text: #include <linux/mm.h>
  #include <linux/slab.h>
  #include <linux/string.h>
  #include <linux/export.h>
  #include <linux/err.h>
  #include <linux/sched.h>
  #include <linux/security.h>
  #include <linux/swap.h>
  #include <linux/swapops.h>
  #include <linux/vmalloc.h>
  #include <asm/uaccess.h>
  
  #include "internal.h"
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/kmem.h>
  
  /**
   * kstrdup - allocate space for and copy an existing string
   * @s: the string to duplicate
   * @gfp: the GFP mask used in the kmalloc() call when allocating memory
   */
  char *kstrdup(const char *s, gfp_t gfp)
  {
  	size_t len;
  	char *buf;
  
  	if (!s)
  		return NULL;
  
  	len = strlen(s) + 1;
  	buf = kmalloc_track_caller(len, gfp);
  	if (buf)
  		memcpy(buf, s, len);
  	return buf;
  }
  EXPORT_SYMBOL(kstrdup);
  
  /**
   * kstrndup - allocate space for and copy an existing string
   * @s: the string to duplicate
   * @max: read at most @max chars from @s
   * @gfp: the GFP mask used in the kmalloc() call when allocating memory
   */
  char *kstrndup(const char *s, size_t max, gfp_t gfp)
  {
  	size_t len;
  	char *buf;
  
  	if (!s)
  		return NULL;
  
  	len = strnlen(s, max);
  	buf = kmalloc_track_caller(len+1, gfp);
  	if (buf) {
  		memcpy(buf, s, len);
  		buf[len] = '\0';
  	}
  	return buf;
  }
  EXPORT_SYMBOL(kstrndup);
  
  /**
   * kmemdup - duplicate region of memory
   *
   * @src: memory region to duplicate
   * @len: memory region length
   * @gfp: GFP mask to use
   */
  void *kmemdup(const void *src, size_t len, gfp_t gfp)
  {
  	void *p;
  
  	p = kmalloc_track_caller(len, gfp);
  	if (p)
  		memcpy(p, src, len);
  	return p;
  }
  EXPORT_SYMBOL(kmemdup);
  
  /**
   * memdup_user - duplicate memory region from user space
   *
   * @src: source address in user space
   * @len: number of bytes to copy
   *
   * Returns an ERR_PTR() on failure.
   */
  void *memdup_user(const void __user *src, size_t len)
  {
  	void *p;
  
  	/*
  	 * Always use GFP_KERNEL, since copy_from_user() can sleep and
  	 * cause pagefault, which makes it pointless to use GFP_NOFS
  	 * or GFP_ATOMIC.
  	 */
  	p = kmalloc_track_caller(len, GFP_KERNEL);
  	if (!p)
  		return ERR_PTR(-ENOMEM);
  
  	if (copy_from_user(p, src, len)) {
  		kfree(p);
  		return ERR_PTR(-EFAULT);
  	}
  
  	return p;
  }
  EXPORT_SYMBOL(memdup_user);
  
  static __always_inline void *__do_krealloc(const void *p, size_t new_size,
  					   gfp_t flags)
  {
  	void *ret;
  	size_t ks = 0;
  
  	if (p)
  		ks = ksize(p);
  
  	if (ks >= new_size)
  		return (void *)p;
  
  	ret = kmalloc_track_caller(new_size, flags);
  	if (ret && p)
  		memcpy(ret, p, ks);
  
  	return ret;
  }
  
  /**
   * __krealloc - like krealloc() but don't free @p.
   * @p: object to reallocate memory for.
   * @new_size: how many bytes of memory are required.
   * @flags: the type of memory to allocate.
   *
   * This function is like krealloc() except it never frees the originally
   * allocated buffer. Use this if you don't want to free the buffer immediately
   * like, for example, with RCU.
   */
  void *__krealloc(const void *p, size_t new_size, gfp_t flags)
  {
  	if (unlikely(!new_size))
  		return ZERO_SIZE_PTR;
  
  	return __do_krealloc(p, new_size, flags);
  
  }
  EXPORT_SYMBOL(__krealloc);
  
  /**
   * krealloc - reallocate memory. The contents will remain unchanged.
   * @p: object to reallocate memory for.
   * @new_size: how many bytes of memory are required.
   * @flags: the type of memory to allocate.
   *
   * The contents of the object pointed to are preserved up to the
   * lesser of the new and old sizes.  If @p is %NULL, krealloc()
   * behaves exactly like kmalloc().  If @new_size is 0 and @p is not a
   * %NULL pointer, the object pointed to is freed.
   */
  void *krealloc(const void *p, size_t new_size, gfp_t flags)
  {
  	void *ret;
  
  	if (unlikely(!new_size)) {
  		kfree(p);
  		return ZERO_SIZE_PTR;
  	}
  
  	ret = __do_krealloc(p, new_size, flags);
  	if (ret && p != ret)
  		kfree(p);
  
  	return ret;
  }
  EXPORT_SYMBOL(krealloc);
  
  /**
   * kzfree - like kfree but zero memory
   * @p: object to free memory of
   *
   * The memory of the object @p points to is zeroed before freed.
   * If @p is %NULL, kzfree() does nothing.
   *
   * Note: this function zeroes the whole allocated buffer which can be a good
   * deal bigger than the requested buffer size passed to kmalloc(). So be
   * careful when using this function in performance sensitive code.
   */
  void kzfree(const void *p)
  {
  	size_t ks;
  	void *mem = (void *)p;
  
  	if (unlikely(ZERO_OR_NULL_PTR(mem)))
  		return;
  	ks = ksize(mem);
  	memset(mem, 0, ks);
  	kfree(mem);
  }
  EXPORT_SYMBOL(kzfree);
  
  /*
   * strndup_user - duplicate an existing string from user space
   * @s: The string to duplicate
   * @n: Maximum number of bytes to copy, including the trailing NUL.
   */
  char *strndup_user(const char __user *s, long n)
  {
  	char *p;
  	long length;
  
  	length = strnlen_user(s, n);
  
  	if (!length)
  		return ERR_PTR(-EFAULT);
  
  	if (length > n)
  		return ERR_PTR(-EINVAL);
  
  	p = memdup_user(s, length);
  
  	if (IS_ERR(p))
  		return p;
  
  	p[length - 1] = '\0';
  
  	return p;
  }
  EXPORT_SYMBOL(strndup_user);
  
  void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
  		struct vm_area_struct *prev, struct rb_node *rb_parent)
  {
  	struct vm_area_struct *next;
  
  	vma->vm_prev = prev;
  	if (prev) {
  		next = prev->vm_next;
  		prev->vm_next = vma;
  	} else {
  		mm->mmap = vma;
  		if (rb_parent)
  			next = rb_entry(rb_parent,
  					struct vm_area_struct, vm_rb);
  		else
  			next = NULL;
  	}
  	vma->vm_next = next;
  	if (next)
  		next->vm_prev = vma;
  }
  
  /* Check if the vma is being used as a stack by this task */
  static int vm_is_stack_for_task(struct task_struct *t,
  				struct vm_area_struct *vma)
  {
  	return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
  }
  
  /*
   * Check if the vma is being used as a stack.
   * If is_group is non-zero, check in the entire thread group or else
   * just check in the current task. Returns the pid of the task that
   * the vma is stack for.
   */
  pid_t vm_is_stack(struct task_struct *task,
  		  struct vm_area_struct *vma, int in_group)
  {
  	pid_t ret = 0;
  
  	if (vm_is_stack_for_task(task, vma))
  		return task->pid;
  
  	if (in_group) {
  		struct task_struct *t;
  
  		rcu_read_lock();
  		for_each_thread(task, t) {
  			if (vm_is_stack_for_task(t, vma)) {
  				ret = t->pid;
  				goto done;
  			}
  		}
  done:
  		rcu_read_unlock();
  	}
  
  	return ret;
  }
  
  #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
  void arch_pick_mmap_layout(struct mm_struct *mm)
  {
  	mm->mmap_base = TASK_UNMAPPED_BASE;
  	mm->get_unmapped_area = arch_get_unmapped_area;
  	mm->unmap_area = arch_unmap_area;
  }
  #endif
  
  /*
   * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
   * back to the regular GUP.
   * If the architecture not support this function, simply return with no
   * page pinned
   */
  int __attribute__((weak)) __get_user_pages_fast(unsigned long start,
  				 int nr_pages, int write, struct page **pages)
  {
  	return 0;
  }
  EXPORT_SYMBOL_GPL(__get_user_pages_fast);
  
  /**
   * get_user_pages_fast() - pin user pages in memory
   * @start:	starting user address
   * @nr_pages:	number of pages from start to pin
   * @write:	whether pages will be written to
   * @pages:	array that receives pointers to the pages pinned.
   *		Should be at least nr_pages long.
   *
   * Returns number of pages pinned. This may be fewer than the number
   * requested. If nr_pages is 0 or negative, returns 0. If no pages
   * were pinned, returns -errno.
   *
   * get_user_pages_fast provides equivalent functionality to get_user_pages,
   * operating on current and current->mm, with force=0 and vma=NULL. However
   * unlike get_user_pages, it must be called without mmap_sem held.
   *
   * get_user_pages_fast may take mmap_sem and page table locks, so no
   * assumptions can be made about lack of locking. get_user_pages_fast is to be
   * implemented in a way that is advantageous (vs get_user_pages()) when the
   * user memory area is already faulted in and present in ptes. However if the
   * pages have to be faulted in, it may turn out to be slightly slower so
   * callers need to carefully consider what to use. On many architectures,
   * get_user_pages_fast simply falls back to get_user_pages.
   */
  int __attribute__((weak)) get_user_pages_fast(unsigned long start,
  				int nr_pages, int write, struct page **pages)
  {
  	struct mm_struct *mm = current->mm;
  	int ret;
  
  	down_read(&mm->mmap_sem);
  	ret = get_user_pages(current, mm, start, nr_pages,
  					write, 0, pages, NULL);
  	up_read(&mm->mmap_sem);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(get_user_pages_fast);
  
  unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
  	unsigned long len, unsigned long prot,
  	unsigned long flag, unsigned long pgoff)
  {
  	unsigned long ret;
  	struct mm_struct *mm = current->mm;
  	unsigned long populate;
  
  	ret = security_mmap_file(file, prot, flag);
  	if (!ret) {
  		down_write(&mm->mmap_sem);
  		ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
  				    &populate);
  		up_write(&mm->mmap_sem);
  		if (populate)
  			mm_populate(ret, populate);
  	}
  	return ret;
  }
  
  unsigned long vm_mmap(struct file *file, unsigned long addr,
  	unsigned long len, unsigned long prot,
  	unsigned long flag, unsigned long offset)
  {
  	if (unlikely(offset + PAGE_ALIGN(len) < offset))
  		return -EINVAL;
  	if (unlikely(offset & ~PAGE_MASK))
  		return -EINVAL;
  
  	return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
  }
  EXPORT_SYMBOL(vm_mmap);
  
  void kvfree(const void *addr)
  {
  	if (is_vmalloc_addr(addr))
  		vfree(addr);
  	else
  		kfree(addr);
  }
  EXPORT_SYMBOL(kvfree);
  
  struct address_space *page_mapping(struct page *page)
  {
  	struct address_space *mapping = page->mapping;
  
  	VM_BUG_ON(PageSlab(page));
  #ifdef CONFIG_SWAP
  	if (unlikely(PageSwapCache(page))) {
  		swp_entry_t entry;
  
  		entry.val = page_private(page);
  		mapping = swap_address_space(entry);
  	} else
  #endif
  	if ((unsigned long)mapping & PAGE_MAPPING_ANON)
  		mapping = NULL;
  	return mapping;
  }
  
  /* Tracepoints definitions. */
  EXPORT_TRACEPOINT_SYMBOL(kmalloc);
  EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
  EXPORT_TRACEPOINT_SYMBOL(kmalloc_node);
  EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc_node);
  EXPORT_TRACEPOINT_SYMBOL(kfree);
  EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);
  