mm/util.c

   1 #include <linux/slab.h>
   2 #include <linux/string.h>
   3 #include <linux/module.h>
   4 #include <linux/err.h>
   5 #include <asm/uaccess.h>
   6
   7 /**
   8  * __kzalloc - allocate memory. The memory is set to zero.
   9  * @size: how many bytes of memory are required.
  10  * @flags: the type of memory to allocate.
  11  */
  12 void *__kzalloc(size_t size, gfp_t flags)
  13 {
  14         void *ret = ____kmalloc(size, flags);
  15         if (ret)
  16                 memset(ret, 0, size);
  17         return ret;
  18 }
  19 EXPORT_SYMBOL(__kzalloc);
  20
  21 /*
  22  * kstrdup - allocate space for and copy an existing string
  23  *
  24  * @s: the string to duplicate
  25  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  26  */
  27 char *kstrdup(const char *s, gfp_t gfp)
  28 {
  29         size_t len;
  30         char *buf;
  31
  32         if (!s)
  33                 return NULL;
  34
  35         len = strlen(s) + 1;
  36         buf = ____kmalloc(len, gfp);
  37         if (buf)
  38                 memcpy(buf, s, len);
  39         return buf;
  40 }
  41 EXPORT_SYMBOL(kstrdup);
  42
  43 /*
  44  * strndup_user - duplicate an existing string from user space
  45  *
  46  * @s: The string to duplicate
  47  * @n: Maximum number of bytes to copy, including the trailing NUL.
  48  */
  49 char *strndup_user(const char __user *s, long n)
  50 {
  51         char *p;
  52         long length;
  53
  54         length = strnlen_user(s, n);
  55
  56         if (!length)
  57                 return ERR_PTR(-EFAULT);
  58
  59         if (length > n)
  60                 return ERR_PTR(-EINVAL);
  61
  62         p = kmalloc(length, GFP_KERNEL);
  63
  64         if (!p)
  65                 return ERR_PTR(-ENOMEM);
  66
  67         if (copy_from_user(p, s, length)) {
  68                 kfree(p);
  69                 return ERR_PTR(-EFAULT);
  70         }
  71
  72         p[length - 1] = '\0';
  73
  74         return p;
  75 }
  76 EXPORT_SYMBOL(strndup_user);