mm/util.c

   1 #include <linux/mm.h>
   2 #include <linux/slab.h>
   3 #include <linux/string.h>
   4 #include <linux/export.h>
   5 #include <linux/err.h>
   6 #include <linux/sched.h>
   7 #include <linux/security.h>
   8 #include <asm/uaccess.h>
   9
  10 #include "internal.h"
  11
  12 #define CREATE_TRACE_POINTS
  13 #include <trace/events/kmem.h>
  14
  15 /**
  16  * kstrdup - allocate space for and copy an existing string
  17  * @s: the string to duplicate
  18  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  19  */
  20 char *kstrdup(const char *s, gfp_t gfp)
  21 {
  22         size_t len;
  23         char *buf;
  24
  25         if (!s)
  26                 return NULL;
  27
  28         len = strlen(s) + 1;
  29         buf = kmalloc_track_caller(len, gfp);
  30         if (buf)
  31                 memcpy(buf, s, len);
  32         return buf;
  33 }
  34 EXPORT_SYMBOL(kstrdup);
  35
  36 /**
  37  * kstrndup - allocate space for and copy an existing string
  38  * @s: the string to duplicate
  39  * @max: read at most @max chars from @s
  40  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  41  */
  42 char *kstrndup(const char *s, size_t max, gfp_t gfp)
  43 {
  44         size_t len;
  45         char *buf;
  46
  47         if (!s)
  48                 return NULL;
  49
  50         len = strnlen(s, max);
  51         buf = kmalloc_track_caller(len+1, gfp);
  52         if (buf) {
  53                 memcpy(buf, s, len);
  54                 buf[len] = '\0';
  55         }
  56         return buf;
  57 }
  58 EXPORT_SYMBOL(kstrndup);
  59
  60 /**
  61  * kmemdup - duplicate region of memory
  62  *
  63  * @src: memory region to duplicate
  64  * @len: memory region length
  65  * @gfp: GFP mask to use
  66  */
  67 void *kmemdup(const void *src, size_t len, gfp_t gfp)
  68 {
  69         void *p;
  70
  71         p = kmalloc_track_caller(len, gfp);
  72         if (p)
  73                 memcpy(p, src, len);
  74         return p;
  75 }
  76 EXPORT_SYMBOL(kmemdup);
  77
  78 /**
  79  * memdup_user - duplicate memory region from user space
  80  *
  81  * @src: source address in user space
  82  * @len: number of bytes to copy
  83  *
  84  * Returns an ERR_PTR() on failure.
  85  */
  86 void *memdup_user(const void __user *src, size_t len)
  87 {
  88         void *p;
  89
  90         /*
  91          * Always use GFP_KERNEL, since copy_from_user() can sleep and
  92          * cause pagefault, which makes it pointless to use GFP_NOFS
  93          * or GFP_ATOMIC.
  94          */
  95         p = kmalloc_track_caller(len, GFP_KERNEL);
  96         if (!p)
  97                 return ERR_PTR(-ENOMEM);
  98
  99         if (copy_from_user(p, src, len)) {
 100                 kfree(p);
 101                 return ERR_PTR(-EFAULT);
 102         }
 103
 104         return p;
 105 }
 106 EXPORT_SYMBOL(memdup_user);
 107
 108 static __always_inline void *__do_krealloc(const void *p, size_t new_size,
 109                                            gfp_t flags)
 110 {
 111         void *ret;
 112         size_t ks = 0;
 113
 114         if (p)
 115                 ks = ksize(p);
 116
 117         if (ks >= new_size)
 118                 return (void *)p;
 119
 120         ret = kmalloc_track_caller(new_size, flags);
 121         if (ret && p)
 122                 memcpy(ret, p, ks);
 123
 124         return ret;
 125 }
 126
 127 /**
 128  * __krealloc - like krealloc() but don't free @p.
 129  * @p: object to reallocate memory for.
 130  * @new_size: how many bytes of memory are required.
 131  * @flags: the type of memory to allocate.
 132  *
 133  * This function is like krealloc() except it never frees the originally
 134  * allocated buffer. Use this if you don't want to free the buffer immediately
 135  * like, for example, with RCU.
 136  */
 137 void *__krealloc(const void *p, size_t new_size, gfp_t flags)
 138 {
 139         if (unlikely(!new_size))
 140                 return ZERO_SIZE_PTR;
 141
 142         return __do_krealloc(p, new_size, flags);
 143
 144 }
 145 EXPORT_SYMBOL(__krealloc);
 146
 147 /**
 148  * krealloc - reallocate memory. The contents will remain unchanged.
 149  * @p: object to reallocate memory for.
 150  * @new_size: how many bytes of memory are required.
 151  * @flags: the type of memory to allocate.
 152  *
 153  * The contents of the object pointed to are preserved up to the
 154  * lesser of the new and old sizes.  If @p is %NULL, krealloc()
 155  * behaves exactly like kmalloc().  If @size is 0 and @p is not a
 156  * %NULL pointer, the object pointed to is freed.
 157  */
 158 void *krealloc(const void *p, size_t new_size, gfp_t flags)
 159 {
 160         void *ret;
 161
 162         if (unlikely(!new_size)) {
 163                 kfree(p);
 164                 return ZERO_SIZE_PTR;
 165         }
 166
 167         ret = __do_krealloc(p, new_size, flags);
 168         if (ret && p != ret)
 169                 kfree(p);
 170
 171         return ret;
 172 }
 173 EXPORT_SYMBOL(krealloc);
 174
 175 /**
 176  * kzfree - like kfree but zero memory
 177  * @p: object to free memory of
 178  *
 179  * The memory of the object @p points to is zeroed before freed.
 180  * If @p is %NULL, kzfree() does nothing.
 181  *
 182  * Note: this function zeroes the whole allocated buffer which can be a good
 183  * deal bigger than the requested buffer size passed to kmalloc(). So be
 184  * careful when using this function in performance sensitive code.
 185  */
 186 void kzfree(const void *p)
 187 {
 188         size_t ks;
 189         void *mem = (void *)p;
 190
 191         if (unlikely(ZERO_OR_NULL_PTR(mem)))
 192                 return;
 193         ks = ksize(mem);
 194         memset(mem, 0, ks);
 195         kfree(mem);
 196 }
 197 EXPORT_SYMBOL(kzfree);
 198
 199 /*
 200  * strndup_user - duplicate an existing string from user space
 201  * @s: The string to duplicate
 202  * @n: Maximum number of bytes to copy, including the trailing NUL.
 203  */
 204 char *strndup_user(const char __user *s, long n)
 205 {
 206         char *p;
 207         long length;
 208
 209         length = strnlen_user(s, n);
 210
 211         if (!length)
 212                 return ERR_PTR(-EFAULT);
 213
 214         if (length > n)
 215                 return ERR_PTR(-EINVAL);
 216
 217         p = memdup_user(s, length);
 218
 219         if (IS_ERR(p))
 220                 return p;
 221
 222         p[length - 1] = '\0';
 223
 224         return p;
 225 }
 226 EXPORT_SYMBOL(strndup_user);
 227
 228 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
 229                 struct vm_area_struct *prev, struct rb_node *rb_parent)
 230 {
 231         struct vm_area_struct *next;
 232
 233         vma->vm_prev = prev;
 234         if (prev) {
 235                 next = prev->vm_next;
 236                 prev->vm_next = vma;
 237         } else {
 238                 mm->mmap = vma;
 239                 if (rb_parent)
 240                         next = rb_entry(rb_parent,
 241                                         struct vm_area_struct, vm_rb);
 242                 else
 243                         next = NULL;
 244         }
 245         vma->vm_next = next;
 246         if (next)
 247                 next->vm_prev = vma;
 248 }
 249
 250 /* Check if the vma is being used as a stack by this task */
 251 static int vm_is_stack_for_task(struct task_struct *t,
 252                                 struct vm_area_struct *vma)
 253 {
 254         return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 255 }
 256
 257 /*
 258  * Check if the vma is being used as a stack.
 259  * If is_group is non-zero, check in the entire thread group or else
 260  * just check in the current task. Returns the pid of the task that
 261  * the vma is stack for.
 262  */
 263 pid_t vm_is_stack(struct task_struct *task,
 264                   struct vm_area_struct *vma, int in_group)
 265 {
 266         pid_t ret = 0;
 267
 268         if (vm_is_stack_for_task(task, vma))
 269                 return task->pid;
 270
 271         if (in_group) {
 272                 struct task_struct *t;
 273                 rcu_read_lock();
 274                 if (!pid_alive(task))
 275                         goto done;
 276
 277                 t = task;
 278                 do {
 279                         if (vm_is_stack_for_task(t, vma)) {
 280                                 ret = t->pid;
 281                                 goto done;
 282                         }
 283                 } while_each_thread(task, t);
 284 done:
 285                 rcu_read_unlock();
 286         }
 287
 288         return ret;
 289 }
 290
 291 #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 292 void arch_pick_mmap_layout(struct mm_struct *mm)
 293 {
 294         mm->mmap_base = TASK_UNMAPPED_BASE;
 295         mm->get_unmapped_area = arch_get_unmapped_area;
 296         mm->unmap_area = arch_unmap_area;
 297 }
 298 #endif
 299
 300 /*
 301  * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
 302  * back to the regular GUP.
 303  * If the architecture not support this function, simply return with no
 304  * page pinned
 305  */
 306 int __attribute__((weak)) __get_user_pages_fast(unsigned long start,
 307                                  int nr_pages, int write, struct page **pages)
 308 {
 309         return 0;
 310 }
 311 EXPORT_SYMBOL_GPL(__get_user_pages_fast);
 312
 313 /**
 314  * get_user_pages_fast() - pin user pages in memory
 315  * @start:      starting user address
 316  * @nr_pages:   number of pages from start to pin
 317  * @write:      whether pages will be written to
 318  * @pages:      array that receives pointers to the pages pinned.
 319  *              Should be at least nr_pages long.
 320  *
 321  * Returns number of pages pinned. This may be fewer than the number
 322  * requested. If nr_pages is 0 or negative, returns 0. If no pages
 323  * were pinned, returns -errno.
 324  *
 325  * get_user_pages_fast provides equivalent functionality to get_user_pages,
 326  * operating on current and current->mm, with force=0 and vma=NULL. However
 327  * unlike get_user_pages, it must be called without mmap_sem held.
 328  *
 329  * get_user_pages_fast may take mmap_sem and page table locks, so no
 330  * assumptions can be made about lack of locking. get_user_pages_fast is to be
 331  * implemented in a way that is advantageous (vs get_user_pages()) when the
 332  * user memory area is already faulted in and present in ptes. However if the
 333  * pages have to be faulted in, it may turn out to be slightly slower so
 334  * callers need to carefully consider what to use. On many architectures,
 335  * get_user_pages_fast simply falls back to get_user_pages.
 336  */
 337 int __attribute__((weak)) get_user_pages_fast(unsigned long start,
 338                                 int nr_pages, int write, struct page **pages)
 339 {
 340         struct mm_struct *mm = current->mm;
 341         int ret;
 342
 343         down_read(&mm->mmap_sem);
 344         ret = get_user_pages(current, mm, start, nr_pages,
 345                                         write, 0, pages, NULL);
 346         up_read(&mm->mmap_sem);
 347
 348         return ret;
 349 }
 350 EXPORT_SYMBOL_GPL(get_user_pages_fast);
 351
 352 unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
 353         unsigned long len, unsigned long prot,
 354         unsigned long flag, unsigned long pgoff)
 355 {
 356         unsigned long ret;
 357         struct mm_struct *mm = current->mm;
 358
 359         ret = security_mmap_file(file, prot, flag);
 360         if (!ret) {
 361                 down_write(&mm->mmap_sem);
 362                 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff);
 363                 up_write(&mm->mmap_sem);
 364         }
 365         return ret;
 366 }
 367
 368 unsigned long vm_mmap(struct file *file, unsigned long addr,
 369         unsigned long len, unsigned long prot,
 370         unsigned long flag, unsigned long offset)
 371 {
 372         if (unlikely(offset + PAGE_ALIGN(len) < offset))
 373                 return -EINVAL;
 374         if (unlikely(offset & ~PAGE_MASK))
 375                 return -EINVAL;
 376
 377         return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
 378 }
 379 EXPORT_SYMBOL(vm_mmap);
 380
 381 /* Tracepoints definitions. */
 382 EXPORT_TRACEPOINT_SYMBOL(kmalloc);
 383 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
 384 EXPORT_TRACEPOINT_SYMBOL(kmalloc_node);
 385 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc_node);
 386 EXPORT_TRACEPOINT_SYMBOL(kfree);
 387 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);