling(struct dma_fence *fence)
 168 {
 169         return true;
 170 }
 171
 172 static void timeline_fence_value_str(struct dma_fence *fence,
 173                                     char *str, int size)
 174 {
 175         snprintf(str, size, "%d", fence->seqno);
 176 }
 177
 178 static void timeline_fence_timeline_value_str(struct dma_fence *fence,
 179                                              char *str, int size)
 180 {
 181         struct sync_timeline *parent = dma_fence_parent(fence);
 182
 183         snprintf(str, size, "%d", parent->value);
 184 }
 185
 186 static const struct dma_fence_ops timeline_fence_ops = {
 187         .get_driver_name = timeline_fence_get_driver_name,
 188         .get_timeline_name = timeline_fence_get_timeline_name,
 189         .enable_signaling = timeline_fence_enable_signaling,
 190         .signaled = timeline_fence_signaled,
 191         .release = timeline_fence_release,
 192         .fence_value_str = timeline_fence_value_str,
 193         .timeline_value_str = timeline_fence_timeline_value_str,
 194 };
 195
 196 /**
 197  * sync_timeline_signal() - signal a status change on a sync_timeline
 198  * @obj:        sync_timeline to signal
 199  * @inc:        num to increment on timeline->value
 200  *
 201  * A sync implementation should call this any time one of it's fences
 202  * has signaled or has an error condition.
 203  */
 204 static void sync_timeline_signal(struct sync_timeline *obj, unsigned int inc)
 205 {
 206         struct sync_pt *pt, *next;
 207
 208         trace_sync_timeline(obj);
 209
 210         spin_lock_irq(&obj->lock);
 211
 212         obj->value += inc;
 213
 214         list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
 215                 if (!timeline_fence_signaled(&pt->base))
 216                         break;
 217
 218                 list_del_init(&pt->link);
 219                 rb_erase(&pt->node, &obj->pt_tree);
 220
 221                 /*
 222                  * A signal callback may release the last reference to this
 223                  * fence, causing it to be freed. That operation has to be
 224                  * last to avoid a use after free inside this loop, and must
 225                  * be after we remove the fence from the timeline in order to
 226                  * prevent deadlocking on timeline->lock inside
 227                  * timeline_fence_release().
 228                  */
 229                 dma_fence_signal_locked(&pt->base);
 230         }
 231
 232         spin_unlock_irq(&obj->lock);
 233 }
 234
 235 /**
 236  * sync_pt_create() - creates a sync pt
 237  * @obj:        parent sync_timeline
 238  * @value:      value of the fence
 239  *
 240  * Creates a new sync_pt (fence) as a child of @parent.  @size bytes will be
 241  * allocated allowing for implementation specific data to be kept after
 242  * the generic sync_timeline struct. Returns the sync_pt object or
 243  * NULL in case of error.
 244  */
 245 static struct sync_pt *sync_pt_create(struct sync_timeline *obj,
 246                                       unsigned int value)
 247 {
 248         struct sync_pt *pt;
 249
 250         pt = kzalloc(sizeof(*pt), GFP_KERNEL);
 251         if (!pt)
 252                 return NULL;
 253
 254         sync_timeline_get(obj);
 255         dma_fence_init(&pt->base, &timeline_fence_ops, &obj->lock,
 256                        obj->context, value);
 257         INIT_LIST_HEAD(&pt->link);
 258
 259         spin_lock_irq(&obj->lock);
 260         if (!dma_fence_is_signaled_locked(&pt->base)) {
 261                 struct rb_node **p = &obj->pt_tree.rb_node;
 262                 struct rb_node *parent = NULL;
 263
 264                 while (*p) {
 265                         struct sync_pt *other;
 266                         int cmp;
 267
 268                         parent = *p;
 269                         other = rb_entry(parent, typeof(*pt), node);
 270                         cmp = value - other->base.seqno;
 271                         if (cmp > 0) {
 272                                 p = &parent->rb_right;
 273                         } else if (cmp < 0) {
 274                                 p = &parent->rb_left;
 275                         } else {
 276                                 if (dma_fence_get_rcu(&other->base)) {
 277                                         dma_fence_put(&pt->base);
 278                                         pt = other;
 279                                         goto unlock;
 280                                 }
 281                                 p = &parent->rb_left;
 282                         }
 283                 }
 284                 rb_link_node(&pt->node, parent, p);
 285                 rb_insert_color(&pt->node, &obj->pt_tree);
 286
 287                 parent = rb_next(&pt->node);
 288                 list_add_tail(&pt->link,
 289                               parent ? &rb_entry(parent, typeof(*pt), node)->link : &obj->pt_list);
 290         }
 291 unlock:
 292         spin_unlock_irq(&obj->lock);
 293
 294         return pt;
 295 }
 296
 297 /*
 298  * *WARNING*
 299  *
 300  * improper use of this can result in deadlocking kernel drivers from userspace.
 301  */
 302
 303 /* opening sw_sync create a new sync obj */
 304 static int sw_sync_debugfs_open(struct inode *inode, struct file *file)
 305 {
 306         struct sync_timeline *obj;
 307         char task_comm[TASK_COMM_LEN];
 308
 309         get_task_comm(task_comm, current);
 310
 311         obj = sync_timeline_create(task_comm);
 312         if (!obj)
 313                 return -ENOMEM;
 314
 315         file->private_data = obj;
 316
 317         return 0;
 318 }
 319
 320 static int sw_sync_debugfs_release(struct inode *inode, struct file *file)
 321 {
 322         struct sync_timeline *obj = file->private_data;
 323         struct sync_pt *pt, *next;
 324
 325         spin_lock_irq(&obj->lock);
 326
 327         list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
 328                 dma_fence_set_error(&pt->base, -ENOENT);
 329                 dma_fence_signal_locked(&pt->base);
 330         }
 331
 332         spin_unlock_irq(&obj->lock);
 333
 334         sync_timeline_put(obj);
 335         return 0;
 336 }
 337
 338 static long sw_sync_ioctl_create_fence(struct sync_timeline *obj,
 339                                        unsigned long arg)
 340 {
 341         int fd = get_unused_fd_flags(O_CLOEXEC);
 342         int err;
 343         struct sync_pt *pt;
 344         struct sync_file *sync_file;
 345         struct sw_sync_create_fence_data data;
 346
 347         if (fd < 0)
 348                 return fd;
 349
 350         if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
 351                 err = -EFAULT;
 352                 goto err;
 353         }
 354
 355         pt = sync_pt_create(obj, data.value);
 356         if (!pt) {
 357                 err = -ENOMEM;
 358                 goto err;
 359         }
 360
 361         sync_file = sync_file_create(&pt->base);
 362         dma_fence_put(&pt->base);
 363         if (!sync_file) {
 364                 err = -ENOMEM;
 365                 goto err;
 366         }
 367
 368         data.fence = fd;
 369         if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
 370                 fput(sync_file->file);
 371                 err = -EFAULT;
 372                 goto err;
 373         }
 374
 375         fd_install(fd, sync_file->file);
 376
 377         return 0;
 378
 379 err:
 380         put_unused_fd(fd);
 381         return err;
 382 }
 383
 384 static long sw_sync_ioctl_inc(struct sync_timeline *obj, unsigned long arg)
 385 {
 386         u32 value;
 387
 388         if (copy_from_user(&value, (void __user *)arg, sizeof(value)))
 389                 return -EFAULT;
 390
 391         while (value > INT_MAX)  {
 392                 sync_timeline_signal(obj, INT_MAX);
 393                 value -= INT_MAX;
 394         }
 395
 396         sync_timeline_signal(obj, value);
 397
 398         return 0;
 399 }
 400
 401 static long sw_sync_ioctl(struct file *file, unsigned int cmd,
 402                           unsigned long arg)
 403 {
 404         struct sync_timeline *obj = file->private_data;
 405
 406         switch (cmd) {
 407         case SW_SYNC_IOC_CREATE_FENCE:
 408                 return sw_sync_ioctl_create_fence(obj, arg);
 409
 410         case SW_SYNC_IOC_INC:
 411                 return sw_sync_ioctl_inc(obj, arg);
 412
 413         default:
 414                 return -ENOTTY;
 415         }
 416 }
 417
 418 const struct file_operations sw_sync_debugfs_fops = {
 419         .open           = sw_sync_debugfs_open,
 420         .release        = sw_sync_debugfs_release,
 421         .unlocked_ioctl = sw_sync_ioctl,
 422         .compat_ioctl   = sw_sync_ioctl,
 423 };