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>
14 #include <linux/kmsan-checks.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>
29 #define kcov_debug(fmt, ...) pr_debug("%s: " fmt, __func__, ##__VA_ARGS__)
31 /* Number of 64-bit words written per one comparison: */
32 #define KCOV_WORDS_PER_CMP 4
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
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).
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
55 /* The lock protects mode, size, area and t. */
58 /* Size of arena (in long's). */
60 /* Coverage buffer shared with user space. */
62 /* Task for which we collect coverage, or NULL. */
63 struct task_struct
*t
;
64 /* Collecting coverage from remote (background) threads. */
66 /* Size of remote area (in long's). */
67 unsigned int remote_size
;
69 * Sequence is incremented each time kcov is reenabled, used by
70 * kcov_remote_stop(), see the comment there.
75 struct kcov_remote_area
{
76 struct list_head list
;
83 struct hlist_node hnode
;
86 static DEFINE_SPINLOCK(kcov_remote_lock
);
87 static DEFINE_HASHTABLE(kcov_remote_map
, 4);
88 static struct list_head kcov_remote_areas
= LIST_HEAD_INIT(kcov_remote_areas
);
90 struct kcov_percpu_data
{
94 unsigned int saved_mode
;
95 unsigned int saved_size
;
97 struct kcov
*saved_kcov
;
101 static DEFINE_PER_CPU(struct kcov_percpu_data
, kcov_percpu_data
) = {
102 .lock
= INIT_LOCAL_LOCK(lock
),
105 /* Must be called with kcov_remote_lock locked. */
106 static struct kcov_remote
*kcov_remote_find(u64 handle
)
108 struct kcov_remote
*remote
;
110 hash_for_each_possible(kcov_remote_map
, remote
, hnode
, handle
) {
111 if (remote
->handle
== handle
)
117 /* Must be called with kcov_remote_lock locked. */
118 static struct kcov_remote
*kcov_remote_add(struct kcov
*kcov
, u64 handle
)
120 struct kcov_remote
*remote
;
122 if (kcov_remote_find(handle
))
123 return ERR_PTR(-EEXIST
);
124 remote
= kmalloc(sizeof(*remote
), GFP_ATOMIC
);
126 return ERR_PTR(-ENOMEM
);
127 remote
->handle
= handle
;
129 hash_add(kcov_remote_map
, &remote
->hnode
, handle
);
133 /* Must be called with kcov_remote_lock locked. */
134 static struct kcov_remote_area
*kcov_remote_area_get(unsigned int size
)
136 struct kcov_remote_area
*area
;
137 struct list_head
*pos
;
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
);
149 /* Must be called with kcov_remote_lock locked. */
150 static void kcov_remote_area_put(struct kcov_remote_area
*area
,
153 INIT_LIST_HEAD(&area
->list
);
155 list_add(&area
->list
, &kcov_remote_areas
);
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().
161 kmsan_unpoison_memory(&area
->list
, sizeof(area
->list
));
164 static notrace
bool check_kcov_mode(enum kcov_mode needed_mode
, struct task_struct
*t
)
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.
173 if (!in_task() && !(in_serving_softirq() && t
->kcov_softirq
))
175 mode
= READ_ONCE(t
->kcov_mode
);
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
184 return mode
== needed_mode
;
187 static notrace
unsigned long canonicalize_ip(unsigned long ip
)
189 #ifdef CONFIG_RANDOMIZE_BASE
190 ip
-= kaslr_offset();
196 * Entry point from instrumented code.
197 * This is called once per basic-block/edge.
199 void notrace
__sanitizer_cov_trace_pc(void)
201 struct task_struct
*t
;
203 unsigned long ip
= canonicalize_ip(_RET_IP_
);
207 if (!check_kcov_mode(KCOV_MODE_TRACE_PC
, t
))
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.
221 WRITE_ONCE(area
[0], pos
);
226 EXPORT_SYMBOL(__sanitizer_cov_trace_pc
);
228 #ifdef CONFIG_KCOV_ENABLE_COMPARISONS
229 static void notrace
write_comp_data(u64 type
, u64 arg1
, u64 arg2
, u64 ip
)
231 struct task_struct
*t
;
233 u64 count
, start_index
, end_pos
, max_pos
;
236 if (!check_kcov_mode(KCOV_MODE_TRACE_CMP
, t
))
239 ip
= canonicalize_ip(ip
);
242 * We write all comparison arguments and types as u64.
243 * The buffer was allocated for t->kcov_size unsigned longs.
245 area
= (u64
*)t
->kcov_area
;
246 max_pos
= t
->kcov_size
* sizeof(unsigned long);
248 count
= READ_ONCE(area
[0]);
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);
257 area
[start_index
] = type
;
258 area
[start_index
+ 1] = arg1
;
259 area
[start_index
+ 2] = arg2
;
260 area
[start_index
+ 3] = ip
;
264 void notrace
__sanitizer_cov_trace_cmp1(u8 arg1
, u8 arg2
)
266 write_comp_data(KCOV_CMP_SIZE(0), arg1
, arg2
, _RET_IP_
);
268 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1
);
270 void notrace
__sanitizer_cov_trace_cmp2(u16 arg1
, u16 arg2
)
272 write_comp_data(KCOV_CMP_SIZE(1), arg1
, arg2
, _RET_IP_
);
274 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2
);
276 void notrace
__sanitizer_cov_trace_cmp4(u32 arg1
, u32 arg2
)
278 write_comp_data(KCOV_CMP_SIZE(2), arg1
, arg2
, _RET_IP_
);
280 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4
);
282 void notrace
__sanitizer_cov_trace_cmp8(kcov_u64 arg1
, kcov_u64 arg2
)
284 write_comp_data(KCOV_CMP_SIZE(3), arg1
, arg2
, _RET_IP_
);
286 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8
);
288 void notrace
__sanitizer_cov_trace_const_cmp1(u8 arg1
, u8 arg2
)
290 write_comp_data(KCOV_CMP_SIZE(0) | KCOV_CMP_CONST
, arg1
, arg2
,
293 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1
);
295 void notrace
__sanitizer_cov_trace_const_cmp2(u16 arg1
, u16 arg2
)
297 write_comp_data(KCOV_CMP_SIZE(1) | KCOV_CMP_CONST
, arg1
, arg2
,
300 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2
);
302 void notrace
__sanitizer_cov_trace_const_cmp4(u32 arg1
, u32 arg2
)
304 write_comp_data(KCOV_CMP_SIZE(2) | KCOV_CMP_CONST
, arg1
, arg2
,
307 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4
);
309 void notrace
__sanitizer_cov_trace_const_cmp8(kcov_u64 arg1
, kcov_u64 arg2
)
311 write_comp_data(KCOV_CMP_SIZE(3) | KCOV_CMP_CONST
, arg1
, arg2
,
314 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8
);
316 void notrace
__sanitizer_cov_trace_switch(kcov_u64 val
, void *arg
)
320 u64 count
= cases
[0];
322 u64 type
= KCOV_CMP_CONST
;
326 type
|= KCOV_CMP_SIZE(0);
329 type
|= KCOV_CMP_SIZE(1);
332 type
|= KCOV_CMP_SIZE(2);
335 type
|= KCOV_CMP_SIZE(3);
340 for (i
= 0; i
< count
; i
++)
341 write_comp_data(type
, cases
[i
+ 2], val
, _RET_IP_
);
343 EXPORT_SYMBOL(__sanitizer_cov_trace_switch
);
344 #endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */
346 static void kcov_start(struct task_struct
*t
, struct kcov
*kcov
,
347 unsigned int size
, void *area
, enum kcov_mode mode
,
350 kcov_debug("t = %px, size = %u, area = %px\n", t
, size
, area
);
352 /* Cache in task struct for performance. */
355 t
->kcov_sequence
= sequence
;
356 /* See comment in check_kcov_mode(). */
358 WRITE_ONCE(t
->kcov_mode
, mode
);
361 static void kcov_stop(struct task_struct
*t
)
363 WRITE_ONCE(t
->kcov_mode
, KCOV_MODE_DISABLED
);
370 static void kcov_task_reset(struct task_struct
*t
)
373 t
->kcov_sequence
= 0;
377 void kcov_task_init(struct task_struct
*t
)
380 t
->kcov_handle
= current
->kcov_handle
;
383 static void kcov_reset(struct kcov
*kcov
)
386 kcov
->mode
= KCOV_MODE_INIT
;
387 kcov
->remote
= false;
388 kcov
->remote_size
= 0;
392 static void kcov_remote_reset(struct kcov
*kcov
)
395 struct kcov_remote
*remote
;
396 struct hlist_node
*tmp
;
399 spin_lock_irqsave(&kcov_remote_lock
, flags
);
400 hash_for_each_safe(kcov_remote_map
, bkt
, tmp
, remote
, hnode
) {
401 if (remote
->kcov
!= kcov
)
403 hash_del(&remote
->hnode
);
406 /* Do reset before unlock to prevent races with kcov_remote_start(). */
408 spin_unlock_irqrestore(&kcov_remote_lock
, flags
);
411 static void kcov_disable(struct task_struct
*t
, struct kcov
*kcov
)
415 kcov_remote_reset(kcov
);
420 static void kcov_get(struct kcov
*kcov
)
422 refcount_inc(&kcov
->refcount
);
425 static void kcov_put(struct kcov
*kcov
)
427 if (refcount_dec_and_test(&kcov
->refcount
)) {
428 kcov_remote_reset(kcov
);
434 void kcov_task_exit(struct task_struct
*t
)
443 spin_lock_irqsave(&kcov
->lock
, flags
);
444 kcov_debug("t = %px, kcov->t = %px\n", t
, kcov
->t
);
446 * For KCOV_ENABLE devices we want to make sure that t->kcov->t == t,
447 * which comes down to:
448 * WARN_ON(!kcov->remote && kcov->t != t);
450 * For KCOV_REMOTE_ENABLE devices, the exiting task is either:
452 * 1. A remote task between kcov_remote_start() and kcov_remote_stop().
453 * In this case we should print a warning right away, since a task
454 * shouldn't be exiting when it's in a kcov coverage collection
455 * section. Here t points to the task that is collecting remote
456 * coverage, and t->kcov->t points to the thread that created the
457 * kcov device. Which means that to detect this case we need to
458 * check that t != t->kcov->t, and this gives us the following:
459 * WARN_ON(kcov->remote && kcov->t != t);
461 * 2. The task that created kcov exiting without calling KCOV_DISABLE,
462 * and then again we make sure that t->kcov->t == t:
463 * WARN_ON(kcov->remote && kcov->t != t);
465 * By combining all three checks into one we get:
467 if (WARN_ON(kcov
->t
!= t
)) {
468 spin_unlock_irqrestore(&kcov
->lock
, flags
);
471 /* Just to not leave dangling references behind. */
472 kcov_disable(t
, kcov
);
473 spin_unlock_irqrestore(&kcov
->lock
, flags
);
477 static int kcov_mmap(struct file
*filep
, struct vm_area_struct
*vma
)
480 struct kcov
*kcov
= vma
->vm_file
->private_data
;
481 unsigned long size
, off
;
485 spin_lock_irqsave(&kcov
->lock
, flags
);
486 size
= kcov
->size
* sizeof(unsigned long);
487 if (kcov
->area
== NULL
|| vma
->vm_pgoff
!= 0 ||
488 vma
->vm_end
- vma
->vm_start
!= size
) {
492 spin_unlock_irqrestore(&kcov
->lock
, flags
);
493 vm_flags_set(vma
, VM_DONTEXPAND
);
494 for (off
= 0; off
< size
; off
+= PAGE_SIZE
) {
495 page
= vmalloc_to_page(kcov
->area
+ off
);
496 res
= vm_insert_page(vma
, vma
->vm_start
+ off
, page
);
498 pr_warn_once("kcov: vm_insert_page() failed\n");
504 spin_unlock_irqrestore(&kcov
->lock
, flags
);
508 static int kcov_open(struct inode
*inode
, struct file
*filep
)
512 kcov
= kzalloc(sizeof(*kcov
), GFP_KERNEL
);
515 kcov
->mode
= KCOV_MODE_DISABLED
;
517 refcount_set(&kcov
->refcount
, 1);
518 spin_lock_init(&kcov
->lock
);
519 filep
->private_data
= kcov
;
520 return nonseekable_open(inode
, filep
);
523 static int kcov_close(struct inode
*inode
, struct file
*filep
)
525 kcov_put(filep
->private_data
);
529 static int kcov_get_mode(unsigned long arg
)
531 if (arg
== KCOV_TRACE_PC
)
532 return KCOV_MODE_TRACE_PC
;
533 else if (arg
== KCOV_TRACE_CMP
)
534 #ifdef CONFIG_KCOV_ENABLE_COMPARISONS
535 return KCOV_MODE_TRACE_CMP
;
544 * Fault in a lazily-faulted vmalloc area before it can be used by
545 * __santizer_cov_trace_pc(), to avoid recursion issues if any code on the
546 * vmalloc fault handling path is instrumented.
548 static void kcov_fault_in_area(struct kcov
*kcov
)
550 unsigned long stride
= PAGE_SIZE
/ sizeof(unsigned long);
551 unsigned long *area
= kcov
->area
;
552 unsigned long offset
;
554 for (offset
= 0; offset
< kcov
->size
; offset
+= stride
)
555 READ_ONCE(area
[offset
]);
558 static inline bool kcov_check_handle(u64 handle
, bool common_valid
,
559 bool uncommon_valid
, bool zero_valid
)
561 if (handle
& ~(KCOV_SUBSYSTEM_MASK
| KCOV_INSTANCE_MASK
))
563 switch (handle
& KCOV_SUBSYSTEM_MASK
) {
564 case KCOV_SUBSYSTEM_COMMON
:
565 return (handle
& KCOV_INSTANCE_MASK
) ?
566 common_valid
: zero_valid
;
567 case KCOV_SUBSYSTEM_USB
:
568 return uncommon_valid
;
575 static int kcov_ioctl_locked(struct kcov
*kcov
, unsigned int cmd
,
578 struct task_struct
*t
;
579 unsigned long flags
, unused
;
581 struct kcov_remote_arg
*remote_arg
;
582 struct kcov_remote
*remote
;
587 * Enable coverage for the current task.
588 * At this point user must have been enabled trace mode,
589 * and mmapped the file. Coverage collection is disabled only
590 * at task exit or voluntary by KCOV_DISABLE. After that it can
591 * be enabled for another task.
593 if (kcov
->mode
!= KCOV_MODE_INIT
|| !kcov
->area
)
596 if (kcov
->t
!= NULL
|| t
->kcov
!= NULL
)
598 mode
= kcov_get_mode(arg
);
601 kcov_fault_in_area(kcov
);
603 kcov_start(t
, kcov
, kcov
->size
, kcov
->area
, kcov
->mode
,
606 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
610 /* Disable coverage for the current task. */
612 if (unused
!= 0 || current
->kcov
!= kcov
)
615 if (WARN_ON(kcov
->t
!= t
))
617 kcov_disable(t
, kcov
);
620 case KCOV_REMOTE_ENABLE
:
621 if (kcov
->mode
!= KCOV_MODE_INIT
|| !kcov
->area
)
624 if (kcov
->t
!= NULL
|| t
->kcov
!= NULL
)
626 remote_arg
= (struct kcov_remote_arg
*)arg
;
627 mode
= kcov_get_mode(remote_arg
->trace_mode
);
630 if (remote_arg
->area_size
> LONG_MAX
/ sizeof(unsigned long))
636 kcov
->remote_size
= remote_arg
->area_size
;
637 spin_lock_irqsave(&kcov_remote_lock
, flags
);
638 for (i
= 0; i
< remote_arg
->num_handles
; i
++) {
639 if (!kcov_check_handle(remote_arg
->handles
[i
],
640 false, true, false)) {
641 spin_unlock_irqrestore(&kcov_remote_lock
,
643 kcov_disable(t
, kcov
);
646 remote
= kcov_remote_add(kcov
, remote_arg
->handles
[i
]);
647 if (IS_ERR(remote
)) {
648 spin_unlock_irqrestore(&kcov_remote_lock
,
650 kcov_disable(t
, kcov
);
651 return PTR_ERR(remote
);
654 if (remote_arg
->common_handle
) {
655 if (!kcov_check_handle(remote_arg
->common_handle
,
656 true, false, false)) {
657 spin_unlock_irqrestore(&kcov_remote_lock
,
659 kcov_disable(t
, kcov
);
662 remote
= kcov_remote_add(kcov
,
663 remote_arg
->common_handle
);
664 if (IS_ERR(remote
)) {
665 spin_unlock_irqrestore(&kcov_remote_lock
,
667 kcov_disable(t
, kcov
);
668 return PTR_ERR(remote
);
670 t
->kcov_handle
= remote_arg
->common_handle
;
672 spin_unlock_irqrestore(&kcov_remote_lock
, flags
);
673 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
681 static long kcov_ioctl(struct file
*filep
, unsigned int cmd
, unsigned long arg
)
685 struct kcov_remote_arg
*remote_arg
= NULL
;
686 unsigned int remote_num_handles
;
687 unsigned long remote_arg_size
;
688 unsigned long size
, flags
;
691 kcov
= filep
->private_data
;
693 case KCOV_INIT_TRACE
:
695 * Enable kcov in trace mode and setup buffer size.
696 * Must happen before anything else.
698 * First check the size argument - it must be at least 2
699 * to hold the current position and one PC.
702 if (size
< 2 || size
> INT_MAX
/ sizeof(unsigned long))
704 area
= vmalloc_user(size
* sizeof(unsigned long));
707 spin_lock_irqsave(&kcov
->lock
, flags
);
708 if (kcov
->mode
!= KCOV_MODE_DISABLED
) {
709 spin_unlock_irqrestore(&kcov
->lock
, flags
);
715 kcov
->mode
= KCOV_MODE_INIT
;
716 spin_unlock_irqrestore(&kcov
->lock
, flags
);
718 case KCOV_REMOTE_ENABLE
:
719 if (get_user(remote_num_handles
, (unsigned __user
*)(arg
+
720 offsetof(struct kcov_remote_arg
, num_handles
))))
722 if (remote_num_handles
> KCOV_REMOTE_MAX_HANDLES
)
724 remote_arg_size
= struct_size(remote_arg
, handles
,
726 remote_arg
= memdup_user((void __user
*)arg
, remote_arg_size
);
727 if (IS_ERR(remote_arg
))
728 return PTR_ERR(remote_arg
);
729 if (remote_arg
->num_handles
!= remote_num_handles
) {
733 arg
= (unsigned long)remote_arg
;
737 * All other commands can be normally executed under a spin lock, so we
738 * obtain and release it here in order to simplify kcov_ioctl_locked().
740 spin_lock_irqsave(&kcov
->lock
, flags
);
741 res
= kcov_ioctl_locked(kcov
, cmd
, arg
);
742 spin_unlock_irqrestore(&kcov
->lock
, flags
);
748 static const struct file_operations kcov_fops
= {
750 .unlocked_ioctl
= kcov_ioctl
,
751 .compat_ioctl
= kcov_ioctl
,
753 .release
= kcov_close
,
757 * kcov_remote_start() and kcov_remote_stop() can be used to annotate a section
758 * of code in a kernel background thread or in a softirq to allow kcov to be
759 * used to collect coverage from that part of code.
761 * The handle argument of kcov_remote_start() identifies a code section that is
762 * used for coverage collection. A userspace process passes this handle to
763 * KCOV_REMOTE_ENABLE ioctl to make the used kcov device start collecting
764 * coverage for the code section identified by this handle.
766 * The usage of these annotations in the kernel code is different depending on
767 * the type of the kernel thread whose code is being annotated.
769 * For global kernel threads that are spawned in a limited number of instances
770 * (e.g. one USB hub_event() worker thread is spawned per USB HCD) and for
771 * softirqs, each instance must be assigned a unique 4-byte instance id. The
772 * instance id is then combined with a 1-byte subsystem id to get a handle via
773 * kcov_remote_handle(subsystem_id, instance_id).
775 * For local kernel threads that are spawned from system calls handler when a
776 * user interacts with some kernel interface (e.g. vhost workers), a handle is
777 * passed from a userspace process as the common_handle field of the
778 * kcov_remote_arg struct (note, that the user must generate a handle by using
779 * kcov_remote_handle() with KCOV_SUBSYSTEM_COMMON as the subsystem id and an
780 * arbitrary 4-byte non-zero number as the instance id). This common handle
781 * then gets saved into the task_struct of the process that issued the
782 * KCOV_REMOTE_ENABLE ioctl. When this process issues system calls that spawn
783 * kernel threads, the common handle must be retrieved via kcov_common_handle()
784 * and passed to the spawned threads via custom annotations. Those kernel
785 * threads must in turn be annotated with kcov_remote_start(common_handle) and
786 * kcov_remote_stop(). All of the threads that are spawned by the same process
787 * obtain the same handle, hence the name "common".
789 * See Documentation/dev-tools/kcov.rst for more details.
791 * Internally, kcov_remote_start() looks up the kcov device associated with the
792 * provided handle, allocates an area for coverage collection, and saves the
793 * pointers to kcov and area into the current task_struct to allow coverage to
794 * be collected via __sanitizer_cov_trace_pc().
795 * In turns kcov_remote_stop() clears those pointers from task_struct to stop
796 * collecting coverage and copies all collected coverage into the kcov area.
799 static inline bool kcov_mode_enabled(unsigned int mode
)
801 return (mode
& ~KCOV_IN_CTXSW
) != KCOV_MODE_DISABLED
;
804 static void kcov_remote_softirq_start(struct task_struct
*t
)
806 struct kcov_percpu_data
*data
= this_cpu_ptr(&kcov_percpu_data
);
809 mode
= READ_ONCE(t
->kcov_mode
);
811 if (kcov_mode_enabled(mode
)) {
812 data
->saved_mode
= mode
;
813 data
->saved_size
= t
->kcov_size
;
814 data
->saved_area
= t
->kcov_area
;
815 data
->saved_sequence
= t
->kcov_sequence
;
816 data
->saved_kcov
= t
->kcov
;
821 static void kcov_remote_softirq_stop(struct task_struct
*t
)
823 struct kcov_percpu_data
*data
= this_cpu_ptr(&kcov_percpu_data
);
825 if (data
->saved_kcov
) {
826 kcov_start(t
, data
->saved_kcov
, data
->saved_size
,
827 data
->saved_area
, data
->saved_mode
,
828 data
->saved_sequence
);
829 data
->saved_mode
= 0;
830 data
->saved_size
= 0;
831 data
->saved_area
= NULL
;
832 data
->saved_sequence
= 0;
833 data
->saved_kcov
= NULL
;
837 void kcov_remote_start(u64 handle
)
839 struct task_struct
*t
= current
;
840 struct kcov_remote
*remote
;
848 if (WARN_ON(!kcov_check_handle(handle
, true, true, true)))
850 if (!in_task() && !in_serving_softirq())
853 local_lock_irqsave(&kcov_percpu_data
.lock
, flags
);
856 * Check that kcov_remote_start() is not called twice in background
857 * threads nor called by user tasks (with enabled kcov).
859 mode
= READ_ONCE(t
->kcov_mode
);
860 if (WARN_ON(in_task() && kcov_mode_enabled(mode
))) {
861 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
865 * Check that kcov_remote_start() is not called twice in softirqs.
866 * Note, that kcov_remote_start() can be called from a softirq that
867 * happened while collecting coverage from a background thread.
869 if (WARN_ON(in_serving_softirq() && t
->kcov_softirq
)) {
870 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
874 spin_lock(&kcov_remote_lock
);
875 remote
= kcov_remote_find(handle
);
877 spin_unlock(&kcov_remote_lock
);
878 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
881 kcov_debug("handle = %llx, context: %s\n", handle
,
882 in_task() ? "task" : "softirq");
884 /* Put in kcov_remote_stop(). */
887 * Read kcov fields before unlock to prevent races with
888 * KCOV_DISABLE / kcov_remote_reset().
891 sequence
= kcov
->sequence
;
893 size
= kcov
->remote_size
;
894 area
= kcov_remote_area_get(size
);
896 size
= CONFIG_KCOV_IRQ_AREA_SIZE
;
897 area
= this_cpu_ptr(&kcov_percpu_data
)->irq_area
;
899 spin_unlock(&kcov_remote_lock
);
901 /* Can only happen when in_task(). */
903 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
904 area
= vmalloc(size
* sizeof(unsigned long));
909 local_lock_irqsave(&kcov_percpu_data
.lock
, flags
);
912 /* Reset coverage size. */
915 if (in_serving_softirq()) {
916 kcov_remote_softirq_start(t
);
919 kcov_start(t
, kcov
, size
, area
, mode
, sequence
);
921 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
924 EXPORT_SYMBOL(kcov_remote_start
);
926 static void kcov_move_area(enum kcov_mode mode
, void *dst_area
,
927 unsigned int dst_area_size
, void *src_area
)
929 u64 word_size
= sizeof(unsigned long);
930 u64 count_size
, entry_size_log
;
931 u64 dst_len
, src_len
;
932 void *dst_entries
, *src_entries
;
933 u64 dst_occupied
, dst_free
, bytes_to_move
, entries_moved
;
935 kcov_debug("%px %u <= %px %lu\n",
936 dst_area
, dst_area_size
, src_area
, *(unsigned long *)src_area
);
939 case KCOV_MODE_TRACE_PC
:
940 dst_len
= READ_ONCE(*(unsigned long *)dst_area
);
941 src_len
= *(unsigned long *)src_area
;
942 count_size
= sizeof(unsigned long);
943 entry_size_log
= __ilog2_u64(sizeof(unsigned long));
945 case KCOV_MODE_TRACE_CMP
:
946 dst_len
= READ_ONCE(*(u64
*)dst_area
);
947 src_len
= *(u64
*)src_area
;
948 count_size
= sizeof(u64
);
949 BUILD_BUG_ON(!is_power_of_2(KCOV_WORDS_PER_CMP
));
950 entry_size_log
= __ilog2_u64(sizeof(u64
) * KCOV_WORDS_PER_CMP
);
957 /* As arm can't divide u64 integers use log of entry size. */
958 if (dst_len
> ((dst_area_size
* word_size
- count_size
) >>
961 dst_occupied
= count_size
+ (dst_len
<< entry_size_log
);
962 dst_free
= dst_area_size
* word_size
- dst_occupied
;
963 bytes_to_move
= min(dst_free
, src_len
<< entry_size_log
);
964 dst_entries
= dst_area
+ dst_occupied
;
965 src_entries
= src_area
+ count_size
;
966 memcpy(dst_entries
, src_entries
, bytes_to_move
);
967 entries_moved
= bytes_to_move
>> entry_size_log
;
970 case KCOV_MODE_TRACE_PC
:
971 WRITE_ONCE(*(unsigned long *)dst_area
, dst_len
+ entries_moved
);
973 case KCOV_MODE_TRACE_CMP
:
974 WRITE_ONCE(*(u64
*)dst_area
, dst_len
+ entries_moved
);
981 /* See the comment before kcov_remote_start() for usage details. */
982 void kcov_remote_stop(void)
984 struct task_struct
*t
= current
;
992 if (!in_task() && !in_serving_softirq())
995 local_lock_irqsave(&kcov_percpu_data
.lock
, flags
);
997 mode
= READ_ONCE(t
->kcov_mode
);
999 if (!kcov_mode_enabled(mode
)) {
1000 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
1004 * When in softirq, check if the corresponding kcov_remote_start()
1005 * actually found the remote handle and started collecting coverage.
1007 if (in_serving_softirq() && !t
->kcov_softirq
) {
1008 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
1011 /* Make sure that kcov_softirq is only set when in softirq. */
1012 if (WARN_ON(!in_serving_softirq() && t
->kcov_softirq
)) {
1013 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
1018 area
= t
->kcov_area
;
1019 size
= t
->kcov_size
;
1020 sequence
= t
->kcov_sequence
;
1023 if (in_serving_softirq()) {
1024 t
->kcov_softirq
= 0;
1025 kcov_remote_softirq_stop(t
);
1028 spin_lock(&kcov
->lock
);
1030 * KCOV_DISABLE could have been called between kcov_remote_start()
1031 * and kcov_remote_stop(), hence the sequence check.
1033 if (sequence
== kcov
->sequence
&& kcov
->remote
)
1034 kcov_move_area(kcov
->mode
, kcov
->area
, kcov
->size
, area
);
1035 spin_unlock(&kcov
->lock
);
1038 spin_lock(&kcov_remote_lock
);
1039 kcov_remote_area_put(area
, size
);
1040 spin_unlock(&kcov_remote_lock
);
1043 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
1045 /* Get in kcov_remote_start(). */
1048 EXPORT_SYMBOL(kcov_remote_stop
);
1050 /* See the comment before kcov_remote_start() for usage details. */
1051 u64
kcov_common_handle(void)
1055 return current
->kcov_handle
;
1057 EXPORT_SYMBOL(kcov_common_handle
);
1059 static int __init
kcov_init(void)
1063 for_each_possible_cpu(cpu
) {
1064 void *area
= vmalloc_node(CONFIG_KCOV_IRQ_AREA_SIZE
*
1065 sizeof(unsigned long), cpu_to_node(cpu
));
1068 per_cpu_ptr(&kcov_percpu_data
, cpu
)->irq_area
= area
;
1072 * The kcov debugfs file won't ever get removed and thus,
1073 * there is no need to protect it against removal races. The
1074 * use of debugfs_create_file_unsafe() is actually safe here.
1076 debugfs_create_file_unsafe("kcov", 0600, NULL
, NULL
, &kcov_fops
);
1081 device_initcall(kcov_init
);