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/init.h>
14 #include <linux/preempt.h>
15 #include <linux/printk.h>
16 #include <linux/sched.h>
17 #include <linux/slab.h>
18 #include <linux/spinlock.h>
19 #include <linux/vmalloc.h>
20 #include <linux/debugfs.h>
21 #include <linux/uaccess.h>
22 #include <linux/kcov.h>
23 #include <asm/setup.h>
26 * kcov descriptor (one per opened debugfs file).
27 * State transitions of the descriptor:
28 * - initial state after open()
29 * - then there must be a single ioctl(KCOV_INIT_TRACE) call
30 * - then, mmap() call (several calls are allowed but not useful)
31 * - then, repeated enable/disable for a task (only one task a time allowed)
35 * Reference counter. We keep one for:
36 * - opened file descriptor
37 * - task with enabled coverage (we can't unwire it from another task)
40 /* The lock protects mode, size, area and t. */
43 /* Size of arena (in long's for KCOV_MODE_TRACE). */
45 /* Coverage buffer shared with user space. */
47 /* Task for which we collect coverage, or NULL. */
48 struct task_struct
*t
;
52 * Entry point from instrumented code.
53 * This is called once per basic-block/edge.
55 void notrace
__sanitizer_cov_trace_pc(void)
57 struct task_struct
*t
;
62 * We are interested in code coverage as a function of a syscall inputs,
63 * so we ignore code executed in interrupts.
67 mode
= READ_ONCE(t
->kcov_mode
);
68 if (mode
== KCOV_MODE_TRACE
) {
71 unsigned long ip
= _RET_IP_
;
73 #ifdef CONFIG_RANDOMIZE_BASE
78 * There is some code that runs in interrupts but for which
79 * in_interrupt() returns false (e.g. preempt_schedule_irq()).
80 * READ_ONCE()/barrier() effectively provides load-acquire wrt
81 * interrupts, there are paired barrier()/WRITE_ONCE() in
82 * kcov_ioctl_locked().
86 /* The first word is number of subsequent PCs. */
87 pos
= READ_ONCE(area
[0]) + 1;
88 if (likely(pos
< t
->kcov_size
)) {
90 WRITE_ONCE(area
[0], pos
);
94 EXPORT_SYMBOL(__sanitizer_cov_trace_pc
);
96 static void kcov_get(struct kcov
*kcov
)
98 atomic_inc(&kcov
->refcount
);
101 static void kcov_put(struct kcov
*kcov
)
103 if (atomic_dec_and_test(&kcov
->refcount
)) {
109 void kcov_task_init(struct task_struct
*t
)
111 WRITE_ONCE(t
->kcov_mode
, KCOV_MODE_DISABLED
);
118 void kcov_task_exit(struct task_struct
*t
)
125 spin_lock(&kcov
->lock
);
126 if (WARN_ON(kcov
->t
!= t
)) {
127 spin_unlock(&kcov
->lock
);
130 /* Just to not leave dangling references behind. */
133 spin_unlock(&kcov
->lock
);
137 static int kcov_mmap(struct file
*filep
, struct vm_area_struct
*vma
)
141 struct kcov
*kcov
= vma
->vm_file
->private_data
;
142 unsigned long size
, off
;
145 area
= vmalloc_user(vma
->vm_end
- vma
->vm_start
);
149 spin_lock(&kcov
->lock
);
150 size
= kcov
->size
* sizeof(unsigned long);
151 if (kcov
->mode
== KCOV_MODE_DISABLED
|| vma
->vm_pgoff
!= 0 ||
152 vma
->vm_end
- vma
->vm_start
!= size
) {
158 vma
->vm_flags
|= VM_DONTEXPAND
;
159 spin_unlock(&kcov
->lock
);
160 for (off
= 0; off
< size
; off
+= PAGE_SIZE
) {
161 page
= vmalloc_to_page(kcov
->area
+ off
);
162 if (vm_insert_page(vma
, vma
->vm_start
+ off
, page
))
163 WARN_ONCE(1, "vm_insert_page() failed");
168 spin_unlock(&kcov
->lock
);
173 static int kcov_open(struct inode
*inode
, struct file
*filep
)
177 kcov
= kzalloc(sizeof(*kcov
), GFP_KERNEL
);
180 atomic_set(&kcov
->refcount
, 1);
181 spin_lock_init(&kcov
->lock
);
182 filep
->private_data
= kcov
;
183 return nonseekable_open(inode
, filep
);
186 static int kcov_close(struct inode
*inode
, struct file
*filep
)
188 kcov_put(filep
->private_data
);
192 static int kcov_ioctl_locked(struct kcov
*kcov
, unsigned int cmd
,
195 struct task_struct
*t
;
196 unsigned long size
, unused
;
199 case KCOV_INIT_TRACE
:
201 * Enable kcov in trace mode and setup buffer size.
202 * Must happen before anything else.
204 if (kcov
->mode
!= KCOV_MODE_DISABLED
)
207 * Size must be at least 2 to hold current position and one PC.
208 * Later we allocate size * sizeof(unsigned long) memory,
209 * that must not overflow.
212 if (size
< 2 || size
> INT_MAX
/ sizeof(unsigned long))
215 kcov
->mode
= KCOV_MODE_TRACE
;
219 * Enable coverage for the current task.
220 * At this point user must have been enabled trace mode,
221 * and mmapped the file. Coverage collection is disabled only
222 * at task exit or voluntary by KCOV_DISABLE. After that it can
223 * be enabled for another task.
226 if (unused
!= 0 || kcov
->mode
== KCOV_MODE_DISABLED
||
230 if (kcov
->t
!= NULL
|| t
->kcov
!= NULL
)
232 /* Cache in task struct for performance. */
233 t
->kcov_size
= kcov
->size
;
234 t
->kcov_area
= kcov
->area
;
235 /* See comment in __sanitizer_cov_trace_pc(). */
237 WRITE_ONCE(t
->kcov_mode
, kcov
->mode
);
240 /* This is put either in kcov_task_exit() or in KCOV_DISABLE. */
244 /* Disable coverage for the current task. */
246 if (unused
!= 0 || current
->kcov
!= kcov
)
249 if (WARN_ON(kcov
->t
!= t
))
260 static long kcov_ioctl(struct file
*filep
, unsigned int cmd
, unsigned long arg
)
265 kcov
= filep
->private_data
;
266 spin_lock(&kcov
->lock
);
267 res
= kcov_ioctl_locked(kcov
, cmd
, arg
);
268 spin_unlock(&kcov
->lock
);
272 static const struct file_operations kcov_fops
= {
274 .unlocked_ioctl
= kcov_ioctl
,
275 .compat_ioctl
= kcov_ioctl
,
277 .release
= kcov_close
,
280 static int __init
kcov_init(void)
283 * The kcov debugfs file won't ever get removed and thus,
284 * there is no need to protect it against removal races. The
285 * use of debugfs_create_file_unsafe() is actually safe here.
287 if (!debugfs_create_file_unsafe("kcov", 0600, NULL
, NULL
, &kcov_fops
)) {
288 pr_err("failed to create kcov in debugfs\n");
294 device_initcall(kcov_init
);