#include <linux/mm.h>

  #include <linux/slab.h>
  #include <linux/string.h>

  #include <linux/compiler.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/mman.h>
  #include <linux/hugetlb.h>

  #include <linux/vmalloc.h>

  #include <asm/uaccess.h>

  #include "internal.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);

  /*
   * 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 task_struct of the task
   * that the vma is stack for. Must be called under rcu_read_lock().

   */

  struct task_struct *task_of_stack(struct task_struct *task,
  				struct vm_area_struct *vma, bool in_group)

  {

  	if (vm_is_stack_for_task(task, vma))

  		return task;

  
  	if (in_group) {
  		struct task_struct *t;

  		for_each_thread(task, t) {

  			if (vm_is_stack_for_task(t, vma))
  				return t;

  		}

  	}

  	return NULL;

  }

  #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;

  }
  #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 __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 __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;

  	/* This happens if someone calls flush_dcache_page on slab page */
  	if (unlikely(PageSlab(page)))
  		return NULL;

  	if (unlikely(PageSwapCache(page))) {
  		swp_entry_t entry;
  
  		entry.val = page_private(page);
  		mapping = swap_address_space(entry);

  	} else if ((unsigned long)mapping & PAGE_MAPPING_ANON)

  		mapping = NULL;
  	return mapping;
  }

  int overcommit_ratio_handler(struct ctl_table *table, int write,
  			     void __user *buffer, size_t *lenp,
  			     loff_t *ppos)
  {
  	int ret;
  
  	ret = proc_dointvec(table, write, buffer, lenp, ppos);
  	if (ret == 0 && write)
  		sysctl_overcommit_kbytes = 0;
  	return ret;
  }
  
  int overcommit_kbytes_handler(struct ctl_table *table, int write,
  			     void __user *buffer, size_t *lenp,
  			     loff_t *ppos)
  {
  	int ret;
  
  	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
  	if (ret == 0 && write)
  		sysctl_overcommit_ratio = 0;
  	return ret;
  }

  /*
   * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
   */
  unsigned long vm_commit_limit(void)
  {

  	unsigned long allowed;
  
  	if (sysctl_overcommit_kbytes)
  		allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
  	else
  		allowed = ((totalram_pages - hugetlb_total_pages())
  			   * sysctl_overcommit_ratio / 100);
  	allowed += total_swap_pages;
  
  	return allowed;

  }

  /**
   * get_cmdline() - copy the cmdline value to a buffer.
   * @task:     the task whose cmdline value to copy.
   * @buffer:   the buffer to copy to.
   * @buflen:   the length of the buffer. Larger cmdline values are truncated
   *            to this length.
   * Returns the size of the cmdline field copied. Note that the copy does
   * not guarantee an ending NULL byte.
   */
  int get_cmdline(struct task_struct *task, char *buffer, int buflen)
  {
  	int res = 0;
  	unsigned int len;
  	struct mm_struct *mm = get_task_mm(task);
  	if (!mm)
  		goto out;
  	if (!mm->arg_end)
  		goto out_mm;	/* Shh! No looking before we're done */
  
  	len = mm->arg_end - mm->arg_start;
  
  	if (len > buflen)
  		len = buflen;
  
  	res = access_process_vm(task, mm->arg_start, buffer, len, 0);
  
  	/*
  	 * If the nul at the end of args has been overwritten, then
  	 * assume application is using setproctitle(3).
  	 */
  	if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
  		len = strnlen(buffer, res);
  		if (len < res) {
  			res = len;
  		} else {
  			len = mm->env_end - mm->env_start;
  			if (len > buflen - res)
  				len = buflen - res;
  			res += access_process_vm(task, mm->env_start,
  						 buffer+res, len, 0);
  			res = strnlen(buffer, res);
  		}
  	}
  out_mm:
  	mmput(mm);
  out:
  	return res;
  }