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  * kstrdup - allocate space for and copy an existing string
   9  * @s: the string to duplicate
  10  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  11  */
  12 char *kstrdup(const char *s, gfp_t gfp)
  13 {
  14         size_t len;
  15         char *buf;
  16
  17         if (!s)
  18                 return NULL;
  19
  20         len = strlen(s) + 1;
  21         buf = kmalloc_track_caller(len, gfp);
  22         if (buf)
  23                 memcpy(buf, s, len);
  24         return buf;
  25 }
  26 EXPORT_SYMBOL(kstrdup);
  27
  28 /**
  29  * kstrndup - allocate space for and copy an existing string
  30  * @s: the string to duplicate
  31  * @max: read at most @max chars from @s
  32  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  33  */
  34 char *kstrndup(const char *s, size_t max, gfp_t gfp)
  35 {
  36         size_t len;
  37         char *buf;
  38
  39         if (!s)
  40                 return NULL;
  41
  42         len = strnlen(s, max);
  43         buf = kmalloc_track_caller(len+1, gfp);
  44         if (buf) {
  45                 memcpy(buf, s, len);
  46                 buf[len] = '\0';
  47         }
  48         return buf;
  49 }
  50 EXPORT_SYMBOL(kstrndup);
  51
  52 /**
  53  * kmemdup - duplicate region of memory
  54  *
  55  * @src: memory region to duplicate
  56  * @len: memory region length
  57  * @gfp: GFP mask to use
  58  */
  59 void *kmemdup(const void *src, size_t len, gfp_t gfp)
  60 {
  61         void *p;
  62
  63         p = kmalloc_track_caller(len, gfp);
  64         if (p)
  65                 memcpy(p, src, len);
  66         return p;
  67 }
  68 EXPORT_SYMBOL(kmemdup);
  69
  70 /**
  71  * krealloc - reallocate memory. The contents will remain unchanged.
  72  * @p: object to reallocate memory for.
  73  * @new_size: how many bytes of memory are required.
  74  * @flags: the type of memory to allocate.
  75  *
  76  * The contents of the object pointed to are preserved up to the
  77  * lesser of the new and old sizes.  If @p is %NULL, krealloc()
  78  * behaves exactly like kmalloc().  If @size is 0 and @p is not a
  79  * %NULL pointer, the object pointed to is freed.
  80  */
  81 void *krealloc(const void *p, size_t new_size, gfp_t flags)
  82 {
  83         void *ret;
  84         size_t ks;
  85
  86         if (unlikely(!new_size)) {
  87                 kfree(p);
  88                 return ZERO_SIZE_PTR;
  89         }
  90
  91         ks = ksize(p);
  92         if (ks >= new_size)
  93                 return (void *)p;
  94
  95         ret = kmalloc_track_caller(new_size, flags);
  96         if (ret) {
  97                 memcpy(ret, p, min(new_size, ks));
  98                 kfree(p);
  99         }
 100         return ret;
 101 }
 102 EXPORT_SYMBOL(krealloc);
 103
 104 /*
 105  * strndup_user - duplicate an existing string from user space
 106  * @s: The string to duplicate
 107  * @n: Maximum number of bytes to copy, including the trailing NUL.
 108  */
 109 char *strndup_user(const char __user *s, long n)
 110 {
 111         char *p;
 112         long length;
 113
 114         length = strnlen_user(s, n);
 115
 116         if (!length)
 117                 return ERR_PTR(-EFAULT);
 118
 119         if (length > n)
 120                 return ERR_PTR(-EINVAL);
 121
 122         p = kmalloc(length, GFP_KERNEL);
 123
 124         if (!p)
 125                 return ERR_PTR(-ENOMEM);
 126
 127         if (copy_from_user(p, s, length)) {
 128                 kfree(p);
 129                 return ERR_PTR(-EFAULT);
 130         }
 131
 132         p[length - 1] = '\0';
 133
 134         return p;
 135 }
 136 EXPORT_SYMBOL(strndup_user);