1 #define pr_fmt(fmt) "kcov: " fmt
3 #define DISABLE_BRANCH_PROFILING
4 #include <linux/compiler.h>
5 #include <linux/types.h>
6 #include <linux/file.h>
9 #include <linux/printk.h>
10 #include <linux/slab.h>
11 #include <linux/spinlock.h>
12 #include <linux/vmalloc.h>
13 #include <linux/debugfs.h>
14 #include <linux/uaccess.h>
15 #include <linux/kcov.h>
18 * kcov descriptor (one per opened debugfs file).
19 * State transitions of the descriptor:
20 * - initial state after open()
21 * - then there must be a single ioctl(KCOV_INIT_TRACE) call
22 * - then, mmap() call (several calls are allowed but not useful)
23 * - then, repeated enable/disable for a task (only one task a time allowed)
27 * Reference counter. We keep one for:
28 * - opened file descriptor
29 * - task with enabled coverage (we can't unwire it from another task)
32 /* The lock protects mode, size, area and t. */
35 /* Size of arena (in long's for KCOV_MODE_TRACE). */
37 /* Coverage buffer shared with user space. */
39 /* Task for which we collect coverage, or NULL. */
40 struct task_struct *t;
44 * Entry point from instrumented code.
45 * This is called once per basic-block/edge.
47 void notrace __sanitizer_cov_trace_pc(void)
49 struct task_struct *t;
54 * We are interested in code coverage as a function of a syscall inputs,
55 * so we ignore code executed in interrupts.
57 if (!t || in_interrupt())
59 mode = READ_ONCE(t->kcov_mode);
60 if (mode == KCOV_MODE_TRACE) {
65 * There is some code that runs in interrupts but for which
66 * in_interrupt() returns false (e.g. preempt_schedule_irq()).
67 * READ_ONCE()/barrier() effectively provides load-acquire wrt
68 * interrupts, there are paired barrier()/WRITE_ONCE() in
69 * kcov_ioctl_locked().
73 /* The first word is number of subsequent PCs. */
74 pos = READ_ONCE(area[0]) + 1;
75 if (likely(pos < t->kcov_size)) {
77 WRITE_ONCE(area[0], pos);
81 EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
83 static void kcov_get(struct kcov *kcov)
85 atomic_inc(&kcov->refcount);
88 static void kcov_put(struct kcov *kcov)
90 if (atomic_dec_and_test(&kcov->refcount)) {
96 void kcov_task_init(struct task_struct *t)
98 t->kcov_mode = KCOV_MODE_DISABLED;
104 void kcov_task_exit(struct task_struct *t)
111 spin_lock(&kcov->lock);
112 if (WARN_ON(kcov->t != t)) {
113 spin_unlock(&kcov->lock);
116 /* Just to not leave dangling references behind. */
119 spin_unlock(&kcov->lock);
123 static int kcov_mmap(struct file *filep, struct vm_area_struct *vma)
127 struct kcov *kcov = vma->vm_file->private_data;
128 unsigned long size, off;
131 area = vmalloc_user(vma->vm_end - vma->vm_start);
135 spin_lock(&kcov->lock);
136 size = kcov->size * sizeof(unsigned long);
137 if (kcov->mode == KCOV_MODE_DISABLED || vma->vm_pgoff != 0 ||
138 vma->vm_end - vma->vm_start != size) {
144 vma->vm_flags |= VM_DONTEXPAND;
145 spin_unlock(&kcov->lock);
146 for (off = 0; off < size; off += PAGE_SIZE) {
147 page = vmalloc_to_page(kcov->area + off);
148 if (vm_insert_page(vma, vma->vm_start + off, page))
149 WARN_ONCE(1, "vm_insert_page() failed");
154 spin_unlock(&kcov->lock);
159 static int kcov_open(struct inode *inode, struct file *filep)
163 kcov = kzalloc(sizeof(*kcov), GFP_KERNEL);
166 atomic_set(&kcov->refcount, 1);
167 spin_lock_init(&kcov->lock);
168 filep->private_data = kcov;
169 return nonseekable_open(inode, filep);
172 static int kcov_close(struct inode *inode, struct file *filep)
174 kcov_put(filep->private_data);
178 static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
181 struct task_struct *t;
182 unsigned long size, unused;
185 case KCOV_INIT_TRACE:
187 * Enable kcov in trace mode and setup buffer size.
188 * Must happen before anything else.
190 if (kcov->mode != KCOV_MODE_DISABLED)
193 * Size must be at least 2 to hold current position and one PC.
194 * Later we allocate size * sizeof(unsigned long) memory,
195 * that must not overflow.
198 if (size < 2 || size > INT_MAX / sizeof(unsigned long))
201 kcov->mode = KCOV_MODE_TRACE;
205 * Enable coverage for the current task.
206 * At this point user must have been enabled trace mode,
207 * and mmapped the file. Coverage collection is disabled only
208 * at task exit or voluntary by KCOV_DISABLE. After that it can
209 * be enabled for another task.
212 if (unused != 0 || kcov->mode == KCOV_MODE_DISABLED ||
218 /* Cache in task struct for performance. */
219 t->kcov_size = kcov->size;
220 t->kcov_area = kcov->area;
221 /* See comment in __sanitizer_cov_trace_pc(). */
223 WRITE_ONCE(t->kcov_mode, kcov->mode);
226 /* This is put either in kcov_task_exit() or in KCOV_DISABLE. */
230 /* Disable coverage for the current task. */
232 if (unused != 0 || current->kcov != kcov)
235 if (WARN_ON(kcov->t != t))
246 static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
251 kcov = filep->private_data;
252 spin_lock(&kcov->lock);
253 res = kcov_ioctl_locked(kcov, cmd, arg);
254 spin_unlock(&kcov->lock);
258 static const struct file_operations kcov_fops = {
260 .unlocked_ioctl = kcov_ioctl,
262 .release = kcov_close,
265 static int __init kcov_init(void)
268 * The kcov debugfs file won't ever get removed and thus,
269 * there is no need to protect it against removal races. The
270 * use of debugfs_create_file_unsafe() is actually safe here.
272 if (!debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops)) {
273 pr_err("failed to create kcov in debugfs\n");
279 device_initcall(kcov_init);