[mirror_ubuntu-bionic-kernel.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>

/* Number of 64-bit words written per one comparison: */
#define KCOV_WORDS_PER_CMP 4

/*
 * 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, ioctl(KCOV_ENABLE, arg), where arg is
 *	KCOV_TRACE_PC - to trace only the PCs
 *	or
 *	KCOV_TRACE_CMP - to trace only the comparison operands
 *  - then, ioctl(KCOV_DISABLE) to disable the task.
 * Enabling/disabling ioctls can be repeated (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;
};

static bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
{
	enum kcov_mode mode;

	/*
	 * We are interested in code coverage as a function of a syscall inputs,
	 * so we ignore code executed in interrupts.
	 */
	if (!in_task())
		return false;
	mode = READ_ONCE(t->kcov_mode);
	/*
	 * 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();
	return mode == needed_mode;
}

static unsigned long canonicalize_ip(unsigned long ip)
{
#ifdef CONFIG_RANDOMIZE_BASE
	ip -= kaslr_offset();
#endif
	return ip;
}

/*
 * Entry point from instrumented code.
 * This is called once per basic-block/edge.
 */
void notrace __sanitizer_cov_trace_pc(void)
{
	struct task_struct *t;
	unsigned long *area;
	unsigned long ip = canonicalize_ip(_RET_IP_);
	unsigned long pos;

	t = current;
	if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t))
		return;

	area = t->kcov_area;
	/* The first 64-bit word is the 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);

#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
static void write_comp_data(u64 type, u64 arg1, u64 arg2, u64 ip)
{
	struct task_struct *t;
	u64 *area;
	u64 count, start_index, end_pos, max_pos;

	t = current;
	if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t))
		return;

	ip = canonicalize_ip(ip);

	/*
	 * We write all comparison arguments and types as u64.
	 * The buffer was allocated for t->kcov_size unsigned longs.
	 */
	area = (u64 *)t->kcov_area;
	max_pos = t->kcov_size * sizeof(unsigned long);

	count = READ_ONCE(area[0]);

	/* Every record is KCOV_WORDS_PER_CMP 64-bit words. */
	start_index = 1 + count * KCOV_WORDS_PER_CMP;
	end_pos = (start_index + KCOV_WORDS_PER_CMP) * sizeof(u64);
	if (likely(end_pos <= max_pos)) {
		area[start_index] = type;
		area[start_index + 1] = arg1;
		area[start_index + 2] = arg2;
		area[start_index + 3] = ip;
		WRITE_ONCE(area[0], count + 1);
	}
}

void notrace __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2)
{
	write_comp_data(KCOV_CMP_SIZE(0), arg1, arg2, _RET_IP_);
}
EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1);

void notrace __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2)
{
	write_comp_data(KCOV_CMP_SIZE(1), arg1, arg2, _RET_IP_);
}
EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2);

void notrace __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2)
{
	write_comp_data(KCOV_CMP_SIZE(2), arg1, arg2, _RET_IP_);
}
EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4);

void notrace __sanitizer_cov_trace_cmp8(u64 arg1, u64 arg2)
{
	write_comp_data(KCOV_CMP_SIZE(3), arg1, arg2, _RET_IP_);
}
EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8);

void notrace __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2)
{
	write_comp_data(KCOV_CMP_SIZE(0) | KCOV_CMP_CONST, arg1, arg2,
			_RET_IP_);
}
EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1);

void notrace __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2)
{
	write_comp_data(KCOV_CMP_SIZE(1) | KCOV_CMP_CONST, arg1, arg2,
			_RET_IP_);
}
EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2);

void notrace __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2)
{
	write_comp_data(KCOV_CMP_SIZE(2) | KCOV_CMP_CONST, arg1, arg2,
			_RET_IP_);
}
EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4);

void notrace __sanitizer_cov_trace_const_cmp8(u64 arg1, u64 arg2)
{
	write_comp_data(KCOV_CMP_SIZE(3) | KCOV_CMP_CONST, arg1, arg2,
			_RET_IP_);
}
EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8);

void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases)
{
	u64 i;
	u64 count = cases[0];
	u64 size = cases[1];
	u64 type = KCOV_CMP_CONST;

	switch (size) {
	case 8:
		type |= KCOV_CMP_SIZE(0);
		break;
	case 16:
		type |= KCOV_CMP_SIZE(1);
		break;
	case 32:
		type |= KCOV_CMP_SIZE(2);
		break;
	case 64:
		type |= KCOV_CMP_SIZE(3);
		break;
	default:
		return;
	}
	for (i = 0; i < count; i++)
		write_comp_data(type, cases[i + 2], val, _RET_IP_);
}
EXPORT_SYMBOL(__sanitizer_cov_trace_switch);
#endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */

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;
	kcov->mode = KCOV_MODE_INIT;
	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_INIT || 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;
	kcov->mode = KCOV_MODE_DISABLED;
	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_INIT;
		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.
		 */
		if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
			return -EINVAL;
		t = current;
		if (kcov->t != NULL || t->kcov != NULL)
			return -EBUSY;
		if (arg == KCOV_TRACE_PC)
			kcov->mode = KCOV_MODE_TRACE_PC;
		else if (arg == KCOV_TRACE_CMP)
#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
			kcov->mode = KCOV_MODE_TRACE_CMP;
#else
		return -ENOTSUPP;
#endif
		else
			return -EINVAL;
		/* Cache in task struct for performance. */
		t->kcov_size = kcov->size;
		t->kcov_area = kcov->area;
		/* See comment in check_kcov_mode(). */
		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->mode = KCOV_MODE_INIT;
		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	24
ded97d2c VC	25	/* Number of 64-bit words written per one comparison: */
	26	#define KCOV_WORDS_PER_CMP 4
	27
5c9a8750 DV	28	/*
	29	* kcov descriptor (one per opened debugfs file).
	30	* State transitions of the descriptor:
	31	* - initial state after open()
	32	* - then there must be a single ioctl(KCOV_INIT_TRACE) call
	33	* - then, mmap() call (several calls are allowed but not useful)
ded97d2c VC	34	* - then, ioctl(KCOV_ENABLE, arg), where arg is
	35	* KCOV_TRACE_PC - to trace only the PCs
	36	* or
	37	* KCOV_TRACE_CMP - to trace only the comparison operands
	38	* - then, ioctl(KCOV_DISABLE) to disable the task.
	39	* Enabling/disabling ioctls can be repeated (only one task a time allowed).
5c9a8750 DV	40	*/
	41	struct kcov {
	42	/*
	43	* Reference counter. We keep one for:
	44	* - opened file descriptor
	45	* - task with enabled coverage (we can't unwire it from another task)
	46	*/
	47	atomic_t refcount;
	48	/* The lock protects mode, size, area and t. */
	49	spinlock_t lock;
	50	enum kcov_mode mode;
	51	/* Size of arena (in long's for KCOV_MODE_TRACE). */
	52	unsigned size;
	53	/* Coverage buffer shared with user space. */
	54	void *area;
	55	/* Task for which we collect coverage, or NULL. */
	56	struct task_struct *t;
	57	};
	58
ded97d2c	59	static bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
5c9a8750	60	{
5c9a8750 DV	61	enum kcov_mode mode;
5c9a8750 DV	62
5c9a8750 DV	63	/*
	64	* We are interested in code coverage as a function of a syscall inputs,
	65	* so we ignore code executed in interrupts.
	66	*/
fcf4edac	67	if (!in_task())
ded97d2c	68	return false;
5c9a8750	69	mode = READ_ONCE(t->kcov_mode);
ded97d2c VC	70	/*
	71	* There is some code that runs in interrupts but for which
	72	* in_interrupt() returns false (e.g. preempt_schedule_irq()).
	73	* READ_ONCE()/barrier() effectively provides load-acquire wrt
	74	* interrupts, there are paired barrier()/WRITE_ONCE() in
	75	* kcov_ioctl_locked().
	76	*/
	77	barrier();
	78	return mode == needed_mode;
	79	}
4983f0ab	80
ded97d2c VC	81	static unsigned long canonicalize_ip(unsigned long ip)
ded97d2c VC	82	{
4983f0ab	83	#ifdef CONFIG_RANDOMIZE_BASE
ded97d2c	84	ip -= kaslr_offset();
4983f0ab	85	#endif
ded97d2c VC	86	return ip;
ded97d2c VC	87	}
5c9a8750	88
ded97d2c VC	89	/*
	90	* Entry point from instrumented code.
	91	* This is called once per basic-block/edge.
	92	*/
	93	void notrace __sanitizer_cov_trace_pc(void)
	94	{
	95	struct task_struct *t;
	96	unsigned long *area;
	97	unsigned long ip = canonicalize_ip(_RET_IP_);
	98	unsigned long pos;
	99
	100	t = current;
	101	if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t))
	102	return;
	103
	104	area = t->kcov_area;
	105	/* The first 64-bit word is the number of subsequent PCs. */
	106	pos = READ_ONCE(area[0]) + 1;
	107	if (likely(pos < t->kcov_size)) {
	108	area[pos] = ip;
	109	WRITE_ONCE(area[0], pos);
5c9a8750 DV	110	}
	111	}
	112	EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
	113
ded97d2c VC	114	#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
	115	static void write_comp_data(u64 type, u64 arg1, u64 arg2, u64 ip)
	116	{
	117	struct task_struct *t;
	118	u64 *area;
	119	u64 count, start_index, end_pos, max_pos;
	120
	121	t = current;
	122	if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t))
	123	return;
	124
	125	ip = canonicalize_ip(ip);
	126
	127	/*
	128	* We write all comparison arguments and types as u64.
	129	* The buffer was allocated for t->kcov_size unsigned longs.
	130	*/
	131	area = (u64 *)t->kcov_area;
	132	max_pos = t->kcov_size * sizeof(unsigned long);
	133
	134	count = READ_ONCE(area[0]);
	135
	136	/* Every record is KCOV_WORDS_PER_CMP 64-bit words. */
	137	start_index = 1 + count * KCOV_WORDS_PER_CMP;
	138	end_pos = (start_index + KCOV_WORDS_PER_CMP) * sizeof(u64);
	139	if (likely(end_pos <= max_pos)) {
	140	area[start_index] = type;
	141	area[start_index + 1] = arg1;
	142	area[start_index + 2] = arg2;
	143	area[start_index + 3] = ip;
	144	WRITE_ONCE(area[0], count + 1);
	145	}
	146	}
	147
	148	void notrace __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2)
	149	{
	150	write_comp_data(KCOV_CMP_SIZE(0), arg1, arg2, _RET_IP_);
	151	}
	152	EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1);
	153
	154	void notrace __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2)
	155	{
	156	write_comp_data(KCOV_CMP_SIZE(1), arg1, arg2, _RET_IP_);
	157	}
	158	EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2);
	159
689d77f0	160	void notrace __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2)
ded97d2c VC	161	{
	162	write_comp_data(KCOV_CMP_SIZE(2), arg1, arg2, _RET_IP_);
	163	}
	164	EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4);
	165
	166	void notrace __sanitizer_cov_trace_cmp8(u64 arg1, u64 arg2)
	167	{
	168	write_comp_data(KCOV_CMP_SIZE(3), arg1, arg2, _RET_IP_);
	169	}
	170	EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8);
	171
	172	void notrace __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2)
	173	{
	174	write_comp_data(KCOV_CMP_SIZE(0) \| KCOV_CMP_CONST, arg1, arg2,
	175	_RET_IP_);
	176	}
	177	EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1);
	178
	179	void notrace __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2)
	180	{
	181	write_comp_data(KCOV_CMP_SIZE(1) \| KCOV_CMP_CONST, arg1, arg2,
	182	_RET_IP_);
	183	}
	184	EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2);
	185
689d77f0	186	void notrace __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2)
ded97d2c VC	187	{
	188	write_comp_data(KCOV_CMP_SIZE(2) \| KCOV_CMP_CONST, arg1, arg2,
	189	_RET_IP_);
	190	}
	191	EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4);
	192
	193	void notrace __sanitizer_cov_trace_const_cmp8(u64 arg1, u64 arg2)
	194	{
	195	write_comp_data(KCOV_CMP_SIZE(3) \| KCOV_CMP_CONST, arg1, arg2,
	196	_RET_IP_);
	197	}
	198	EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8);
	199
	200	void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases)
	201	{
	202	u64 i;
	203	u64 count = cases[0];
	204	u64 size = cases[1];
	205	u64 type = KCOV_CMP_CONST;
	206
	207	switch (size) {
	208	case 8:
	209	type \|= KCOV_CMP_SIZE(0);
	210	break;
	211	case 16:
	212	type \|= KCOV_CMP_SIZE(1);
	213	break;
	214	case 32:
	215	type \|= KCOV_CMP_SIZE(2);
	216	break;
	217	case 64:
	218	type \|= KCOV_CMP_SIZE(3);
	219	break;
	220	default:
	221	return;
	222	}
	223	for (i = 0; i < count; i++)
	224	write_comp_data(type, cases[i + 2], val, _RET_IP_);
	225	}
	226	EXPORT_SYMBOL(__sanitizer_cov_trace_switch);
	227	#endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */
	228
5c9a8750 DV	229	static void kcov_get(struct kcov *kcov)
	230	{
	231	atomic_inc(&kcov->refcount);
	232	}
	233
	234	static void kcov_put(struct kcov *kcov)
	235	{
	236	if (atomic_dec_and_test(&kcov->refcount)) {
	237	vfree(kcov->area);
	238	kfree(kcov);
	239	}
	240	}
	241
	242	void kcov_task_init(struct task_struct *t)
	243	{
e90e4ae2 MR	244	WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);
e90e4ae2 MR	245	barrier();
5c9a8750 DV	246	t->kcov_size = 0;
	247	t->kcov_area = NULL;
	248	t->kcov = NULL;
	249	}
	250
	251	void kcov_task_exit(struct task_struct *t)
	252	{
	253	struct kcov *kcov;
	254
	255	kcov = t->kcov;
	256	if (kcov == NULL)
	257	return;
	258	spin_lock(&kcov->lock);
	259	if (WARN_ON(kcov->t != t)) {
	260	spin_unlock(&kcov->lock);
	261	return;
	262	}
	263	/* Just to not leave dangling references behind. */
	264	kcov_task_init(t);
	265	kcov->t = NULL;
ded97d2c	266	kcov->mode = KCOV_MODE_INIT;
5c9a8750 DV	267	spin_unlock(&kcov->lock);
	268	kcov_put(kcov);
	269	}
	270
	271	static int kcov_mmap(struct file filep, struct vm_area_struct vma)
	272	{
	273	int res = 0;
	274	void *area;
	275	struct kcov *kcov = vma->vm_file->private_data;
	276	unsigned long size, off;
	277	struct page *page;
	278
	279	area = vmalloc_user(vma->vm_end - vma->vm_start);
	280	if (!area)
	281	return -ENOMEM;
	282
	283	spin_lock(&kcov->lock);
	284	size = kcov->size * sizeof(unsigned long);
ded97d2c	285	if (kcov->mode != KCOV_MODE_INIT \|\| vma->vm_pgoff != 0 \|\|
5c9a8750 DV	286	vma->vm_end - vma->vm_start != size) {
	287	res = -EINVAL;
	288	goto exit;
	289	}
	290	if (!kcov->area) {
	291	kcov->area = area;
	292	vma->vm_flags \|= VM_DONTEXPAND;
	293	spin_unlock(&kcov->lock);
	294	for (off = 0; off < size; off += PAGE_SIZE) {
	295	page = vmalloc_to_page(kcov->area + off);
	296	if (vm_insert_page(vma, vma->vm_start + off, page))
	297	WARN_ONCE(1, "vm_insert_page() failed");
	298	}
	299	return 0;
	300	}
	301	exit:
	302	spin_unlock(&kcov->lock);
	303	vfree(area);
	304	return res;
	305	}
	306
	307	static int kcov_open(struct inode inode, struct file filep)
	308	{
	309	struct kcov *kcov;
	310
	311	kcov = kzalloc(sizeof(*kcov), GFP_KERNEL);
	312	if (!kcov)
	313	return -ENOMEM;
ded97d2c	314	kcov->mode = KCOV_MODE_DISABLED;
5c9a8750 DV	315	atomic_set(&kcov->refcount, 1);
	316	spin_lock_init(&kcov->lock);
	317	filep->private_data = kcov;
	318	return nonseekable_open(inode, filep);
	319	}
	320
	321	static int kcov_close(struct inode inode, struct file filep)
	322	{
	323	kcov_put(filep->private_data);
	324	return 0;
	325	}
	326
	327	static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
	328	unsigned long arg)
	329	{
	330	struct task_struct *t;
	331	unsigned long size, unused;
	332
	333	switch (cmd) {
	334	case KCOV_INIT_TRACE:
	335	/*
	336	* Enable kcov in trace mode and setup buffer size.
	337	* Must happen before anything else.
	338	*/
	339	if (kcov->mode != KCOV_MODE_DISABLED)
	340	return -EBUSY;
	341	/*
	342	* Size must be at least 2 to hold current position and one PC.
	343	* Later we allocate size * sizeof(unsigned long) memory,
	344	* that must not overflow.
	345	*/
	346	size = arg;
	347	if (size < 2 \|\| size > INT_MAX / sizeof(unsigned long))
	348	return -EINVAL;
	349	kcov->size = size;
ded97d2c	350	kcov->mode = KCOV_MODE_INIT;
5c9a8750 DV	351	return 0;
	352	case KCOV_ENABLE:
	353	/*
	354	* Enable coverage for the current task.
	355	* At this point user must have been enabled trace mode,
	356	* and mmapped the file. Coverage collection is disabled only
	357	* at task exit or voluntary by KCOV_DISABLE. After that it can
	358	* be enabled for another task.
	359	*/
ded97d2c	360	if (kcov->mode != KCOV_MODE_INIT \|\| !kcov->area)
5c9a8750	361	return -EINVAL;
9bdc046c DV	362	t = current;
9bdc046c DV	363	if (kcov->t != NULL \|\| t->kcov != NULL)
5c9a8750	364	return -EBUSY;
ded97d2c VC	365	if (arg == KCOV_TRACE_PC)
	366	kcov->mode = KCOV_MODE_TRACE_PC;
	367	else if (arg == KCOV_TRACE_CMP)
	368	#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
	369	kcov->mode = KCOV_MODE_TRACE_CMP;
	370	#else
	371	return -ENOTSUPP;
	372	#endif
	373	else
	374	return -EINVAL;
5c9a8750 DV	375	/* Cache in task struct for performance. */
	376	t->kcov_size = kcov->size;
	377	t->kcov_area = kcov->area;
ded97d2c	378	/* See comment in check_kcov_mode(). */
5c9a8750 DV	379	barrier();
	380	WRITE_ONCE(t->kcov_mode, kcov->mode);
	381	t->kcov = kcov;
	382	kcov->t = t;
	383	/* This is put either in kcov_task_exit() or in KCOV_DISABLE. */
	384	kcov_get(kcov);
	385	return 0;
	386	case KCOV_DISABLE:
	387	/* Disable coverage for the current task. */
	388	unused = arg;
	389	if (unused != 0 \|\| current->kcov != kcov)
	390	return -EINVAL;
	391	t = current;
	392	if (WARN_ON(kcov->t != t))
	393	return -EINVAL;
	394	kcov_task_init(t);
	395	kcov->t = NULL;
ded97d2c	396	kcov->mode = KCOV_MODE_INIT;
5c9a8750 DV	397	kcov_put(kcov);
	398	return 0;
	399	default:
	400	return -ENOTTY;
	401	}
	402	}
	403
	404	static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
	405	{
	406	struct kcov *kcov;
	407	int res;
	408
	409	kcov = filep->private_data;
	410	spin_lock(&kcov->lock);
	411	res = kcov_ioctl_locked(kcov, cmd, arg);
	412	spin_unlock(&kcov->lock);
	413	return res;
	414	}
	415
	416	static const struct file_operations kcov_fops = {
	417	.open = kcov_open,
	418	.unlocked_ioctl = kcov_ioctl,
7483e5d4	419	.compat_ioctl = kcov_ioctl,
5c9a8750 DV	420	.mmap = kcov_mmap,
	421	.release = kcov_close,
	422	};
	423
	424	static int __init kcov_init(void)
	425	{
df4565f9 NS	426	/*
	427	* The kcov debugfs file won't ever get removed and thus,
	428	* there is no need to protect it against removal races. The
	429	* use of debugfs_create_file_unsafe() is actually safe here.
	430	*/
	431	if (!debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops)) {
5c9a8750 DV	432	pr_err("failed to create kcov in debugfs\n");
	433	return -ENOMEM;
	434	}
	435	return 0;
	436	}
	437
	438	device_initcall(kcov_init);