mm/util.c

   1 #include <linux/mm.h>
   2 #include <linux/slab.h>
   3 #include <linux/string.h>
   4 #include <linux/compiler.h>
   5 #include <linux/export.h>
   6 #include <linux/err.h>
   7 #include <linux/sched.h>
   8 #include <linux/security.h>
   9 #include <linux/swap.h>
  10 #include <linux/swapops.h>
  11 #include <linux/mman.h>
  12 #include <linux/hugetlb.h>
  13 #include <linux/vmalloc.h>
  14
  15 #include <asm/sections.h>
  16 #include <asm/uaccess.h>
  17
  18 #include "internal.h"
  19
  20 static inline int is_kernel_rodata(unsigned long addr)
  21 {
  22         return addr >= (unsigned long)__start_rodata &&
  23                 addr < (unsigned long)__end_rodata;
  24 }
  25
  26 /**
  27  * kfree_const - conditionally free memory
  28  * @x: pointer to the memory
  29  *
  30  * Function calls kfree only if @x is not in .rodata section.
  31  */
  32 void kfree_const(const void *x)
  33 {
  34         if (!is_kernel_rodata((unsigned long)x))
  35                 kfree(x);
  36 }
  37 EXPORT_SYMBOL(kfree_const);
  38
  39 /**
  40  * kstrdup - allocate space for and copy an existing string
  41  * @s: the string to duplicate
  42  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  43  */
  44 char *kstrdup(const char *s, gfp_t gfp)
  45 {
  46         size_t len;
  47         char *buf;
  48
  49         if (!s)
  50                 return NULL;
  51
  52         len = strlen(s) + 1;
  53         buf = kmalloc_track_caller(len, gfp);
  54         if (buf)
  55                 memcpy(buf, s, len);
  56         return buf;
  57 }
  58 EXPORT_SYMBOL(kstrdup);
  59
  60 /**
  61  * kstrdup_const - conditionally duplicate an existing const string
  62  * @s: the string to duplicate
  63  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  64  *
  65  * Function returns source string if it is in .rodata section otherwise it
  66  * fallbacks to kstrdup.
  67  * Strings allocated by kstrdup_const should be freed by kfree_const.
  68  */
  69 const char *kstrdup_const(const char *s, gfp_t gfp)
  70 {
  71         if (is_kernel_rodata((unsigned long)s))
  72                 return s;
  73
  74         return kstrdup(s, gfp);
  75 }
  76 EXPORT_SYMBOL(kstrdup_const);
  77
  78 /**
  79  * kstrndup - allocate space for and copy an existing string
  80  * @s: the string to duplicate
  81  * @max: read at most @max chars from @s
  82  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  83  */
  84 char *kstrndup(const char *s, size_t max, gfp_t gfp)
  85 {
  86         size_t len;
  87         char *buf;
  88
  89         if (!s)
  90                 return NULL;
  91
  92         len = strnlen(s, max);
  93         buf = kmalloc_track_caller(len+1, gfp);
  94         if (buf) {
  95                 memcpy(buf, s, len);
  96                 buf[len] = '\0';
  97         }
  98         return buf;
  99 }
 100 EXPORT_SYMBOL(kstrndup);
 101
 102 /**
 103  * kmemdup - duplicate region of memory
 104  *
 105  * @src: memory region to duplicate
 106  * @len: memory region length
 107  * @gfp: GFP mask to use
 108  */
 109 void *kmemdup(const void *src, size_t len, gfp_t gfp)
 110 {
 111         void *p;
 112
 113         p = kmalloc_track_caller(len, gfp);
 114         if (p)
 115                 memcpy(p, src, len);
 116         return p;
 117 }
 118 EXPORT_SYMBOL(kmemdup);
 119
 120 /**
 121  * memdup_user - duplicate memory region from user space
 122  *
 123  * @src: source address in user space
 124  * @len: number of bytes to copy
 125  *
 126  * Returns an ERR_PTR() on failure.
 127  */
 128 void *memdup_user(const void __user *src, size_t len)
 129 {
 130         void *p;
 131
 132         /*
 133          * Always use GFP_KERNEL, since copy_from_user() can sleep and
 134          * cause pagefault, which makes it pointless to use GFP_NOFS
 135          * or GFP_ATOMIC.
 136          */
 137         p = kmalloc_track_caller(len, GFP_KERNEL);
 138         if (!p)
 139                 return ERR_PTR(-ENOMEM);
 140
 141         if (copy_from_user(p, src, len)) {
 142                 kfree(p);
 143                 return ERR_PTR(-EFAULT);
 144         }
 145
 146         return p;
 147 }
 148 EXPORT_SYMBOL(memdup_user);
 149
 150 /*
 151  * strndup_user - duplicate an existing string from user space
 152  * @s: The string to duplicate
 153  * @n: Maximum number of bytes to copy, including the trailing NUL.
 154  */
 155 char *strndup_user(const char __user *s, long n)
 156 {
 157         char *p;
 158         long length;
 159
 160         length = strnlen_user(s, n);
 161
 162         if (!length)
 163                 return ERR_PTR(-EFAULT);
 164
 165         if (length > n)
 166                 return ERR_PTR(-EINVAL);
 167
 168         p = memdup_user(s, length);
 169
 170         if (IS_ERR(p))
 171                 return p;
 172
 173         p[length - 1] = '\0';
 174
 175         return p;
 176 }
 177 EXPORT_SYMBOL(strndup_user);
 178
 179 /**
 180  * memdup_user_nul - duplicate memory region from user space and NUL-terminate
 181  *
 182  * @src: source address in user space
 183  * @len: number of bytes to copy
 184  *
 185  * Returns an ERR_PTR() on failure.
 186  */
 187 void *memdup_user_nul(const void __user *src, size_t len)
 188 {
 189         char *p;
 190
 191         /*
 192          * Always use GFP_KERNEL, since copy_from_user() can sleep and
 193          * cause pagefault, which makes it pointless to use GFP_NOFS
 194          * or GFP_ATOMIC.
 195          */
 196         p = kmalloc_track_caller(len + 1, GFP_KERNEL);
 197         if (!p)
 198                 return ERR_PTR(-ENOMEM);
 199
 200         if (copy_from_user(p, src, len)) {
 201                 kfree(p);
 202                 return ERR_PTR(-EFAULT);
 203         }
 204         p[len] = '\0';
 205
 206         return p;
 207 }
 208 EXPORT_SYMBOL(memdup_user_nul);
 209
 210 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
 211                 struct vm_area_struct *prev, struct rb_node *rb_parent)
 212 {
 213         struct vm_area_struct *next;
 214
 215         vma->vm_prev = prev;
 216         if (prev) {
 217                 next = prev->vm_next;
 218                 prev->vm_next = vma;
 219         } else {
 220                 mm->mmap = vma;
 221                 if (rb_parent)
 222                         next = rb_entry(rb_parent,
 223                                         struct vm_area_struct, vm_rb);
 224                 else
 225                         next = NULL;
 226         }
 227         vma->vm_next = next;
 228         if (next)
 229                 next->vm_prev = vma;
 230 }
 231
 232 /* Check if the vma is being used as a stack by this task */
 233 static int vm_is_stack_for_task(struct task_struct *t,
 234                                 struct vm_area_struct *vma)
 235 {
 236         return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 237 }
 238
 239 /*
 240  * Check if the vma is being used as a stack.
 241  * If is_group is non-zero, check in the entire thread group or else
 242  * just check in the current task. Returns the task_struct of the task
 243  * that the vma is stack for. Must be called under rcu_read_lock().
 244  */
 245 struct task_struct *task_of_stack(struct task_struct *task,
 246                                 struct vm_area_struct *vma, bool in_group)
 247 {
 248         if (vm_is_stack_for_task(task, vma))
 249                 return task;
 250
 251         if (in_group) {
 252                 struct task_struct *t;
 253
 254                 for_each_thread(task, t) {
 255                         if (vm_is_stack_for_task(t, vma))
 256                                 return t;
 257                 }
 258         }
 259
 260         return NULL;
 261 }
 262
 263 #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 264 void arch_pick_mmap_layout(struct mm_struct *mm)
 265 {
 266         mm->mmap_base = TASK_UNMAPPED_BASE;
 267         mm->get_unmapped_area = arch_get_unmapped_area;
 268 }
 269 #endif
 270
 271 /*
 272  * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
 273  * back to the regular GUP.
 274  * If the architecture not support this function, simply return with no
 275  * page pinned
 276  */
 277 int __weak __get_user_pages_fast(unsigned long start,
 278                                  int nr_pages, int write, struct page **pages)
 279 {
 280         return 0;
 281 }
 282 EXPORT_SYMBOL_GPL(__get_user_pages_fast);
 283
 284 /**
 285  * get_user_pages_fast() - pin user pages in memory
 286  * @start:      starting user address
 287  * @nr_pages:   number of pages from start to pin
 288  * @write:      whether pages will be written to
 289  * @pages:      array that receives pointers to the pages pinned.
 290  *              Should be at least nr_pages long.
 291  *
 292  * Returns number of pages pinned. This may be fewer than the number
 293  * requested. If nr_pages is 0 or negative, returns 0. If no pages
 294  * were pinned, returns -errno.
 295  *
 296  * get_user_pages_fast provides equivalent functionality to get_user_pages,
 297  * operating on current and current->mm, with force=0 and vma=NULL. However
 298  * unlike get_user_pages, it must be called without mmap_sem held.
 299  *
 300  * get_user_pages_fast may take mmap_sem and page table locks, so no
 301  * assumptions can be made about lack of locking. get_user_pages_fast is to be
 302  * implemented in a way that is advantageous (vs get_user_pages()) when the
 303  * user memory area is already faulted in and present in ptes. However if the
 304  * pages have to be faulted in, it may turn out to be slightly slower so
 305  * callers need to carefully consider what to use. On many architectures,
 306  * get_user_pages_fast simply falls back to get_user_pages.
 307  */
 308 int __weak get_user_pages_fast(unsigned long start,
 309                                 int nr_pages, int write, struct page **pages)
 310 {
 311         struct mm_struct *mm = current->mm;
 312         return get_user_pages_unlocked(current, mm, start, nr_pages,
 313                                        write, 0, pages);
 314 }
 315 EXPORT_SYMBOL_GPL(get_user_pages_fast);
 316
 317 unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
 318         unsigned long len, unsigned long prot,
 319         unsigned long flag, unsigned long pgoff)
 320 {
 321         unsigned long ret;
 322         struct mm_struct *mm = current->mm;
 323         unsigned long populate;
 324
 325         ret = security_mmap_file(file, prot, flag);
 326         if (!ret) {
 327                 down_write(&mm->mmap_sem);
 328                 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
 329                                     &populate);
 330                 up_write(&mm->mmap_sem);
 331                 if (populate)
 332                         mm_populate(ret, populate);
 333         }
 334         return ret;
 335 }
 336
 337 unsigned long vm_mmap(struct file *file, unsigned long addr,
 338         unsigned long len, unsigned long prot,
 339         unsigned long flag, unsigned long offset)
 340 {
 341         if (unlikely(offset + PAGE_ALIGN(len) < offset))
 342                 return -EINVAL;
 343         if (unlikely(offset_in_page(offset)))
 344                 return -EINVAL;
 345
 346         return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
 347 }
 348 EXPORT_SYMBOL(vm_mmap);
 349
 350 void kvfree(const void *addr)
 351 {
 352         if (is_vmalloc_addr(addr))
 353                 vfree(addr);
 354         else
 355                 kfree(addr);
 356 }
 357 EXPORT_SYMBOL(kvfree);
 358
 359 static inline void *__page_rmapping(struct page *page)
 360 {
 361         unsigned long mapping;
 362
 363         mapping = (unsigned long)page->mapping;
 364         mapping &= ~PAGE_MAPPING_FLAGS;
 365
 366         return (void *)mapping;
 367 }
 368
 369 /* Neutral page->mapping pointer to address_space or anon_vma or other */
 370 void *page_rmapping(struct page *page)
 371 {
 372         page = compound_head(page);
 373         return __page_rmapping(page);
 374 }
 375
 376 struct anon_vma *page_anon_vma(struct page *page)
 377 {
 378         unsigned long mapping;
 379
 380         page = compound_head(page);
 381         mapping = (unsigned long)page->mapping;
 382         if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
 383                 return NULL;
 384         return __page_rmapping(page);
 385 }
 386
 387 struct address_space *page_mapping(struct page *page)
 388 {
 389         struct address_space *mapping;
 390
 391         page = compound_head(page);
 392
 393         /* This happens if someone calls flush_dcache_page on slab page */
 394         if (unlikely(PageSlab(page)))
 395                 return NULL;
 396
 397         if (unlikely(PageSwapCache(page))) {
 398                 swp_entry_t entry;
 399
 400                 entry.val = page_private(page);
 401                 return swap_address_space(entry);
 402         }
 403
 404         mapping = page->mapping;
 405         if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
 406                 return NULL;
 407         return mapping;
 408 }
 409
 410 /* Slow path of page_mapcount() for compound pages */
 411 int __page_mapcount(struct page *page)
 412 {
 413         int ret;
 414
 415         ret = atomic_read(&page->_mapcount) + 1;
 416         page = compound_head(page);
 417         ret += atomic_read(compound_mapcount_ptr(page)) + 1;
 418         if (PageDoubleMap(page))
 419                 ret--;
 420         return ret;
 421 }
 422 EXPORT_SYMBOL_GPL(__page_mapcount);
 423
 424 int overcommit_ratio_handler(struct ctl_table *table, int write,
 425                              void __user *buffer, size_t *lenp,
 426                              loff_t *ppos)
 427 {
 428         int ret;
 429
 430         ret = proc_dointvec(table, write, buffer, lenp, ppos);
 431         if (ret == 0 && write)
 432                 sysctl_overcommit_kbytes = 0;
 433         return ret;
 434 }
 435
 436 int overcommit_kbytes_handler(struct ctl_table *table, int write,
 437                              void __user *buffer, size_t *lenp,
 438                              loff_t *ppos)
 439 {
 440         int ret;
 441
 442         ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 443         if (ret == 0 && write)
 444                 sysctl_overcommit_ratio = 0;
 445         return ret;
 446 }
 447
 448 /*
 449  * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
 450  */
 451 unsigned long vm_commit_limit(void)
 452 {
 453         unsigned long allowed;
 454
 455         if (sysctl_overcommit_kbytes)
 456                 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
 457         else
 458                 allowed = ((totalram_pages - hugetlb_total_pages())
 459                            * sysctl_overcommit_ratio / 100);
 460         allowed += total_swap_pages;
 461
 462         return allowed;
 463 }
 464
 465 /**
 466  * get_cmdline() - copy the cmdline value to a buffer.
 467  * @task:     the task whose cmdline value to copy.
 468  * @buffer:   the buffer to copy to.
 469  * @buflen:   the length of the buffer. Larger cmdline values are truncated
 470  *            to this length.
 471  * Returns the size of the cmdline field copied. Note that the copy does
 472  * not guarantee an ending NULL byte.
 473  */
 474 int get_cmdline(struct task_struct *task, char *buffer, int buflen)
 475 {
 476         int res = 0;
 477         unsigned int len;
 478         struct mm_struct *mm = get_task_mm(task);
 479         unsigned long arg_start, arg_end, env_start, env_end;
 480         if (!mm)
 481                 goto out;
 482         if (!mm->arg_end)
 483                 goto out_mm;    /* Shh! No looking before we're done */
 484
 485         down_read(&mm->mmap_sem);
 486         arg_start = mm->arg_start;
 487         arg_end = mm->arg_end;
 488         env_start = mm->env_start;
 489         env_end = mm->env_end;
 490         up_read(&mm->mmap_sem);
 491
 492         len = arg_end - arg_start;
 493
 494         if (len > buflen)
 495                 len = buflen;
 496
 497         res = access_process_vm(task, arg_start, buffer, len, 0);
 498
 499         /*
 500          * If the nul at the end of args has been overwritten, then
 501          * assume application is using setproctitle(3).
 502          */
 503         if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
 504                 len = strnlen(buffer, res);
 505                 if (len < res) {
 506                         res = len;
 507                 } else {
 508                         len = env_end - env_start;
 509                         if (len > buflen - res)
 510                                 len = buflen - res;
 511                         res += access_process_vm(task, env_start,
 512                                                  buffer+res, len, 0);
 513                         res = strnlen(buffer, res);
 514                 }
 515         }
 516 out_mm:
 517         mmput(mm);
 518 out:
 519         return res;
 520 }