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 struct kcov_percpu_data
{
93 unsigned int saved_mode
;
94 unsigned int saved_size
;
96 struct kcov
*saved_kcov
;
100 static DEFINE_PER_CPU(struct kcov_percpu_data
, kcov_percpu_data
) = {
101 .lock
= INIT_LOCAL_LOCK(lock
),
104 /* Must be called with kcov_remote_lock locked. */
105 static struct kcov_remote
*kcov_remote_find(u64 handle
)
107 struct kcov_remote
*remote
;
109 hash_for_each_possible(kcov_remote_map
, remote
, hnode
, handle
) {
110 if (remote
->handle
== handle
)
116 /* Must be called with kcov_remote_lock locked. */
117 static struct kcov_remote
*kcov_remote_add(struct kcov
*kcov
, u64 handle
)
119 struct kcov_remote
*remote
;
121 if (kcov_remote_find(handle
))
122 return ERR_PTR(-EEXIST
);
123 remote
= kmalloc(sizeof(*remote
), GFP_ATOMIC
);
125 return ERR_PTR(-ENOMEM
);
126 remote
->handle
= handle
;
128 hash_add(kcov_remote_map
, &remote
->hnode
, handle
);
132 /* Must be called with kcov_remote_lock locked. */
133 static struct kcov_remote_area
*kcov_remote_area_get(unsigned int size
)
135 struct kcov_remote_area
*area
;
136 struct list_head
*pos
;
138 list_for_each(pos
, &kcov_remote_areas
) {
139 area
= list_entry(pos
, struct kcov_remote_area
, list
);
140 if (area
->size
== size
) {
141 list_del(&area
->list
);
148 /* Must be called with kcov_remote_lock locked. */
149 static void kcov_remote_area_put(struct kcov_remote_area
*area
,
152 INIT_LIST_HEAD(&area
->list
);
154 list_add(&area
->list
, &kcov_remote_areas
);
157 static notrace
bool check_kcov_mode(enum kcov_mode needed_mode
, struct task_struct
*t
)
162 * We are interested in code coverage as a function of a syscall inputs,
163 * so we ignore code executed in interrupts, unless we are in a remote
164 * coverage collection section in a softirq.
166 if (!in_task() && !(in_serving_softirq() && t
->kcov_softirq
))
168 mode
= READ_ONCE(t
->kcov_mode
);
170 * There is some code that runs in interrupts but for which
171 * in_interrupt() returns false (e.g. preempt_schedule_irq()).
172 * READ_ONCE()/barrier() effectively provides load-acquire wrt
173 * interrupts, there are paired barrier()/WRITE_ONCE() in
177 return mode
== needed_mode
;
180 static notrace
unsigned long canonicalize_ip(unsigned long ip
)
182 #ifdef CONFIG_RANDOMIZE_BASE
183 ip
-= kaslr_offset();
189 * Entry point from instrumented code.
190 * This is called once per basic-block/edge.
192 void notrace
__sanitizer_cov_trace_pc(void)
194 struct task_struct
*t
;
196 unsigned long ip
= canonicalize_ip(_RET_IP_
);
200 if (!check_kcov_mode(KCOV_MODE_TRACE_PC
, t
))
204 /* The first 64-bit word is the number of subsequent PCs. */
205 pos
= READ_ONCE(area
[0]) + 1;
206 if (likely(pos
< t
->kcov_size
)) {
208 WRITE_ONCE(area
[0], pos
);
211 EXPORT_SYMBOL(__sanitizer_cov_trace_pc
);
213 #ifdef CONFIG_KCOV_ENABLE_COMPARISONS
214 static void notrace
write_comp_data(u64 type
, u64 arg1
, u64 arg2
, u64 ip
)
216 struct task_struct
*t
;
218 u64 count
, start_index
, end_pos
, max_pos
;
221 if (!check_kcov_mode(KCOV_MODE_TRACE_CMP
, t
))
224 ip
= canonicalize_ip(ip
);
227 * We write all comparison arguments and types as u64.
228 * The buffer was allocated for t->kcov_size unsigned longs.
230 area
= (u64
*)t
->kcov_area
;
231 max_pos
= t
->kcov_size
* sizeof(unsigned long);
233 count
= READ_ONCE(area
[0]);
235 /* Every record is KCOV_WORDS_PER_CMP 64-bit words. */
236 start_index
= 1 + count
* KCOV_WORDS_PER_CMP
;
237 end_pos
= (start_index
+ KCOV_WORDS_PER_CMP
) * sizeof(u64
);
238 if (likely(end_pos
<= max_pos
)) {
239 area
[start_index
] = type
;
240 area
[start_index
+ 1] = arg1
;
241 area
[start_index
+ 2] = arg2
;
242 area
[start_index
+ 3] = ip
;
243 WRITE_ONCE(area
[0], count
+ 1);
247 void notrace
__sanitizer_cov_trace_cmp1(u8 arg1
, u8 arg2
)
249 write_comp_data(KCOV_CMP_SIZE(0), arg1
, arg2
, _RET_IP_
);
251 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1
);
253 void notrace
__sanitizer_cov_trace_cmp2(u16 arg1
, u16 arg2
)
255 write_comp_data(KCOV_CMP_SIZE(1), arg1
, arg2
, _RET_IP_
);
257 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2
);
259 void notrace
__sanitizer_cov_trace_cmp4(u32 arg1
, u32 arg2
)
261 write_comp_data(KCOV_CMP_SIZE(2), arg1
, arg2
, _RET_IP_
);
263 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4
);
265 void notrace
__sanitizer_cov_trace_cmp8(u64 arg1
, u64 arg2
)
267 write_comp_data(KCOV_CMP_SIZE(3), arg1
, arg2
, _RET_IP_
);
269 EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8
);
271 void notrace
__sanitizer_cov_trace_const_cmp1(u8 arg1
, u8 arg2
)
273 write_comp_data(KCOV_CMP_SIZE(0) | KCOV_CMP_CONST
, arg1
, arg2
,
276 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1
);
278 void notrace
__sanitizer_cov_trace_const_cmp2(u16 arg1
, u16 arg2
)
280 write_comp_data(KCOV_CMP_SIZE(1) | KCOV_CMP_CONST
, arg1
, arg2
,
283 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2
);
285 void notrace
__sanitizer_cov_trace_const_cmp4(u32 arg1
, u32 arg2
)
287 write_comp_data(KCOV_CMP_SIZE(2) | KCOV_CMP_CONST
, arg1
, arg2
,
290 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4
);
292 void notrace
__sanitizer_cov_trace_const_cmp8(u64 arg1
, u64 arg2
)
294 write_comp_data(KCOV_CMP_SIZE(3) | KCOV_CMP_CONST
, arg1
, arg2
,
297 EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8
);
299 void notrace
__sanitizer_cov_trace_switch(u64 val
, u64
*cases
)
302 u64 count
= cases
[0];
304 u64 type
= KCOV_CMP_CONST
;
308 type
|= KCOV_CMP_SIZE(0);
311 type
|= KCOV_CMP_SIZE(1);
314 type
|= KCOV_CMP_SIZE(2);
317 type
|= KCOV_CMP_SIZE(3);
322 for (i
= 0; i
< count
; i
++)
323 write_comp_data(type
, cases
[i
+ 2], val
, _RET_IP_
);
325 EXPORT_SYMBOL(__sanitizer_cov_trace_switch
);
326 #endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */
328 static void kcov_start(struct task_struct
*t
, struct kcov
*kcov
,
329 unsigned int size
, void *area
, enum kcov_mode mode
,
332 kcov_debug("t = %px, size = %u, area = %px\n", t
, size
, area
);
334 /* Cache in task struct for performance. */
337 t
->kcov_sequence
= sequence
;
338 /* See comment in check_kcov_mode(). */
340 WRITE_ONCE(t
->kcov_mode
, mode
);
343 static void kcov_stop(struct task_struct
*t
)
345 WRITE_ONCE(t
->kcov_mode
, KCOV_MODE_DISABLED
);
352 static void kcov_task_reset(struct task_struct
*t
)
355 t
->kcov_sequence
= 0;
359 void kcov_task_init(struct task_struct
*t
)
362 t
->kcov_handle
= current
->kcov_handle
;
365 static void kcov_reset(struct kcov
*kcov
)
368 kcov
->mode
= KCOV_MODE_INIT
;
369 kcov
->remote
= false;
370 kcov
->remote_size
= 0;
374 static void kcov_remote_reset(struct kcov
*kcov
)
377 struct kcov_remote
*remote
;
378 struct hlist_node
*tmp
;
381 spin_lock_irqsave(&kcov_remote_lock
, flags
);
382 hash_for_each_safe(kcov_remote_map
, bkt
, tmp
, remote
, hnode
) {
383 if (remote
->kcov
!= kcov
)
385 hash_del(&remote
->hnode
);
388 /* Do reset before unlock to prevent races with kcov_remote_start(). */
390 spin_unlock_irqrestore(&kcov_remote_lock
, flags
);
393 static void kcov_disable(struct task_struct
*t
, struct kcov
*kcov
)
397 kcov_remote_reset(kcov
);
402 static void kcov_get(struct kcov
*kcov
)
404 refcount_inc(&kcov
->refcount
);
407 static void kcov_put(struct kcov
*kcov
)
409 if (refcount_dec_and_test(&kcov
->refcount
)) {
410 kcov_remote_reset(kcov
);
416 void kcov_task_exit(struct task_struct
*t
)
425 spin_lock_irqsave(&kcov
->lock
, flags
);
426 kcov_debug("t = %px, kcov->t = %px\n", t
, kcov
->t
);
428 * For KCOV_ENABLE devices we want to make sure that t->kcov->t == t,
429 * which comes down to:
430 * WARN_ON(!kcov->remote && kcov->t != t);
432 * For KCOV_REMOTE_ENABLE devices, the exiting task is either:
434 * 1. A remote task between kcov_remote_start() and kcov_remote_stop().
435 * In this case we should print a warning right away, since a task
436 * shouldn't be exiting when it's in a kcov coverage collection
437 * section. Here t points to the task that is collecting remote
438 * coverage, and t->kcov->t points to the thread that created the
439 * kcov device. Which means that to detect this case we need to
440 * check that t != t->kcov->t, and this gives us the following:
441 * WARN_ON(kcov->remote && kcov->t != t);
443 * 2. The task that created kcov exiting without calling KCOV_DISABLE,
444 * and then again we make sure that t->kcov->t == t:
445 * WARN_ON(kcov->remote && kcov->t != t);
447 * By combining all three checks into one we get:
449 if (WARN_ON(kcov
->t
!= t
)) {
450 spin_unlock_irqrestore(&kcov
->lock
, flags
);
453 /* Just to not leave dangling references behind. */
454 kcov_disable(t
, kcov
);
455 spin_unlock_irqrestore(&kcov
->lock
, flags
);
459 static int kcov_mmap(struct file
*filep
, struct vm_area_struct
*vma
)
462 struct kcov
*kcov
= vma
->vm_file
->private_data
;
463 unsigned long size
, off
;
467 spin_lock_irqsave(&kcov
->lock
, flags
);
468 size
= kcov
->size
* sizeof(unsigned long);
469 if (kcov
->area
== NULL
|| vma
->vm_pgoff
!= 0 ||
470 vma
->vm_end
- vma
->vm_start
!= size
) {
474 spin_unlock_irqrestore(&kcov
->lock
, flags
);
475 vma
->vm_flags
|= VM_DONTEXPAND
;
476 for (off
= 0; off
< size
; off
+= PAGE_SIZE
) {
477 page
= vmalloc_to_page(kcov
->area
+ off
);
478 res
= vm_insert_page(vma
, vma
->vm_start
+ off
, page
);
480 pr_warn_once("kcov: vm_insert_page() failed\n");
486 spin_unlock_irqrestore(&kcov
->lock
, flags
);
490 static int kcov_open(struct inode
*inode
, struct file
*filep
)
494 kcov
= kzalloc(sizeof(*kcov
), GFP_KERNEL
);
497 kcov
->mode
= KCOV_MODE_DISABLED
;
499 refcount_set(&kcov
->refcount
, 1);
500 spin_lock_init(&kcov
->lock
);
501 filep
->private_data
= kcov
;
502 return nonseekable_open(inode
, filep
);
505 static int kcov_close(struct inode
*inode
, struct file
*filep
)
507 kcov_put(filep
->private_data
);
511 static int kcov_get_mode(unsigned long arg
)
513 if (arg
== KCOV_TRACE_PC
)
514 return KCOV_MODE_TRACE_PC
;
515 else if (arg
== KCOV_TRACE_CMP
)
516 #ifdef CONFIG_KCOV_ENABLE_COMPARISONS
517 return KCOV_MODE_TRACE_CMP
;
526 * Fault in a lazily-faulted vmalloc area before it can be used by
527 * __santizer_cov_trace_pc(), to avoid recursion issues if any code on the
528 * vmalloc fault handling path is instrumented.
530 static void kcov_fault_in_area(struct kcov
*kcov
)
532 unsigned long stride
= PAGE_SIZE
/ sizeof(unsigned long);
533 unsigned long *area
= kcov
->area
;
534 unsigned long offset
;
536 for (offset
= 0; offset
< kcov
->size
; offset
+= stride
)
537 READ_ONCE(area
[offset
]);
540 static inline bool kcov_check_handle(u64 handle
, bool common_valid
,
541 bool uncommon_valid
, bool zero_valid
)
543 if (handle
& ~(KCOV_SUBSYSTEM_MASK
| KCOV_INSTANCE_MASK
))
545 switch (handle
& KCOV_SUBSYSTEM_MASK
) {
546 case KCOV_SUBSYSTEM_COMMON
:
547 return (handle
& KCOV_INSTANCE_MASK
) ?
548 common_valid
: zero_valid
;
549 case KCOV_SUBSYSTEM_USB
:
550 return uncommon_valid
;
557 static int kcov_ioctl_locked(struct kcov
*kcov
, unsigned int cmd
,
560 struct task_struct
*t
;
561 unsigned long flags
, unused
;
563 struct kcov_remote_arg
*remote_arg
;
564 struct kcov_remote
*remote
;
569 * Enable coverage for the current task.
570 * At this point user must have been enabled trace mode,
571 * and mmapped the file. Coverage collection is disabled only
572 * at task exit or voluntary by KCOV_DISABLE. After that it can
573 * be enabled for another task.
575 if (kcov
->mode
!= KCOV_MODE_INIT
|| !kcov
->area
)
578 if (kcov
->t
!= NULL
|| t
->kcov
!= NULL
)
580 mode
= kcov_get_mode(arg
);
583 kcov_fault_in_area(kcov
);
585 kcov_start(t
, kcov
, kcov
->size
, kcov
->area
, kcov
->mode
,
588 /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
592 /* Disable coverage for the current task. */
594 if (unused
!= 0 || current
->kcov
!= kcov
)
597 if (WARN_ON(kcov
->t
!= t
))
599 kcov_disable(t
, kcov
);
602 case KCOV_REMOTE_ENABLE
:
603 if (kcov
->mode
!= KCOV_MODE_INIT
|| !kcov
->area
)
606 if (kcov
->t
!= NULL
|| t
->kcov
!= NULL
)
608 remote_arg
= (struct kcov_remote_arg
*)arg
;
609 mode
= kcov_get_mode(remote_arg
->trace_mode
);
612 if (remote_arg
->area_size
> LONG_MAX
/ sizeof(unsigned long))
618 kcov
->remote_size
= remote_arg
->area_size
;
619 spin_lock_irqsave(&kcov_remote_lock
, flags
);
620 for (i
= 0; i
< remote_arg
->num_handles
; i
++) {
621 if (!kcov_check_handle(remote_arg
->handles
[i
],
622 false, true, false)) {
623 spin_unlock_irqrestore(&kcov_remote_lock
,
625 kcov_disable(t
, kcov
);
628 remote
= kcov_remote_add(kcov
, remote_arg
->handles
[i
]);
629 if (IS_ERR(remote
)) {
630 spin_unlock_irqrestore(&kcov_remote_lock
,
632 kcov_disable(t
, kcov
);
633 return PTR_ERR(remote
);
636 if (remote_arg
->common_handle
) {
637 if (!kcov_check_handle(remote_arg
->common_handle
,
638 true, false, false)) {
639 spin_unlock_irqrestore(&kcov_remote_lock
,
641 kcov_disable(t
, kcov
);
644 remote
= kcov_remote_add(kcov
,
645 remote_arg
->common_handle
);
646 if (IS_ERR(remote
)) {
647 spin_unlock_irqrestore(&kcov_remote_lock
,
649 kcov_disable(t
, kcov
);
650 return PTR_ERR(remote
);
652 t
->kcov_handle
= remote_arg
->common_handle
;
654 spin_unlock_irqrestore(&kcov_remote_lock
, flags
);
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
;
670 unsigned long size
, flags
;
673 kcov
= filep
->private_data
;
675 case KCOV_INIT_TRACE
:
677 * Enable kcov in trace mode and setup buffer size.
678 * Must happen before anything else.
680 * First check the size argument - it must be at least 2
681 * to hold the current position and one PC.
684 if (size
< 2 || size
> INT_MAX
/ sizeof(unsigned long))
686 area
= vmalloc_user(size
* sizeof(unsigned long));
689 spin_lock_irqsave(&kcov
->lock
, flags
);
690 if (kcov
->mode
!= KCOV_MODE_DISABLED
) {
691 spin_unlock_irqrestore(&kcov
->lock
, flags
);
697 kcov
->mode
= KCOV_MODE_INIT
;
698 spin_unlock_irqrestore(&kcov
->lock
, flags
);
700 case KCOV_REMOTE_ENABLE
:
701 if (get_user(remote_num_handles
, (unsigned __user
*)(arg
+
702 offsetof(struct kcov_remote_arg
, num_handles
))))
704 if (remote_num_handles
> KCOV_REMOTE_MAX_HANDLES
)
706 remote_arg_size
= struct_size(remote_arg
, handles
,
708 remote_arg
= memdup_user((void __user
*)arg
, remote_arg_size
);
709 if (IS_ERR(remote_arg
))
710 return PTR_ERR(remote_arg
);
711 if (remote_arg
->num_handles
!= remote_num_handles
) {
715 arg
= (unsigned long)remote_arg
;
719 * All other commands can be normally executed under a spin lock, so we
720 * obtain and release it here in order to simplify kcov_ioctl_locked().
722 spin_lock_irqsave(&kcov
->lock
, flags
);
723 res
= kcov_ioctl_locked(kcov
, cmd
, arg
);
724 spin_unlock_irqrestore(&kcov
->lock
, flags
);
730 static const struct file_operations kcov_fops
= {
732 .unlocked_ioctl
= kcov_ioctl
,
733 .compat_ioctl
= kcov_ioctl
,
735 .release
= kcov_close
,
739 * kcov_remote_start() and kcov_remote_stop() can be used to annotate a section
740 * of code in a kernel background thread or in a softirq to allow kcov to be
741 * used to collect coverage from that part of code.
743 * The handle argument of kcov_remote_start() identifies a code section that is
744 * used for coverage collection. A userspace process passes this handle to
745 * KCOV_REMOTE_ENABLE ioctl to make the used kcov device start collecting
746 * coverage for the code section identified by this handle.
748 * The usage of these annotations in the kernel code is different depending on
749 * the type of the kernel thread whose code is being annotated.
751 * For global kernel threads that are spawned in a limited number of instances
752 * (e.g. one USB hub_event() worker thread is spawned per USB HCD) and for
753 * softirqs, each instance must be assigned a unique 4-byte instance id. The
754 * instance id is then combined with a 1-byte subsystem id to get a handle via
755 * kcov_remote_handle(subsystem_id, instance_id).
757 * For local kernel threads that are spawned from system calls handler when a
758 * user interacts with some kernel interface (e.g. vhost workers), a handle is
759 * passed from a userspace process as the common_handle field of the
760 * kcov_remote_arg struct (note, that the user must generate a handle by using
761 * kcov_remote_handle() with KCOV_SUBSYSTEM_COMMON as the subsystem id and an
762 * arbitrary 4-byte non-zero number as the instance id). This common handle
763 * then gets saved into the task_struct of the process that issued the
764 * KCOV_REMOTE_ENABLE ioctl. When this process issues system calls that spawn
765 * kernel threads, the common handle must be retrieved via kcov_common_handle()
766 * and passed to the spawned threads via custom annotations. Those kernel
767 * threads must in turn be annotated with kcov_remote_start(common_handle) and
768 * kcov_remote_stop(). All of the threads that are spawned by the same process
769 * obtain the same handle, hence the name "common".
771 * See Documentation/dev-tools/kcov.rst for more details.
773 * Internally, kcov_remote_start() looks up the kcov device associated with the
774 * provided handle, allocates an area for coverage collection, and saves the
775 * pointers to kcov and area into the current task_struct to allow coverage to
776 * be collected via __sanitizer_cov_trace_pc().
777 * In turns kcov_remote_stop() clears those pointers from task_struct to stop
778 * collecting coverage and copies all collected coverage into the kcov area.
781 static inline bool kcov_mode_enabled(unsigned int mode
)
783 return (mode
& ~KCOV_IN_CTXSW
) != KCOV_MODE_DISABLED
;
786 static void kcov_remote_softirq_start(struct task_struct
*t
)
788 struct kcov_percpu_data
*data
= this_cpu_ptr(&kcov_percpu_data
);
791 mode
= READ_ONCE(t
->kcov_mode
);
793 if (kcov_mode_enabled(mode
)) {
794 data
->saved_mode
= mode
;
795 data
->saved_size
= t
->kcov_size
;
796 data
->saved_area
= t
->kcov_area
;
797 data
->saved_sequence
= t
->kcov_sequence
;
798 data
->saved_kcov
= t
->kcov
;
803 static void kcov_remote_softirq_stop(struct task_struct
*t
)
805 struct kcov_percpu_data
*data
= this_cpu_ptr(&kcov_percpu_data
);
807 if (data
->saved_kcov
) {
808 kcov_start(t
, data
->saved_kcov
, data
->saved_size
,
809 data
->saved_area
, data
->saved_mode
,
810 data
->saved_sequence
);
811 data
->saved_mode
= 0;
812 data
->saved_size
= 0;
813 data
->saved_area
= NULL
;
814 data
->saved_sequence
= 0;
815 data
->saved_kcov
= NULL
;
819 void kcov_remote_start(u64 handle
)
821 struct task_struct
*t
= current
;
822 struct kcov_remote
*remote
;
830 if (WARN_ON(!kcov_check_handle(handle
, true, true, true)))
832 if (!in_task() && !in_serving_softirq())
835 local_lock_irqsave(&kcov_percpu_data
.lock
, flags
);
838 * Check that kcov_remote_start() is not called twice in background
839 * threads nor called by user tasks (with enabled kcov).
841 mode
= READ_ONCE(t
->kcov_mode
);
842 if (WARN_ON(in_task() && kcov_mode_enabled(mode
))) {
843 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
847 * Check that kcov_remote_start() is not called twice in softirqs.
848 * Note, that kcov_remote_start() can be called from a softirq that
849 * happened while collecting coverage from a background thread.
851 if (WARN_ON(in_serving_softirq() && t
->kcov_softirq
)) {
852 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
856 spin_lock(&kcov_remote_lock
);
857 remote
= kcov_remote_find(handle
);
859 spin_unlock(&kcov_remote_lock
);
860 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
863 kcov_debug("handle = %llx, context: %s\n", handle
,
864 in_task() ? "task" : "softirq");
866 /* Put in kcov_remote_stop(). */
869 * Read kcov fields before unlock to prevent races with
870 * KCOV_DISABLE / kcov_remote_reset().
873 sequence
= kcov
->sequence
;
875 size
= kcov
->remote_size
;
876 area
= kcov_remote_area_get(size
);
878 size
= CONFIG_KCOV_IRQ_AREA_SIZE
;
879 area
= this_cpu_ptr(&kcov_percpu_data
)->irq_area
;
881 spin_unlock(&kcov_remote_lock
);
883 /* Can only happen when in_task(). */
885 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
886 area
= vmalloc(size
* sizeof(unsigned long));
891 local_lock_irqsave(&kcov_percpu_data
.lock
, flags
);
894 /* Reset coverage size. */
897 if (in_serving_softirq()) {
898 kcov_remote_softirq_start(t
);
901 kcov_start(t
, kcov
, size
, area
, mode
, sequence
);
903 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
906 EXPORT_SYMBOL(kcov_remote_start
);
908 static void kcov_move_area(enum kcov_mode mode
, void *dst_area
,
909 unsigned int dst_area_size
, void *src_area
)
911 u64 word_size
= sizeof(unsigned long);
912 u64 count_size
, entry_size_log
;
913 u64 dst_len
, src_len
;
914 void *dst_entries
, *src_entries
;
915 u64 dst_occupied
, dst_free
, bytes_to_move
, entries_moved
;
917 kcov_debug("%px %u <= %px %lu\n",
918 dst_area
, dst_area_size
, src_area
, *(unsigned long *)src_area
);
921 case KCOV_MODE_TRACE_PC
:
922 dst_len
= READ_ONCE(*(unsigned long *)dst_area
);
923 src_len
= *(unsigned long *)src_area
;
924 count_size
= sizeof(unsigned long);
925 entry_size_log
= __ilog2_u64(sizeof(unsigned long));
927 case KCOV_MODE_TRACE_CMP
:
928 dst_len
= READ_ONCE(*(u64
*)dst_area
);
929 src_len
= *(u64
*)src_area
;
930 count_size
= sizeof(u64
);
931 BUILD_BUG_ON(!is_power_of_2(KCOV_WORDS_PER_CMP
));
932 entry_size_log
= __ilog2_u64(sizeof(u64
) * KCOV_WORDS_PER_CMP
);
939 /* As arm can't divide u64 integers use log of entry size. */
940 if (dst_len
> ((dst_area_size
* word_size
- count_size
) >>
943 dst_occupied
= count_size
+ (dst_len
<< entry_size_log
);
944 dst_free
= dst_area_size
* word_size
- dst_occupied
;
945 bytes_to_move
= min(dst_free
, src_len
<< entry_size_log
);
946 dst_entries
= dst_area
+ dst_occupied
;
947 src_entries
= src_area
+ count_size
;
948 memcpy(dst_entries
, src_entries
, bytes_to_move
);
949 entries_moved
= bytes_to_move
>> entry_size_log
;
952 case KCOV_MODE_TRACE_PC
:
953 WRITE_ONCE(*(unsigned long *)dst_area
, dst_len
+ entries_moved
);
955 case KCOV_MODE_TRACE_CMP
:
956 WRITE_ONCE(*(u64
*)dst_area
, dst_len
+ entries_moved
);
963 /* See the comment before kcov_remote_start() for usage details. */
964 void kcov_remote_stop(void)
966 struct task_struct
*t
= current
;
974 if (!in_task() && !in_serving_softirq())
977 local_lock_irqsave(&kcov_percpu_data
.lock
, flags
);
979 mode
= READ_ONCE(t
->kcov_mode
);
981 if (!kcov_mode_enabled(mode
)) {
982 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
986 * When in softirq, check if the corresponding kcov_remote_start()
987 * actually found the remote handle and started collecting coverage.
989 if (in_serving_softirq() && !t
->kcov_softirq
) {
990 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
993 /* Make sure that kcov_softirq is only set when in softirq. */
994 if (WARN_ON(!in_serving_softirq() && t
->kcov_softirq
)) {
995 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
1000 area
= t
->kcov_area
;
1001 size
= t
->kcov_size
;
1002 sequence
= t
->kcov_sequence
;
1005 if (in_serving_softirq()) {
1006 t
->kcov_softirq
= 0;
1007 kcov_remote_softirq_stop(t
);
1010 spin_lock(&kcov
->lock
);
1012 * KCOV_DISABLE could have been called between kcov_remote_start()
1013 * and kcov_remote_stop(), hence the sequence check.
1015 if (sequence
== kcov
->sequence
&& kcov
->remote
)
1016 kcov_move_area(kcov
->mode
, kcov
->area
, kcov
->size
, area
);
1017 spin_unlock(&kcov
->lock
);
1020 spin_lock(&kcov_remote_lock
);
1021 kcov_remote_area_put(area
, size
);
1022 spin_unlock(&kcov_remote_lock
);
1025 local_unlock_irqrestore(&kcov_percpu_data
.lock
, flags
);
1027 /* Get in kcov_remote_start(). */
1030 EXPORT_SYMBOL(kcov_remote_stop
);
1032 /* See the comment before kcov_remote_start() for usage details. */
1033 u64
kcov_common_handle(void)
1037 return current
->kcov_handle
;
1039 EXPORT_SYMBOL(kcov_common_handle
);
1041 static int __init
kcov_init(void)
1045 for_each_possible_cpu(cpu
) {
1046 void *area
= vmalloc_node(CONFIG_KCOV_IRQ_AREA_SIZE
*
1047 sizeof(unsigned long), cpu_to_node(cpu
));
1050 per_cpu_ptr(&kcov_percpu_data
, cpu
)->irq_area
= area
;
1054 * The kcov debugfs file won't ever get removed and thus,
1055 * there is no need to protect it against removal races. The
1056 * use of debugfs_create_file_unsafe() is actually safe here.
1058 debugfs_create_file_unsafe("kcov", 0600, NULL
, NULL
, &kcov_fops
);
1063 device_initcall(kcov_init
);