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 int vma_is_stack_for_task(struct vm_area_struct *vma, struct task_struct *t)
 234 {
 235         return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 236 }
 237
 238 #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 239 void arch_pick_mmap_layout(struct mm_struct *mm)
 240 {
 241         mm->mmap_base = TASK_UNMAPPED_BASE;
 242         mm->get_unmapped_area = arch_get_unmapped_area;
 243 }
 244 #endif
 245
 246 /*
 247  * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
 248  * back to the regular GUP.
 249  * If the architecture not support this function, simply return with no
 250  * page pinned
 251  */
 252 int __weak __get_user_pages_fast(unsigned long start,
 253                                  int nr_pages, int write, struct page **pages)
 254 {
 255         return 0;
 256 }
 257 EXPORT_SYMBOL_GPL(__get_user_pages_fast);
 258
 259 /**
 260  * get_user_pages_fast() - pin user pages in memory
 261  * @start:      starting user address
 262  * @nr_pages:   number of pages from start to pin
 263  * @write:      whether pages will be written to
 264  * @pages:      array that receives pointers to the pages pinned.
 265  *              Should be at least nr_pages long.
 266  *
 267  * Returns number of pages pinned. This may be fewer than the number
 268  * requested. If nr_pages is 0 or negative, returns 0. If no pages
 269  * were pinned, returns -errno.
 270  *
 271  * get_user_pages_fast provides equivalent functionality to get_user_pages,
 272  * operating on current and current->mm, with force=0 and vma=NULL. However
 273  * unlike get_user_pages, it must be called without mmap_sem held.
 274  *
 275  * get_user_pages_fast may take mmap_sem and page table locks, so no
 276  * assumptions can be made about lack of locking. get_user_pages_fast is to be
 277  * implemented in a way that is advantageous (vs get_user_pages()) when the
 278  * user memory area is already faulted in and present in ptes. However if the
 279  * pages have to be faulted in, it may turn out to be slightly slower so
 280  * callers need to carefully consider what to use. On many architectures,
 281  * get_user_pages_fast simply falls back to get_user_pages.
 282  */
 283 int __weak get_user_pages_fast(unsigned long start,
 284                                 int nr_pages, int write, struct page **pages)
 285 {
 286         return get_user_pages_unlocked(start, nr_pages, write, 0, pages);
 287 }
 288 EXPORT_SYMBOL_GPL(get_user_pages_fast);
 289
 290 unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
 291         unsigned long len, unsigned long prot,
 292         unsigned long flag, unsigned long pgoff)
 293 {
 294         unsigned long ret;
 295         struct mm_struct *mm = current->mm;
 296         unsigned long populate;
 297
 298         ret = security_mmap_file(file, prot, flag);
 299         if (!ret) {
 300                 if (down_write_killable(&mm->mmap_sem))
 301                         return -EINTR;
 302                 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
 303                                     &populate);
 304                 up_write(&mm->mmap_sem);
 305                 if (populate)
 306                         mm_populate(ret, populate);
 307         }
 308         return ret;
 309 }
 310
 311 unsigned long vm_mmap(struct file *file, unsigned long addr,
 312         unsigned long len, unsigned long prot,
 313         unsigned long flag, unsigned long offset)
 314 {
 315         if (unlikely(offset + PAGE_ALIGN(len) < offset))
 316                 return -EINVAL;
 317         if (unlikely(offset_in_page(offset)))
 318                 return -EINVAL;
 319
 320         return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
 321 }
 322 EXPORT_SYMBOL(vm_mmap);
 323
 324 void kvfree(const void *addr)
 325 {
 326         if (is_vmalloc_addr(addr))
 327                 vfree(addr);
 328         else
 329                 kfree(addr);
 330 }
 331 EXPORT_SYMBOL(kvfree);
 332
 333 static inline void *__page_rmapping(struct page *page)
 334 {
 335         unsigned long mapping;
 336
 337         mapping = (unsigned long)page->mapping;
 338         mapping &= ~PAGE_MAPPING_FLAGS;
 339
 340         return (void *)mapping;
 341 }
 342
 343 /* Neutral page->mapping pointer to address_space or anon_vma or other */
 344 void *page_rmapping(struct page *page)
 345 {
 346         page = compound_head(page);
 347         return __page_rmapping(page);
 348 }
 349
 350 /*
 351  * Return true if this page is mapped into pagetables.
 352  * For compound page it returns true if any subpage of compound page is mapped.
 353  */
 354 bool page_mapped(struct page *page)
 355 {
 356         int i;
 357
 358         if (likely(!PageCompound(page)))
 359                 return atomic_read(&page->_mapcount) >= 0;
 360         page = compound_head(page);
 361         if (atomic_read(compound_mapcount_ptr(page)) >= 0)
 362                 return true;
 363         if (PageHuge(page))
 364                 return false;
 365         for (i = 0; i < hpage_nr_pages(page); i++) {
 366                 if (atomic_read(&page[i]._mapcount) >= 0)
 367                         return true;
 368         }
 369         return false;
 370 }
 371 EXPORT_SYMBOL(page_mapped);
 372
 373 struct anon_vma *page_anon_vma(struct page *page)
 374 {
 375         unsigned long mapping;
 376
 377         page = compound_head(page);
 378         mapping = (unsigned long)page->mapping;
 379         if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
 380                 return NULL;
 381         return __page_rmapping(page);
 382 }
 383
 384 struct address_space *page_mapping(struct page *page)
 385 {
 386         struct address_space *mapping;
 387
 388         page = compound_head(page);
 389
 390         /* This happens if someone calls flush_dcache_page on slab page */
 391         if (unlikely(PageSlab(page)))
 392                 return NULL;
 393
 394         if (unlikely(PageSwapCache(page))) {
 395                 swp_entry_t entry;
 396
 397                 entry.val = page_private(page);
 398                 return swap_address_space(entry);
 399         }
 400
 401         mapping = page->mapping;
 402         if ((unsigned long)mapping & PAGE_MAPPING_ANON)
 403                 return NULL;
 404
 405         return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
 406 }
 407 EXPORT_SYMBOL(page_mapping);
 408
 409 /* Slow path of page_mapcount() for compound pages */
 410 int __page_mapcount(struct page *page)
 411 {
 412         int ret;
 413
 414         ret = atomic_read(&page->_mapcount) + 1;
 415         /*
 416          * For file THP page->_mapcount contains total number of mapping
 417          * of the page: no need to look into compound_mapcount.
 418          */
 419         if (!PageAnon(page) && !PageHuge(page))
 420                 return ret;
 421         page = compound_head(page);
 422         ret += atomic_read(compound_mapcount_ptr(page)) + 1;
 423         if (PageDoubleMap(page))
 424                 ret--;
 425         return ret;
 426 }
 427 EXPORT_SYMBOL_GPL(__page_mapcount);
 428
 429 int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
 430 int sysctl_overcommit_ratio __read_mostly = 50;
 431 unsigned long sysctl_overcommit_kbytes __read_mostly;
 432 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
 433 unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
 434 unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
 435
 436 int overcommit_ratio_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_dointvec(table, write, buffer, lenp, ppos);
 443         if (ret == 0 && write)
 444                 sysctl_overcommit_kbytes = 0;
 445         return ret;
 446 }
 447
 448 int overcommit_kbytes_handler(struct ctl_table *table, int write,
 449                              void __user *buffer, size_t *lenp,
 450                              loff_t *ppos)
 451 {
 452         int ret;
 453
 454         ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 455         if (ret == 0 && write)
 456                 sysctl_overcommit_ratio = 0;
 457         return ret;
 458 }
 459
 460 /*
 461  * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
 462  */
 463 unsigned long vm_commit_limit(void)
 464 {
 465         unsigned long allowed;
 466
 467         if (sysctl_overcommit_kbytes)
 468                 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
 469         else
 470                 allowed = ((totalram_pages - hugetlb_total_pages())
 471                            * sysctl_overcommit_ratio / 100);
 472         allowed += total_swap_pages;
 473
 474         return allowed;
 475 }
 476
 477 /*
 478  * Make sure vm_committed_as in one cacheline and not cacheline shared with
 479  * other variables. It can be updated by several CPUs frequently.
 480  */
 481 struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
 482
 483 /*
 484  * The global memory commitment made in the system can be a metric
 485  * that can be used to drive ballooning decisions when Linux is hosted
 486  * as a guest. On Hyper-V, the host implements a policy engine for dynamically
 487  * balancing memory across competing virtual machines that are hosted.
 488  * Several metrics drive this policy engine including the guest reported
 489  * memory commitment.
 490  */
 491 unsigned long vm_memory_committed(void)
 492 {
 493         return percpu_counter_read_positive(&vm_committed_as);
 494 }
 495 EXPORT_SYMBOL_GPL(vm_memory_committed);
 496
 497 /*
 498  * Check that a process has enough memory to allocate a new virtual
 499  * mapping. 0 means there is enough memory for the allocation to
 500  * succeed and -ENOMEM implies there is not.
 501  *
 502  * We currently support three overcommit policies, which are set via the
 503  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
 504  *
 505  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 506  * Additional code 2002 Jul 20 by Robert Love.
 507  *
 508  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
 509  *
 510  * Note this is a helper function intended to be used by LSMs which
 511  * wish to use this logic.
 512  */
 513 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
 514 {
 515         long free, allowed, reserve;
 516
 517         VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
 518                         -(s64)vm_committed_as_batch * num_online_cpus(),
 519                         "memory commitment underflow");
 520
 521         vm_acct_memory(pages);
 522
 523         /*
 524          * Sometimes we want to use more memory than we have
 525          */
 526         if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
 527                 return 0;
 528
 529         if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
 530                 free = global_page_state(NR_FREE_PAGES);
 531                 free += global_node_page_state(NR_FILE_PAGES);
 532
 533                 /*
 534                  * shmem pages shouldn't be counted as free in this
 535                  * case, they can't be purged, only swapped out, and
 536                  * that won't affect the overall amount of available
 537                  * memory in the system.
 538                  */
 539                 free -= global_node_page_state(NR_SHMEM);
 540
 541                 free += get_nr_swap_pages();
 542
 543                 /*
 544                  * Any slabs which are created with the
 545                  * SLAB_RECLAIM_ACCOUNT flag claim to have contents
 546                  * which are reclaimable, under pressure.  The dentry
 547                  * cache and most inode caches should fall into this
 548                  */
 549                 free += global_page_state(NR_SLAB_RECLAIMABLE);
 550
 551                 /*
 552                  * Leave reserved pages. The pages are not for anonymous pages.
 553                  */
 554                 if (free <= totalreserve_pages)
 555                         goto error;
 556                 else
 557                         free -= totalreserve_pages;
 558
 559                 /*
 560                  * Reserve some for root
 561                  */
 562                 if (!cap_sys_admin)
 563                         free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
 564
 565                 if (free > pages)
 566                         return 0;
 567
 568                 goto error;
 569         }
 570
 571         allowed = vm_commit_limit();
 572         /*
 573          * Reserve some for root
 574          */
 575         if (!cap_sys_admin)
 576                 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
 577
 578         /*
 579          * Don't let a single process grow so big a user can't recover
 580          */
 581         if (mm) {
 582                 reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
 583                 allowed -= min_t(long, mm->total_vm / 32, reserve);
 584         }
 585
 586         if (percpu_counter_read_positive(&vm_committed_as) < allowed)
 587                 return 0;
 588 error:
 589         vm_unacct_memory(pages);
 590
 591         return -ENOMEM;
 592 }
 593
 594 /**
 595  * get_cmdline() - copy the cmdline value to a buffer.
 596  * @task:     the task whose cmdline value to copy.
 597  * @buffer:   the buffer to copy to.
 598  * @buflen:   the length of the buffer. Larger cmdline values are truncated
 599  *            to this length.
 600  * Returns the size of the cmdline field copied. Note that the copy does
 601  * not guarantee an ending NULL byte.
 602  */
 603 int get_cmdline(struct task_struct *task, char *buffer, int buflen)
 604 {
 605         int res = 0;
 606         unsigned int len;
 607         struct mm_struct *mm = get_task_mm(task);
 608         unsigned long arg_start, arg_end, env_start, env_end;
 609         if (!mm)
 610                 goto out;
 611         if (!mm->arg_end)
 612                 goto out_mm;    /* Shh! No looking before we're done */
 613
 614         down_read(&mm->mmap_sem);
 615         arg_start = mm->arg_start;
 616         arg_end = mm->arg_end;
 617         env_start = mm->env_start;
 618         env_end = mm->env_end;
 619         up_read(&mm->mmap_sem);
 620
 621         len = arg_end - arg_start;
 622
 623         if (len > buflen)
 624                 len = buflen;
 625
 626         res = access_process_vm(task, arg_start, buffer, len, 0);
 627
 628         /*
 629          * If the nul at the end of args has been overwritten, then
 630          * assume application is using setproctitle(3).
 631          */
 632         if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
 633                 len = strnlen(buffer, res);
 634                 if (len < res) {
 635                         res = len;
 636                 } else {
 637                         len = env_end - env_start;
 638                         if (len > buflen - res)
 639                                 len = buflen - res;
 640                         res += access_process_vm(task, env_start,
 641                                                  buffer+res, len, 0);
 642                         res = strnlen(buffer, res);
 643                 }
 644         }
 645 out_mm:
 646         mmput(mm);
 647 out:
 648         return res;
 649 }