// 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/hashtable.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 <linux/log2.h>

  #include <asm/setup.h>

  #define kcov_debug(fmt, ...) pr_debug("%s: " fmt, __func__, ##__VA_ARGS__)

  /* 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)

  	 *  - each code section for remote coverage collection

  	 */

  	refcount_t		refcount;

  	/* The lock protects mode, size, area and t. */
  	spinlock_t		lock;
  	enum kcov_mode		mode;

  	/* Size of arena (in long's). */
  	unsigned int		size;

  	/* Coverage buffer shared with user space. */
  	void			*area;
  	/* Task for which we collect coverage, or NULL. */
  	struct task_struct	*t;

  	/* Collecting coverage from remote (background) threads. */
  	bool			remote;
  	/* Size of remote area (in long's). */
  	unsigned int		remote_size;
  	/*
  	 * Sequence is incremented each time kcov is reenabled, used by
  	 * kcov_remote_stop(), see the comment there.
  	 */
  	int			sequence;

  };

  struct kcov_remote_area {
  	struct list_head	list;
  	unsigned int		size;
  };
  
  struct kcov_remote {
  	u64			handle;
  	struct kcov		*kcov;
  	struct hlist_node	hnode;
  };
  
  static DEFINE_SPINLOCK(kcov_remote_lock);
  static DEFINE_HASHTABLE(kcov_remote_map, 4);
  static struct list_head kcov_remote_areas = LIST_HEAD_INIT(kcov_remote_areas);

  struct kcov_percpu_data {
  	void			*irq_area;
  
  	unsigned int		saved_mode;
  	unsigned int		saved_size;
  	void			*saved_area;
  	struct kcov		*saved_kcov;
  	int			saved_sequence;
  };

  static DEFINE_PER_CPU(struct kcov_percpu_data, kcov_percpu_data);

  /* Must be called with kcov_remote_lock locked. */
  static struct kcov_remote *kcov_remote_find(u64 handle)
  {
  	struct kcov_remote *remote;
  
  	hash_for_each_possible(kcov_remote_map, remote, hnode, handle) {
  		if (remote->handle == handle)
  			return remote;
  	}
  	return NULL;
  }

  /* Must be called with kcov_remote_lock locked. */

  static struct kcov_remote *kcov_remote_add(struct kcov *kcov, u64 handle)
  {
  	struct kcov_remote *remote;
  
  	if (kcov_remote_find(handle))
  		return ERR_PTR(-EEXIST);
  	remote = kmalloc(sizeof(*remote), GFP_ATOMIC);
  	if (!remote)
  		return ERR_PTR(-ENOMEM);
  	remote->handle = handle;
  	remote->kcov = kcov;
  	hash_add(kcov_remote_map, &remote->hnode, handle);
  	return remote;
  }
  
  /* Must be called with kcov_remote_lock locked. */
  static struct kcov_remote_area *kcov_remote_area_get(unsigned int size)
  {
  	struct kcov_remote_area *area;
  	struct list_head *pos;

  	list_for_each(pos, &kcov_remote_areas) {
  		area = list_entry(pos, struct kcov_remote_area, list);
  		if (area->size == size) {
  			list_del(&area->list);

  			return area;
  		}
  	}

  	return NULL;
  }
  
  /* Must be called with kcov_remote_lock locked. */
  static void kcov_remote_area_put(struct kcov_remote_area *area,
  					unsigned int size)
  {

  	INIT_LIST_HEAD(&area->list);
  	area->size = size;
  	list_add(&area->list, &kcov_remote_areas);
  }

  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, unless we are in a remote
  	 * coverage collection section in a softirq.

  	 */

  	if (!in_task() && !(in_serving_softirq() && t->kcov_softirq))

  		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_start().

  	 */
  	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_start(struct task_struct *t, struct kcov *kcov,
  			unsigned int size, void *area, enum kcov_mode mode,
  			int sequence)

  {
  	kcov_debug("t = %px, size = %u, area = %px
  ", t, size, area);

  	t->kcov = kcov;

  	/* Cache in task struct for performance. */
  	t->kcov_size = size;
  	t->kcov_area = area;

  	t->kcov_sequence = sequence;

  	/* See comment in check_kcov_mode(). */
  	barrier();
  	WRITE_ONCE(t->kcov_mode, mode);

  }
  
  static void kcov_stop(struct task_struct *t)
  {
  	WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);
  	barrier();

  	t->kcov = NULL;

  	t->kcov_size = 0;
  	t->kcov_area = NULL;
  }
  
  static void kcov_task_reset(struct task_struct *t)
  {
  	kcov_stop(t);

  	t->kcov_sequence = 0;
  	t->kcov_handle = 0;
  }
  
  void kcov_task_init(struct task_struct *t)
  {
  	kcov_task_reset(t);
  	t->kcov_handle = current->kcov_handle;
  }
  
  static void kcov_reset(struct kcov *kcov)
  {
  	kcov->t = NULL;
  	kcov->mode = KCOV_MODE_INIT;
  	kcov->remote = false;
  	kcov->remote_size = 0;
  	kcov->sequence++;
  }
  
  static void kcov_remote_reset(struct kcov *kcov)
  {
  	int bkt;
  	struct kcov_remote *remote;
  	struct hlist_node *tmp;

  	unsigned long flags;

  	spin_lock_irqsave(&kcov_remote_lock, flags);

  	hash_for_each_safe(kcov_remote_map, bkt, tmp, remote, hnode) {
  		if (remote->kcov != kcov)
  			continue;

  		hash_del(&remote->hnode);
  		kfree(remote);
  	}
  	/* Do reset before unlock to prevent races with kcov_remote_start(). */
  	kcov_reset(kcov);

  	spin_unlock_irqrestore(&kcov_remote_lock, flags);

  }
  
  static void kcov_disable(struct task_struct *t, struct kcov *kcov)
  {
  	kcov_task_reset(t);
  	if (kcov->remote)
  		kcov_remote_reset(kcov);
  	else
  		kcov_reset(kcov);
  }

  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)) {

  		kcov_remote_reset(kcov);

  		vfree(kcov->area);
  		kfree(kcov);
  	}
  }

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

  	unsigned long flags;

  
  	kcov = t->kcov;
  	if (kcov == NULL)
  		return;

  	spin_lock_irqsave(&kcov->lock, flags);

  	kcov_debug("t = %px, kcov->t = %px
  ", t, kcov->t);
  	/*
  	 * For KCOV_ENABLE devices we want to make sure that t->kcov->t == t,
  	 * which comes down to:
  	 *        WARN_ON(!kcov->remote && kcov->t != t);
  	 *
  	 * For KCOV_REMOTE_ENABLE devices, the exiting task is either:

  	 *
  	 * 1. A remote task between kcov_remote_start() and kcov_remote_stop().

  	 *    In this case we should print a warning right away, since a task
  	 *    shouldn't be exiting when it's in a kcov coverage collection
  	 *    section. Here t points to the task that is collecting remote
  	 *    coverage, and t->kcov->t points to the thread that created the
  	 *    kcov device. Which means that to detect this case we need to
  	 *    check that t != t->kcov->t, and this gives us the following:
  	 *        WARN_ON(kcov->remote && kcov->t != t);
  	 *
  	 * 2. The task that created kcov exiting without calling KCOV_DISABLE,

  	 *    and then again we make sure that t->kcov->t == t:

  	 *        WARN_ON(kcov->remote && kcov->t != t);
  	 *
  	 * By combining all three checks into one we get:
  	 */

  	if (WARN_ON(kcov->t != t)) {

  		spin_unlock_irqrestore(&kcov->lock, flags);

  		return;
  	}
  	/* Just to not leave dangling references behind. */

  	kcov_disable(t, kcov);

  	spin_unlock_irqrestore(&kcov->lock, flags);

  	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;

  	unsigned long flags;

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

  	spin_lock_irqsave(&kcov->lock, flags);

  	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_irqrestore(&kcov->lock, flags);

  		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_irqrestore(&kcov->lock, flags);

  	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;

  	kcov->sequence = 1;

  	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;
  }

  static int kcov_get_mode(unsigned long arg)
  {
  	if (arg == KCOV_TRACE_PC)
  		return KCOV_MODE_TRACE_PC;
  	else if (arg == KCOV_TRACE_CMP)
  #ifdef CONFIG_KCOV_ENABLE_COMPARISONS
  		return KCOV_MODE_TRACE_CMP;
  #else
  		return -ENOTSUPP;
  #endif
  	else
  		return -EINVAL;
  }

  /*
   * 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 inline bool kcov_check_handle(u64 handle, bool common_valid,
  				bool uncommon_valid, bool zero_valid)
  {
  	if (handle & ~(KCOV_SUBSYSTEM_MASK | KCOV_INSTANCE_MASK))
  		return false;
  	switch (handle & KCOV_SUBSYSTEM_MASK) {
  	case KCOV_SUBSYSTEM_COMMON:
  		return (handle & KCOV_INSTANCE_MASK) ?
  			common_valid : zero_valid;
  	case KCOV_SUBSYSTEM_USB:
  		return uncommon_valid;
  	default:
  		return false;
  	}
  	return false;
  }

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

  	int mode, i;
  	struct kcov_remote_arg *remote_arg;
  	struct kcov_remote *remote;

  	unsigned long flags;

  
  	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;

  		mode = kcov_get_mode(arg);
  		if (mode < 0)
  			return mode;

  		kcov_fault_in_area(kcov);

  		kcov->mode = mode;

  		kcov_start(t, kcov, kcov->size, kcov->area, kcov->mode,

  				kcov->sequence);

  		kcov->t = t;

  		/* 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_disable(t, kcov);

  		kcov_put(kcov);
  		return 0;

  	case KCOV_REMOTE_ENABLE:

  		if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
  			return -EINVAL;
  		t = current;
  		if (kcov->t != NULL || t->kcov != NULL)
  			return -EBUSY;
  		remote_arg = (struct kcov_remote_arg *)arg;
  		mode = kcov_get_mode(remote_arg->trace_mode);
  		if (mode < 0)
  			return mode;
  		if (remote_arg->area_size > LONG_MAX / sizeof(unsigned long))
  			return -EINVAL;
  		kcov->mode = mode;
  		t->kcov = kcov;
  		kcov->t = t;
  		kcov->remote = true;
  		kcov->remote_size = remote_arg->area_size;

  		spin_lock_irqsave(&kcov_remote_lock, flags);

  		for (i = 0; i < remote_arg->num_handles; i++) {

  			if (!kcov_check_handle(remote_arg->handles[i],
  						false, true, false)) {

  				spin_unlock_irqrestore(&kcov_remote_lock,
  							flags);

  				kcov_disable(t, kcov);
  				return -EINVAL;
  			}
  			remote = kcov_remote_add(kcov, remote_arg->handles[i]);
  			if (IS_ERR(remote)) {

  				spin_unlock_irqrestore(&kcov_remote_lock,
  							flags);

  				kcov_disable(t, kcov);
  				return PTR_ERR(remote);
  			}
  		}
  		if (remote_arg->common_handle) {

  			if (!kcov_check_handle(remote_arg->common_handle,
  						true, false, false)) {

  				spin_unlock_irqrestore(&kcov_remote_lock,
  							flags);

  				kcov_disable(t, kcov);
  				return -EINVAL;
  			}
  			remote = kcov_remote_add(kcov,
  					remote_arg->common_handle);
  			if (IS_ERR(remote)) {

  				spin_unlock_irqrestore(&kcov_remote_lock,
  							flags);

  				kcov_disable(t, kcov);
  				return PTR_ERR(remote);
  			}
  			t->kcov_handle = remote_arg->common_handle;
  		}

  		spin_unlock_irqrestore(&kcov_remote_lock, flags);

  		/* Put either in kcov_task_exit() or in KCOV_DISABLE. */
  		kcov_get(kcov);
  		return 0;

  	default:
  		return -ENOTTY;
  	}
  }
  
  static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
  {
  	struct kcov *kcov;
  	int res;

  	struct kcov_remote_arg *remote_arg = NULL;
  	unsigned int remote_num_handles;
  	unsigned long remote_arg_size;

  	unsigned long flags;

  
  	if (cmd == KCOV_REMOTE_ENABLE) {
  		if (get_user(remote_num_handles, (unsigned __user *)(arg +
  				offsetof(struct kcov_remote_arg, num_handles))))
  			return -EFAULT;
  		if (remote_num_handles > KCOV_REMOTE_MAX_HANDLES)
  			return -EINVAL;
  		remote_arg_size = struct_size(remote_arg, handles,
  					remote_num_handles);
  		remote_arg = memdup_user((void __user *)arg, remote_arg_size);
  		if (IS_ERR(remote_arg))
  			return PTR_ERR(remote_arg);
  		if (remote_arg->num_handles != remote_num_handles) {
  			kfree(remote_arg);
  			return -EINVAL;
  		}
  		arg = (unsigned long)remote_arg;
  	}

  
  	kcov = filep->private_data;

  	spin_lock_irqsave(&kcov->lock, flags);

  	res = kcov_ioctl_locked(kcov, cmd, arg);

  	spin_unlock_irqrestore(&kcov->lock, flags);

  
  	kfree(remote_arg);

  	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,
  };

  /*
   * kcov_remote_start() and kcov_remote_stop() can be used to annotate a section

   * of code in a kernel background thread or in a softirq to allow kcov to be
   * used to collect coverage from that part of code.

   *
   * The handle argument of kcov_remote_start() identifies a code section that is
   * used for coverage collection. A userspace process passes this handle to
   * KCOV_REMOTE_ENABLE ioctl to make the used kcov device start collecting
   * coverage for the code section identified by this handle.
   *
   * The usage of these annotations in the kernel code is different depending on
   * the type of the kernel thread whose code is being annotated.
   *
   * For global kernel threads that are spawned in a limited number of instances

   * (e.g. one USB hub_event() worker thread is spawned per USB HCD) and for
   * softirqs, each instance must be assigned a unique 4-byte instance id. The
   * instance id is then combined with a 1-byte subsystem id to get a handle via

   * kcov_remote_handle(subsystem_id, instance_id).
   *
   * For local kernel threads that are spawned from system calls handler when a
   * user interacts with some kernel interface (e.g. vhost workers), a handle is
   * passed from a userspace process as the common_handle field of the
   * kcov_remote_arg struct (note, that the user must generate a handle by using
   * kcov_remote_handle() with KCOV_SUBSYSTEM_COMMON as the subsystem id and an
   * arbitrary 4-byte non-zero number as the instance id). This common handle
   * then gets saved into the task_struct of the process that issued the

   * KCOV_REMOTE_ENABLE ioctl. When this process issues system calls that spawn
   * kernel threads, the common handle must be retrieved via kcov_common_handle()

   * and passed to the spawned threads via custom annotations. Those kernel
   * threads must in turn be annotated with kcov_remote_start(common_handle) and
   * kcov_remote_stop(). All of the threads that are spawned by the same process
   * obtain the same handle, hence the name "common".
   *
   * See Documentation/dev-tools/kcov.rst for more details.
   *

   * Internally, kcov_remote_start() looks up the kcov device associated with the

   * provided handle, allocates an area for coverage collection, and saves the
   * pointers to kcov and area into the current task_struct to allow coverage to

   * be collected via __sanitizer_cov_trace_pc().

   * In turns kcov_remote_stop() clears those pointers from task_struct to stop
   * collecting coverage and copies all collected coverage into the kcov area.
   */

  
  static inline bool kcov_mode_enabled(unsigned int mode)
  {
  	return (mode & ~KCOV_IN_CTXSW) != KCOV_MODE_DISABLED;
  }

  static void kcov_remote_softirq_start(struct task_struct *t)

  {
  	struct kcov_percpu_data *data = this_cpu_ptr(&kcov_percpu_data);
  	unsigned int mode;
  
  	mode = READ_ONCE(t->kcov_mode);
  	barrier();
  	if (kcov_mode_enabled(mode)) {
  		data->saved_mode = mode;
  		data->saved_size = t->kcov_size;
  		data->saved_area = t->kcov_area;
  		data->saved_sequence = t->kcov_sequence;
  		data->saved_kcov = t->kcov;
  		kcov_stop(t);
  	}
  }

  static void kcov_remote_softirq_stop(struct task_struct *t)

  {
  	struct kcov_percpu_data *data = this_cpu_ptr(&kcov_percpu_data);
  
  	if (data->saved_kcov) {
  		kcov_start(t, data->saved_kcov, data->saved_size,
  				data->saved_area, data->saved_mode,
  				data->saved_sequence);
  		data->saved_mode = 0;
  		data->saved_size = 0;
  		data->saved_area = NULL;
  		data->saved_sequence = 0;
  		data->saved_kcov = NULL;
  	}
  }

  void kcov_remote_start(u64 handle)
  {

  	struct task_struct *t = current;

  	struct kcov_remote *remote;

  	struct kcov *kcov;

  	unsigned int mode;

  	void *area;

  	unsigned int size;

  	int sequence;

  	unsigned long flags;

  
  	if (WARN_ON(!kcov_check_handle(handle, true, true, true)))
  		return;

  	if (!in_task() && !in_serving_softirq())

  		return;

  	local_irq_save(flags);

  	/*

  	 * Check that kcov_remote_start() is not called twice in background
  	 * threads nor called by user tasks (with enabled kcov).

  	 */

  	mode = READ_ONCE(t->kcov_mode);

  	if (WARN_ON(in_task() && kcov_mode_enabled(mode))) {
  		local_irq_restore(flags);

  		return;

  	}
  	/*
  	 * Check that kcov_remote_start() is not called twice in softirqs.
  	 * Note, that kcov_remote_start() can be called from a softirq that
  	 * happened while collecting coverage from a background thread.
  	 */
  	if (WARN_ON(in_serving_softirq() && t->kcov_softirq)) {
  		local_irq_restore(flags);
  		return;
  	}

  
  	spin_lock(&kcov_remote_lock);
  	remote = kcov_remote_find(handle);
  	if (!remote) {

  		spin_unlock_irqrestore(&kcov_remote_lock, flags);

  		return;
  	}

  	kcov_debug("handle = %llx, context: %s
  ", handle,
  			in_task() ? "task" : "softirq");

  	kcov = remote->kcov;

  	/* Put in kcov_remote_stop(). */

  	kcov_get(kcov);

  	/*
  	 * Read kcov fields before unlock to prevent races with
  	 * KCOV_DISABLE / kcov_remote_reset().
  	 */

  	mode = kcov->mode;
  	sequence = kcov->sequence;

  	if (in_task()) {
  		size = kcov->remote_size;
  		area = kcov_remote_area_get(size);
  	} else {
  		size = CONFIG_KCOV_IRQ_AREA_SIZE;
  		area = this_cpu_ptr(&kcov_percpu_data)->irq_area;
  	}
  	spin_unlock_irqrestore(&kcov_remote_lock, flags);

  	/* Can only happen when in_task(). */

  	if (!area) {
  		area = vmalloc(size * sizeof(unsigned long));
  		if (!area) {

  			kcov_put(kcov);

  			return;
  		}
  	}

  
  	local_irq_save(flags);

  	/* Reset coverage size. */
  	*(u64 *)area = 0;

  	if (in_serving_softirq()) {
  		kcov_remote_softirq_start(t);
  		t->kcov_softirq = 1;
  	}

  	kcov_start(t, kcov, size, area, mode, sequence);

  	local_irq_restore(flags);

  }
  EXPORT_SYMBOL(kcov_remote_start);
  
  static void kcov_move_area(enum kcov_mode mode, void *dst_area,
  				unsigned int dst_area_size, void *src_area)
  {
  	u64 word_size = sizeof(unsigned long);
  	u64 count_size, entry_size_log;
  	u64 dst_len, src_len;
  	void *dst_entries, *src_entries;
  	u64 dst_occupied, dst_free, bytes_to_move, entries_moved;
  
  	kcov_debug("%px %u <= %px %lu
  ",
  		dst_area, dst_area_size, src_area, *(unsigned long *)src_area);
  
  	switch (mode) {
  	case KCOV_MODE_TRACE_PC:
  		dst_len = READ_ONCE(*(unsigned long *)dst_area);
  		src_len = *(unsigned long *)src_area;
  		count_size = sizeof(unsigned long);
  		entry_size_log = __ilog2_u64(sizeof(unsigned long));
  		break;
  	case KCOV_MODE_TRACE_CMP:
  		dst_len = READ_ONCE(*(u64 *)dst_area);
  		src_len = *(u64 *)src_area;
  		count_size = sizeof(u64);
  		BUILD_BUG_ON(!is_power_of_2(KCOV_WORDS_PER_CMP));
  		entry_size_log = __ilog2_u64(sizeof(u64) * KCOV_WORDS_PER_CMP);
  		break;
  	default:
  		WARN_ON(1);
  		return;
  	}
  
  	/* As arm can't divide u64 integers use log of entry size. */
  	if (dst_len > ((dst_area_size * word_size - count_size) >>
  				entry_size_log))
  		return;
  	dst_occupied = count_size + (dst_len << entry_size_log);
  	dst_free = dst_area_size * word_size - dst_occupied;
  	bytes_to_move = min(dst_free, src_len << entry_size_log);
  	dst_entries = dst_area + dst_occupied;
  	src_entries = src_area + count_size;
  	memcpy(dst_entries, src_entries, bytes_to_move);
  	entries_moved = bytes_to_move >> entry_size_log;
  
  	switch (mode) {
  	case KCOV_MODE_TRACE_PC:
  		WRITE_ONCE(*(unsigned long *)dst_area, dst_len + entries_moved);
  		break;
  	case KCOV_MODE_TRACE_CMP:
  		WRITE_ONCE(*(u64 *)dst_area, dst_len + entries_moved);
  		break;
  	default:
  		break;
  	}
  }
  
  /* See the comment before kcov_remote_start() for usage details. */
  void kcov_remote_stop(void)
  {
  	struct task_struct *t = current;

  	struct kcov *kcov;
  	unsigned int mode;
  	void *area;
  	unsigned int size;
  	int sequence;

  	unsigned long flags;
  
  	if (!in_task() && !in_serving_softirq())
  		return;
  
  	local_irq_save(flags);

  	mode = READ_ONCE(t->kcov_mode);
  	barrier();

  	if (!kcov_mode_enabled(mode)) {
  		local_irq_restore(flags);

  		return;

  	}

  	/*
  	 * When in softirq, check if the corresponding kcov_remote_start()
  	 * actually found the remote handle and started collecting coverage.
  	 */
  	if (in_serving_softirq() && !t->kcov_softirq) {
  		local_irq_restore(flags);
  		return;
  	}
  	/* Make sure that kcov_softirq is only set when in softirq. */

  	if (WARN_ON(!in_serving_softirq() && t->kcov_softirq)) {
  		local_irq_restore(flags);
  		return;
  	}

  	kcov = t->kcov;
  	area = t->kcov_area;
  	size = t->kcov_size;
  	sequence = t->kcov_sequence;

  	kcov_stop(t);

  	if (in_serving_softirq()) {
  		t->kcov_softirq = 0;
  		kcov_remote_softirq_stop(t);
  	}

  
  	spin_lock(&kcov->lock);
  	/*
  	 * KCOV_DISABLE could have been called between kcov_remote_start()

  	 * and kcov_remote_stop(), hence the sequence check.

  	 */

  	if (sequence == kcov->sequence && kcov->remote)
  		kcov_move_area(kcov->mode, kcov->area, kcov->size, area);
  	spin_unlock(&kcov->lock);

  	if (in_task()) {
  		spin_lock(&kcov_remote_lock);
  		kcov_remote_area_put(area, size);
  		spin_unlock(&kcov_remote_lock);
  	}

  	local_irq_restore(flags);
  
  	/* Get in kcov_remote_start(). */

  	kcov_put(kcov);
  }
  EXPORT_SYMBOL(kcov_remote_stop);
  
  /* See the comment before kcov_remote_start() for usage details. */
  u64 kcov_common_handle(void)
  {
  	return current->kcov_handle;
  }
  EXPORT_SYMBOL(kcov_common_handle);

  static int __init kcov_init(void)
  {

  	int cpu;
  
  	for_each_possible_cpu(cpu) {
  		void *area = vmalloc(CONFIG_KCOV_IRQ_AREA_SIZE *
  				sizeof(unsigned long));
  		if (!area)
  			return -ENOMEM;
  		per_cpu_ptr(&kcov_percpu_data, cpu)->irq_area = area;
  	}

  	/*
  	 * 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);