[GitHub/moto-9609/android_kernel_motorola_exynos9610.git] / kernel / kcov.c

// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) "kcov: " fmt

#define DISABLE_BRANCH_PROFILING
#include <linux/atomic.h>
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/types.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/preempt.h>
#include <linux/printk.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/vmalloc.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/kcov.h>
#include <asm/setup.h>

/*
 * kcov descriptor (one per opened debugfs file).
 * State transitions of the descriptor:
 *  - initial state after open()
 *  - then there must be a single ioctl(KCOV_INIT_TRACE) call
 *  - then, mmap() call (several calls are allowed but not useful)
 *  - then, repeated enable/disable for a task (only one task a time allowed)
 */
struct kcov {
	/*
	 * Reference counter. We keep one for:
	 *  - opened file descriptor
	 *  - task with enabled coverage (we can't unwire it from another task)
	 */
	atomic_t		refcount;
	/* The lock protects mode, size, area and t. */
	spinlock_t		lock;
	enum kcov_mode		mode;
	/* Size of arena (in long's for KCOV_MODE_TRACE). */
	unsigned		size;
	/* Coverage buffer shared with user space. */
	void			*area;
	/* Task for which we collect coverage, or NULL. */
	struct task_struct	*t;
};

/*
 * Entry point from instrumented code.
 * This is called once per basic-block/edge.
 */
void notrace __sanitizer_cov_trace_pc(void)
{
	struct task_struct *t;
	enum kcov_mode mode;

	t = current;
	/*
	 * We are interested in code coverage as a function of a syscall inputs,
	 * so we ignore code executed in interrupts.
	 */
	if (!t || !in_task())
		return;
	mode = READ_ONCE(t->kcov_mode);
	if (mode == KCOV_MODE_TRACE) {
		unsigned long *area;
		unsigned long pos;
		unsigned long ip = _RET_IP_;

#ifdef CONFIG_RANDOMIZE_BASE
		ip -= kaslr_offset();
#endif

		/*
		 * There is some code that runs in interrupts but for which
		 * in_interrupt() returns false (e.g. preempt_schedule_irq()).
		 * READ_ONCE()/barrier() effectively provides load-acquire wrt
		 * interrupts, there are paired barrier()/WRITE_ONCE() in
		 * kcov_ioctl_locked().
		 */
		barrier();
		area = t->kcov_area;
		/* The first word is number of subsequent PCs. */
		pos = READ_ONCE(area[0]) + 1;
		if (likely(pos < t->kcov_size)) {
			area[pos] = ip;
			WRITE_ONCE(area[0], pos);
		}
	}
}
EXPORT_SYMBOL(__sanitizer_cov_trace_pc);

static void kcov_get(struct kcov *kcov)
{
	atomic_inc(&kcov->refcount);
}

static void kcov_put(struct kcov *kcov)
{
	if (atomic_dec_and_test(&kcov->refcount)) {
		vfree(kcov->area);
		kfree(kcov);
	}
}

void kcov_task_init(struct task_struct *t)
{
	WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);
	barrier();
	t->kcov_size = 0;
	t->kcov_area = NULL;
	t->kcov = NULL;
}

void kcov_task_exit(struct task_struct *t)
{
	struct kcov *kcov;

	kcov = t->kcov;
	if (kcov == NULL)
		return;
	spin_lock(&kcov->lock);
	if (WARN_ON(kcov->t != t)) {
		spin_unlock(&kcov->lock);
		return;
	}
	/* Just to not leave dangling references behind. */
	kcov_task_init(t);
	kcov->t = NULL;
	spin_unlock(&kcov->lock);
	kcov_put(kcov);
}

static int kcov_mmap(struct file *filep, struct vm_area_struct *vma)
{
	int res = 0;
	void *area;
	struct kcov *kcov = vma->vm_file->private_data;
	unsigned long size, off;
	struct page *page;

	area = vmalloc_user(vma->vm_end - vma->vm_start);
	if (!area)
		return -ENOMEM;

	spin_lock(&kcov->lock);
	size = kcov->size * sizeof(unsigned long);
	if (kcov->mode == KCOV_MODE_DISABLED || vma->vm_pgoff != 0 ||
	    vma->vm_end - vma->vm_start != size) {
		res = -EINVAL;
		goto exit;
	}
	if (!kcov->area) {
		kcov->area = area;
		vma->vm_flags |= VM_DONTEXPAND;
		spin_unlock(&kcov->lock);
		for (off = 0; off < size; off += PAGE_SIZE) {
			page = vmalloc_to_page(kcov->area + off);
			if (vm_insert_page(vma, vma->vm_start + off, page))
				WARN_ONCE(1, "vm_insert_page() failed");
		}
		return 0;
	}
exit:
	spin_unlock(&kcov->lock);
	vfree(area);
	return res;
}

static int kcov_open(struct inode *inode, struct file *filep)
{
	struct kcov *kcov;

	kcov = kzalloc(sizeof(*kcov), GFP_KERNEL);
	if (!kcov)
		return -ENOMEM;
	atomic_set(&kcov->refcount, 1);
	spin_lock_init(&kcov->lock);
	filep->private_data = kcov;
	return nonseekable_open(inode, filep);
}

static int kcov_close(struct inode *inode, struct file *filep)
{
	kcov_put(filep->private_data);
	return 0;
}

static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
			     unsigned long arg)
{
	struct task_struct *t;
	unsigned long size, unused;

	switch (cmd) {
	case KCOV_INIT_TRACE:
		/*
		 * Enable kcov in trace mode and setup buffer size.
		 * Must happen before anything else.
		 */
		if (kcov->mode != KCOV_MODE_DISABLED)
			return -EBUSY;
		/*
		 * Size must be at least 2 to hold current position and one PC.
		 * Later we allocate size * sizeof(unsigned long) memory,
		 * that must not overflow.
		 */
		size = arg;
		if (size < 2 || size > INT_MAX / sizeof(unsigned long))
			return -EINVAL;
		kcov->size = size;
		kcov->mode = KCOV_MODE_TRACE;
		return 0;
	case KCOV_ENABLE:
		/*
		 * Enable coverage for the current task.
		 * At this point user must have been enabled trace mode,
		 * and mmapped the file. Coverage collection is disabled only
		 * at task exit or voluntary by KCOV_DISABLE. After that it can
		 * be enabled for another task.
		 */
		unused = arg;
		if (unused != 0 || kcov->mode == KCOV_MODE_DISABLED ||
		    kcov->area == NULL)
			return -EINVAL;
		t = current;
		if (kcov->t != NULL || t->kcov != NULL)
			return -EBUSY;
		/* Cache in task struct for performance. */
		t->kcov_size = kcov->size;
		t->kcov_area = kcov->area;
		/* See comment in __sanitizer_cov_trace_pc(). */
		barrier();
		WRITE_ONCE(t->kcov_mode, kcov->mode);
		t->kcov = kcov;
		kcov->t = t;
		/* This is put either in kcov_task_exit() or in KCOV_DISABLE. */
		kcov_get(kcov);
		return 0;
	case KCOV_DISABLE:
		/* Disable coverage for the current task. */
		unused = arg;
		if (unused != 0 || current->kcov != kcov)
			return -EINVAL;
		t = current;
		if (WARN_ON(kcov->t != t))
			return -EINVAL;
		kcov_task_init(t);
		kcov->t = NULL;
		kcov_put(kcov);
		return 0;
	default:
		return -ENOTTY;
	}
}

static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
{
	struct kcov *kcov;
	int res;

	kcov = filep->private_data;
	spin_lock(&kcov->lock);
	res = kcov_ioctl_locked(kcov, cmd, arg);
	spin_unlock(&kcov->lock);
	return res;
}

static const struct file_operations kcov_fops = {
	.open		= kcov_open,
	.unlocked_ioctl	= kcov_ioctl,
	.compat_ioctl	= kcov_ioctl,
	.mmap		= kcov_mmap,
	.release        = kcov_close,
};

static int __init kcov_init(void)
{
	/*
	 * The kcov debugfs file won't ever get removed and thus,
	 * there is no need to protect it against removal races. The
	 * use of debugfs_create_file_unsafe() is actually safe here.
	 */
	if (!debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops)) {
		pr_err("failed to create kcov in debugfs\n");
		return -ENOMEM;
	}
	return 0;
}

device_initcall(kcov_init);
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
5c9a8750 DV	2	#define pr_fmt(fmt) "kcov: " fmt
5c9a8750 DV	3
36f05ae8	4	#define DISABLE_BRANCH_PROFILING
db862358	5	#include <linux/atomic.h>
5c9a8750	6	#include <linux/compiler.h>
db862358 KW	7	#include <linux/errno.h>
db862358 KW	8	#include <linux/export.h>
5c9a8750 DV	9	#include <linux/types.h>
	10	#include <linux/file.h>
	11	#include <linux/fs.h>
db862358	12	#include <linux/init.h>
5c9a8750	13	#include <linux/mm.h>
db862358	14	#include <linux/preempt.h>
5c9a8750	15	#include <linux/printk.h>
166ad0e1	16	#include <linux/sched.h>
5c9a8750 DV	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>
4983f0ab	23	#include <asm/setup.h>
5c9a8750 DV	24
	25	/*
	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)
	32	*/
	33	struct kcov {
	34	/*
	35	* Reference counter. We keep one for:
	36	* - opened file descriptor
	37	* - task with enabled coverage (we can't unwire it from another task)
	38	*/
	39	atomic_t refcount;
	40	/* The lock protects mode, size, area and t. */
	41	spinlock_t lock;
	42	enum kcov_mode mode;
	43	/* Size of arena (in long's for KCOV_MODE_TRACE). */
	44	unsigned size;
	45	/* Coverage buffer shared with user space. */
	46	void *area;
	47	/* Task for which we collect coverage, or NULL. */
	48	struct task_struct *t;
	49	};
	50
	51	/*
	52	* Entry point from instrumented code.
	53	* This is called once per basic-block/edge.
	54	*/
bdab42df	55	void notrace __sanitizer_cov_trace_pc(void)
5c9a8750 DV	56	{
	57	struct task_struct *t;
	58	enum kcov_mode mode;
	59
	60	t = current;
	61	/*
	62	* We are interested in code coverage as a function of a syscall inputs,
	63	* so we ignore code executed in interrupts.
	64	*/
f61e869d	65	if (!t \|\| !in_task())
5c9a8750 DV	66	return;
	67	mode = READ_ONCE(t->kcov_mode);
	68	if (mode == KCOV_MODE_TRACE) {
	69	unsigned long *area;
	70	unsigned long pos;
4983f0ab AP	71	unsigned long ip = _RET_IP_;
	72
	73	#ifdef CONFIG_RANDOMIZE_BASE
	74	ip -= kaslr_offset();
	75	#endif
5c9a8750 DV	76
	77	/*
	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().
	83	*/
	84	barrier();
	85	area = t->kcov_area;
	86	/* The first word is number of subsequent PCs. */
	87	pos = READ_ONCE(area[0]) + 1;
	88	if (likely(pos < t->kcov_size)) {
4983f0ab	89	area[pos] = ip;
5c9a8750 DV	90	WRITE_ONCE(area[0], pos);
	91	}
	92	}
	93	}
	94	EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
	95
	96	static void kcov_get(struct kcov *kcov)
	97	{
	98	atomic_inc(&kcov->refcount);
	99	}
	100
	101	static void kcov_put(struct kcov *kcov)
	102	{
	103	if (atomic_dec_and_test(&kcov->refcount)) {
	104	vfree(kcov->area);
	105	kfree(kcov);
	106	}
	107	}
	108
	109	void kcov_task_init(struct task_struct *t)
	110	{
a45f5ee6 MR	111	WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);
a45f5ee6 MR	112	barrier();
5c9a8750 DV	113	t->kcov_size = 0;
	114	t->kcov_area = NULL;
	115	t->kcov = NULL;
	116	}
	117
	118	void kcov_task_exit(struct task_struct *t)
	119	{
	120	struct kcov *kcov;
	121
	122	kcov = t->kcov;
	123	if (kcov == NULL)
	124	return;
	125	spin_lock(&kcov->lock);
	126	if (WARN_ON(kcov->t != t)) {
	127	spin_unlock(&kcov->lock);
	128	return;
	129	}
	130	/* Just to not leave dangling references behind. */
	131	kcov_task_init(t);
	132	kcov->t = NULL;
	133	spin_unlock(&kcov->lock);
	134	kcov_put(kcov);
	135	}
	136
	137	static int kcov_mmap(struct file filep, struct vm_area_struct vma)
	138	{
	139	int res = 0;
	140	void *area;
	141	struct kcov *kcov = vma->vm_file->private_data;
	142	unsigned long size, off;
	143	struct page *page;
	144
	145	area = vmalloc_user(vma->vm_end - vma->vm_start);
	146	if (!area)
	147	return -ENOMEM;
	148
	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) {
	153	res = -EINVAL;
	154	goto exit;
	155	}
	156	if (!kcov->area) {
	157	kcov->area = area;
	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");
	164	}
	165	return 0;
	166	}
	167	exit:
	168	spin_unlock(&kcov->lock);
	169	vfree(area);
	170	return res;
	171	}
	172
	173	static int kcov_open(struct inode inode, struct file filep)
	174	{
	175	struct kcov *kcov;
	176
177	kcov = kzalloc(sizeof(*kcov), GFP_KERNEL);
178	if (!kcov)
179	return -ENOMEM;
180	atomic_set(&kcov->refcount, 1);
181	spin_lock_init(&kcov->lock);
182	filep->private_data = kcov;
183	return nonseekable_open(inode, filep);
184	}
185
186	static int kcov_close(struct inode inode, struct file filep)
187	{
188	kcov_put(filep->private_data);
189	return 0;
190	}
191
192	static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
193	unsigned long arg)
194	{
195	struct task_struct *t;
196	unsigned long size, unused;
197
198	switch (cmd) {
199	case KCOV_INIT_TRACE:
200	/*
201	* Enable kcov in trace mode and setup buffer size.
202	* Must happen before anything else.
203	*/
204	if (kcov->mode != KCOV_MODE_DISABLED)
205	return -EBUSY;
206	/*
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.
210	*/
211	size = arg;
212	if (size < 2 \|\| size > INT_MAX / sizeof(unsigned long))
213	return -EINVAL;
214	kcov->size = size;
215	kcov->mode = KCOV_MODE_TRACE;
216	return 0;
217	case KCOV_ENABLE:
218	/*
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.
224	*/
225	unused = arg;
226	if (unused != 0 \|\| kcov->mode == KCOV_MODE_DISABLED \|\|
227	kcov->area == NULL)
228	return -EINVAL;
5c9a8750	229	t = current;
4249e8af DV	230	if (kcov->t != NULL \|\| t->kcov != NULL)
4249e8af DV	231	return -EBUSY;
5c9a8750 DV	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(). */
	236	barrier();
	237	WRITE_ONCE(t->kcov_mode, kcov->mode);
	238	t->kcov = kcov;
	239	kcov->t = t;
	240	/* This is put either in kcov_task_exit() or in KCOV_DISABLE. */
	241	kcov_get(kcov);
	242	return 0;
	243	case KCOV_DISABLE:
	244	/* Disable coverage for the current task. */
	245	unused = arg;
	246	if (unused != 0 \|\| current->kcov != kcov)
	247	return -EINVAL;
	248	t = current;
	249	if (WARN_ON(kcov->t != t))
	250	return -EINVAL;
	251	kcov_task_init(t);
	252	kcov->t = NULL;
	253	kcov_put(kcov);
	254	return 0;
	255	default:
	256	return -ENOTTY;
	257	}
	258	}
	259
	260	static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
	261	{
	262	struct kcov *kcov;
	263	int res;
	264
	265	kcov = filep->private_data;
	266	spin_lock(&kcov->lock);
	267	res = kcov_ioctl_locked(kcov, cmd, arg);
	268	spin_unlock(&kcov->lock);
	269	return res;
	270	}
	271
	272	static const struct file_operations kcov_fops = {
	273	.open = kcov_open,
	274	.unlocked_ioctl = kcov_ioctl,
7483e5d4	275	.compat_ioctl = kcov_ioctl,
5c9a8750 DV	276	.mmap = kcov_mmap,
	277	.release = kcov_close,
	278	};
	279
	280	static int __init kcov_init(void)
	281	{
df4565f9 NS	282	/*
	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.
	286	*/
	287	if (!debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops)) {
5c9a8750 DV	288	pr_err("failed to create kcov in debugfs\n");
	289	return -ENOMEM;
	290	}
	291	return 0;
	292	}
	293
	294	device_initcall(kcov_init);