projects/linux·blob v6.1 · refs

1080 lines · 29.2 KiB

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/kmsan-checks.h>
15#include <linux/mm.h>
16#include <linux/preempt.h>
17#include <linux/printk.h>
18#include <linux/sched.h>
19#include <linux/slab.h>
20#include <linux/spinlock.h>
21#include <linux/vmalloc.h>
22#include <linux/debugfs.h>
23#include <linux/uaccess.h>
24#include <linux/kcov.h>
25#include <linux/refcount.h>
26#include <linux/log2.h>
27#include <asm/setup.h>
28
29#define kcov_debug(fmt, ...) pr_debug("%s: " fmt, __func__, ##__VA_ARGS__)
30
31/* Number of 64-bit words written per one comparison: */
32#define KCOV_WORDS_PER_CMP 4
33
34/*
35 * kcov descriptor (one per opened debugfs file).
36 * State transitions of the descriptor:
37 * - initial state after open()
38 * - then there must be a single ioctl(KCOV_INIT_TRACE) call
39 * - then, mmap() call (several calls are allowed but not useful)
40 * - then, ioctl(KCOV_ENABLE, arg), where arg is
41 * KCOV_TRACE_PC - to trace only the PCs
42 * or
43 * KCOV_TRACE_CMP - to trace only the comparison operands
44 * - then, ioctl(KCOV_DISABLE) to disable the task.
45 * Enabling/disabling ioctls can be repeated (only one task a time allowed).
46 */
47struct kcov {
48 /*
49 * Reference counter. We keep one for:
50 * - opened file descriptor
51 * - task with enabled coverage (we can't unwire it from another task)
52 * - each code section for remote coverage collection
53 */
54 refcount_t refcount;
55 /* The lock protects mode, size, area and t. */
56 spinlock_t lock;
57 enum kcov_mode mode;
58 /* Size of arena (in long's). */
59 unsigned int size;
60 /* Coverage buffer shared with user space. */
61 void *area;
62 /* Task for which we collect coverage, or NULL. */
63 struct task_struct *t;
64 /* Collecting coverage from remote (background) threads. */
65 bool remote;
66 /* Size of remote area (in long's). */
67 unsigned int remote_size;
68 /*
69 * Sequence is incremented each time kcov is reenabled, used by
70 * kcov_remote_stop(), see the comment there.
71 */
72 int sequence;
73};
74
75struct kcov_remote_area {
76 struct list_head list;
77 unsigned int size;
78};
79
80struct kcov_remote {
81 u64 handle;
82 struct kcov *kcov;
83 struct hlist_node hnode;
84};
85
86static DEFINE_SPINLOCK(kcov_remote_lock);
87static DEFINE_HASHTABLE(kcov_remote_map, 4);
88static struct list_head kcov_remote_areas = LIST_HEAD_INIT(kcov_remote_areas);
89
90struct kcov_percpu_data {
91 void *irq_area;
92 local_lock_t lock;
93
94 unsigned int saved_mode;
95 unsigned int saved_size;
96 void *saved_area;
97 struct kcov *saved_kcov;
98 int saved_sequence;
99};
100
101static DEFINE_PER_CPU(struct kcov_percpu_data, kcov_percpu_data) = {
102 .lock = INIT_LOCAL_LOCK(lock),
103};
104
105/* Must be called with kcov_remote_lock locked. */
106static struct kcov_remote *kcov_remote_find(u64 handle)
107{
108 struct kcov_remote *remote;
109
110 hash_for_each_possible(kcov_remote_map, remote, hnode, handle) {
111 if (remote->handle == handle)
112 return remote;
113 }
114 return NULL;
115}
116
117/* Must be called with kcov_remote_lock locked. */
118static struct kcov_remote *kcov_remote_add(struct kcov *kcov, u64 handle)
119{
120 struct kcov_remote *remote;
121
122 if (kcov_remote_find(handle))
123 return ERR_PTR(-EEXIST);
124 remote = kmalloc(sizeof(*remote), GFP_ATOMIC);
125 if (!remote)
126 return ERR_PTR(-ENOMEM);
127 remote->handle = handle;
128 remote->kcov = kcov;
129 hash_add(kcov_remote_map, &remote->hnode, handle);
130 return remote;
131}
132
133/* Must be called with kcov_remote_lock locked. */
134static struct kcov_remote_area *kcov_remote_area_get(unsigned int size)
135{
136 struct kcov_remote_area *area;
137 struct list_head *pos;
138
139 list_for_each(pos, &kcov_remote_areas) {
140 area = list_entry(pos, struct kcov_remote_area, list);
141 if (area->size == size) {
142 list_del(&area->list);
143 return area;
144 }
145 }
146 return NULL;
147}
148
149/* Must be called with kcov_remote_lock locked. */
150static void kcov_remote_area_put(struct kcov_remote_area *area,
151 unsigned int size)
152{
153 INIT_LIST_HEAD(&area->list);
154 area->size = size;
155 list_add(&area->list, &kcov_remote_areas);
156 /*
157 * KMSAN doesn't instrument this file, so it may not know area->list
158 * is initialized. Unpoison it explicitly to avoid reports in
159 * kcov_remote_area_get().
160 */
161 kmsan_unpoison_memory(&area->list, sizeof(area->list));
162}
163
164static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
165{
166 unsigned int mode;
167
168 /*
169 * We are interested in code coverage as a function of a syscall inputs,
170 * so we ignore code executed in interrupts, unless we are in a remote
171 * coverage collection section in a softirq.
172 */
173 if (!in_task() && !(in_serving_softirq() && t->kcov_softirq))
174 return false;
175 mode = READ_ONCE(t->kcov_mode);
176 /*
177 * There is some code that runs in interrupts but for which
178 * in_interrupt() returns false (e.g. preempt_schedule_irq()).
179 * READ_ONCE()/barrier() effectively provides load-acquire wrt
180 * interrupts, there are paired barrier()/WRITE_ONCE() in
181 * kcov_start().
182 */
183 barrier();
184 return mode == needed_mode;
185}
186
187static notrace unsigned long canonicalize_ip(unsigned long ip)
188{
189#ifdef CONFIG_RANDOMIZE_BASE
190 ip -= kaslr_offset();
191#endif
192 return ip;
193}
194
195/*
196 * Entry point from instrumented code.
197 * This is called once per basic-block/edge.
198 */
199void notrace __sanitizer_cov_trace_pc(void)
200{
201 struct task_struct *t;
202 unsigned long *area;
203 unsigned long ip = canonicalize_ip(_RET_IP_);
204 unsigned long pos;
205
206 t = current;
207 if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t))
208 return;
209
210 area = t->kcov_area;
211 /* The first 64-bit word is the number of subsequent PCs. */
212 pos = READ_ONCE(area[0]) + 1;
213 if (likely(pos < t->kcov_size)) {
214 /* Previously we write pc before updating pos. However, some
215 * early interrupt code could bypass check_kcov_mode() check
216 * and invoke __sanitizer_cov_trace_pc(). If such interrupt is
217 * raised between writing pc and updating pos, the pc could be
218 * overitten by the recursive __sanitizer_cov_trace_pc().
219 * Update pos before writing pc to avoid such interleaving.
220 */
221 WRITE_ONCE(area[0], pos);
222 barrier();
223 area[pos] = ip;
224 }
225}
226EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
227
228#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
229static void notrace write_comp_data(u64 type, u64 arg1, u64 arg2, u64 ip)
230{
231 struct task_struct *t;
232 u64 *area;
233 u64 count, start_index, end_pos, max_pos;
234
235 t = current;
236 if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t))
237 return;
238
239 ip = canonicalize_ip(ip);
240
241 /*
242 * We write all comparison arguments and types as u64.
243 * The buffer was allocated for t->kcov_size unsigned longs.
244 */
245 area = (u64 *)t->kcov_area;
246 max_pos = t->kcov_size * sizeof(unsigned long);
247
248 count = READ_ONCE(area[0]);
249
250 /* Every record is KCOV_WORDS_PER_CMP 64-bit words. */
251 start_index = 1 + count * KCOV_WORDS_PER_CMP;
252 end_pos = (start_index + KCOV_WORDS_PER_CMP) * sizeof(u64);
253 if (likely(end_pos <= max_pos)) {
254 /* See comment in __sanitizer_cov_trace_pc(). */
255 WRITE_ONCE(area[0], count + 1);
256 barrier();
257 area[start_index] = type;
258 area[start_index + 1] = arg1;
259 area[start_index + 2] = arg2;
260 area[start_index + 3] = ip;
261 }
262}
263
264void notrace __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2)
265{
266 write_comp_data(KCOV_CMP_SIZE(0), arg1, arg2, _RET_IP_);
267}
268EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1);
269
270void notrace __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2)
271{
272 write_comp_data(KCOV_CMP_SIZE(1), arg1, arg2, _RET_IP_);
273}
274EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2);
275
276void notrace __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2)
277{
278 write_comp_data(KCOV_CMP_SIZE(2), arg1, arg2, _RET_IP_);
279}
280EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4);
281
282void notrace __sanitizer_cov_trace_cmp8(u64 arg1, u64 arg2)
283{
284 write_comp_data(KCOV_CMP_SIZE(3), arg1, arg2, _RET_IP_);
285}
286EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8);
287
288void notrace __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2)
289{
290 write_comp_data(KCOV_CMP_SIZE(0) | KCOV_CMP_CONST, arg1, arg2,
291 _RET_IP_);
292}
293EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1);
294
295void notrace __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2)
296{
297 write_comp_data(KCOV_CMP_SIZE(1) | KCOV_CMP_CONST, arg1, arg2,
298 _RET_IP_);
299}
300EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2);
301
302void notrace __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2)
303{
304 write_comp_data(KCOV_CMP_SIZE(2) | KCOV_CMP_CONST, arg1, arg2,
305 _RET_IP_);
306}
307EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4);
308
309void notrace __sanitizer_cov_trace_const_cmp8(u64 arg1, u64 arg2)
310{
311 write_comp_data(KCOV_CMP_SIZE(3) | KCOV_CMP_CONST, arg1, arg2,
312 _RET_IP_);
313}
314EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8);
315
316void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases)
317{
318 u64 i;
319 u64 count = cases[0];
320 u64 size = cases[1];
321 u64 type = KCOV_CMP_CONST;
322
323 switch (size) {
324 case 8:
325 type |= KCOV_CMP_SIZE(0);
326 break;
327 case 16:
328 type |= KCOV_CMP_SIZE(1);
329 break;
330 case 32:
331 type |= KCOV_CMP_SIZE(2);
332 break;
333 case 64:
334 type |= KCOV_CMP_SIZE(3);
335 break;
336 default:
337 return;
338 }
339 for (i = 0; i < count; i++)
340 write_comp_data(type, cases[i + 2], val, _RET_IP_);
341}
342EXPORT_SYMBOL(__sanitizer_cov_trace_switch);
343#endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */
344
345static void kcov_start(struct task_struct *t, struct kcov *kcov,
346 unsigned int size, void *area, enum kcov_mode mode,
347 int sequence)
348{
349 kcov_debug("t = %px, size = %u, area = %px\n", t, size, area);
350 t->kcov = kcov;
351 /* Cache in task struct for performance. */
352 t->kcov_size = size;
353 t->kcov_area = area;
354 t->kcov_sequence = sequence;
355 /* See comment in check_kcov_mode(). */
356 barrier();
357 WRITE_ONCE(t->kcov_mode, mode);
358}
359
360static void kcov_stop(struct task_struct *t)
361{
362 WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);
363 barrier();
364 t->kcov = NULL;
365 t->kcov_size = 0;
366 t->kcov_area = NULL;
367}
368
369static void kcov_task_reset(struct task_struct *t)
370{
371 kcov_stop(t);
372 t->kcov_sequence = 0;
373 t->kcov_handle = 0;
374}
375
376void kcov_task_init(struct task_struct *t)
377{
378 kcov_task_reset(t);
379 t->kcov_handle = current->kcov_handle;
380}
381
382static void kcov_reset(struct kcov *kcov)
383{
384 kcov->t = NULL;
385 kcov->mode = KCOV_MODE_INIT;
386 kcov->remote = false;
387 kcov->remote_size = 0;
388 kcov->sequence++;
389}
390
391static void kcov_remote_reset(struct kcov *kcov)
392{
393 int bkt;
394 struct kcov_remote *remote;
395 struct hlist_node *tmp;
396 unsigned long flags;
397
398 spin_lock_irqsave(&kcov_remote_lock, flags);
399 hash_for_each_safe(kcov_remote_map, bkt, tmp, remote, hnode) {
400 if (remote->kcov != kcov)
401 continue;
402 hash_del(&remote->hnode);
403 kfree(remote);
404 }
405 /* Do reset before unlock to prevent races with kcov_remote_start(). */
406 kcov_reset(kcov);
407 spin_unlock_irqrestore(&kcov_remote_lock, flags);
408}
409
410static void kcov_disable(struct task_struct *t, struct kcov *kcov)
411{
412 kcov_task_reset(t);
413 if (kcov->remote)
414 kcov_remote_reset(kcov);
415 else
416 kcov_reset(kcov);
417}
418
419static void kcov_get(struct kcov *kcov)
420{
421 refcount_inc(&kcov->refcount);
422}
423
424static void kcov_put(struct kcov *kcov)
425{
426 if (refcount_dec_and_test(&kcov->refcount)) {
427 kcov_remote_reset(kcov);
428 vfree(kcov->area);
429 kfree(kcov);
430 }
431}
432
433void kcov_task_exit(struct task_struct *t)
434{
435 struct kcov *kcov;
436 unsigned long flags;
437
438 kcov = t->kcov;
439 if (kcov == NULL)
440 return;
441
442 spin_lock_irqsave(&kcov->lock, flags);
443 kcov_debug("t = %px, kcov->t = %px\n", t, kcov->t);
444 /*
445 * For KCOV_ENABLE devices we want to make sure that t->kcov->t == t,
446 * which comes down to:
447 * WARN_ON(!kcov->remote && kcov->t != t);
448 *
449 * For KCOV_REMOTE_ENABLE devices, the exiting task is either:
450 *
451 * 1. A remote task between kcov_remote_start() and kcov_remote_stop().
452 * In this case we should print a warning right away, since a task
453 * shouldn't be exiting when it's in a kcov coverage collection
454 * section. Here t points to the task that is collecting remote
455 * coverage, and t->kcov->t points to the thread that created the
456 * kcov device. Which means that to detect this case we need to
457 * check that t != t->kcov->t, and this gives us the following:
458 * WARN_ON(kcov->remote && kcov->t != t);
459 *
460 * 2. The task that created kcov exiting without calling KCOV_DISABLE,
461 * and then again we make sure that t->kcov->t == t:
462 * WARN_ON(kcov->remote && kcov->t != t);
463 *
464 * By combining all three checks into one we get:
465 */
466 if (WARN_ON(kcov->t != t)) {
467 spin_unlock_irqrestore(&kcov->lock, flags);
468 return;
469 }
470 /* Just to not leave dangling references behind. */
471 kcov_disable(t, kcov);
472 spin_unlock_irqrestore(&kcov->lock, flags);
473 kcov_put(kcov);
474}
475
476static int kcov_mmap(struct file *filep, struct vm_area_struct *vma)
477{
478 int res = 0;
479 struct kcov *kcov = vma->vm_file->private_data;
480 unsigned long size, off;
481 struct page *page;
482 unsigned long flags;
483
484 spin_lock_irqsave(&kcov->lock, flags);
485 size = kcov->size * sizeof(unsigned long);
486 if (kcov->area == NULL || vma->vm_pgoff != 0 ||
487 vma->vm_end - vma->vm_start != size) {
488 res = -EINVAL;
489 goto exit;
490 }
491 spin_unlock_irqrestore(&kcov->lock, flags);
492 vma->vm_flags |= VM_DONTEXPAND;
493 for (off = 0; off < size; off += PAGE_SIZE) {
494 page = vmalloc_to_page(kcov->area + off);
495 res = vm_insert_page(vma, vma->vm_start + off, page);
496 if (res) {
497 pr_warn_once("kcov: vm_insert_page() failed\n");
498 return res;
499 }
500 }
501 return 0;
502exit:
503 spin_unlock_irqrestore(&kcov->lock, flags);
504 return res;
505}
506
507static int kcov_open(struct inode *inode, struct file *filep)
508{
509 struct kcov *kcov;
510
511 kcov = kzalloc(sizeof(*kcov), GFP_KERNEL);
512 if (!kcov)
513 return -ENOMEM;
514 kcov->mode = KCOV_MODE_DISABLED;
515 kcov->sequence = 1;
516 refcount_set(&kcov->refcount, 1);
517 spin_lock_init(&kcov->lock);
518 filep->private_data = kcov;
519 return nonseekable_open(inode, filep);
520}
521
522static int kcov_close(struct inode *inode, struct file *filep)
523{
524 kcov_put(filep->private_data);
525 return 0;
526}
527
528static int kcov_get_mode(unsigned long arg)
529{
530 if (arg == KCOV_TRACE_PC)
531 return KCOV_MODE_TRACE_PC;
532 else if (arg == KCOV_TRACE_CMP)
533#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
534 return KCOV_MODE_TRACE_CMP;
535#else
536 return -ENOTSUPP;
537#endif
538 else
539 return -EINVAL;
540}
541
542/*
543 * Fault in a lazily-faulted vmalloc area before it can be used by
544 * __santizer_cov_trace_pc(), to avoid recursion issues if any code on the
545 * vmalloc fault handling path is instrumented.
546 */
547static void kcov_fault_in_area(struct kcov *kcov)
548{
549 unsigned long stride = PAGE_SIZE / sizeof(unsigned long);
550 unsigned long *area = kcov->area;
551 unsigned long offset;
552
553 for (offset = 0; offset < kcov->size; offset += stride)
554 READ_ONCE(area[offset]);
555}
556
557static inline bool kcov_check_handle(u64 handle, bool common_valid,
558 bool uncommon_valid, bool zero_valid)
559{
560 if (handle & ~(KCOV_SUBSYSTEM_MASK | KCOV_INSTANCE_MASK))
561 return false;
562 switch (handle & KCOV_SUBSYSTEM_MASK) {
563 case KCOV_SUBSYSTEM_COMMON:
564 return (handle & KCOV_INSTANCE_MASK) ?
565 common_valid : zero_valid;
566 case KCOV_SUBSYSTEM_USB:
567 return uncommon_valid;
568 default:
569 return false;
570 }
571 return false;
572}
573
574static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
575 unsigned long arg)
576{
577 struct task_struct *t;
578 unsigned long flags, unused;
579 int mode, i;
580 struct kcov_remote_arg *remote_arg;
581 struct kcov_remote *remote;
582
583 switch (cmd) {
584 case KCOV_ENABLE:
585 /*
586 * Enable coverage for the current task.
587 * At this point user must have been enabled trace mode,
588 * and mmapped the file. Coverage collection is disabled only
589 * at task exit or voluntary by KCOV_DISABLE. After that it can
590 * be enabled for another task.
591 */
592 if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
593 return -EINVAL;
594 t = current;
595 if (kcov->t != NULL || t->kcov != NULL)
596 return -EBUSY;
597 mode = kcov_get_mode(arg);
598 if (mode < 0)
599 return mode;
600 kcov_fault_in_area(kcov);
601 kcov->mode = mode;
602 kcov_start(t, kcov, kcov->size, kcov->area, kcov->mode,
603 kcov->sequence);
604 kcov->t = t;
605 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
606 kcov_get(kcov);
607 return 0;
608 case KCOV_DISABLE:
609 /* Disable coverage for the current task. */
610 unused = arg;
611 if (unused != 0 || current->kcov != kcov)
612 return -EINVAL;
613 t = current;
614 if (WARN_ON(kcov->t != t))
615 return -EINVAL;
616 kcov_disable(t, kcov);
617 kcov_put(kcov);
618 return 0;
619 case KCOV_REMOTE_ENABLE:
620 if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
621 return -EINVAL;
622 t = current;
623 if (kcov->t != NULL || t->kcov != NULL)
624 return -EBUSY;
625 remote_arg = (struct kcov_remote_arg *)arg;
626 mode = kcov_get_mode(remote_arg->trace_mode);
627 if (mode < 0)
628 return mode;
629 if (remote_arg->area_size > LONG_MAX / sizeof(unsigned long))
630 return -EINVAL;
631 kcov->mode = mode;
632 t->kcov = kcov;
633 kcov->t = t;
634 kcov->remote = true;
635 kcov->remote_size = remote_arg->area_size;
636 spin_lock_irqsave(&kcov_remote_lock, flags);
637 for (i = 0; i < remote_arg->num_handles; i++) {
638 if (!kcov_check_handle(remote_arg->handles[i],
639 false, true, false)) {
640 spin_unlock_irqrestore(&kcov_remote_lock,
641 flags);
642 kcov_disable(t, kcov);
643 return -EINVAL;
644 }
645 remote = kcov_remote_add(kcov, remote_arg->handles[i]);
646 if (IS_ERR(remote)) {
647 spin_unlock_irqrestore(&kcov_remote_lock,
648 flags);
649 kcov_disable(t, kcov);
650 return PTR_ERR(remote);
651 }
652 }
653 if (remote_arg->common_handle) {
654 if (!kcov_check_handle(remote_arg->common_handle,
655 true, false, false)) {
656 spin_unlock_irqrestore(&kcov_remote_lock,
657 flags);
658 kcov_disable(t, kcov);
659 return -EINVAL;
660 }
661 remote = kcov_remote_add(kcov,
662 remote_arg->common_handle);
663 if (IS_ERR(remote)) {
664 spin_unlock_irqrestore(&kcov_remote_lock,
665 flags);
666 kcov_disable(t, kcov);
667 return PTR_ERR(remote);
668 }
669 t->kcov_handle = remote_arg->common_handle;
670 }
671 spin_unlock_irqrestore(&kcov_remote_lock, flags);
672 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
673 kcov_get(kcov);
674 return 0;
675 default:
676 return -ENOTTY;
677 }
678}
679
680static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
681{
682 struct kcov *kcov;
683 int res;
684 struct kcov_remote_arg *remote_arg = NULL;
685 unsigned int remote_num_handles;
686 unsigned long remote_arg_size;
687 unsigned long size, flags;
688 void *area;
689
690 kcov = filep->private_data;
691 switch (cmd) {
692 case KCOV_INIT_TRACE:
693 /*
694 * Enable kcov in trace mode and setup buffer size.
695 * Must happen before anything else.
696 *
697 * First check the size argument - it must be at least 2
698 * to hold the current position and one PC.
699 */
700 size = arg;
701 if (size < 2 || size > INT_MAX / sizeof(unsigned long))
702 return -EINVAL;
703 area = vmalloc_user(size * sizeof(unsigned long));
704 if (area == NULL)
705 return -ENOMEM;
706 spin_lock_irqsave(&kcov->lock, flags);
707 if (kcov->mode != KCOV_MODE_DISABLED) {
708 spin_unlock_irqrestore(&kcov->lock, flags);
709 vfree(area);
710 return -EBUSY;
711 }
712 kcov->area = area;
713 kcov->size = size;
714 kcov->mode = KCOV_MODE_INIT;
715 spin_unlock_irqrestore(&kcov->lock, flags);
716 return 0;
717 case KCOV_REMOTE_ENABLE:
718 if (get_user(remote_num_handles, (unsigned __user *)(arg +
719 offsetof(struct kcov_remote_arg, num_handles))))
720 return -EFAULT;
721 if (remote_num_handles > KCOV_REMOTE_MAX_HANDLES)
722 return -EINVAL;
723 remote_arg_size = struct_size(remote_arg, handles,
724 remote_num_handles);
725 remote_arg = memdup_user((void __user *)arg, remote_arg_size);
726 if (IS_ERR(remote_arg))
727 return PTR_ERR(remote_arg);
728 if (remote_arg->num_handles != remote_num_handles) {
729 kfree(remote_arg);
730 return -EINVAL;
731 }
732 arg = (unsigned long)remote_arg;
733 fallthrough;
734 default:
735 /*
736 * All other commands can be normally executed under a spin lock, so we
737 * obtain and release it here in order to simplify kcov_ioctl_locked().
738 */
739 spin_lock_irqsave(&kcov->lock, flags);
740 res = kcov_ioctl_locked(kcov, cmd, arg);
741 spin_unlock_irqrestore(&kcov->lock, flags);
742 kfree(remote_arg);
743 return res;
744 }
745}
746
747static const struct file_operations kcov_fops = {
748 .open = kcov_open,
749 .unlocked_ioctl = kcov_ioctl,
750 .compat_ioctl = kcov_ioctl,
751 .mmap = kcov_mmap,
752 .release = kcov_close,
753};
754
755/*
756 * kcov_remote_start() and kcov_remote_stop() can be used to annotate a section
757 * of code in a kernel background thread or in a softirq to allow kcov to be
758 * used to collect coverage from that part of code.
759 *
760 * The handle argument of kcov_remote_start() identifies a code section that is
761 * used for coverage collection. A userspace process passes this handle to
762 * KCOV_REMOTE_ENABLE ioctl to make the used kcov device start collecting
763 * coverage for the code section identified by this handle.
764 *
765 * The usage of these annotations in the kernel code is different depending on
766 * the type of the kernel thread whose code is being annotated.
767 *
768 * For global kernel threads that are spawned in a limited number of instances
769 * (e.g. one USB hub_event() worker thread is spawned per USB HCD) and for
770 * softirqs, each instance must be assigned a unique 4-byte instance id. The
771 * instance id is then combined with a 1-byte subsystem id to get a handle via
772 * kcov_remote_handle(subsystem_id, instance_id).
773 *
774 * For local kernel threads that are spawned from system calls handler when a
775 * user interacts with some kernel interface (e.g. vhost workers), a handle is
776 * passed from a userspace process as the common_handle field of the
777 * kcov_remote_arg struct (note, that the user must generate a handle by using
778 * kcov_remote_handle() with KCOV_SUBSYSTEM_COMMON as the subsystem id and an
779 * arbitrary 4-byte non-zero number as the instance id). This common handle
780 * then gets saved into the task_struct of the process that issued the
781 * KCOV_REMOTE_ENABLE ioctl. When this process issues system calls that spawn
782 * kernel threads, the common handle must be retrieved via kcov_common_handle()
783 * and passed to the spawned threads via custom annotations. Those kernel
784 * threads must in turn be annotated with kcov_remote_start(common_handle) and
785 * kcov_remote_stop(). All of the threads that are spawned by the same process
786 * obtain the same handle, hence the name "common".
787 *
788 * See Documentation/dev-tools/kcov.rst for more details.
789 *
790 * Internally, kcov_remote_start() looks up the kcov device associated with the
791 * provided handle, allocates an area for coverage collection, and saves the
792 * pointers to kcov and area into the current task_struct to allow coverage to
793 * be collected via __sanitizer_cov_trace_pc().
794 * In turns kcov_remote_stop() clears those pointers from task_struct to stop
795 * collecting coverage and copies all collected coverage into the kcov area.
796 */
797
798static inline bool kcov_mode_enabled(unsigned int mode)
799{
800 return (mode & ~KCOV_IN_CTXSW) != KCOV_MODE_DISABLED;
801}
802
803static void kcov_remote_softirq_start(struct task_struct *t)
804{
805 struct kcov_percpu_data *data = this_cpu_ptr(&kcov_percpu_data);
806 unsigned int mode;
807
808 mode = READ_ONCE(t->kcov_mode);
809 barrier();
810 if (kcov_mode_enabled(mode)) {
811 data->saved_mode = mode;
812 data->saved_size = t->kcov_size;
813 data->saved_area = t->kcov_area;
814 data->saved_sequence = t->kcov_sequence;
815 data->saved_kcov = t->kcov;
816 kcov_stop(t);
817 }
818}
819
820static void kcov_remote_softirq_stop(struct task_struct *t)
821{
822 struct kcov_percpu_data *data = this_cpu_ptr(&kcov_percpu_data);
823
824 if (data->saved_kcov) {
825 kcov_start(t, data->saved_kcov, data->saved_size,
826 data->saved_area, data->saved_mode,
827 data->saved_sequence);
828 data->saved_mode = 0;
829 data->saved_size = 0;
830 data->saved_area = NULL;
831 data->saved_sequence = 0;
832 data->saved_kcov = NULL;
833 }
834}
835
836void kcov_remote_start(u64 handle)
837{
838 struct task_struct *t = current;
839 struct kcov_remote *remote;
840 struct kcov *kcov;
841 unsigned int mode;
842 void *area;
843 unsigned int size;
844 int sequence;
845 unsigned long flags;
846
847 if (WARN_ON(!kcov_check_handle(handle, true, true, true)))
848 return;
849 if (!in_task() && !in_serving_softirq())
850 return;
851
852 local_lock_irqsave(&kcov_percpu_data.lock, flags);
853
854 /*
855 * Check that kcov_remote_start() is not called twice in background
856 * threads nor called by user tasks (with enabled kcov).
857 */
858 mode = READ_ONCE(t->kcov_mode);
859 if (WARN_ON(in_task() && kcov_mode_enabled(mode))) {
860 local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
861 return;
862 }
863 /*
864 * Check that kcov_remote_start() is not called twice in softirqs.
865 * Note, that kcov_remote_start() can be called from a softirq that
866 * happened while collecting coverage from a background thread.
867 */
868 if (WARN_ON(in_serving_softirq() && t->kcov_softirq)) {
869 local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
870 return;
871 }
872
873 spin_lock(&kcov_remote_lock);
874 remote = kcov_remote_find(handle);
875 if (!remote) {
876 spin_unlock(&kcov_remote_lock);
877 local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
878 return;
879 }
880 kcov_debug("handle = %llx, context: %s\n", handle,
881 in_task() ? "task" : "softirq");
882 kcov = remote->kcov;
883 /* Put in kcov_remote_stop(). */
884 kcov_get(kcov);
885 /*
886 * Read kcov fields before unlock to prevent races with
887 * KCOV_DISABLE / kcov_remote_reset().
888 */
889 mode = kcov->mode;
890 sequence = kcov->sequence;
891 if (in_task()) {
892 size = kcov->remote_size;
893 area = kcov_remote_area_get(size);
894 } else {
895 size = CONFIG_KCOV_IRQ_AREA_SIZE;
896 area = this_cpu_ptr(&kcov_percpu_data)->irq_area;
897 }
898 spin_unlock(&kcov_remote_lock);
899
900 /* Can only happen when in_task(). */
901 if (!area) {
902 local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
903 area = vmalloc(size * sizeof(unsigned long));
904 if (!area) {
905 kcov_put(kcov);
906 return;
907 }
908 local_lock_irqsave(&kcov_percpu_data.lock, flags);
909 }
910
911 /* Reset coverage size. */
912 *(u64 *)area = 0;
913
914 if (in_serving_softirq()) {
915 kcov_remote_softirq_start(t);
916 t->kcov_softirq = 1;
917 }
918 kcov_start(t, kcov, size, area, mode, sequence);
919
920 local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
921
922}
923EXPORT_SYMBOL(kcov_remote_start);
924
925static void kcov_move_area(enum kcov_mode mode, void *dst_area,
926 unsigned int dst_area_size, void *src_area)
927{
928 u64 word_size = sizeof(unsigned long);
929 u64 count_size, entry_size_log;
930 u64 dst_len, src_len;
931 void *dst_entries, *src_entries;
932 u64 dst_occupied, dst_free, bytes_to_move, entries_moved;
933
934 kcov_debug("%px %u <= %px %lu\n",
935 dst_area, dst_area_size, src_area, *(unsigned long *)src_area);
936
937 switch (mode) {
938 case KCOV_MODE_TRACE_PC:
939 dst_len = READ_ONCE(*(unsigned long *)dst_area);
940 src_len = *(unsigned long *)src_area;
941 count_size = sizeof(unsigned long);
942 entry_size_log = __ilog2_u64(sizeof(unsigned long));
943 break;
944 case KCOV_MODE_TRACE_CMP:
945 dst_len = READ_ONCE(*(u64 *)dst_area);
946 src_len = *(u64 *)src_area;
947 count_size = sizeof(u64);
948 BUILD_BUG_ON(!is_power_of_2(KCOV_WORDS_PER_CMP));
949 entry_size_log = __ilog2_u64(sizeof(u64) * KCOV_WORDS_PER_CMP);
950 break;
951 default:
952 WARN_ON(1);
953 return;
954 }
955
956 /* As arm can't divide u64 integers use log of entry size. */
957 if (dst_len > ((dst_area_size * word_size - count_size) >>
958 entry_size_log))
959 return;
960 dst_occupied = count_size + (dst_len << entry_size_log);
961 dst_free = dst_area_size * word_size - dst_occupied;
962 bytes_to_move = min(dst_free, src_len << entry_size_log);
963 dst_entries = dst_area + dst_occupied;
964 src_entries = src_area + count_size;
965 memcpy(dst_entries, src_entries, bytes_to_move);
966 entries_moved = bytes_to_move >> entry_size_log;
967
968 switch (mode) {
969 case KCOV_MODE_TRACE_PC:
970 WRITE_ONCE(*(unsigned long *)dst_area, dst_len + entries_moved);
971 break;
972 case KCOV_MODE_TRACE_CMP:
973 WRITE_ONCE(*(u64 *)dst_area, dst_len + entries_moved);
974 break;
975 default:
976 break;
977 }
978}
979
980/* See the comment before kcov_remote_start() for usage details. */
981void kcov_remote_stop(void)
982{
983 struct task_struct *t = current;
984 struct kcov *kcov;
985 unsigned int mode;
986 void *area;
987 unsigned int size;
988 int sequence;
989 unsigned long flags;
990
991 if (!in_task() && !in_serving_softirq())
992 return;
993
994 local_lock_irqsave(&kcov_percpu_data.lock, flags);
995
996 mode = READ_ONCE(t->kcov_mode);
997 barrier();
998 if (!kcov_mode_enabled(mode)) {
999 local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
1000 return;
1001 }
1002 /*
1003 * When in softirq, check if the corresponding kcov_remote_start()
1004 * actually found the remote handle and started collecting coverage.
1005 */
1006 if (in_serving_softirq() && !t->kcov_softirq) {
1007 local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
1008 return;
1009 }
1010 /* Make sure that kcov_softirq is only set when in softirq. */
1011 if (WARN_ON(!in_serving_softirq() && t->kcov_softirq)) {
1012 local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
1013 return;
1014 }
1015
1016 kcov = t->kcov;
1017 area = t->kcov_area;
1018 size = t->kcov_size;
1019 sequence = t->kcov_sequence;
1020
1021 kcov_stop(t);
1022 if (in_serving_softirq()) {
1023 t->kcov_softirq = 0;
1024 kcov_remote_softirq_stop(t);
1025 }
1026
1027 spin_lock(&kcov->lock);
1028 /*
1029 * KCOV_DISABLE could have been called between kcov_remote_start()
1030 * and kcov_remote_stop(), hence the sequence check.
1031 */
1032 if (sequence == kcov->sequence && kcov->remote)
1033 kcov_move_area(kcov->mode, kcov->area, kcov->size, area);
1034 spin_unlock(&kcov->lock);
1035
1036 if (in_task()) {
1037 spin_lock(&kcov_remote_lock);
1038 kcov_remote_area_put(area, size);
1039 spin_unlock(&kcov_remote_lock);
1040 }
1041
1042 local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
1043
1044 /* Get in kcov_remote_start(). */
1045 kcov_put(kcov);
1046}
1047EXPORT_SYMBOL(kcov_remote_stop);
1048
1049/* See the comment before kcov_remote_start() for usage details. */
1050u64 kcov_common_handle(void)
1051{
1052 if (!in_task())
1053 return 0;
1054 return current->kcov_handle;
1055}
1056EXPORT_SYMBOL(kcov_common_handle);
1057
1058static int __init kcov_init(void)
1059{
1060 int cpu;
1061
1062 for_each_possible_cpu(cpu) {
1063 void *area = vmalloc_node(CONFIG_KCOV_IRQ_AREA_SIZE *
1064 sizeof(unsigned long), cpu_to_node(cpu));
1065 if (!area)
1066 return -ENOMEM;
1067 per_cpu_ptr(&kcov_percpu_data, cpu)->irq_area = area;
1068 }
1069
1070 /*
1071 * The kcov debugfs file won't ever get removed and thus,
1072 * there is no need to protect it against removal races. The
1073 * use of debugfs_create_file_unsafe() is actually safe here.
1074 */
1075 debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops);
1076
1077 return 0;
1078}
1079
1080device_initcall(kcov_init);