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         unsigned long flags;
 145
 146         spin_lock_irqsave(fence->lock, flags);
 147         if (!list_empty(&pt->link)) {
 148                 list_del(&pt->link);
 149                 rb_erase(&pt->node, &parent->pt_tree);
 150         }
 151         spin_unlock_irqrestore(fence->lock, flags);
 152
 153         sync_timeline_put(parent);
 154         dma_fence_free(fence);
 155 }
 156
 157 static bool timeline_fence_signaled(struct dma_fence *fence)
 158 {
 159         struct sync_timeline *parent = dma_fence_parent(fence);
 160
 161         return !__dma_fence_is_later(fence->seqno, parent->value);
 162 }
 163
 164 static bool timeline_fence_enable_signaling(struct dma_fence *fence)
 165 {
 166         return true;
 167 }
 168
 169 static void timeline_fence_value_str(struct dma_fence *fence,
 170                                     char *str, int size)
 171 {
 172         snprintf(str, size, "%d", fence->seqno);
 173 }
 174
 175 static void timeline_fence_timeline_value_str(struct dma_fence *fence,
 176                                              char *str, int size)
 177 {
 178         struct sync_timeline *parent = dma_fence_parent(fence);
 179
 180         snprintf(str, size, "%d", parent->value);
 181 }
 182
 183 static const struct dma_fence_ops timeline_fence_ops = {
 184         .get_driver_name = timeline_fence_get_driver_name,
 185         .get_timeline_name = timeline_fence_get_timeline_name,
 186         .enable_signaling = timeline_fence_enable_signaling,
 187         .signaled = timeline_fence_signaled,
 188         .release = timeline_fence_release,
 189         .fence_value_str = timeline_fence_value_str,
 190         .timeline_value_str = timeline_fence_timeline_value_str,
 191 };
 192
 193 /**
 194  * sync_timeline_signal() - signal a status change on a sync_timeline
 195  * @obj:        sync_timeline to signal
 196  * @inc:        num to increment on timeline->value
 197  *
 198  * A sync implementation should call this any time one of it's fences
 199  * has signaled or has an error condition.
 200  */
 201 static void sync_timeline_signal(struct sync_timeline *obj, unsigned int inc)
 202 {
 203         struct sync_pt *pt, *next;
 204
 205         trace_sync_timeline(obj);
 206
 207         spin_lock_irq(&obj->lock);
 208
 209         obj->value += inc;
 210
 211         list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
 212                 if (!timeline_fence_signaled(&pt->base))
 213                         break;
 214
 215                 list_del_init(&pt->link);
 216                 rb_erase(&pt->node, &obj->pt_tree);
 217
 218                 /*
 219                  * A signal callback may release the last reference to this
 220                  * fence, causing it to be freed. That operation has to be
 221                  * last to avoid a use after free inside this loop, and must
 222                  * be after we remove the fence from the timeline in order to
 223                  * prevent deadlocking on timeline->lock inside
 224                  * timeline_fence_release().
 225                  */
 226                 dma_fence_signal_locked(&pt->base);
 227         }
 228
 229         spin_unlock_irq(&obj->lock);
 230 }
 231
 232 /**
 233  * sync_pt_create() - creates a sync pt
 234  * @obj:        parent sync_timeline
 235  * @value:      value of the fence
 236  *
 237  * Creates a new sync_pt (fence) as a child of @parent.  @size bytes will be
 238  * allocated allowing for implementation specific data to be kept after
 239  * the generic sync_timeline struct. Returns the sync_pt object or
 240  * NULL in case of error.
 241  */
 242 static struct sync_pt *sync_pt_create(struct sync_timeline *obj,
 243                                       unsigned int value)
 244 {
 245         struct sync_pt *pt;
 246
 247         pt = kzalloc(sizeof(*pt), GFP_KERNEL);
 248         if (!pt)
 249                 return NULL;
 250
 251         sync_timeline_get(obj);
 252         dma_fence_init(&pt->base, &timeline_fence_ops, &obj->lock,
 253                        obj->context, value);
 254         INIT_LIST_HEAD(&pt->link);
 255
 256         spin_lock_irq(&obj->lock);
 257         if (!dma_fence_is_signaled_locked(&pt->base)) {
 258                 struct rb_node **p = &obj->pt_tree.rb_node;
 259                 struct rb_node *parent = NULL;
 260
 261                 while (*p) {
 262                         struct sync_pt *other;
 263                         int cmp;
 264
 265                         parent = *p;
 266                         other = rb_entry(parent, typeof(*pt), node);
 267                         cmp = value - other->base.seqno;
 268                         if (cmp > 0) {
 269                                 p = &parent->rb_right;
 270                         } else if (cmp < 0) {
 271                                 p = &parent->rb_left;
 272                         } else {
 273                                 if (dma_fence_get_rcu(&other->base)) {
 274                                         sync_timeline_put(obj);
 275                                         kfree(pt);
 276                                         pt = other;
 277                                         goto unlock;
 278                                 }
 279                                 p = &parent->rb_left;
 280                         }
 281                 }
 282                 rb_link_node(&pt->node, parent, p);
 283                 rb_insert_color(&pt->node, &obj->pt_tree);
 284
 285                 parent = rb_next(&pt->node);
 286                 list_add_tail(&pt->link,
 287                               parent ? &rb_entry(parent, typeof(*pt), node)->link : &obj->pt_list);
 288         }
 289 unlock:
 290         spin_unlock_irq(&obj->lock);
 291
 292         return pt;
 293 }
 294
 295 /*
 296  * *WARNING*
 297  *
 298  * improper use of this can result in deadlocking kernel drivers from userspace.
 299  */
 300
 301 /* opening sw_sync create a new sync obj */
 302 static int sw_sync_debugfs_open(struct inode *inode, struct file *file)
 303 {
 304         struct sync_timeline *obj;
 305         char task_comm[TASK_COMM_LEN];
 306
 307         get_task_comm(task_comm, current);
 308
 309         obj = sync_timeline_create(task_comm);
 310         if (!obj)
 311                 return -ENOMEM;
 312
 313         file->private_data = obj;
 314
 315         return 0;
 316 }
 317
 318 static int sw_sync_debugfs_release(struct inode *inode, struct file *file)
 319 {
 320         struct sync_timeline *obj = file->private_data;
 321         struct sync_pt *pt, *next;
 322
 323         spin_lock_irq(&obj->lock);
 324
 325         list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
 326                 dma_fence_set_error(&pt->base, -ENOENT);
 327                 dma_fence_signal_locked(&pt->base);
 328         }
 329
 330         spin_unlock_irq(&obj->lock);
 331
 332         sync_timeline_put(obj);
 333         return 0;
 334 }
 335
 336 static long sw_sync_ioctl_create_fence(struct sync_timeline *obj,
 337                                        unsigned long arg)
 338 {
 339         int fd = get_unused_fd_flags(O_CLOEXEC);
 340         int err;
 341         struct sync_pt *pt;
 342         struct sync_file *sync_file;
 343         struct sw_sync_create_fence_data data;
 344
 345         if (fd < 0)
 346                 return fd;
 347
 348         if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
 349                 err = -EFAULT;
 350                 goto err;
 351         }
 352
 353         pt = sync_pt_create(obj, data.value);
 354         if (!pt) {
 355                 err = -ENOMEM;
 356                 goto err;
 357         }
 358
 359         sync_file = sync_file_create(&pt->base);
 360         dma_fence_put(&pt->base);
 361         if (!sync_file) {
 362                 err = -ENOMEM;
 363                 goto err;
 364         }
 365
 366         data.fence = fd;
 367         if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
 368                 fput(sync_file->file);
 369                 err = -EFAULT;
 370                 goto err;
 371         }
 372
 373         fd_install(fd, sync_file->file);
 374
 375         return 0;
 376
 377 err:
 378         put_unused_fd(fd);
 379         return err;
 380 }
 381
 382 static long sw_sync_ioctl_inc(struct sync_timeline *obj, unsigned long arg)
 383 {
 384         u32 value;
 385
 386         if (copy_from_user(&value, (void __user *)arg, sizeof(value)))
 387                 return -EFAULT;
 388
 389         while (value > INT_MAX)  {
 390                 sync_timeline_signal(obj, INT_MAX);
 391                 value -= INT_MAX;
 392         }
 393
 394         sync_timeline_signal(obj, value);
 395
 396         return 0;
 397 }
 398
 399 static long sw_sync_ioctl(struct file *file, unsigned int cmd,
 400                           unsigned long arg)
 401 {
 402         struct sync_timeline *obj = file->private_data;
 403
 404         switch (cmd) {
 405         case SW_SYNC_IOC_CREATE_FENCE:
 406                 return sw_sync_ioctl_create_fence(obj, arg);
 407
 408         case SW_SYNC_IOC_INC:
 409                 return sw_sync_ioctl_inc(obj, arg);
 410
 411         default:
 412                 return -ENOTTY;
 413         }
 414 }
 415
 416 const struct file_operations sw_sync_debugfs_fops = {
 417         .open           = sw_sync_debugfs_open,
 418         .release        = sw_sync_debugfs_release,
 419         .unlocked_ioctl = sw_sync_ioctl,
 420         .compat_ioctl   = sw_sync_ioctl,
 421 };