[thirdparty/linux.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 <linux/refcount.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)
	 */
	refcount_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 notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
{
	unsigned int 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 notrace 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 notrace 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)
{
	refcount_inc(&kcov->refcount);
}

static void kcov_put(struct kcov *kcov)
{
	if (refcount_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;
	refcount_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;
}

/*
 * Fault in a lazily-faulted vmalloc area before it can be used by
 * __santizer_cov_trace_pc(), to avoid recursion issues if any code on the
 * vmalloc fault handling path is instrumented.
 */
static void kcov_fault_in_area(struct kcov *kcov)
{
	unsigned long stride = PAGE_SIZE / sizeof(unsigned long);
	unsigned long *area = kcov->area;
	unsigned long offset;

	for (offset = 0; offset < kcov->size; offset += stride)
		READ_ONCE(area[offset]);
}

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;
		kcov_fault_in_area(kcov);
		/* 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.
	 */
	debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops);

	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>
39e07cb6	23	#include <linux/refcount.h>
4983f0ab	24	#include <asm/setup.h>
5c9a8750	25
ded97d2c VC	26	/* Number of 64-bit words written per one comparison: */
	27	#define KCOV_WORDS_PER_CMP 4
	28
5c9a8750 DV	29	/*
	30	* kcov descriptor (one per opened debugfs file).
	31	* State transitions of the descriptor:
	32	* - initial state after open()
	33	* - then there must be a single ioctl(KCOV_INIT_TRACE) call
	34	* - then, mmap() call (several calls are allowed but not useful)
ded97d2c VC	35	* - then, ioctl(KCOV_ENABLE, arg), where arg is
	36	* KCOV_TRACE_PC - to trace only the PCs
	37	* or
	38	* KCOV_TRACE_CMP - to trace only the comparison operands
	39	* - then, ioctl(KCOV_DISABLE) to disable the task.
	40	* Enabling/disabling ioctls can be repeated (only one task a time allowed).
5c9a8750 DV	41	*/
	42	struct kcov {
	43	/*
	44	* Reference counter. We keep one for:
	45	* - opened file descriptor
	46	* - task with enabled coverage (we can't unwire it from another task)
	47	*/
39e07cb6	48	refcount_t refcount;
5c9a8750 DV	49	/* The lock protects mode, size, area and t. */
	50	spinlock_t lock;
	51	enum kcov_mode mode;
	52	/* Size of arena (in long's for KCOV_MODE_TRACE). */
	53	unsigned size;
	54	/* Coverage buffer shared with user space. */
	55	void *area;
	56	/* Task for which we collect coverage, or NULL. */
	57	struct task_struct *t;
	58	};
	59
903e8ff8	60	static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
5c9a8750	61	{
0ed557aa	62	unsigned int mode;
5c9a8750	63
5c9a8750 DV	64	/*
	65	* We are interested in code coverage as a function of a syscall inputs,
	66	* so we ignore code executed in interrupts.
	67	*/
fcf4edac	68	if (!in_task())
ded97d2c	69	return false;
5c9a8750	70	mode = READ_ONCE(t->kcov_mode);
ded97d2c VC	71	/*
	72	* There is some code that runs in interrupts but for which
	73	* in_interrupt() returns false (e.g. preempt_schedule_irq()).
	74	* READ_ONCE()/barrier() effectively provides load-acquire wrt
	75	* interrupts, there are paired barrier()/WRITE_ONCE() in
	76	* kcov_ioctl_locked().
	77	*/
	78	barrier();
	79	return mode == needed_mode;
	80	}
4983f0ab	81
903e8ff8	82	static notrace unsigned long canonicalize_ip(unsigned long ip)
ded97d2c	83	{
4983f0ab	84	#ifdef CONFIG_RANDOMIZE_BASE
ded97d2c	85	ip -= kaslr_offset();
4983f0ab	86	#endif
ded97d2c VC	87	return ip;
ded97d2c VC	88	}
5c9a8750	89
ded97d2c VC	90	/*
	91	* Entry point from instrumented code.
	92	* This is called once per basic-block/edge.
	93	*/
	94	void notrace __sanitizer_cov_trace_pc(void)
	95	{
	96	struct task_struct *t;
	97	unsigned long *area;
	98	unsigned long ip = canonicalize_ip(_RET_IP_);
	99	unsigned long pos;
	100
	101	t = current;
	102	if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t))
	103	return;
	104
	105	area = t->kcov_area;
	106	/* The first 64-bit word is the number of subsequent PCs. */
	107	pos = READ_ONCE(area[0]) + 1;
	108	if (likely(pos < t->kcov_size)) {
	109	area[pos] = ip;
	110	WRITE_ONCE(area[0], pos);
5c9a8750 DV	111	}
	112	}
	113	EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
	114
ded97d2c	115	#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
63472443	116	static void notrace write_comp_data(u64 type, u64 arg1, u64 arg2, u64 ip)
ded97d2c VC	117	{
	118	struct task_struct *t;
	119	u64 *area;
	120	u64 count, start_index, end_pos, max_pos;
	121
	122	t = current;
	123	if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t))
	124	return;
	125
	126	ip = canonicalize_ip(ip);
	127
	128	/*
	129	* We write all comparison arguments and types as u64.
	130	* The buffer was allocated for t->kcov_size unsigned longs.
	131	*/
	132	area = (u64 *)t->kcov_area;
	133	max_pos = t->kcov_size * sizeof(unsigned long);
	134
	135	count = READ_ONCE(area[0]);
	136
	137	/* Every record is KCOV_WORDS_PER_CMP 64-bit words. */
	138	start_index = 1 + count * KCOV_WORDS_PER_CMP;
	139	end_pos = (start_index + KCOV_WORDS_PER_CMP) * sizeof(u64);
	140	if (likely(end_pos <= max_pos)) {
	141	area[start_index] = type;
	142	area[start_index + 1] = arg1;
	143	area[start_index + 2] = arg2;
	144	area[start_index + 3] = ip;
	145	WRITE_ONCE(area[0], count + 1);
	146	}
	147	}
	148
	149	void notrace __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2)
	150	{
	151	write_comp_data(KCOV_CMP_SIZE(0), arg1, arg2, _RET_IP_);
	152	}
	153	EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1);
	154
	155	void notrace __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2)
	156	{
	157	write_comp_data(KCOV_CMP_SIZE(1), arg1, arg2, _RET_IP_);
	158	}
	159	EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2);
	160
689d77f0	161	void notrace __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2)
ded97d2c VC	162	{
	163	write_comp_data(KCOV_CMP_SIZE(2), arg1, arg2, _RET_IP_);
	164	}
	165	EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4);
	166
	167	void notrace __sanitizer_cov_trace_cmp8(u64 arg1, u64 arg2)
	168	{
	169	write_comp_data(KCOV_CMP_SIZE(3), arg1, arg2, _RET_IP_);
	170	}
	171	EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8);
	172
	173	void notrace __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2)
	174	{
	175	write_comp_data(KCOV_CMP_SIZE(0) \| KCOV_CMP_CONST, arg1, arg2,
	176	_RET_IP_);
	177	}
	178	EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1);
	179
	180	void notrace __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2)
	181	{
	182	write_comp_data(KCOV_CMP_SIZE(1) \| KCOV_CMP_CONST, arg1, arg2,
	183	_RET_IP_);
	184	}
	185	EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2);
	186
689d77f0	187	void notrace __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2)
ded97d2c VC	188	{
	189	write_comp_data(KCOV_CMP_SIZE(2) \| KCOV_CMP_CONST, arg1, arg2,
	190	_RET_IP_);
	191	}
	192	EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4);
	193
	194	void notrace __sanitizer_cov_trace_const_cmp8(u64 arg1, u64 arg2)
	195	{
	196	write_comp_data(KCOV_CMP_SIZE(3) \| KCOV_CMP_CONST, arg1, arg2,
	197	_RET_IP_);
	198	}
	199	EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8);
	200
	201	void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases)
	202	{
	203	u64 i;
	204	u64 count = cases[0];
	205	u64 size = cases[1];
	206	u64 type = KCOV_CMP_CONST;
	207
	208	switch (size) {
	209	case 8:
	210	type \|= KCOV_CMP_SIZE(0);
	211	break;
	212	case 16:
	213	type \|= KCOV_CMP_SIZE(1);
	214	break;
	215	case 32:
	216	type \|= KCOV_CMP_SIZE(2);
	217	break;
	218	case 64:
	219	type \|= KCOV_CMP_SIZE(3);
	220	break;
	221	default:
	222	return;
	223	}
	224	for (i = 0; i < count; i++)
	225	write_comp_data(type, cases[i + 2], val, _RET_IP_);
	226	}
	227	EXPORT_SYMBOL(__sanitizer_cov_trace_switch);
	228	#endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */
	229
5c9a8750 DV	230	static void kcov_get(struct kcov *kcov)
5c9a8750 DV	231	{
39e07cb6	232	refcount_inc(&kcov->refcount);
5c9a8750 DV	233	}
	234
	235	static void kcov_put(struct kcov *kcov)
	236	{
39e07cb6	237	if (refcount_dec_and_test(&kcov->refcount)) {
5c9a8750 DV	238	vfree(kcov->area);
	239	kfree(kcov);
	240	}
	241	}
	242
	243	void kcov_task_init(struct task_struct *t)
	244	{
c9484b98 MR	245	WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);
c9484b98 MR	246	barrier();
5c9a8750 DV	247	t->kcov_size = 0;
	248	t->kcov_area = NULL;
	249	t->kcov = NULL;
	250	}
	251
	252	void kcov_task_exit(struct task_struct *t)
	253	{
	254	struct kcov *kcov;
	255
	256	kcov = t->kcov;
	257	if (kcov == NULL)
	258	return;
	259	spin_lock(&kcov->lock);
	260	if (WARN_ON(kcov->t != t)) {
	261	spin_unlock(&kcov->lock);
	262	return;
	263	}
	264	/* Just to not leave dangling references behind. */
	265	kcov_task_init(t);
	266	kcov->t = NULL;
ded97d2c	267	kcov->mode = KCOV_MODE_INIT;
5c9a8750 DV	268	spin_unlock(&kcov->lock);
	269	kcov_put(kcov);
	270	}
	271
	272	static int kcov_mmap(struct file filep, struct vm_area_struct vma)
	273	{
	274	int res = 0;
	275	void *area;
	276	struct kcov *kcov = vma->vm_file->private_data;
	277	unsigned long size, off;
	278	struct page *page;
	279
	280	area = vmalloc_user(vma->vm_end - vma->vm_start);
	281	if (!area)
	282	return -ENOMEM;
	283
	284	spin_lock(&kcov->lock);
	285	size = kcov->size * sizeof(unsigned long);
ded97d2c	286	if (kcov->mode != KCOV_MODE_INIT \|\| vma->vm_pgoff != 0 \|\|
5c9a8750 DV	287	vma->vm_end - vma->vm_start != size) {
	288	res = -EINVAL;
	289	goto exit;
	290	}
	291	if (!kcov->area) {
	292	kcov->area = area;
	293	vma->vm_flags \|= VM_DONTEXPAND;
	294	spin_unlock(&kcov->lock);
	295	for (off = 0; off < size; off += PAGE_SIZE) {
	296	page = vmalloc_to_page(kcov->area + off);
	297	if (vm_insert_page(vma, vma->vm_start + off, page))
	298	WARN_ONCE(1, "vm_insert_page() failed");
	299	}
	300	return 0;
	301	}
	302	exit:
	303	spin_unlock(&kcov->lock);
	304	vfree(area);
	305	return res;
	306	}
	307
	308	static int kcov_open(struct inode inode, struct file filep)
	309	{
	310	struct kcov *kcov;
	311
	312	kcov = kzalloc(sizeof(*kcov), GFP_KERNEL);
	313	if (!kcov)
	314	return -ENOMEM;
ded97d2c	315	kcov->mode = KCOV_MODE_DISABLED;
39e07cb6	316	refcount_set(&kcov->refcount, 1);
5c9a8750 DV	317	spin_lock_init(&kcov->lock);
	318	filep->private_data = kcov;
	319	return nonseekable_open(inode, filep);
	320	}
	321
	322	static int kcov_close(struct inode inode, struct file filep)
	323	{
	324	kcov_put(filep->private_data);
	325	return 0;
	326	}
	327
dc55daff MR	328	/*
	329	* Fault in a lazily-faulted vmalloc area before it can be used by
	330	* __santizer_cov_trace_pc(), to avoid recursion issues if any code on the
	331	* vmalloc fault handling path is instrumented.
	332	*/
	333	static void kcov_fault_in_area(struct kcov *kcov)
	334	{
	335	unsigned long stride = PAGE_SIZE / sizeof(unsigned long);
	336	unsigned long *area = kcov->area;
	337	unsigned long offset;
	338
	339	for (offset = 0; offset < kcov->size; offset += stride)
	340	READ_ONCE(area[offset]);
	341	}
	342
5c9a8750 DV	343	static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
	344	unsigned long arg)
	345	{
	346	struct task_struct *t;
	347	unsigned long size, unused;
	348
	349	switch (cmd) {
	350	case KCOV_INIT_TRACE:
	351	/*
	352	* Enable kcov in trace mode and setup buffer size.
	353	* Must happen before anything else.
	354	*/
	355	if (kcov->mode != KCOV_MODE_DISABLED)
	356	return -EBUSY;
	357	/*
	358	* Size must be at least 2 to hold current position and one PC.
	359	* Later we allocate size * sizeof(unsigned long) memory,
	360	* that must not overflow.
	361	*/
	362	size = arg;
	363	if (size < 2 \|\| size > INT_MAX / sizeof(unsigned long))
	364	return -EINVAL;
	365	kcov->size = size;
ded97d2c	366	kcov->mode = KCOV_MODE_INIT;
5c9a8750 DV	367	return 0;
	368	case KCOV_ENABLE:
	369	/*
	370	* Enable coverage for the current task.
	371	* At this point user must have been enabled trace mode,
	372	* and mmapped the file. Coverage collection is disabled only
	373	* at task exit or voluntary by KCOV_DISABLE. After that it can
	374	* be enabled for another task.
	375	*/
ded97d2c	376	if (kcov->mode != KCOV_MODE_INIT \|\| !kcov->area)
5c9a8750	377	return -EINVAL;
a77660d2 DV	378	t = current;
a77660d2 DV	379	if (kcov->t != NULL \|\| t->kcov != NULL)
5c9a8750	380	return -EBUSY;
ded97d2c VC	381	if (arg == KCOV_TRACE_PC)
	382	kcov->mode = KCOV_MODE_TRACE_PC;
	383	else if (arg == KCOV_TRACE_CMP)
	384	#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
	385	kcov->mode = KCOV_MODE_TRACE_CMP;
	386	#else
	387	return -ENOTSUPP;
	388	#endif
	389	else
	390	return -EINVAL;
dc55daff	391	kcov_fault_in_area(kcov);
5c9a8750 DV	392	/* Cache in task struct for performance. */
	393	t->kcov_size = kcov->size;
	394	t->kcov_area = kcov->area;
ded97d2c	395	/* See comment in check_kcov_mode(). */
5c9a8750 DV	396	barrier();
	397	WRITE_ONCE(t->kcov_mode, kcov->mode);
	398	t->kcov = kcov;
	399	kcov->t = t;
	400	/* This is put either in kcov_task_exit() or in KCOV_DISABLE. */
	401	kcov_get(kcov);
	402	return 0;
	403	case KCOV_DISABLE:
	404	/* Disable coverage for the current task. */
	405	unused = arg;
	406	if (unused != 0 \|\| current->kcov != kcov)
	407	return -EINVAL;
	408	t = current;
	409	if (WARN_ON(kcov->t != t))
	410	return -EINVAL;
	411	kcov_task_init(t);
	412	kcov->t = NULL;
ded97d2c	413	kcov->mode = KCOV_MODE_INIT;
5c9a8750 DV	414	kcov_put(kcov);
	415	return 0;
	416	default:
	417	return -ENOTTY;
	418	}
	419	}
	420
	421	static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
	422	{
	423	struct kcov *kcov;
	424	int res;
	425
	426	kcov = filep->private_data;
	427	spin_lock(&kcov->lock);
	428	res = kcov_ioctl_locked(kcov, cmd, arg);
	429	spin_unlock(&kcov->lock);
	430	return res;
	431	}
	432
	433	static const struct file_operations kcov_fops = {
	434	.open = kcov_open,
	435	.unlocked_ioctl = kcov_ioctl,
7483e5d4	436	.compat_ioctl = kcov_ioctl,
5c9a8750 DV	437	.mmap = kcov_mmap,
	438	.release = kcov_close,
	439	};
	440
	441	static int __init kcov_init(void)
	442	{
df4565f9 NS	443	/*
	444	* The kcov debugfs file won't ever get removed and thus,
	445	* there is no need to protect it against removal races. The
	446	* use of debugfs_create_file_unsafe() is actually safe here.
	447	*/
ec9672d5 GKH	448	debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops);
ec9672d5 GKH	449
5c9a8750 DV	450	return 0;
	451	}
	452
	453	device_initcall(kcov_init);