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(u64 arg1
, 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(u64 arg1
, 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(u64 val
, u64
*cases
)
319 u64 count
= cases
[0];
321 u64 type
= KCOV_CMP_CONST
;
325 type
|= KCOV_CMP_SIZE(0);
328 type
|= KCOV_CMP_SIZE(1);
331 type
|= KCOV_CMP_SIZE(2);
334 type
|= KCOV_CMP_SIZE(3);
339 for (i
= 0; i
< count
; i
++)
340 write_comp_data(type
, cases
[i
+ 2], val
, _RET_IP_
);
342 EXPORT_SYMBOL(__sanitizer_cov_trace_switch
);
343 #endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */
345 static void kcov_start(struct task_struct
*t
, struct kcov
*kcov
,
346 unsigned int size
, void *area
, enum kcov_mode mode
,
349 kcov_debug("t = %px, size = %u, area = %px\n", t
, size
, area
);
351 /* Cache in task struct for performance. */
354 t
->kcov_sequence
= sequence
;
355 /* See comment in check_kcov_mode(). */
357 WRITE_ONCE(t
->kcov_mode
, mode
);
360 static void kcov_stop(struct task_struct
*t
)
362 WRITE_ONCE(t
->kcov_mode
, KCOV_MODE_DISABLED
);
369 static void kcov_task_reset(struct task_struct
*t
)
372 t
->kcov_sequence
= 0;
376 void kcov_task_init(struct task_struct
*t
)
379 t
->kcov_handle
= current
->kcov_handle
;
382 static void kcov_reset(struct kcov
*kcov
)
385 kcov
->mode
= KCOV_MODE_INIT
;
386 kcov
->remote
= false;
387 kcov
->remote_size
= 0;
391 static void kcov_remote_reset(struct kcov
*kcov
)
394 struct kcov_remote
*remote
;
395 struct hlist_node
*tmp
;
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
)
402 hash_del(&remote
->hnode
);
405 /* Do reset before unlock to prevent races with kcov_remote_start(). */
407 spin_unlock_irqrestore(&kcov_remote_lock
, flags
);
410 static void kcov_disable(struct task_struct
*t
, struct kcov
*kcov
)
414 kcov_remote_reset(kcov
);
419 static void kcov_get(struct kcov
*kcov
)
421 refcount_inc(&kcov
->refcount
);
424 static void kcov_put(struct kcov
*kcov
)
426 if (refcount_dec_and_test(&kcov
->refcount
)) {
427 kcov_remote_reset(kcov
);
433 void kcov_task_exit(struct task_struct
*t
)
442 spin_lock_irqsave(&kcov
->lock
, flags
);
443 kcov_debug("t = %px, kcov->t = %px\n", t
, kcov
->t
);
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);
449 * For KCOV_REMOTE_ENABLE devices, the exiting task is either:
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);
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);
464 * By combining all three checks into one we get:
466 if (WARN_ON(kcov
->t
!= t
)) {
467 spin_unlock_irqrestore(&kcov
->lock
, flags
);
470 /* Just to not leave dangling references behind. */
471 kcov_disable(t
, kcov
);
472 spin_unlock_irqrestore(&kcov
->lock
, flags
);
476 static int kcov_mmap(struct file
*filep
, struct vm_area_struct
*vma
)
479 struct kcov
*kcov
= vma
->vm_file
->private_data
;
480 unsigned long size
, off
;
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
) {
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
);
497 pr_warn_once("kcov: vm_insert_page() failed\n");
503 spin_unlock_irqrestore(&kcov
->lock
, flags
);
507 static int kcov_open(struct inode
*inode
, struct file
*filep
)
511 kcov
= kzalloc(sizeof(*kcov
), GFP_KERNEL
);
514 kcov
->mode
= KCOV_MODE_DISABLED
;
516 refcount_set(&kcov
->refcount
, 1);
517 spin_lock_init(&kcov
->lock
);
518 filep
->private_data
= kcov
;
519 return nonseekable_open(inode
, filep
);
522 static int kcov_close(struct inode
*inode
, struct file
*filep
)
524 kcov_put(filep
->private_data
);
528 static int kcov_get_mode(unsigned long arg
)
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
;
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.
547 static void kcov_fault_in_area(struct kcov
*kcov
)
549 unsigned long stride
= PAGE_SIZE
/ sizeof(unsigned long);
550 unsigned long *area
= kcov
->area
;
551 unsigned long offset
;
553 for (offset
= 0; offset
< kcov
->size
; offset
+= stride
)
554 READ_ONCE(area
[offset
]);
557 static inline bool kcov_check_handle(u64 handle
, bool common_valid
,
558 bool uncommon_valid
, bool zero_valid
)
560 if (handle
& ~(KCOV_SUBSYSTEM_MASK
| KCOV_INSTANCE_MASK
))
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
;
574 static int kcov_ioctl_locked(struct kcov
*kcov
, unsigned int cmd
,
577 struct task_struct
*t
;
578 unsigned long flags
, unused
;
580 struct kcov_remote_arg
*remote_arg
;
581 struct kcov_remote
*remote
;
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.
592 if (kcov
->mode
!= KCOV_MODE_INIT
|| !kcov
->area
)
595 if (kcov
->t
!= NULL
|| t
->kcov
!= NULL
)
597 mode
= kcov_get_mode(arg
);
600 kcov_fault_in_area(kcov
);
602 kcov_start(t
, kcov
, kcov
->size
, kcov
->area
, kcov
->mode
,
605 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
609 /* Disable coverage for the current task. */
611 if (unused
!= 0 || current
->kcov
!= kcov
)
614 if (WARN_ON(kcov
->t
!= t
))
616 kcov_disable(t
, kcov
);
619 case KCOV_REMOTE_ENABLE
:
620 if (kcov
->mode
!= KCOV_MODE_INIT
|| !kcov
->area
)
623 if (kcov
->t
!= NULL
|| t
->kcov
!= NULL
)
625 remote_arg
= (struct kcov_remote_arg
*)arg
;
626 mode
= kcov_get_mode(remote_arg
->trace_mode
);
629 if (remote_arg
->area_size
> LONG_MAX
/ sizeof(unsigned long))
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
,
642 kcov_disable(t
, kcov
);
645 remote
= kcov_remote_add(kcov
, remote_arg
->handles
[i
]);
646 if (IS_ERR(remote
)) {
647 spin_unlock_irqrestore(&kcov_remote_lock
,
649 kcov_disable(t
, kcov
);
650 return PTR_ERR(remote
);
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
,
658 kcov_disable(t
, kcov
);
661 remote
= kcov_remote_add(kcov
,
662 remote_arg
->common_handle
);
663 if (IS_ERR(remote
)) {
664 spin_unlock_irqrestore(&kcov_remote_lock
,
666 kcov_disable(t
, kcov
);
667 return PTR_ERR(remote
);
669 t
->kcov_handle
= remote_arg
->common_handle
;
671 spin_unlock_irqrestore(&kcov_remote_lock
, flags
);
672 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
680 static long kcov_ioctl(struct file
*filep
, unsigned int cmd
, unsigned long arg
)
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
;
690 kcov
= filep
->private_data
;
692 case KCOV_INIT_TRACE
:
694 * Enable kcov in trace mode and setup buffer size.
695 * Must happen before anything else.
697 * First check the size argument - it must be at least 2
698 * to hold the current position and one PC.
701 if (size
< 2 || size
> INT_MAX
/ sizeof(unsigned long))
703 area
= vmalloc_user(size
* sizeof(unsigned long));
706 spin_lock_irqsave(&kcov
->lock
, flags
);
707 if (kcov
->mode
!= KCOV_MODE_DISABLED
) {
708 spin_unlock_irqrestore(&kcov
->lock
, flags
);
714 kcov
->mode
= KCOV_MODE_INIT
;
715 spin_unlock_irqrestore(&kcov
->lock
, flags
);
717 case KCOV_REMOTE_ENABLE
:
718 if (get_user(remote_num_handles
, (unsigned __user
*)(arg
+
719 offsetof(struct kcov_remote_arg
, num_handles
))))
721 if (remote_num_handles
> KCOV_REMOTE_MAX_HANDLES
)
723 remote_arg_size
= struct_size(remote_arg
, 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
) {
732 arg
= (unsigned long)remote_arg
;
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().
739 spin_lock_irqsave(&kcov
->lock
, flags
);
740 res
= kcov_ioctl_locked(kcov
, cmd
, arg
);
741 spin_unlock_irqrestore(&kcov
->lock
, flags
);
747 static const struct file_operations kcov_fops
= {
749 .unlocked_ioctl
= kcov_ioctl
,
750 .compat_ioctl
= kcov_ioctl
,
752 .release
= kcov_close
,
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.
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.
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.
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).
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".
788 * See Documentation/dev-tools/kcov.rst for more details.
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.
798 static inline bool kcov_mode_enabled(unsigned int mode
)
800 return (mode
& ~KCOV_IN_CTXSW
) != KCOV_MODE_DISABLED
;
803 static void kcov_remote_softirq_start(struct task_struct
*t
)
805 struct kcov_percpu_data
*data
= this_cpu_ptr(&kcov_percpu_data
);
808 mode
= READ_ONCE(t
->kcov_mode
);
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
;
820 static void kcov_remote_softirq_stop(struct task_struct
*t
)
822 struct kcov_percpu_data
*data
= this_cpu_ptr(&kcov_percpu_data
);
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
;
836 void kcov_remote_start(u64 handle
)
838 struct task_struct
*t
= current
;
839 struct kcov_remote
*remote
;
847 if (WARN_ON(!kcov_check_handle(handle
, true, true, true)))
849 if (!in_task() && !in_serving_softirq())
852 local_lock_irqsave(&kcov_percpu_data
.lock
, flags
);
855 * Check that kcov_remote_start() is not called twice in background
856 * threads nor called by user tasks (with enabled kcov).
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
);
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.
868 if (WARN_ON(in_serving_softirq() && t
->kcov_softirq
)) {
869 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
873 spin_lock(&kcov_remote_lock
);
874 remote
= kcov_remote_find(handle
);
876 spin_unlock(&kcov_remote_lock
);
877 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
880 kcov_debug("handle = %llx, context: %s\n", handle
,
881 in_task() ? "task" : "softirq");
883 /* Put in kcov_remote_stop(). */
886 * Read kcov fields before unlock to prevent races with
887 * KCOV_DISABLE / kcov_remote_reset().
890 sequence
= kcov
->sequence
;
892 size
= kcov
->remote_size
;
893 area
= kcov_remote_area_get(size
);
895 size
= CONFIG_KCOV_IRQ_AREA_SIZE
;
896 area
= this_cpu_ptr(&kcov_percpu_data
)->irq_area
;
898 spin_unlock(&kcov_remote_lock
);
900 /* Can only happen when in_task(). */
902 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
903 area
= vmalloc(size
* sizeof(unsigned long));
908 local_lock_irqsave(&kcov_percpu_data
.lock
, flags
);
911 /* Reset coverage size. */
914 if (in_serving_softirq()) {
915 kcov_remote_softirq_start(t
);
918 kcov_start(t
, kcov
, size
, area
, mode
, sequence
);
920 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
923 EXPORT_SYMBOL(kcov_remote_start
);
925 static void kcov_move_area(enum kcov_mode mode
, void *dst_area
,
926 unsigned int dst_area_size
, void *src_area
)
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
;
934 kcov_debug("%px %u <= %px %lu\n",
935 dst_area
, dst_area_size
, src_area
, *(unsigned long *)src_area
);
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));
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
);
956 /* As arm can't divide u64 integers use log of entry size. */
957 if (dst_len
> ((dst_area_size
* word_size
- count_size
) >>
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
;
969 case KCOV_MODE_TRACE_PC
:
970 WRITE_ONCE(*(unsigned long *)dst_area
, dst_len
+ entries_moved
);
972 case KCOV_MODE_TRACE_CMP
:
973 WRITE_ONCE(*(u64
*)dst_area
, dst_len
+ entries_moved
);
980 /* See the comment before kcov_remote_start() for usage details. */
981 void kcov_remote_stop(void)
983 struct task_struct
*t
= current
;
991 if (!in_task() && !in_serving_softirq())
994 local_lock_irqsave(&kcov_percpu_data
.lock
, flags
);
996 mode
= READ_ONCE(t
->kcov_mode
);
998 if (!kcov_mode_enabled(mode
)) {
999 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
1003 * When in softirq, check if the corresponding kcov_remote_start()
1004 * actually found the remote handle and started collecting coverage.
1006 if (in_serving_softirq() && !t
->kcov_softirq
) {
1007 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
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
);
1017 area
= t
->kcov_area
;
1018 size
= t
->kcov_size
;
1019 sequence
= t
->kcov_sequence
;
1022 if (in_serving_softirq()) {
1023 t
->kcov_softirq
= 0;
1024 kcov_remote_softirq_stop(t
);
1027 spin_lock(&kcov
->lock
);
1029 * KCOV_DISABLE could have been called between kcov_remote_start()
1030 * and kcov_remote_stop(), hence the sequence check.
1032 if (sequence
== kcov
->sequence
&& kcov
->remote
)
1033 kcov_move_area(kcov
->mode
, kcov
->area
, kcov
->size
, area
);
1034 spin_unlock(&kcov
->lock
);
1037 spin_lock(&kcov_remote_lock
);
1038 kcov_remote_area_put(area
, size
);
1039 spin_unlock(&kcov_remote_lock
);
1042 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
1044 /* Get in kcov_remote_start(). */
1047 EXPORT_SYMBOL(kcov_remote_stop
);
1049 /* See the comment before kcov_remote_start() for usage details. */
1050 u64
kcov_common_handle(void)
1054 return current
->kcov_handle
;
1056 EXPORT_SYMBOL(kcov_common_handle
);
1058 static int __init
kcov_init(void)
1062 for_each_possible_cpu(cpu
) {
1063 void *area
= vmalloc_node(CONFIG_KCOV_IRQ_AREA_SIZE
*
1064 sizeof(unsigned long), cpu_to_node(cpu
));
1067 per_cpu_ptr(&kcov_percpu_data
, cpu
)->irq_area
= area
;
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.
1075 debugfs_create_file_unsafe("kcov", 0600, NULL
, NULL
, &kcov_fops
);
1080 device_initcall(kcov_init
);