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Merge tag 'io_uring-5.7-2020-05-22' of git://git.kernel.dk/linux-block
[thirdparty/linux.git] / kernel / kcov.c
1 // SPDX-License-Identifier: GPL-2.0
2 #define pr_fmt(fmt) "kcov: " fmt
3
4 #define DISABLE_BRANCH_PROFILING
5 #include <linux/atomic.h>
6 #include <linux/compiler.h>
7 #include <linux/errno.h>
8 #include <linux/export.h>
9 #include <linux/types.h>
10 #include <linux/file.h>
11 #include <linux/fs.h>
12 #include <linux/hashtable.h>
13 #include <linux/init.h>
14 #include <linux/mm.h>
15 #include <linux/preempt.h>
16 #include <linux/printk.h>
17 #include <linux/sched.h>
18 #include <linux/slab.h>
19 #include <linux/spinlock.h>
20 #include <linux/vmalloc.h>
21 #include <linux/debugfs.h>
22 #include <linux/uaccess.h>
23 #include <linux/kcov.h>
24 #include <linux/refcount.h>
25 #include <linux/log2.h>
26 #include <asm/setup.h>
27
28 #define kcov_debug(fmt, ...) pr_debug("%s: " fmt, __func__, ##__VA_ARGS__)
29
30 /* Number of 64-bit words written per one comparison: */
31 #define KCOV_WORDS_PER_CMP 4
32
33 /*
34 * kcov descriptor (one per opened debugfs file).
35 * State transitions of the descriptor:
36 * - initial state after open()
37 * - then there must be a single ioctl(KCOV_INIT_TRACE) call
38 * - then, mmap() call (several calls are allowed but not useful)
39 * - then, ioctl(KCOV_ENABLE, arg), where arg is
40 * KCOV_TRACE_PC - to trace only the PCs
41 * or
42 * KCOV_TRACE_CMP - to trace only the comparison operands
43 * - then, ioctl(KCOV_DISABLE) to disable the task.
44 * Enabling/disabling ioctls can be repeated (only one task a time allowed).
45 */
46 struct kcov {
47 /*
48 * Reference counter. We keep one for:
49 * - opened file descriptor
50 * - task with enabled coverage (we can't unwire it from another task)
51 * - each code section for remote coverage collection
52 */
53 refcount_t refcount;
54 /* The lock protects mode, size, area and t. */
55 spinlock_t lock;
56 enum kcov_mode mode;
57 /* Size of arena (in long's). */
58 unsigned int size;
59 /* Coverage buffer shared with user space. */
60 void *area;
61 /* Task for which we collect coverage, or NULL. */
62 struct task_struct *t;
63 /* Collecting coverage from remote (background) threads. */
64 bool remote;
65 /* Size of remote area (in long's). */
66 unsigned int remote_size;
67 /*
68 * Sequence is incremented each time kcov is reenabled, used by
69 * kcov_remote_stop(), see the comment there.
70 */
71 int sequence;
72 };
73
74 struct kcov_remote_area {
75 struct list_head list;
76 unsigned int size;
77 };
78
79 struct kcov_remote {
80 u64 handle;
81 struct kcov *kcov;
82 struct hlist_node hnode;
83 };
84
85 static DEFINE_SPINLOCK(kcov_remote_lock);
86 static DEFINE_HASHTABLE(kcov_remote_map, 4);
87 static struct list_head kcov_remote_areas = LIST_HEAD_INIT(kcov_remote_areas);
88
89 /* Must be called with kcov_remote_lock locked. */
90 static struct kcov_remote *kcov_remote_find(u64 handle)
91 {
92 struct kcov_remote *remote;
93
94 hash_for_each_possible(kcov_remote_map, remote, hnode, handle) {
95 if (remote->handle == handle)
96 return remote;
97 }
98 return NULL;
99 }
100
101 static struct kcov_remote *kcov_remote_add(struct kcov *kcov, u64 handle)
102 {
103 struct kcov_remote *remote;
104
105 if (kcov_remote_find(handle))
106 return ERR_PTR(-EEXIST);
107 remote = kmalloc(sizeof(*remote), GFP_ATOMIC);
108 if (!remote)
109 return ERR_PTR(-ENOMEM);
110 remote->handle = handle;
111 remote->kcov = kcov;
112 hash_add(kcov_remote_map, &remote->hnode, handle);
113 return remote;
114 }
115
116 /* Must be called with kcov_remote_lock locked. */
117 static struct kcov_remote_area *kcov_remote_area_get(unsigned int size)
118 {
119 struct kcov_remote_area *area;
120 struct list_head *pos;
121
122 kcov_debug("size = %u\n", size);
123 list_for_each(pos, &kcov_remote_areas) {
124 area = list_entry(pos, struct kcov_remote_area, list);
125 if (area->size == size) {
126 list_del(&area->list);
127 kcov_debug("rv = %px\n", area);
128 return area;
129 }
130 }
131 kcov_debug("rv = NULL\n");
132 return NULL;
133 }
134
135 /* Must be called with kcov_remote_lock locked. */
136 static void kcov_remote_area_put(struct kcov_remote_area *area,
137 unsigned int size)
138 {
139 kcov_debug("area = %px, size = %u\n", area, size);
140 INIT_LIST_HEAD(&area->list);
141 area->size = size;
142 list_add(&area->list, &kcov_remote_areas);
143 }
144
145 static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
146 {
147 unsigned int mode;
148
149 /*
150 * We are interested in code coverage as a function of a syscall inputs,
151 * so we ignore code executed in interrupts.
152 */
153 if (!in_task())
154 return false;
155 mode = READ_ONCE(t->kcov_mode);
156 /*
157 * There is some code that runs in interrupts but for which
158 * in_interrupt() returns false (e.g. preempt_schedule_irq()).
159 * READ_ONCE()/barrier() effectively provides load-acquire wrt
160 * interrupts, there are paired barrier()/WRITE_ONCE() in
161 * kcov_start().
162 */
163 barrier();
164 return mode == needed_mode;
165 }
166
167 static notrace unsigned long canonicalize_ip(unsigned long ip)
168 {
169 #ifdef CONFIG_RANDOMIZE_BASE
170 ip -= kaslr_offset();
171 #endif
172 return ip;
173 }
174
175 /*
176 * Entry point from instrumented code.
177 * This is called once per basic-block/edge.
178 */
179 void notrace __sanitizer_cov_trace_pc(void)
180 {
181 struct task_struct *t;
182 unsigned long *area;
183 unsigned long ip = canonicalize_ip(_RET_IP_);
184 unsigned long pos;
185
186 t = current;
187 if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t))
188 return;
189
190 area = t->kcov_area;
191 /* The first 64-bit word is the number of subsequent PCs. */
192 pos = READ_ONCE(area[0]) + 1;
193 if (likely(pos < t->kcov_size)) {
194 area[pos] = ip;
195 WRITE_ONCE(area[0], pos);
196 }
197 }
198 EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
199
200 #ifdef CONFIG_KCOV_ENABLE_COMPARISONS
201 static void notrace write_comp_data(u64 type, u64 arg1, u64 arg2, u64 ip)
202 {
203 struct task_struct *t;
204 u64 *area;
205 u64 count, start_index, end_pos, max_pos;
206
207 t = current;
208 if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t))
209 return;
210
211 ip = canonicalize_ip(ip);
212
213 /*
214 * We write all comparison arguments and types as u64.
215 * The buffer was allocated for t->kcov_size unsigned longs.
216 */
217 area = (u64 *)t->kcov_area;
218 max_pos = t->kcov_size * sizeof(unsigned long);
219
220 count = READ_ONCE(area[0]);
221
222 /* Every record is KCOV_WORDS_PER_CMP 64-bit words. */
223 start_index = 1 + count * KCOV_WORDS_PER_CMP;
224 end_pos = (start_index + KCOV_WORDS_PER_CMP) * sizeof(u64);
225 if (likely(end_pos <= max_pos)) {
226 area[start_index] = type;
227 area[start_index + 1] = arg1;
228 area[start_index + 2] = arg2;
229 area[start_index + 3] = ip;
230 WRITE_ONCE(area[0], count + 1);
231 }
232 }
233
234 void notrace __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2)
235 {
236 write_comp_data(KCOV_CMP_SIZE(0), arg1, arg2, _RET_IP_);
237 }
238 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1);
239
240 void notrace __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2)
241 {
242 write_comp_data(KCOV_CMP_SIZE(1), arg1, arg2, _RET_IP_);
243 }
244 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2);
245
246 void notrace __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2)
247 {
248 write_comp_data(KCOV_CMP_SIZE(2), arg1, arg2, _RET_IP_);
249 }
250 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4);
251
252 void notrace __sanitizer_cov_trace_cmp8(u64 arg1, u64 arg2)
253 {
254 write_comp_data(KCOV_CMP_SIZE(3), arg1, arg2, _RET_IP_);
255 }
256 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8);
257
258 void notrace __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2)
259 {
260 write_comp_data(KCOV_CMP_SIZE(0) | KCOV_CMP_CONST, arg1, arg2,
261 _RET_IP_);
262 }
263 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1);
264
265 void notrace __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2)
266 {
267 write_comp_data(KCOV_CMP_SIZE(1) | KCOV_CMP_CONST, arg1, arg2,
268 _RET_IP_);
269 }
270 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2);
271
272 void notrace __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2)
273 {
274 write_comp_data(KCOV_CMP_SIZE(2) | KCOV_CMP_CONST, arg1, arg2,
275 _RET_IP_);
276 }
277 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4);
278
279 void notrace __sanitizer_cov_trace_const_cmp8(u64 arg1, u64 arg2)
280 {
281 write_comp_data(KCOV_CMP_SIZE(3) | KCOV_CMP_CONST, arg1, arg2,
282 _RET_IP_);
283 }
284 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8);
285
286 void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases)
287 {
288 u64 i;
289 u64 count = cases[0];
290 u64 size = cases[1];
291 u64 type = KCOV_CMP_CONST;
292
293 switch (size) {
294 case 8:
295 type |= KCOV_CMP_SIZE(0);
296 break;
297 case 16:
298 type |= KCOV_CMP_SIZE(1);
299 break;
300 case 32:
301 type |= KCOV_CMP_SIZE(2);
302 break;
303 case 64:
304 type |= KCOV_CMP_SIZE(3);
305 break;
306 default:
307 return;
308 }
309 for (i = 0; i < count; i++)
310 write_comp_data(type, cases[i + 2], val, _RET_IP_);
311 }
312 EXPORT_SYMBOL(__sanitizer_cov_trace_switch);
313 #endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */
314
315 static void kcov_start(struct task_struct *t, unsigned int size,
316 void *area, enum kcov_mode mode, int sequence)
317 {
318 kcov_debug("t = %px, size = %u, area = %px\n", t, size, area);
319 /* Cache in task struct for performance. */
320 t->kcov_size = size;
321 t->kcov_area = area;
322 /* See comment in check_kcov_mode(). */
323 barrier();
324 WRITE_ONCE(t->kcov_mode, mode);
325 t->kcov_sequence = sequence;
326 }
327
328 static void kcov_stop(struct task_struct *t)
329 {
330 WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);
331 barrier();
332 t->kcov_size = 0;
333 t->kcov_area = NULL;
334 }
335
336 static void kcov_task_reset(struct task_struct *t)
337 {
338 kcov_stop(t);
339 t->kcov = NULL;
340 t->kcov_sequence = 0;
341 t->kcov_handle = 0;
342 }
343
344 void kcov_task_init(struct task_struct *t)
345 {
346 kcov_task_reset(t);
347 t->kcov_handle = current->kcov_handle;
348 }
349
350 static void kcov_reset(struct kcov *kcov)
351 {
352 kcov->t = NULL;
353 kcov->mode = KCOV_MODE_INIT;
354 kcov->remote = false;
355 kcov->remote_size = 0;
356 kcov->sequence++;
357 }
358
359 static void kcov_remote_reset(struct kcov *kcov)
360 {
361 int bkt;
362 struct kcov_remote *remote;
363 struct hlist_node *tmp;
364
365 spin_lock(&kcov_remote_lock);
366 hash_for_each_safe(kcov_remote_map, bkt, tmp, remote, hnode) {
367 if (remote->kcov != kcov)
368 continue;
369 kcov_debug("removing handle %llx\n", remote->handle);
370 hash_del(&remote->hnode);
371 kfree(remote);
372 }
373 /* Do reset before unlock to prevent races with kcov_remote_start(). */
374 kcov_reset(kcov);
375 spin_unlock(&kcov_remote_lock);
376 }
377
378 static void kcov_disable(struct task_struct *t, struct kcov *kcov)
379 {
380 kcov_task_reset(t);
381 if (kcov->remote)
382 kcov_remote_reset(kcov);
383 else
384 kcov_reset(kcov);
385 }
386
387 static void kcov_get(struct kcov *kcov)
388 {
389 refcount_inc(&kcov->refcount);
390 }
391
392 static void kcov_put(struct kcov *kcov)
393 {
394 if (refcount_dec_and_test(&kcov->refcount)) {
395 kcov_remote_reset(kcov);
396 vfree(kcov->area);
397 kfree(kcov);
398 }
399 }
400
401 void kcov_task_exit(struct task_struct *t)
402 {
403 struct kcov *kcov;
404
405 kcov = t->kcov;
406 if (kcov == NULL)
407 return;
408
409 spin_lock(&kcov->lock);
410 kcov_debug("t = %px, kcov->t = %px\n", t, kcov->t);
411 /*
412 * For KCOV_ENABLE devices we want to make sure that t->kcov->t == t,
413 * which comes down to:
414 * WARN_ON(!kcov->remote && kcov->t != t);
415 *
416 * For KCOV_REMOTE_ENABLE devices, the exiting task is either:
417 * 2. A remote task between kcov_remote_start() and kcov_remote_stop().
418 * In this case we should print a warning right away, since a task
419 * shouldn't be exiting when it's in a kcov coverage collection
420 * section. Here t points to the task that is collecting remote
421 * coverage, and t->kcov->t points to the thread that created the
422 * kcov device. Which means that to detect this case we need to
423 * check that t != t->kcov->t, and this gives us the following:
424 * WARN_ON(kcov->remote && kcov->t != t);
425 *
426 * 2. The task that created kcov exiting without calling KCOV_DISABLE,
427 * and then again we can make sure that t->kcov->t == t:
428 * WARN_ON(kcov->remote && kcov->t != t);
429 *
430 * By combining all three checks into one we get:
431 */
432 if (WARN_ON(kcov->t != t)) {
433 spin_unlock(&kcov->lock);
434 return;
435 }
436 /* Just to not leave dangling references behind. */
437 kcov_disable(t, kcov);
438 spin_unlock(&kcov->lock);
439 kcov_put(kcov);
440 }
441
442 static int kcov_mmap(struct file *filep, struct vm_area_struct *vma)
443 {
444 int res = 0;
445 void *area;
446 struct kcov *kcov = vma->vm_file->private_data;
447 unsigned long size, off;
448 struct page *page;
449
450 area = vmalloc_user(vma->vm_end - vma->vm_start);
451 if (!area)
452 return -ENOMEM;
453
454 spin_lock(&kcov->lock);
455 size = kcov->size * sizeof(unsigned long);
456 if (kcov->mode != KCOV_MODE_INIT || vma->vm_pgoff != 0 ||
457 vma->vm_end - vma->vm_start != size) {
458 res = -EINVAL;
459 goto exit;
460 }
461 if (!kcov->area) {
462 kcov->area = area;
463 vma->vm_flags |= VM_DONTEXPAND;
464 spin_unlock(&kcov->lock);
465 for (off = 0; off < size; off += PAGE_SIZE) {
466 page = vmalloc_to_page(kcov->area + off);
467 if (vm_insert_page(vma, vma->vm_start + off, page))
468 WARN_ONCE(1, "vm_insert_page() failed");
469 }
470 return 0;
471 }
472 exit:
473 spin_unlock(&kcov->lock);
474 vfree(area);
475 return res;
476 }
477
478 static int kcov_open(struct inode *inode, struct file *filep)
479 {
480 struct kcov *kcov;
481
482 kcov = kzalloc(sizeof(*kcov), GFP_KERNEL);
483 if (!kcov)
484 return -ENOMEM;
485 kcov->mode = KCOV_MODE_DISABLED;
486 kcov->sequence = 1;
487 refcount_set(&kcov->refcount, 1);
488 spin_lock_init(&kcov->lock);
489 filep->private_data = kcov;
490 return nonseekable_open(inode, filep);
491 }
492
493 static int kcov_close(struct inode *inode, struct file *filep)
494 {
495 kcov_put(filep->private_data);
496 return 0;
497 }
498
499 static int kcov_get_mode(unsigned long arg)
500 {
501 if (arg == KCOV_TRACE_PC)
502 return KCOV_MODE_TRACE_PC;
503 else if (arg == KCOV_TRACE_CMP)
504 #ifdef CONFIG_KCOV_ENABLE_COMPARISONS
505 return KCOV_MODE_TRACE_CMP;
506 #else
507 return -ENOTSUPP;
508 #endif
509 else
510 return -EINVAL;
511 }
512
513 /*
514 * Fault in a lazily-faulted vmalloc area before it can be used by
515 * __santizer_cov_trace_pc(), to avoid recursion issues if any code on the
516 * vmalloc fault handling path is instrumented.
517 */
518 static void kcov_fault_in_area(struct kcov *kcov)
519 {
520 unsigned long stride = PAGE_SIZE / sizeof(unsigned long);
521 unsigned long *area = kcov->area;
522 unsigned long offset;
523
524 for (offset = 0; offset < kcov->size; offset += stride)
525 READ_ONCE(area[offset]);
526 }
527
528 static inline bool kcov_check_handle(u64 handle, bool common_valid,
529 bool uncommon_valid, bool zero_valid)
530 {
531 if (handle & ~(KCOV_SUBSYSTEM_MASK | KCOV_INSTANCE_MASK))
532 return false;
533 switch (handle & KCOV_SUBSYSTEM_MASK) {
534 case KCOV_SUBSYSTEM_COMMON:
535 return (handle & KCOV_INSTANCE_MASK) ?
536 common_valid : zero_valid;
537 case KCOV_SUBSYSTEM_USB:
538 return uncommon_valid;
539 default:
540 return false;
541 }
542 return false;
543 }
544
545 static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
546 unsigned long arg)
547 {
548 struct task_struct *t;
549 unsigned long size, unused;
550 int mode, i;
551 struct kcov_remote_arg *remote_arg;
552 struct kcov_remote *remote;
553
554 switch (cmd) {
555 case KCOV_INIT_TRACE:
556 kcov_debug("KCOV_INIT_TRACE\n");
557 /*
558 * Enable kcov in trace mode and setup buffer size.
559 * Must happen before anything else.
560 */
561 if (kcov->mode != KCOV_MODE_DISABLED)
562 return -EBUSY;
563 /*
564 * Size must be at least 2 to hold current position and one PC.
565 * Later we allocate size * sizeof(unsigned long) memory,
566 * that must not overflow.
567 */
568 size = arg;
569 if (size < 2 || size > INT_MAX / sizeof(unsigned long))
570 return -EINVAL;
571 kcov->size = size;
572 kcov->mode = KCOV_MODE_INIT;
573 return 0;
574 case KCOV_ENABLE:
575 kcov_debug("KCOV_ENABLE\n");
576 /*
577 * Enable coverage for the current task.
578 * At this point user must have been enabled trace mode,
579 * and mmapped the file. Coverage collection is disabled only
580 * at task exit or voluntary by KCOV_DISABLE. After that it can
581 * be enabled for another task.
582 */
583 if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
584 return -EINVAL;
585 t = current;
586 if (kcov->t != NULL || t->kcov != NULL)
587 return -EBUSY;
588 mode = kcov_get_mode(arg);
589 if (mode < 0)
590 return mode;
591 kcov_fault_in_area(kcov);
592 kcov->mode = mode;
593 kcov_start(t, kcov->size, kcov->area, kcov->mode,
594 kcov->sequence);
595 t->kcov = kcov;
596 kcov->t = t;
597 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
598 kcov_get(kcov);
599 return 0;
600 case KCOV_DISABLE:
601 kcov_debug("KCOV_DISABLE\n");
602 /* Disable coverage for the current task. */
603 unused = arg;
604 if (unused != 0 || current->kcov != kcov)
605 return -EINVAL;
606 t = current;
607 if (WARN_ON(kcov->t != t))
608 return -EINVAL;
609 kcov_disable(t, kcov);
610 kcov_put(kcov);
611 return 0;
612 case KCOV_REMOTE_ENABLE:
613 kcov_debug("KCOV_REMOTE_ENABLE\n");
614 if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
615 return -EINVAL;
616 t = current;
617 if (kcov->t != NULL || t->kcov != NULL)
618 return -EBUSY;
619 remote_arg = (struct kcov_remote_arg *)arg;
620 mode = kcov_get_mode(remote_arg->trace_mode);
621 if (mode < 0)
622 return mode;
623 if (remote_arg->area_size > LONG_MAX / sizeof(unsigned long))
624 return -EINVAL;
625 kcov->mode = mode;
626 t->kcov = kcov;
627 kcov->t = t;
628 kcov->remote = true;
629 kcov->remote_size = remote_arg->area_size;
630 spin_lock(&kcov_remote_lock);
631 for (i = 0; i < remote_arg->num_handles; i++) {
632 kcov_debug("handle %llx\n", remote_arg->handles[i]);
633 if (!kcov_check_handle(remote_arg->handles[i],
634 false, true, false)) {
635 spin_unlock(&kcov_remote_lock);
636 kcov_disable(t, kcov);
637 return -EINVAL;
638 }
639 remote = kcov_remote_add(kcov, remote_arg->handles[i]);
640 if (IS_ERR(remote)) {
641 spin_unlock(&kcov_remote_lock);
642 kcov_disable(t, kcov);
643 return PTR_ERR(remote);
644 }
645 }
646 if (remote_arg->common_handle) {
647 kcov_debug("common handle %llx\n",
648 remote_arg->common_handle);
649 if (!kcov_check_handle(remote_arg->common_handle,
650 true, false, false)) {
651 spin_unlock(&kcov_remote_lock);
652 kcov_disable(t, kcov);
653 return -EINVAL;
654 }
655 remote = kcov_remote_add(kcov,
656 remote_arg->common_handle);
657 if (IS_ERR(remote)) {
658 spin_unlock(&kcov_remote_lock);
659 kcov_disable(t, kcov);
660 return PTR_ERR(remote);
661 }
662 t->kcov_handle = remote_arg->common_handle;
663 }
664 spin_unlock(&kcov_remote_lock);
665 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
666 kcov_get(kcov);
667 return 0;
668 default:
669 return -ENOTTY;
670 }
671 }
672
673 static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
674 {
675 struct kcov *kcov;
676 int res;
677 struct kcov_remote_arg *remote_arg = NULL;
678 unsigned int remote_num_handles;
679 unsigned long remote_arg_size;
680
681 if (cmd == KCOV_REMOTE_ENABLE) {
682 if (get_user(remote_num_handles, (unsigned __user *)(arg +
683 offsetof(struct kcov_remote_arg, num_handles))))
684 return -EFAULT;
685 if (remote_num_handles > KCOV_REMOTE_MAX_HANDLES)
686 return -EINVAL;
687 remote_arg_size = struct_size(remote_arg, handles,
688 remote_num_handles);
689 remote_arg = memdup_user((void __user *)arg, remote_arg_size);
690 if (IS_ERR(remote_arg))
691 return PTR_ERR(remote_arg);
692 if (remote_arg->num_handles != remote_num_handles) {
693 kfree(remote_arg);
694 return -EINVAL;
695 }
696 arg = (unsigned long)remote_arg;
697 }
698
699 kcov = filep->private_data;
700 spin_lock(&kcov->lock);
701 res = kcov_ioctl_locked(kcov, cmd, arg);
702 spin_unlock(&kcov->lock);
703
704 kfree(remote_arg);
705
706 return res;
707 }
708
709 static const struct file_operations kcov_fops = {
710 .open = kcov_open,
711 .unlocked_ioctl = kcov_ioctl,
712 .compat_ioctl = kcov_ioctl,
713 .mmap = kcov_mmap,
714 .release = kcov_close,
715 };
716
717 /*
718 * kcov_remote_start() and kcov_remote_stop() can be used to annotate a section
719 * of code in a kernel background thread to allow kcov to be used to collect
720 * coverage from that part of code.
721 *
722 * The handle argument of kcov_remote_start() identifies a code section that is
723 * used for coverage collection. A userspace process passes this handle to
724 * KCOV_REMOTE_ENABLE ioctl to make the used kcov device start collecting
725 * coverage for the code section identified by this handle.
726 *
727 * The usage of these annotations in the kernel code is different depending on
728 * the type of the kernel thread whose code is being annotated.
729 *
730 * For global kernel threads that are spawned in a limited number of instances
731 * (e.g. one USB hub_event() worker thread is spawned per USB HCD), each
732 * instance must be assigned a unique 4-byte instance id. The instance id is
733 * then combined with a 1-byte subsystem id to get a handle via
734 * kcov_remote_handle(subsystem_id, instance_id).
735 *
736 * For local kernel threads that are spawned from system calls handler when a
737 * user interacts with some kernel interface (e.g. vhost workers), a handle is
738 * passed from a userspace process as the common_handle field of the
739 * kcov_remote_arg struct (note, that the user must generate a handle by using
740 * kcov_remote_handle() with KCOV_SUBSYSTEM_COMMON as the subsystem id and an
741 * arbitrary 4-byte non-zero number as the instance id). This common handle
742 * then gets saved into the task_struct of the process that issued the
743 * KCOV_REMOTE_ENABLE ioctl. When this process issues system calls that spawn
744 * kernel threads, the common handle must be retrieved via kcov_common_handle()
745 * and passed to the spawned threads via custom annotations. Those kernel
746 * threads must in turn be annotated with kcov_remote_start(common_handle) and
747 * kcov_remote_stop(). All of the threads that are spawned by the same process
748 * obtain the same handle, hence the name "common".
749 *
750 * See Documentation/dev-tools/kcov.rst for more details.
751 *
752 * Internally, this function looks up the kcov device associated with the
753 * provided handle, allocates an area for coverage collection, and saves the
754 * pointers to kcov and area into the current task_struct to allow coverage to
755 * be collected via __sanitizer_cov_trace_pc()
756 * In turns kcov_remote_stop() clears those pointers from task_struct to stop
757 * collecting coverage and copies all collected coverage into the kcov area.
758 */
759 void kcov_remote_start(u64 handle)
760 {
761 struct kcov_remote *remote;
762 void *area;
763 struct task_struct *t;
764 unsigned int size;
765 enum kcov_mode mode;
766 int sequence;
767
768 if (WARN_ON(!kcov_check_handle(handle, true, true, true)))
769 return;
770 if (WARN_ON(!in_task()))
771 return;
772 t = current;
773 /*
774 * Check that kcov_remote_start is not called twice
775 * nor called by user tasks (with enabled kcov).
776 */
777 if (WARN_ON(t->kcov))
778 return;
779
780 kcov_debug("handle = %llx\n", handle);
781
782 spin_lock(&kcov_remote_lock);
783 remote = kcov_remote_find(handle);
784 if (!remote) {
785 kcov_debug("no remote found");
786 spin_unlock(&kcov_remote_lock);
787 return;
788 }
789 /* Put in kcov_remote_stop(). */
790 kcov_get(remote->kcov);
791 t->kcov = remote->kcov;
792 /*
793 * Read kcov fields before unlock to prevent races with
794 * KCOV_DISABLE / kcov_remote_reset().
795 */
796 size = remote->kcov->remote_size;
797 mode = remote->kcov->mode;
798 sequence = remote->kcov->sequence;
799 area = kcov_remote_area_get(size);
800 spin_unlock(&kcov_remote_lock);
801
802 if (!area) {
803 area = vmalloc(size * sizeof(unsigned long));
804 if (!area) {
805 t->kcov = NULL;
806 kcov_put(remote->kcov);
807 return;
808 }
809 }
810 /* Reset coverage size. */
811 *(u64 *)area = 0;
812
813 kcov_debug("area = %px, size = %u", area, size);
814
815 kcov_start(t, size, area, mode, sequence);
816
817 }
818 EXPORT_SYMBOL(kcov_remote_start);
819
820 static void kcov_move_area(enum kcov_mode mode, void *dst_area,
821 unsigned int dst_area_size, void *src_area)
822 {
823 u64 word_size = sizeof(unsigned long);
824 u64 count_size, entry_size_log;
825 u64 dst_len, src_len;
826 void *dst_entries, *src_entries;
827 u64 dst_occupied, dst_free, bytes_to_move, entries_moved;
828
829 kcov_debug("%px %u <= %px %lu\n",
830 dst_area, dst_area_size, src_area, *(unsigned long *)src_area);
831
832 switch (mode) {
833 case KCOV_MODE_TRACE_PC:
834 dst_len = READ_ONCE(*(unsigned long *)dst_area);
835 src_len = *(unsigned long *)src_area;
836 count_size = sizeof(unsigned long);
837 entry_size_log = __ilog2_u64(sizeof(unsigned long));
838 break;
839 case KCOV_MODE_TRACE_CMP:
840 dst_len = READ_ONCE(*(u64 *)dst_area);
841 src_len = *(u64 *)src_area;
842 count_size = sizeof(u64);
843 BUILD_BUG_ON(!is_power_of_2(KCOV_WORDS_PER_CMP));
844 entry_size_log = __ilog2_u64(sizeof(u64) * KCOV_WORDS_PER_CMP);
845 break;
846 default:
847 WARN_ON(1);
848 return;
849 }
850
851 /* As arm can't divide u64 integers use log of entry size. */
852 if (dst_len > ((dst_area_size * word_size - count_size) >>
853 entry_size_log))
854 return;
855 dst_occupied = count_size + (dst_len << entry_size_log);
856 dst_free = dst_area_size * word_size - dst_occupied;
857 bytes_to_move = min(dst_free, src_len << entry_size_log);
858 dst_entries = dst_area + dst_occupied;
859 src_entries = src_area + count_size;
860 memcpy(dst_entries, src_entries, bytes_to_move);
861 entries_moved = bytes_to_move >> entry_size_log;
862
863 switch (mode) {
864 case KCOV_MODE_TRACE_PC:
865 WRITE_ONCE(*(unsigned long *)dst_area, dst_len + entries_moved);
866 break;
867 case KCOV_MODE_TRACE_CMP:
868 WRITE_ONCE(*(u64 *)dst_area, dst_len + entries_moved);
869 break;
870 default:
871 break;
872 }
873 }
874
875 /* See the comment before kcov_remote_start() for usage details. */
876 void kcov_remote_stop(void)
877 {
878 struct task_struct *t = current;
879 struct kcov *kcov = t->kcov;
880 void *area = t->kcov_area;
881 unsigned int size = t->kcov_size;
882 int sequence = t->kcov_sequence;
883
884 if (!kcov) {
885 kcov_debug("no kcov found\n");
886 return;
887 }
888
889 kcov_stop(t);
890 t->kcov = NULL;
891
892 spin_lock(&kcov->lock);
893 /*
894 * KCOV_DISABLE could have been called between kcov_remote_start()
895 * and kcov_remote_stop(), hence the check.
896 */
897 kcov_debug("move if: %d == %d && %d\n",
898 sequence, kcov->sequence, (int)kcov->remote);
899 if (sequence == kcov->sequence && kcov->remote)
900 kcov_move_area(kcov->mode, kcov->area, kcov->size, area);
901 spin_unlock(&kcov->lock);
902
903 spin_lock(&kcov_remote_lock);
904 kcov_remote_area_put(area, size);
905 spin_unlock(&kcov_remote_lock);
906
907 kcov_put(kcov);
908 }
909 EXPORT_SYMBOL(kcov_remote_stop);
910
911 /* See the comment before kcov_remote_start() for usage details. */
912 u64 kcov_common_handle(void)
913 {
914 return current->kcov_handle;
915 }
916 EXPORT_SYMBOL(kcov_common_handle);
917
918 static int __init kcov_init(void)
919 {
920 /*
921 * The kcov debugfs file won't ever get removed and thus,
922 * there is no need to protect it against removal races. The
923 * use of debugfs_create_file_unsafe() is actually safe here.
924 */
925 debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops);
926
927 return 0;
928 }
929
930 device_initcall(kcov_init);