1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Sync File validation framework
4 *
5 * Copyright (C) 2012 Google, Inc.
6 */
7
8#include <linux/file.h>
9#include <linux/fs.h>
10#include <linux/uaccess.h>
11#include <linux/slab.h>
12#include <linux/sync_file.h>
13
14#include "sync_debug.h"
15
16#define CREATE_TRACE_POINTS
17#include "sync_trace.h"
18
19/*
20 * SW SYNC validation framework
21 *
22 * A sync object driver that uses a 32bit counter to coordinate
23 * synchronization. Useful when there is no hardware primitive backing
24 * the synchronization.
25 *
26 * To start the framework just open:
27 *
28 * <debugfs>/sync/sw_sync
29 *
30 * That will create a sync timeline, all fences created under this timeline
31 * file descriptor will belong to the this timeline.
32 *
33 * The 'sw_sync' file can be opened many times as to create different
34 * timelines.
35 *
36 * Fences can be created with SW_SYNC_IOC_CREATE_FENCE ioctl with struct
37 * sw_sync_create_fence_data as parameter.
38 *
39 * To increment the timeline counter, SW_SYNC_IOC_INC ioctl should be used
40 * with the increment as u32. This will update the last signaled value
41 * from the timeline and signal any fence that has a seqno smaller or equal
42 * to it.
43 *
44 * struct sw_sync_create_fence_data
45 * @value: the seqno to initialise the fence with
46 * @name: the name of the new sync point
47 * @fence: return the fd of the new sync_file with the created fence
48 */
49struct sw_sync_create_fence_data {
50 __u32 value;
51 char name[32];
52 __s32 fence; /* fd of new fence */
53};
54
55#define SW_SYNC_IOC_MAGIC 'W'
56
57#define SW_SYNC_IOC_CREATE_FENCE _IOWR(SW_SYNC_IOC_MAGIC, 0,\
58 struct sw_sync_create_fence_data)
59
60#define SW_SYNC_IOC_INC _IOW(SW_SYNC_IOC_MAGIC, 1, __u32)
61
62static const struct dma_fence_ops timeline_fence_ops;
63
64static inline struct sync_pt *dma_fence_to_sync_pt(struct dma_fence *fence)
65{
66 if (fence->ops != &timeline_fence_ops)
67 return NULL;
68 return container_of(fence, struct sync_pt, base);
69}
70
71/**
72 * sync_timeline_create() - creates a sync object
73 * @name: sync_timeline name
74 *
75 * Creates a new sync_timeline. Returns the sync_timeline object or NULL in
76 * case of error.
77 */
78static struct sync_timeline *sync_timeline_create(const char *name)
79{
80 struct sync_timeline *obj;
81
82 obj = kzalloc(size: sizeof(*obj), GFP_KERNEL);
83 if (!obj)
84 return NULL;
85
86 kref_init(kref: &obj->kref);
87 obj->context = dma_fence_context_alloc(num: 1);
88 strscpy(p: obj->name, q: name, size: sizeof(obj->name));
89
90 obj->pt_tree = RB_ROOT;
91 INIT_LIST_HEAD(list: &obj->pt_list);
92 spin_lock_init(&obj->lock);
93
94 sync_timeline_debug_add(obj);
95
96 return obj;
97}
98
99static void sync_timeline_free(struct kref *kref)
100{
101 struct sync_timeline *obj =
102 container_of(kref, struct sync_timeline, kref);
103
104 sync_timeline_debug_remove(obj);
105
106 kfree(objp: obj);
107}
108
109static void sync_timeline_get(struct sync_timeline *obj)
110{
111 kref_get(kref: &obj->kref);
112}
113
114static void sync_timeline_put(struct sync_timeline *obj)
115{
116 kref_put(kref: &obj->kref, release: sync_timeline_free);
117}
118
119static const char *timeline_fence_get_driver_name(struct dma_fence *fence)
120{
121 return "sw_sync";
122}
123
124static const char *timeline_fence_get_timeline_name(struct dma_fence *fence)
125{
126 struct sync_timeline *parent = dma_fence_parent(fence);
127
128 return parent->name;
129}
130
131static void timeline_fence_release(struct dma_fence *fence)
132{
133 struct sync_pt *pt = dma_fence_to_sync_pt(fence);
134 struct sync_timeline *parent = dma_fence_parent(fence);
135 unsigned long flags;
136
137 spin_lock_irqsave(fence->lock, flags);
138 if (!list_empty(head: &pt->link)) {
139 list_del(entry: &pt->link);
140 rb_erase(&pt->node, &parent->pt_tree);
141 }
142 spin_unlock_irqrestore(lock: fence->lock, flags);
143
144 sync_timeline_put(obj: parent);
145 dma_fence_free(fence);
146}
147
148static bool timeline_fence_signaled(struct dma_fence *fence)
149{
150 struct sync_timeline *parent = dma_fence_parent(fence);
151
152 return !__dma_fence_is_later(f1: fence->seqno, f2: parent->value, ops: fence->ops);
153}
154
155static bool timeline_fence_enable_signaling(struct dma_fence *fence)
156{
157 return true;
158}
159
160static void timeline_fence_value_str(struct dma_fence *fence,
161 char *str, int size)
162{
163 snprintf(buf: str, size, fmt: "%lld", fence->seqno);
164}
165
166static void timeline_fence_timeline_value_str(struct dma_fence *fence,
167 char *str, int size)
168{
169 struct sync_timeline *parent = dma_fence_parent(fence);
170
171 snprintf(buf: str, size, fmt: "%d", parent->value);
172}
173
174static const struct dma_fence_ops timeline_fence_ops = {
175 .get_driver_name = timeline_fence_get_driver_name,
176 .get_timeline_name = timeline_fence_get_timeline_name,
177 .enable_signaling = timeline_fence_enable_signaling,
178 .signaled = timeline_fence_signaled,
179 .release = timeline_fence_release,
180 .fence_value_str = timeline_fence_value_str,
181 .timeline_value_str = timeline_fence_timeline_value_str,
182};
183
184/**
185 * sync_timeline_signal() - signal a status change on a sync_timeline
186 * @obj: sync_timeline to signal
187 * @inc: num to increment on timeline->value
188 *
189 * A sync implementation should call this any time one of it's fences
190 * has signaled or has an error condition.
191 */
192static void sync_timeline_signal(struct sync_timeline *obj, unsigned int inc)
193{
194 LIST_HEAD(signalled);
195 struct sync_pt *pt, *next;
196
197 trace_sync_timeline(timeline: obj);
198
199 spin_lock_irq(lock: &obj->lock);
200
201 obj->value += inc;
202
203 list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
204 if (!timeline_fence_signaled(fence: &pt->base))
205 break;
206
207 dma_fence_get(fence: &pt->base);
208
209 list_move_tail(list: &pt->link, head: &signalled);
210 rb_erase(&pt->node, &obj->pt_tree);
211
212 dma_fence_signal_locked(fence: &pt->base);
213 }
214
215 spin_unlock_irq(lock: &obj->lock);
216
217 list_for_each_entry_safe(pt, next, &signalled, link) {
218 list_del_init(entry: &pt->link);
219 dma_fence_put(fence: &pt->base);
220 }
221}
222
223/**
224 * sync_pt_create() - creates a sync pt
225 * @obj: parent sync_timeline
226 * @value: value of the fence
227 *
228 * Creates a new sync_pt (fence) as a child of @parent. @size bytes will be
229 * allocated allowing for implementation specific data to be kept after
230 * the generic sync_timeline struct. Returns the sync_pt object or
231 * NULL in case of error.
232 */
233static struct sync_pt *sync_pt_create(struct sync_timeline *obj,
234 unsigned int value)
235{
236 struct sync_pt *pt;
237
238 pt = kzalloc(size: sizeof(*pt), GFP_KERNEL);
239 if (!pt)
240 return NULL;
241
242 sync_timeline_get(obj);
243 dma_fence_init(fence: &pt->base, ops: &timeline_fence_ops, lock: &obj->lock,
244 context: obj->context, seqno: value);
245 INIT_LIST_HEAD(list: &pt->link);
246
247 spin_lock_irq(lock: &obj->lock);
248 if (!dma_fence_is_signaled_locked(fence: &pt->base)) {
249 struct rb_node **p = &obj->pt_tree.rb_node;
250 struct rb_node *parent = NULL;
251
252 while (*p) {
253 struct sync_pt *other;
254 int cmp;
255
256 parent = *p;
257 other = rb_entry(parent, typeof(*pt), node);
258 cmp = value - other->base.seqno;
259 if (cmp > 0) {
260 p = &parent->rb_right;
261 } else if (cmp < 0) {
262 p = &parent->rb_left;
263 } else {
264 if (dma_fence_get_rcu(fence: &other->base)) {
265 sync_timeline_put(obj);
266 kfree(objp: pt);
267 pt = other;
268 goto unlock;
269 }
270 p = &parent->rb_left;
271 }
272 }
273 rb_link_node(node: &pt->node, parent, rb_link: p);
274 rb_insert_color(&pt->node, &obj->pt_tree);
275
276 parent = rb_next(&pt->node);
277 list_add_tail(new: &pt->link,
278 head: parent ? &rb_entry(parent, typeof(*pt), node)->link : &obj->pt_list);
279 }
280unlock:
281 spin_unlock_irq(lock: &obj->lock);
282
283 return pt;
284}
285
286/*
287 * *WARNING*
288 *
289 * improper use of this can result in deadlocking kernel drivers from userspace.
290 */
291
292/* opening sw_sync create a new sync obj */
293static int sw_sync_debugfs_open(struct inode *inode, struct file *file)
294{
295 struct sync_timeline *obj;
296 char task_comm[TASK_COMM_LEN];
297
298 get_task_comm(task_comm, current);
299
300 obj = sync_timeline_create(name: task_comm);
301 if (!obj)
302 return -ENOMEM;
303
304 file->private_data = obj;
305
306 return 0;
307}
308
309static int sw_sync_debugfs_release(struct inode *inode, struct file *file)
310{
311 struct sync_timeline *obj = file->private_data;
312 struct sync_pt *pt, *next;
313
314 spin_lock_irq(lock: &obj->lock);
315
316 list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
317 dma_fence_set_error(fence: &pt->base, error: -ENOENT);
318 dma_fence_signal_locked(fence: &pt->base);
319 }
320
321 spin_unlock_irq(lock: &obj->lock);
322
323 sync_timeline_put(obj);
324 return 0;
325}
326
327static long sw_sync_ioctl_create_fence(struct sync_timeline *obj,
328 unsigned long arg)
329{
330 int fd = get_unused_fd_flags(O_CLOEXEC);
331 int err;
332 struct sync_pt *pt;
333 struct sync_file *sync_file;
334 struct sw_sync_create_fence_data data;
335
336 if (fd < 0)
337 return fd;
338
339 if (copy_from_user(to: &data, from: (void __user *)arg, n: sizeof(data))) {
340 err = -EFAULT;
341 goto err;
342 }
343
344 pt = sync_pt_create(obj, value: data.value);
345 if (!pt) {
346 err = -ENOMEM;
347 goto err;
348 }
349
350 sync_file = sync_file_create(fence: &pt->base);
351 dma_fence_put(fence: &pt->base);
352 if (!sync_file) {
353 err = -ENOMEM;
354 goto err;
355 }
356
357 data.fence = fd;
358 if (copy_to_user(to: (void __user *)arg, from: &data, n: sizeof(data))) {
359 fput(sync_file->file);
360 err = -EFAULT;
361 goto err;
362 }
363
364 fd_install(fd, file: sync_file->file);
365
366 return 0;
367
368err:
369 put_unused_fd(fd);
370 return err;
371}
372
373static long sw_sync_ioctl_inc(struct sync_timeline *obj, unsigned long arg)
374{
375 u32 value;
376
377 if (copy_from_user(to: &value, from: (void __user *)arg, n: sizeof(value)))
378 return -EFAULT;
379
380 while (value > INT_MAX) {
381 sync_timeline_signal(obj, INT_MAX);
382 value -= INT_MAX;
383 }
384
385 sync_timeline_signal(obj, inc: value);
386
387 return 0;
388}
389
390static long sw_sync_ioctl(struct file *file, unsigned int cmd,
391 unsigned long arg)
392{
393 struct sync_timeline *obj = file->private_data;
394
395 switch (cmd) {
396 case SW_SYNC_IOC_CREATE_FENCE:
397 return sw_sync_ioctl_create_fence(obj, arg);
398
399 case SW_SYNC_IOC_INC:
400 return sw_sync_ioctl_inc(obj, arg);
401
402 default:
403 return -ENOTTY;
404 }
405}
406
407const struct file_operations sw_sync_debugfs_fops = {
408 .open = sw_sync_debugfs_open,
409 .release = sw_sync_debugfs_release,
410 .unlocked_ioctl = sw_sync_ioctl,
411 .compat_ioctl = compat_ptr_ioctl,
412};
413

source code of linux/drivers/dma-buf/sw_sync.c