mm/util.c

   1 #include <linux/mm.h>
   2 #include <linux/slab.h>
   3 #include <linux/string.h>
   4 #include <linux/module.h>
   5 #include <linux/err.h>
   6 #include <linux/sched.h>
   7 #include <asm/uaccess.h>
   8
   9 /**
  10  * kstrdup - allocate space for and copy an existing string
  11  * @s: the string to duplicate
  12  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  13  */
  14 char *kstrdup(const char *s, gfp_t gfp)
  15 {
  16         size_t len;
  17         char *buf;
  18
  19         if (!s)
  20                 return NULL;
  21
  22         len = strlen(s) + 1;
  23         buf = kmalloc_track_caller(len, gfp);
  24         if (buf)
  25                 memcpy(buf, s, len);
  26         return buf;
  27 }
  28 EXPORT_SYMBOL(kstrdup);
  29
  30 /**
  31  * kstrndup - allocate space for and copy an existing string
  32  * @s: the string to duplicate
  33  * @max: read at most @max chars from @s
  34  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  35  */
  36 char *kstrndup(const char *s, size_t max, gfp_t gfp)
  37 {
  38         size_t len;
  39         char *buf;
  40
  41         if (!s)
  42                 return NULL;
  43
  44         len = strnlen(s, max);
  45         buf = kmalloc_track_caller(len+1, gfp);
  46         if (buf) {
  47                 memcpy(buf, s, len);
  48                 buf[len] = '\0';
  49         }
  50         return buf;
  51 }
  52 EXPORT_SYMBOL(kstrndup);
  53
  54 /**
  55  * kmemdup - duplicate region of memory
  56  *
  57  * @src: memory region to duplicate
  58  * @len: memory region length
  59  * @gfp: GFP mask to use
  60  */
  61 void *kmemdup(const void *src, size_t len, gfp_t gfp)
  62 {
  63         void *p;
  64
  65         p = kmalloc_track_caller(len, gfp);
  66         if (p)
  67                 memcpy(p, src, len);
  68         return p;
  69 }
  70 EXPORT_SYMBOL(kmemdup);
  71
  72 /**
  73  * memdup_user - duplicate memory region from user space
  74  *
  75  * @src: source address in user space
  76  * @len: number of bytes to copy
  77  *
  78  * Returns an ERR_PTR() on failure.
  79  */
  80 void *memdup_user(const void __user *src, size_t len)
  81 {
  82         void *p;
  83
  84         /*
  85          * Always use GFP_KERNEL, since copy_from_user() can sleep and
  86          * cause pagefault, which makes it pointless to use GFP_NOFS
  87          * or GFP_ATOMIC.
  88          */
  89         p = kmalloc_track_caller(len, GFP_KERNEL);
  90         if (!p)
  91                 return ERR_PTR(-ENOMEM);
  92
  93         if (copy_from_user(p, src, len)) {
  94                 kfree(p);
  95                 return ERR_PTR(-EFAULT);
  96         }
  97
  98         return p;
  99 }
 100 EXPORT_SYMBOL(memdup_user);
 101
 102 /**
 103  * __krealloc - like krealloc() but don't free @p.
 104  * @p: object to reallocate memory for.
 105  * @new_size: how many bytes of memory are required.
 106  * @flags: the type of memory to allocate.
 107  *
 108  * This function is like krealloc() except it never frees the originally
 109  * allocated buffer. Use this if you don't want to free the buffer immediately
 110  * like, for example, with RCU.
 111  */
 112 void *__krealloc(const void *p, size_t new_size, gfp_t flags)
 113 {
 114         void *ret;
 115         size_t ks = 0;
 116
 117         if (unlikely(!new_size))
 118                 return ZERO_SIZE_PTR;
 119
 120         if (p)
 121                 ks = ksize(p);
 122
 123         if (ks >= new_size)
 124                 return (void *)p;
 125
 126         ret = kmalloc_track_caller(new_size, flags);
 127         if (ret && p)
 128                 memcpy(ret, p, ks);
 129
 130         return ret;
 131 }
 132 EXPORT_SYMBOL(__krealloc);
 133
 134 /**
 135  * krealloc - reallocate memory. The contents will remain unchanged.
 136  * @p: object to reallocate memory for.
 137  * @new_size: how many bytes of memory are required.
 138  * @flags: the type of memory to allocate.
 139  *
 140  * The contents of the object pointed to are preserved up to the
 141  * lesser of the new and old sizes.  If @p is %NULL, krealloc()
 142  * behaves exactly like kmalloc().  If @size is 0 and @p is not a
 143  * %NULL pointer, the object pointed to is freed.
 144  */
 145 void *krealloc(const void *p, size_t new_size, gfp_t flags)
 146 {
 147         void *ret;
 148
 149         if (unlikely(!new_size)) {
 150                 kfree(p);
 151                 return ZERO_SIZE_PTR;
 152         }
 153
 154         ret = __krealloc(p, new_size, flags);
 155         if (ret && p != ret)
 156                 kfree(p);
 157
 158         return ret;
 159 }
 160 EXPORT_SYMBOL(krealloc);
 161
 162 /**
 163  * kzfree - like kfree but zero memory
 164  * @p: object to free memory of
 165  *
 166  * The memory of the object @p points to is zeroed before freed.
 167  * If @p is %NULL, kzfree() does nothing.
 168  */
 169 void kzfree(const void *p)
 170 {
 171         size_t ks;
 172         void *mem = (void *)p;
 173
 174         if (unlikely(ZERO_OR_NULL_PTR(mem)))
 175                 return;
 176         ks = ksize(mem);
 177         memset(mem, 0, ks);
 178         kfree(mem);
 179 }
 180 EXPORT_SYMBOL(kzfree);
 181
 182 /*
 183  * strndup_user - duplicate an existing string from user space
 184  * @s: The string to duplicate
 185  * @n: Maximum number of bytes to copy, including the trailing NUL.
 186  */
 187 char *strndup_user(const char __user *s, long n)
 188 {
 189         char *p;
 190         long length;
 191
 192         length = strnlen_user(s, n);
 193
 194         if (!length)
 195                 return ERR_PTR(-EFAULT);
 196
 197         if (length > n)
 198                 return ERR_PTR(-EINVAL);
 199
 200         p = kmalloc(length, GFP_KERNEL);
 201
 202         if (!p)
 203                 return ERR_PTR(-ENOMEM);
 204
 205         if (copy_from_user(p, s, length)) {
 206                 kfree(p);
 207                 return ERR_PTR(-EFAULT);
 208         }
 209
 210         p[length - 1] = '\0';
 211
 212         return p;
 213 }
 214 EXPORT_SYMBOL(strndup_user);
 215
 216 #ifndef HAVE_ARCH_PICK_MMAP_LAYOUT
 217 void arch_pick_mmap_layout(struct mm_struct *mm)
 218 {
 219         mm->mmap_base = TASK_UNMAPPED_BASE;
 220         mm->get_unmapped_area = arch_get_unmapped_area;
 221         mm->unmap_area = arch_unmap_area;
 222 }
 223 #endif
 224
 225 int __attribute__((weak)) get_user_pages_fast(unsigned long start,
 226                                 int nr_pages, int write, struct page **pages)
 227 {
 228         struct mm_struct *mm = current->mm;
 229         int ret;
 230
 231         down_read(&mm->mmap_sem);
 232         ret = get_user_pages(current, mm, start, nr_pages,
 233                                         write, 0, pages, NULL);
 234         up_read(&mm->mmap_sem);
 235
 236         return ret;
 237 }
 238 EXPORT_SYMBOL_GPL(get_user_pages_fast);