1 // SPDX-License-Identifier: GPL-2.0
2 #define pr_fmt(fmt) "kcov: " fmt
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>
12 #include <linux/hashtable.h>
13 #include <linux/init.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>
28 #define kcov_debug(fmt, ...) pr_debug("%s: " fmt, __func__, ##__VA_ARGS__)
30 /* Number of 64-bit words written per one comparison: */
31 #define KCOV_WORDS_PER_CMP 4
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
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).
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
54 /* The lock protects mode, size, area and t. */
57 /* Size of arena (in long's). */
59 /* Coverage buffer shared with user space. */
61 /* Task for which we collect coverage, or NULL. */
62 struct task_struct *t;
63 /* Collecting coverage from remote (background) threads. */
65 /* Size of remote area (in long's). */
66 unsigned int remote_size;
68 * Sequence is incremented each time kcov is reenabled, used by
69 * kcov_remote_stop(), see the comment there.
74 struct kcov_remote_area {
75 struct list_head list;
82 struct hlist_node hnode;
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);
89 /* Must be called with kcov_remote_lock locked. */
90 static struct kcov_remote *kcov_remote_find(u64 handle)
92 struct kcov_remote *remote;
94 hash_for_each_possible(kcov_remote_map, remote, hnode, handle) {
95 if (remote->handle == handle)
101 /* Must be called with kcov_remote_lock locked. */
102 static struct kcov_remote *kcov_remote_add(struct kcov *kcov, u64 handle)
104 struct kcov_remote *remote;
106 if (kcov_remote_find(handle))
107 return ERR_PTR(-EEXIST);
108 remote = kmalloc(sizeof(*remote), GFP_ATOMIC);
110 return ERR_PTR(-ENOMEM);
111 remote->handle = handle;
113 hash_add(kcov_remote_map, &remote->hnode, handle);
117 /* Must be called with kcov_remote_lock locked. */
118 static struct kcov_remote_area *kcov_remote_area_get(unsigned int size)
120 struct kcov_remote_area *area;
121 struct list_head *pos;
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);
133 /* Must be called with kcov_remote_lock locked. */
134 static void kcov_remote_area_put(struct kcov_remote_area *area,
137 INIT_LIST_HEAD(&area->list);
139 list_add(&area->list, &kcov_remote_areas);
142 static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
147 * We are interested in code coverage as a function of a syscall inputs,
148 * so we ignore code executed in interrupts.
152 mode = READ_ONCE(t->kcov_mode);
154 * There is some code that runs in interrupts but for which
155 * in_interrupt() returns false (e.g. preempt_schedule_irq()).
156 * READ_ONCE()/barrier() effectively provides load-acquire wrt
157 * interrupts, there are paired barrier()/WRITE_ONCE() in
161 return mode == needed_mode;
164 static notrace unsigned long canonicalize_ip(unsigned long ip)
166 #ifdef CONFIG_RANDOMIZE_BASE
167 ip -= kaslr_offset();
173 * Entry point from instrumented code.
174 * This is called once per basic-block/edge.
176 void notrace __sanitizer_cov_trace_pc(void)
178 struct task_struct *t;
180 unsigned long ip = canonicalize_ip(_RET_IP_);
184 if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t))
188 /* The first 64-bit word is the number of subsequent PCs. */
189 pos = READ_ONCE(area[0]) + 1;
190 if (likely(pos < t->kcov_size)) {
192 WRITE_ONCE(area[0], pos);
195 EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
197 #ifdef CONFIG_KCOV_ENABLE_COMPARISONS
198 static void notrace write_comp_data(u64 type, u64 arg1, u64 arg2, u64 ip)
200 struct task_struct *t;
202 u64 count, start_index, end_pos, max_pos;
205 if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t))
208 ip = canonicalize_ip(ip);
211 * We write all comparison arguments and types as u64.
212 * The buffer was allocated for t->kcov_size unsigned longs.
214 area = (u64 *)t->kcov_area;
215 max_pos = t->kcov_size * sizeof(unsigned long);
217 count = READ_ONCE(area[0]);
219 /* Every record is KCOV_WORDS_PER_CMP 64-bit words. */
220 start_index = 1 + count * KCOV_WORDS_PER_CMP;
221 end_pos = (start_index + KCOV_WORDS_PER_CMP) * sizeof(u64);
222 if (likely(end_pos <= max_pos)) {
223 area[start_index] = type;
224 area[start_index + 1] = arg1;
225 area[start_index + 2] = arg2;
226 area[start_index + 3] = ip;
227 WRITE_ONCE(area[0], count + 1);
231 void notrace __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2)
233 write_comp_data(KCOV_CMP_SIZE(0), arg1, arg2, _RET_IP_);
235 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1);
237 void notrace __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2)
239 write_comp_data(KCOV_CMP_SIZE(1), arg1, arg2, _RET_IP_);
241 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2);
243 void notrace __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2)
245 write_comp_data(KCOV_CMP_SIZE(2), arg1, arg2, _RET_IP_);
247 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4);
249 void notrace __sanitizer_cov_trace_cmp8(u64 arg1, u64 arg2)
251 write_comp_data(KCOV_CMP_SIZE(3), arg1, arg2, _RET_IP_);
253 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8);
255 void notrace __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2)
257 write_comp_data(KCOV_CMP_SIZE(0) | KCOV_CMP_CONST, arg1, arg2,
260 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1);
262 void notrace __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2)
264 write_comp_data(KCOV_CMP_SIZE(1) | KCOV_CMP_CONST, arg1, arg2,
267 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2);
269 void notrace __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2)
271 write_comp_data(KCOV_CMP_SIZE(2) | KCOV_CMP_CONST, arg1, arg2,
274 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4);
276 void notrace __sanitizer_cov_trace_const_cmp8(u64 arg1, u64 arg2)
278 write_comp_data(KCOV_CMP_SIZE(3) | KCOV_CMP_CONST, arg1, arg2,
281 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8);
283 void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases)
286 u64 count = cases[0];
288 u64 type = KCOV_CMP_CONST;
292 type |= KCOV_CMP_SIZE(0);
295 type |= KCOV_CMP_SIZE(1);
298 type |= KCOV_CMP_SIZE(2);
301 type |= KCOV_CMP_SIZE(3);
306 for (i = 0; i < count; i++)
307 write_comp_data(type, cases[i + 2], val, _RET_IP_);
309 EXPORT_SYMBOL(__sanitizer_cov_trace_switch);
310 #endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */
312 static void kcov_start(struct task_struct *t, struct kcov *kcov,
313 unsigned int size, void *area, enum kcov_mode mode,
316 kcov_debug("t = %px, size = %u, area = %px\n", t, size, area);
318 /* Cache in task struct for performance. */
321 t->kcov_sequence = sequence;
322 /* See comment in check_kcov_mode(). */
324 WRITE_ONCE(t->kcov_mode, mode);
327 static void kcov_stop(struct task_struct *t)
329 WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);
336 static void kcov_task_reset(struct task_struct *t)
339 t->kcov_sequence = 0;
343 void kcov_task_init(struct task_struct *t)
346 t->kcov_handle = current->kcov_handle;
349 static void kcov_reset(struct kcov *kcov)
352 kcov->mode = KCOV_MODE_INIT;
353 kcov->remote = false;
354 kcov->remote_size = 0;
358 static void kcov_remote_reset(struct kcov *kcov)
361 struct kcov_remote *remote;
362 struct hlist_node *tmp;
364 spin_lock(&kcov_remote_lock);
365 hash_for_each_safe(kcov_remote_map, bkt, tmp, remote, hnode) {
366 if (remote->kcov != kcov)
368 hash_del(&remote->hnode);
371 /* Do reset before unlock to prevent races with kcov_remote_start(). */
373 spin_unlock(&kcov_remote_lock);
376 static void kcov_disable(struct task_struct *t, struct kcov *kcov)
380 kcov_remote_reset(kcov);
385 static void kcov_get(struct kcov *kcov)
387 refcount_inc(&kcov->refcount);
390 static void kcov_put(struct kcov *kcov)
392 if (refcount_dec_and_test(&kcov->refcount)) {
393 kcov_remote_reset(kcov);
399 void kcov_task_exit(struct task_struct *t)
407 spin_lock(&kcov->lock);
408 kcov_debug("t = %px, kcov->t = %px\n", t, kcov->t);
410 * For KCOV_ENABLE devices we want to make sure that t->kcov->t == t,
411 * which comes down to:
412 * WARN_ON(!kcov->remote && kcov->t != t);
414 * For KCOV_REMOTE_ENABLE devices, the exiting task is either:
415 * 2. A remote task between kcov_remote_start() and kcov_remote_stop().
416 * In this case we should print a warning right away, since a task
417 * shouldn't be exiting when it's in a kcov coverage collection
418 * section. Here t points to the task that is collecting remote
419 * coverage, and t->kcov->t points to the thread that created the
420 * kcov device. Which means that to detect this case we need to
421 * check that t != t->kcov->t, and this gives us the following:
422 * WARN_ON(kcov->remote && kcov->t != t);
424 * 2. The task that created kcov exiting without calling KCOV_DISABLE,
425 * and then again we can make sure that t->kcov->t == t:
426 * WARN_ON(kcov->remote && kcov->t != t);
428 * By combining all three checks into one we get:
430 if (WARN_ON(kcov->t != t)) {
431 spin_unlock(&kcov->lock);
434 /* Just to not leave dangling references behind. */
435 kcov_disable(t, kcov);
436 spin_unlock(&kcov->lock);
440 static int kcov_mmap(struct file *filep, struct vm_area_struct *vma)
444 struct kcov *kcov = vma->vm_file->private_data;
445 unsigned long size, off;
448 area = vmalloc_user(vma->vm_end - vma->vm_start);
452 spin_lock(&kcov->lock);
453 size = kcov->size * sizeof(unsigned long);
454 if (kcov->mode != KCOV_MODE_INIT || vma->vm_pgoff != 0 ||
455 vma->vm_end - vma->vm_start != size) {
461 vma->vm_flags |= VM_DONTEXPAND;
462 spin_unlock(&kcov->lock);
463 for (off = 0; off < size; off += PAGE_SIZE) {
464 page = vmalloc_to_page(kcov->area + off);
465 if (vm_insert_page(vma, vma->vm_start + off, page))
466 WARN_ONCE(1, "vm_insert_page() failed");
471 spin_unlock(&kcov->lock);
476 static int kcov_open(struct inode *inode, struct file *filep)
480 kcov = kzalloc(sizeof(*kcov), GFP_KERNEL);
483 kcov->mode = KCOV_MODE_DISABLED;
485 refcount_set(&kcov->refcount, 1);
486 spin_lock_init(&kcov->lock);
487 filep->private_data = kcov;
488 return nonseekable_open(inode, filep);
491 static int kcov_close(struct inode *inode, struct file *filep)
493 kcov_put(filep->private_data);
497 static int kcov_get_mode(unsigned long arg)
499 if (arg == KCOV_TRACE_PC)
500 return KCOV_MODE_TRACE_PC;
501 else if (arg == KCOV_TRACE_CMP)
502 #ifdef CONFIG_KCOV_ENABLE_COMPARISONS
503 return KCOV_MODE_TRACE_CMP;
512 * Fault in a lazily-faulted vmalloc area before it can be used by
513 * __santizer_cov_trace_pc(), to avoid recursion issues if any code on the
514 * vmalloc fault handling path is instrumented.
516 static void kcov_fault_in_area(struct kcov *kcov)
518 unsigned long stride = PAGE_SIZE / sizeof(unsigned long);
519 unsigned long *area = kcov->area;
520 unsigned long offset;
522 for (offset = 0; offset < kcov->size; offset += stride)
523 READ_ONCE(area[offset]);
526 static inline bool kcov_check_handle(u64 handle, bool common_valid,
527 bool uncommon_valid, bool zero_valid)
529 if (handle & ~(KCOV_SUBSYSTEM_MASK | KCOV_INSTANCE_MASK))
531 switch (handle & KCOV_SUBSYSTEM_MASK) {
532 case KCOV_SUBSYSTEM_COMMON:
533 return (handle & KCOV_INSTANCE_MASK) ?
534 common_valid : zero_valid;
535 case KCOV_SUBSYSTEM_USB:
536 return uncommon_valid;
543 static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
546 struct task_struct *t;
547 unsigned long size, unused;
549 struct kcov_remote_arg *remote_arg;
550 struct kcov_remote *remote;
553 case KCOV_INIT_TRACE:
555 * Enable kcov in trace mode and setup buffer size.
556 * Must happen before anything else.
558 if (kcov->mode != KCOV_MODE_DISABLED)
561 * Size must be at least 2 to hold current position and one PC.
562 * Later we allocate size * sizeof(unsigned long) memory,
563 * that must not overflow.
566 if (size < 2 || size > INT_MAX / sizeof(unsigned long))
569 kcov->mode = KCOV_MODE_INIT;
573 * Enable coverage for the current task.
574 * At this point user must have been enabled trace mode,
575 * and mmapped the file. Coverage collection is disabled only
576 * at task exit or voluntary by KCOV_DISABLE. After that it can
577 * be enabled for another task.
579 if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
582 if (kcov->t != NULL || t->kcov != NULL)
584 mode = kcov_get_mode(arg);
587 kcov_fault_in_area(kcov);
589 kcov_start(t, kcov, kcov->size, kcov->area, kcov->mode,
592 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
596 /* Disable coverage for the current task. */
598 if (unused != 0 || current->kcov != kcov)
601 if (WARN_ON(kcov->t != t))
603 kcov_disable(t, kcov);
606 case KCOV_REMOTE_ENABLE:
607 if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
610 if (kcov->t != NULL || t->kcov != NULL)
612 remote_arg = (struct kcov_remote_arg *)arg;
613 mode = kcov_get_mode(remote_arg->trace_mode);
616 if (remote_arg->area_size > LONG_MAX / sizeof(unsigned long))
622 kcov->remote_size = remote_arg->area_size;
623 spin_lock(&kcov_remote_lock);
624 for (i = 0; i < remote_arg->num_handles; i++) {
625 if (!kcov_check_handle(remote_arg->handles[i],
626 false, true, false)) {
627 spin_unlock(&kcov_remote_lock);
628 kcov_disable(t, kcov);
631 remote = kcov_remote_add(kcov, remote_arg->handles[i]);
632 if (IS_ERR(remote)) {
633 spin_unlock(&kcov_remote_lock);
634 kcov_disable(t, kcov);
635 return PTR_ERR(remote);
638 if (remote_arg->common_handle) {
639 if (!kcov_check_handle(remote_arg->common_handle,
640 true, false, false)) {
641 spin_unlock(&kcov_remote_lock);
642 kcov_disable(t, kcov);
645 remote = kcov_remote_add(kcov,
646 remote_arg->common_handle);
647 if (IS_ERR(remote)) {
648 spin_unlock(&kcov_remote_lock);
649 kcov_disable(t, kcov);
650 return PTR_ERR(remote);
652 t->kcov_handle = remote_arg->common_handle;
654 spin_unlock(&kcov_remote_lock);
655 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
663 static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
667 struct kcov_remote_arg *remote_arg = NULL;
668 unsigned int remote_num_handles;
669 unsigned long remote_arg_size;
671 if (cmd == KCOV_REMOTE_ENABLE) {
672 if (get_user(remote_num_handles, (unsigned __user *)(arg +
673 offsetof(struct kcov_remote_arg, num_handles))))
675 if (remote_num_handles > KCOV_REMOTE_MAX_HANDLES)
677 remote_arg_size = struct_size(remote_arg, handles,
679 remote_arg = memdup_user((void __user *)arg, remote_arg_size);
680 if (IS_ERR(remote_arg))
681 return PTR_ERR(remote_arg);
682 if (remote_arg->num_handles != remote_num_handles) {
686 arg = (unsigned long)remote_arg;
689 kcov = filep->private_data;
690 spin_lock(&kcov->lock);
691 res = kcov_ioctl_locked(kcov, cmd, arg);
692 spin_unlock(&kcov->lock);
699 static const struct file_operations kcov_fops = {
701 .unlocked_ioctl = kcov_ioctl,
702 .compat_ioctl = kcov_ioctl,
704 .release = kcov_close,
708 * kcov_remote_start() and kcov_remote_stop() can be used to annotate a section
709 * of code in a kernel background thread to allow kcov to be used to collect
710 * coverage from that part of code.
712 * The handle argument of kcov_remote_start() identifies a code section that is
713 * used for coverage collection. A userspace process passes this handle to
714 * KCOV_REMOTE_ENABLE ioctl to make the used kcov device start collecting
715 * coverage for the code section identified by this handle.
717 * The usage of these annotations in the kernel code is different depending on
718 * the type of the kernel thread whose code is being annotated.
720 * For global kernel threads that are spawned in a limited number of instances
721 * (e.g. one USB hub_event() worker thread is spawned per USB HCD), each
722 * instance must be assigned a unique 4-byte instance id. The instance id is
723 * then combined with a 1-byte subsystem id to get a handle via
724 * kcov_remote_handle(subsystem_id, instance_id).
726 * For local kernel threads that are spawned from system calls handler when a
727 * user interacts with some kernel interface (e.g. vhost workers), a handle is
728 * passed from a userspace process as the common_handle field of the
729 * kcov_remote_arg struct (note, that the user must generate a handle by using
730 * kcov_remote_handle() with KCOV_SUBSYSTEM_COMMON as the subsystem id and an
731 * arbitrary 4-byte non-zero number as the instance id). This common handle
732 * then gets saved into the task_struct of the process that issued the
733 * KCOV_REMOTE_ENABLE ioctl. When this process issues system calls that spawn
734 * kernel threads, the common handle must be retrieved via kcov_common_handle()
735 * and passed to the spawned threads via custom annotations. Those kernel
736 * threads must in turn be annotated with kcov_remote_start(common_handle) and
737 * kcov_remote_stop(). All of the threads that are spawned by the same process
738 * obtain the same handle, hence the name "common".
740 * See Documentation/dev-tools/kcov.rst for more details.
742 * Internally, this function looks up the kcov device associated with the
743 * provided handle, allocates an area for coverage collection, and saves the
744 * pointers to kcov and area into the current task_struct to allow coverage to
745 * be collected via __sanitizer_cov_trace_pc()
746 * In turns kcov_remote_stop() clears those pointers from task_struct to stop
747 * collecting coverage and copies all collected coverage into the kcov area.
750 static inline bool kcov_mode_enabled(unsigned int mode)
752 return (mode & ~KCOV_IN_CTXSW) != KCOV_MODE_DISABLED;
755 void kcov_remote_start(u64 handle)
757 struct task_struct *t = current;
758 struct kcov_remote *remote;
765 if (WARN_ON(!kcov_check_handle(handle, true, true, true)))
767 if (WARN_ON(!in_task()))
771 * Check that kcov_remote_start is not called twice
772 * nor called by user tasks (with enabled kcov).
774 mode = READ_ONCE(t->kcov_mode);
775 if (WARN_ON(kcov_mode_enabled(mode)))
778 kcov_debug("handle = %llx\n", handle);
780 spin_lock(&kcov_remote_lock);
781 remote = kcov_remote_find(handle);
783 spin_unlock(&kcov_remote_lock);
787 /* Put in kcov_remote_stop(). */
790 * Read kcov fields before unlock to prevent races with
791 * KCOV_DISABLE / kcov_remote_reset().
793 size = kcov->remote_size;
795 sequence = kcov->sequence;
796 area = kcov_remote_area_get(size);
797 spin_unlock(&kcov_remote_lock);
800 area = vmalloc(size * sizeof(unsigned long));
806 /* Reset coverage size. */
809 kcov_start(t, kcov, size, area, mode, sequence);
812 EXPORT_SYMBOL(kcov_remote_start);
814 static void kcov_move_area(enum kcov_mode mode, void *dst_area,
815 unsigned int dst_area_size, void *src_area)
817 u64 word_size = sizeof(unsigned long);
818 u64 count_size, entry_size_log;
819 u64 dst_len, src_len;
820 void *dst_entries, *src_entries;
821 u64 dst_occupied, dst_free, bytes_to_move, entries_moved;
823 kcov_debug("%px %u <= %px %lu\n",
824 dst_area, dst_area_size, src_area, *(unsigned long *)src_area);
827 case KCOV_MODE_TRACE_PC:
828 dst_len = READ_ONCE(*(unsigned long *)dst_area);
829 src_len = *(unsigned long *)src_area;
830 count_size = sizeof(unsigned long);
831 entry_size_log = __ilog2_u64(sizeof(unsigned long));
833 case KCOV_MODE_TRACE_CMP:
834 dst_len = READ_ONCE(*(u64 *)dst_area);
835 src_len = *(u64 *)src_area;
836 count_size = sizeof(u64);
837 BUILD_BUG_ON(!is_power_of_2(KCOV_WORDS_PER_CMP));
838 entry_size_log = __ilog2_u64(sizeof(u64) * KCOV_WORDS_PER_CMP);
845 /* As arm can't divide u64 integers use log of entry size. */
846 if (dst_len > ((dst_area_size * word_size - count_size) >>
849 dst_occupied = count_size + (dst_len << entry_size_log);
850 dst_free = dst_area_size * word_size - dst_occupied;
851 bytes_to_move = min(dst_free, src_len << entry_size_log);
852 dst_entries = dst_area + dst_occupied;
853 src_entries = src_area + count_size;
854 memcpy(dst_entries, src_entries, bytes_to_move);
855 entries_moved = bytes_to_move >> entry_size_log;
858 case KCOV_MODE_TRACE_PC:
859 WRITE_ONCE(*(unsigned long *)dst_area, dst_len + entries_moved);
861 case KCOV_MODE_TRACE_CMP:
862 WRITE_ONCE(*(u64 *)dst_area, dst_len + entries_moved);
869 /* See the comment before kcov_remote_start() for usage details. */
870 void kcov_remote_stop(void)
872 struct task_struct *t = current;
879 mode = READ_ONCE(t->kcov_mode);
881 if (!kcov_mode_enabled(mode))
886 sequence = t->kcov_sequence;
890 spin_lock(&kcov->lock);
892 * KCOV_DISABLE could have been called between kcov_remote_start()
893 * and kcov_remote_stop(), hence the check.
895 if (sequence == kcov->sequence && kcov->remote)
896 kcov_move_area(kcov->mode, kcov->area, kcov->size, area);
897 spin_unlock(&kcov->lock);
899 spin_lock(&kcov_remote_lock);
900 kcov_remote_area_put(area, size);
901 spin_unlock(&kcov_remote_lock);
905 EXPORT_SYMBOL(kcov_remote_stop);
907 /* See the comment before kcov_remote_start() for usage details. */
908 u64 kcov_common_handle(void)
910 return current->kcov_handle;
912 EXPORT_SYMBOL(kcov_common_handle);
914 static int __init kcov_init(void)
917 * The kcov debugfs file won't ever get removed and thus,
918 * there is no need to protect it against removal races. The
919 * use of debugfs_create_file_unsafe() is actually safe here.
921 debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops);
926 device_initcall(kcov_init);