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 <linux/tracepoint.h>
   8 #include <asm/uaccess.h>
   9
  10 /**
  11  * kstrdup - allocate space for and copy an existing string
  12  * @s: the string to duplicate
  13  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  14  */
  15 char *kstrdup(const char *s, gfp_t gfp)
  16 {
  17         size_t len;
  18         char *buf;
  19
  20         if (!s)
  21                 return NULL;
  22
  23         len = strlen(s) + 1;
  24         buf = kmalloc_track_caller(len, gfp);
  25         if (buf)
  26                 memcpy(buf, s, len);
  27         return buf;
  28 }
  29 EXPORT_SYMBOL(kstrdup);
  30
  31 /**
  32  * kstrndup - allocate space for and copy an existing string
  33  * @s: the string to duplicate
  34  * @max: read at most @max chars from @s
  35  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  36  */
  37 char *kstrndup(const char *s, size_t max, gfp_t gfp)
  38 {
  39         size_t len;
  40         char *buf;
  41
  42         if (!s)
  43                 return NULL;
  44
  45         len = strnlen(s, max);
  46         buf = kmalloc_track_caller(len+1, gfp);
  47         if (buf) {
  48                 memcpy(buf, s, len);
  49                 buf[len] = '\0';
  50         }
  51         return buf;
  52 }
  53 EXPORT_SYMBOL(kstrndup);
  54
  55 /**
  56  * kmemdup - duplicate region of memory
  57  *
  58  * @src: memory region to duplicate
  59  * @len: memory region length
  60  * @gfp: GFP mask to use
  61  */
  62 void *kmemdup(const void *src, size_t len, gfp_t gfp)
  63 {
  64         void *p;
  65
  66         p = kmalloc_track_caller(len, gfp);
  67         if (p)
  68                 memcpy(p, src, len);
  69         return p;
  70 }
  71 EXPORT_SYMBOL(kmemdup);
  72
  73 /**
  74  * memdup_user - duplicate memory region from user space
  75  *
  76  * @src: source address in user space
  77  * @len: number of bytes to copy
  78  *
  79  * Returns an ERR_PTR() on failure.
  80  */
  81 void *memdup_user(const void __user *src, size_t len)
  82 {
  83         void *p;
  84
  85         /*
  86          * Always use GFP_KERNEL, since copy_from_user() can sleep and
  87          * cause pagefault, which makes it pointless to use GFP_NOFS
  88          * or GFP_ATOMIC.
  89          */
  90         p = kmalloc_track_caller(len, GFP_KERNEL);
  91         if (!p)
  92                 return ERR_PTR(-ENOMEM);
  93
  94         if (copy_from_user(p, src, len)) {
  95                 kfree(p);
  96                 return ERR_PTR(-EFAULT);
  97         }
  98
  99         return p;
 100 }
 101 EXPORT_SYMBOL(memdup_user);
 102
 103 /**
 104  * __krealloc - like krealloc() but don't free @p.
 105  * @p: object to reallocate memory for.
 106  * @new_size: how many bytes of memory are required.
 107  * @flags: the type of memory to allocate.
 108  *
 109  * This function is like krealloc() except it never frees the originally
 110  * allocated buffer. Use this if you don't want to free the buffer immediately
 111  * like, for example, with RCU.
 112  */
 113 void *__krealloc(const void *p, size_t new_size, gfp_t flags)
 114 {
 115         void *ret;
 116         size_t ks = 0;
 117
 118         if (unlikely(!new_size))
 119                 return ZERO_SIZE_PTR;
 120
 121         if (p)
 122                 ks = ksize(p);
 123
 124         if (ks >= new_size)
 125                 return (void *)p;
 126
 127         ret = kmalloc_track_caller(new_size, flags);
 128         if (ret && p)
 129                 memcpy(ret, p, ks);
 130
 131         return ret;
 132 }
 133 EXPORT_SYMBOL(__krealloc);
 134
 135 /**
 136  * krealloc - reallocate memory. The contents will remain unchanged.
 137  * @p: object to reallocate memory for.
 138  * @new_size: how many bytes of memory are required.
 139  * @flags: the type of memory to allocate.
 140  *
 141  * The contents of the object pointed to are preserved up to the
 142  * lesser of the new and old sizes.  If @p is %NULL, krealloc()
 143  * behaves exactly like kmalloc().  If @size is 0 and @p is not a
 144  * %NULL pointer, the object pointed to is freed.
 145  */
 146 void *krealloc(const void *p, size_t new_size, gfp_t flags)
 147 {
 148         void *ret;
 149
 150         if (unlikely(!new_size)) {
 151                 kfree(p);
 152                 return ZERO_SIZE_PTR;
 153         }
 154
 155         ret = __krealloc(p, new_size, flags);
 156         if (ret && p != ret)
 157                 kfree(p);
 158
 159         return ret;
 160 }
 161 EXPORT_SYMBOL(krealloc);
 162
 163 /**
 164  * kzfree - like kfree but zero memory
 165  * @p: object to free memory of
 166  *
 167  * The memory of the object @p points to is zeroed before freed.
 168  * If @p is %NULL, kzfree() does nothing.
 169  */
 170 void kzfree(const void *p)
 171 {
 172         size_t ks;
 173         void *mem = (void *)p;
 174
 175         if (unlikely(ZERO_OR_NULL_PTR(mem)))
 176                 return;
 177         ks = ksize(mem);
 178         memset(mem, 0, ks);
 179         kfree(mem);
 180 }
 181 EXPORT_SYMBOL(kzfree);
 182
 183 /*
 184  * strndup_user - duplicate an existing string from user space
 185  * @s: The string to duplicate
 186  * @n: Maximum number of bytes to copy, including the trailing NUL.
 187  */
 188 char *strndup_user(const char __user *s, long n)
 189 {
 190         char *p;
 191         long length;
 192
 193         length = strnlen_user(s, n);
 194
 195         if (!length)
 196                 return ERR_PTR(-EFAULT);
 197
 198         if (length > n)
 199                 return ERR_PTR(-EINVAL);
 200
 201         p = kmalloc(length, GFP_KERNEL);
 202
 203         if (!p)
 204                 return ERR_PTR(-ENOMEM);
 205
 206         if (copy_from_user(p, s, length)) {
 207                 kfree(p);
 208                 return ERR_PTR(-EFAULT);
 209         }
 210
 211         p[length - 1] = '\0';
 212
 213         return p;
 214 }
 215 EXPORT_SYMBOL(strndup_user);
 216
 217 #ifndef HAVE_ARCH_PICK_MMAP_LAYOUT
 218 void arch_pick_mmap_layout(struct mm_struct *mm)
 219 {
 220         mm->mmap_base = TASK_UNMAPPED_BASE;
 221         mm->get_unmapped_area = arch_get_unmapped_area;
 222         mm->unmap_area = arch_unmap_area;
 223 }
 224 #endif
 225
 226 /**
 227  * get_user_pages_fast() - pin user pages in memory
 228  * @start:      starting user address
 229  * @nr_pages:   number of pages from start to pin
 230  * @write:      whether pages will be written to
 231  * @pages:      array that receives pointers to the pages pinned.
 232  *              Should be at least nr_pages long.
 233  *
 234  * Attempt to pin user pages in memory without taking mm->mmap_sem.
 235  * If not successful, it will fall back to taking the lock and
 236  * calling get_user_pages().
 237  *
 238  * Returns number of pages pinned. This may be fewer than the number
 239  * requested. If nr_pages is 0 or negative, returns 0. If no pages
 240  * were pinned, returns -errno.
 241  */
 242 int __attribute__((weak)) get_user_pages_fast(unsigned long start,
 243                                 int nr_pages, int write, struct page **pages)
 244 {
 245         struct mm_struct *mm = current->mm;
 246         int ret;
 247
 248         down_read(&mm->mmap_sem);
 249         ret = get_user_pages(current, mm, start, nr_pages,
 250                                         write, 0, pages, NULL);
 251         up_read(&mm->mmap_sem);
 252
 253         return ret;
 254 }
 255 EXPORT_SYMBOL_GPL(get_user_pages_fast);
 256
 257 /* Tracepoints definitions. */
 258 DEFINE_TRACE(kmalloc);
 259 DEFINE_TRACE(kmem_cache_alloc);
 260 DEFINE_TRACE(kmalloc_node);
 261 DEFINE_TRACE(kmem_cache_alloc_node);
 262 DEFINE_TRACE(kfree);
 263 DEFINE_TRACE(kmem_cache_free);
 264
 265 EXPORT_TRACEPOINT_SYMBOL(kmalloc);
 266 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
 267 EXPORT_TRACEPOINT_SYMBOL(kmalloc_node);
 268 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc_node);
 269 EXPORT_TRACEPOINT_SYMBOL(kfree);
 270 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);