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_ioctl_create_fence 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_ioctl_create_fence
  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 fence_ops timeline_fence_ops;
  72
  73 static inline struct sync_pt *fence_to_sync_pt(struct 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 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 = 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 fence *fence)
 129 {
 130         return "sw_sync";
 131 }
 132
 133 static const char *timeline_fence_get_timeline_name(struct fence *fence)
 134 {
 135         struct sync_timeline *parent = fence_parent(fence);
 136
 137         return parent->name;
 138 }
 139
 140 static void timeline_fence_release(struct fence *fence)
 141 {
 142         struct sync_pt *pt = fence_to_sync_pt(fence);
 143         struct sync_timeline *parent = 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         fence_free(fence);
 158 }
 159
 160 static bool timeline_fence_signaled(struct fence *fence)
 161 {
 162         struct sync_timeline *parent = fence_parent(fence);
 163
 164         return !__fence_is_later(fence->seqno, parent->value);
 165 }
 166
 167 static bool timeline_fence_enable_signaling(struct fence *fence)
 168 {
 169         return true;
 170 }
 171
 172 static void timeline_fence_value_str(struct 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 fence *fence,
 179                                              char *str, int size)
 180 {
 181         struct sync_timeline *parent = fence_parent(fence);
 182
 183         snprintf(str, size, "%d", parent->value);
 184 }
 185
 186 static const struct 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         .wait = fence_default_wait,
 192         .release = timeline_fence_release,
 193         .fence_value_str = timeline_fence_value_str,
 194         .timeline_value_str = timeline_fence_timeline_value_str,
 195 };
 196
 197 /**
 198  * sync_timeline_signal() - signal a status change on a sync_timeline
 199  * @obj:        sync_timeline to signal
 200  * @inc:        num to increment on timeline->value
 201  *
 202  * A sync implementation should call this any time one of it's fences
 203  * has signaled or has an error condition.
 204  */
 205 static void sync_timeline_signal(struct sync_timeline *obj, unsigned int inc)
 206 {
 207         struct sync_pt *pt, *next;
 208
 209         trace_sync_timeline(obj);
 210
 211         spin_lock_irq(&obj->lock);
 212
 213         obj->value += inc;
 214
 215         list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
 216                 if (!timeline_fence_signaled(&pt->base))
 217                         break;
 218
 219                 list_del_init(&pt->link);
 220                 rb_erase(&pt->node, &obj->pt_tree);
 221
 222                 /*
 223                  * A signal callback may release the last reference to this
 224                  * fence, causing it to be freed. That operation has to be
 225                  * last to avoid a use after free inside this loop, and must
 226                  * be after we remove the fence from the timeline in order to
 227                  * prevent deadlocking on timeline->lock inside
 228                  * timeline_fence_release().
 229                  */
 230                 fence_signal_locked(&pt->base);
 231         }
 232
 233         spin_unlock_irq(&obj->lock);
 234 }
 235
 236 /**
 237  * sync_pt_create() - creates a sync pt
 238  * @parent:     fence's parent sync_timeline
 239  * @inc:        value of the fence
 240  *
 241  * Creates a new sync_pt as a child of @parent.  @size bytes will be
 242  * allocated allowing for implementation specific data to be kept after
 243  * the generic sync_timeline struct. Returns the sync_pt object or
 244  * NULL in case of error.
 245  */
 246 static struct sync_pt *sync_pt_create(struct sync_timeline *obj,
 247                                       unsigned int value)
 248 {
 249         struct sync_pt *pt;
 250
 251         pt = kzalloc(sizeof(*pt), GFP_KERNEL);
 252         if (!pt)
 253                 return NULL;
 254
 255         sync_timeline_get(obj);
 256         fence_init(&pt->base, &timeline_fence_ops, &obj->lock,
 257                    obj->context, value);
 258         INIT_LIST_HEAD(&pt->link);
 259
 260         spin_lock_irq(&obj->lock);
 261         if (!fence_is_signaled_locked(&pt->base)) {
 262                 struct rb_node **p = &obj->pt_tree.rb_node;
 263                 struct rb_node *parent = NULL;
 264
 265                 while (*p) {
 266                         struct sync_pt *other;
 267                         int cmp;
 268
 269                         parent = *p;
 270                         other = rb_entry(parent, typeof(*pt), node);
 271                         cmp = value - other->base.seqno;
 272                         if (cmp > 0) {
 273                                 p = &parent->rb_right;
 274                         } else if (cmp < 0) {
 275                                 p = &parent->rb_left;
 276                         } else {
 277                                 if (fence_get_rcu(&other->base)) {
 278                                         fence_put(&pt->base);
 279                                         pt = other;
 280                                         goto unlock;
 281                                 }
 282                                 p = &parent->rb_left;
 283                         }
 284                 }
 285                 rb_link_node(&pt->node, parent, p);
 286                 rb_insert_color(&pt->node, &obj->pt_tree);
 287
 288                 parent = rb_next(&pt->node);
 289                 list_add_tail(&pt->link,
 290                               parent ? &rb_entry(parent, typeof(*pt), node)->link : &obj->pt_list);
 291         }
 292 unlock:
 293         spin_unlock_irq(&obj->lock);
 294
 295         return pt;
 296 }
 297
 298 /*
 299  * *WARNING*
 300  *
 301  * improper use of this can result in deadlocking kernel drivers from userspace.
 302  */
 303
 304 /* opening sw_sync create a new sync obj */
 305 static int sw_sync_debugfs_open(struct inode *inode, struct file *file)
 306 {
 307         struct sync_timeline *obj;
 308         char task_comm[TASK_COMM_LEN];
 309
 310         get_task_comm(task_comm, current);
 311
 312         obj = sync_timeline_create(task_comm);
 313         if (!obj)
 314                 return -ENOMEM;
 315
 316         file->private_data = obj;
 317
 318         return 0;
 319 }
 320
 321 static int sw_sync_debugfs_release(struct inode *inode, struct file *file)
 322 {
 323         struct sync_timeline *obj = file->private_data;
 324         struct sync_pt *pt, *next;
 325
 326         spin_lock_irq(&obj->lock);
 327
 328         list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
 329                 fence_set_error(&pt->base, -ENOENT);
 330                 fence_signal_locked(&pt->base);
 331         }
 332
 333         spin_unlock_irq(&obj->lock);
 334
 335         sync_timeline_put(obj);
 336         return 0;
 337 }
 338
 339 static long sw_sync_ioctl_create_fence(struct sync_timeline *obj,
 340                                        unsigned long arg)
 341 {
 342         int fd = get_unused_fd_flags(O_CLOEXEC);
 343         int err;
 344         struct sync_pt *pt;
 345         struct sync_file *sync_file;
 346         struct sw_sync_create_fence_data data;
 347
 348         if (fd < 0)
 349                 return fd;
 350
 351         if (copy_from_user(&data, (void __user *)arg, sizeof(data))) {
 352                 err = -EFAULT;
 353                 goto err;
 354         }
 355
 356         pt = sync_pt_create(obj, data.value);
 357         if (!pt) {
 358                 err = -ENOMEM;
 359                 goto err;
 360         }
 361
 362         sync_file = sync_file_create(&pt->base);
 363         if (!sync_file) {
 364                 fence_put(&pt->base);
 365                 err = -ENOMEM;
 366                 goto err;
 367         }
 368
 369         data.fence = fd;
 370         if (copy_to_user((void __user *)arg, &data, sizeof(data))) {
 371                 fput(sync_file->file);
 372                 err = -EFAULT;
 373                 goto err;
 374         }
 375
 376         fd_install(fd, sync_file->file);
 377
 378         return 0;
 379
 380 err:
 381         put_unused_fd(fd);
 382         return err;
 383 }
 384
 385 static long sw_sync_ioctl_inc(struct sync_timeline *obj, unsigned long arg)
 386 {
 387         u32 value;
 388
 389         if (copy_from_user(&value, (void __user *)arg, sizeof(value)))
 390                 return -EFAULT;
 391
 392         while (value > INT_MAX)  {
 393                 sync_timeline_signal(obj, INT_MAX);
 394                 value -= INT_MAX;
 395         }
 396
 397         sync_timeline_signal(obj, value);
 398
 399         return 0;
 400 }
 401
 402 static long sw_sync_ioctl(struct file *file, unsigned int cmd,
 403                           unsigned long arg)
 404 {
 405         struct sync_timeline *obj = file->private_data;
 406
 407         switch (cmd) {
 408         case SW_SYNC_IOC_CREATE_FENCE:
 409                 return sw_sync_ioctl_create_fence(obj, arg);
 410
 411         case SW_SYNC_IOC_INC:
 412                 return sw_sync_ioctl_inc(obj, arg);
 413
 414         default:
 415                 return -ENOTTY;
 416         }
 417 }
 418
 419 const struct file_operations sw_sync_debugfs_fops = {
 420         .open           = sw_sync_debugfs_open,
 421         .release        = sw_sync_debugfs_release,
 422         .unlocked_ioctl = sw_sync_ioctl,
 423         .compat_ioctl   = sw_sync_ioctl,
 424 };