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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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;
     local_lock_t        lock;
 
     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) = {
     .lock = INIT_LOCAL_LOCK(lock),
 };
 
 /* 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)) {
         /* Previously we write pc before updating pos. However, some
          * early interrupt code could bypass check_kcov_mode() check
          * and invoke __sanitizer_cov_trace_pc(). If such interrupt is
          * raised between writing pc and updating pos, the pc could be
          * overitten by the recursive __sanitizer_cov_trace_pc().
          * Update pos before writing pc to avoid such interleaving.
          */
         WRITE_ONCE(area[0], pos);
         barrier();
         area[pos] = ip;
     }
 }
 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)) {
         /* See comment in __sanitizer_cov_trace_pc(). */
         WRITE_ONCE(area[0], count + 1);
         barrier();
         area[start_index] = type;
         area[start_index + 1] = arg1;
         area[start_index + 2] = arg2;
         area[start_index + 3] = ip;
     }
 }
 
 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\n", 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\n", 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;
     struct kcov *kcov = vma->vm_file->private_data;
     unsigned long size, off;
     struct page *page;
     unsigned long flags;
 
     spin_lock_irqsave(&kcov->lock, flags);
     size = kcov->size * sizeof(unsigned long);
     if (kcov->area == NULL || vma->vm_pgoff != 0 ||
         vma->vm_end - vma->vm_start != size) {
         res = -EINVAL;
         goto exit;
     }
     spin_unlock_irqrestore(&kcov->lock, flags);
     vma->vm_flags |= VM_DONTEXPAND;
     for (off = 0; off < size; off += PAGE_SIZE) {
         page = vmalloc_to_page(kcov->area + off);
         res = vm_insert_page(vma, vma->vm_start + off, page);
         if (res) {
             pr_warn_once("kcov: vm_insert_page() failed\n");
             return res;
         }
     }
     return 0;
 exit:
     spin_unlock_irqrestore(&kcov->lock, flags);
     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 flags, unused;
     int mode, i;
     struct kcov_remote_arg *remote_arg;
     struct kcov_remote *remote;
 
     switch (cmd) {
     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 size, flags;
     void *area;
 
     kcov = filep->private_data;
     switch (cmd) {
     case KCOV_INIT_TRACE:
         /*
          * Enable kcov in trace mode and setup buffer size.
          * Must happen before anything else.
          *
          * First check the size argument - it must be at least 2
          * to hold the current position and one PC.
          */
         size = arg;
         if (size < 2 || size > INT_MAX / sizeof(unsigned long))
             return -EINVAL;
         area = vmalloc_user(size * sizeof(unsigned long));
         if (area == NULL)
             return -ENOMEM;
         spin_lock_irqsave(&kcov->lock, flags);
         if (kcov->mode != KCOV_MODE_DISABLED) {
             spin_unlock_irqrestore(&kcov->lock, flags);
             vfree(area);
             return -EBUSY;
         }
         kcov->area = area;
         kcov->size = size;
         kcov->mode = KCOV_MODE_INIT;
         spin_unlock_irqrestore(&kcov->lock, flags);
         return 0;
     case 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;
         fallthrough;
     default:
         /*
          * All other commands can be normally executed under a spin lock, so we
          * obtain and release it here in order to simplify kcov_ioctl_locked().
          */
         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_lock_irqsave(&kcov_percpu_data.lock, 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_unlock_irqrestore(&kcov_percpu_data.lock, 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_unlock_irqrestore(&kcov_percpu_data.lock, flags);
         return;
     }
 
     spin_lock(&kcov_remote_lock);
     remote = kcov_remote_find(handle);
     if (!remote) {
         spin_unlock(&kcov_remote_lock);
         local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
         return;
     }
     kcov_debug("handle = %llx, context: %s\n", 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(&kcov_remote_lock);
 
     /* Can only happen when in_task(). */
     if (!area) {
         local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
         area = vmalloc(size * sizeof(unsigned long));
         if (!area) {
             kcov_put(kcov);
             return;
         }
         local_lock_irqsave(&kcov_percpu_data.lock, 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_unlock_irqrestore(&kcov_percpu_data.lock, 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\n",
         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_lock_irqsave(&kcov_percpu_data.lock, flags);
 
     mode = READ_ONCE(t->kcov_mode);
     barrier();
     if (!kcov_mode_enabled(mode)) {
         local_unlock_irqrestore(&kcov_percpu_data.lock, 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_unlock_irqrestore(&kcov_percpu_data.lock, flags);
         return;
     }
     /* Make sure that kcov_softirq is only set when in softirq. */
     if (WARN_ON(!in_serving_softirq() && t->kcov_softirq)) {
         local_unlock_irqrestore(&kcov_percpu_data.lock, 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_unlock_irqrestore(&kcov_percpu_data.lock, 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)
 {
     if (!in_task())
         return 0;
     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_node(CONFIG_KCOV_IRQ_AREA_SIZE *
                 sizeof(unsigned long), cpu_to_node(cpu));
         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);

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