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 #include <linux/userfaultfd_k.h>
  15
  16 #include <asm/sections.h>
  17 #include <linux/uaccess.h>
  18
  19 #include "internal.h"
  20
  21 static inline int is_kernel_rodata(unsigned long addr)
  22 {
  23         return addr >= (unsigned long)__start_rodata &&
  24                 addr < (unsigned long)__end_rodata;
  25 }
  26
  27 /**
  28  * kfree_const - conditionally free memory
  29  * @x: pointer to the memory
  30  *
  31  * Function calls kfree only if @x is not in .rodata section.
  32  */
  33 void kfree_const(const void *x)
  34 {
  35         if (!is_kernel_rodata((unsigned long)x))
  36                 kfree(x);
  37 }
  38 EXPORT_SYMBOL(kfree_const);
  39
  40 /**
  41  * kstrdup - allocate space for and copy an existing string
  42  * @s: the string to duplicate
  43  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  44  */
  45 char *kstrdup(const char *s, gfp_t gfp)
  46 {
  47         size_t len;
  48         char *buf;
  49
  50         if (!s)
  51                 return NULL;
  52
  53         len = strlen(s) + 1;
  54         buf = kmalloc_track_caller(len, gfp);
  55         if (buf)
  56                 memcpy(buf, s, len);
  57         return buf;
  58 }
  59 EXPORT_SYMBOL(kstrdup);
  60
  61 /**
  62  * kstrdup_const - conditionally duplicate an existing const string
  63  * @s: the string to duplicate
  64  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  65  *
  66  * Function returns source string if it is in .rodata section otherwise it
  67  * fallbacks to kstrdup.
  68  * Strings allocated by kstrdup_const should be freed by kfree_const.
  69  */
  70 const char *kstrdup_const(const char *s, gfp_t gfp)
  71 {
  72         if (is_kernel_rodata((unsigned long)s))
  73                 return s;
  74
  75         return kstrdup(s, gfp);
  76 }
  77 EXPORT_SYMBOL(kstrdup_const);
  78
  79 /**
  80  * kstrndup - allocate space for and copy an existing string
  81  * @s: the string to duplicate
  82  * @max: read at most @max chars from @s
  83  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  84  */
  85 char *kstrndup(const char *s, size_t max, gfp_t gfp)
  86 {
  87         size_t len;
  88         char *buf;
  89
  90         if (!s)
  91                 return NULL;
  92
  93         len = strnlen(s, max);
  94         buf = kmalloc_track_caller(len+1, gfp);
  95         if (buf) {
  96                 memcpy(buf, s, len);
  97                 buf[len] = '\0';
  98         }
  99         return buf;
 100 }
 101 EXPORT_SYMBOL(kstrndup);
 102
 103 /**
 104  * kmemdup - duplicate region of memory
 105  *
 106  * @src: memory region to duplicate
 107  * @len: memory region length
 108  * @gfp: GFP mask to use
 109  */
 110 void *kmemdup(const void *src, size_t len, gfp_t gfp)
 111 {
 112         void *p;
 113
 114         p = kmalloc_track_caller(len, gfp);
 115         if (p)
 116                 memcpy(p, src, len);
 117         return p;
 118 }
 119 EXPORT_SYMBOL(kmemdup);
 120
 121 /**
 122  * memdup_user - duplicate memory region from user space
 123  *
 124  * @src: source address in user space
 125  * @len: number of bytes to copy
 126  *
 127  * Returns an ERR_PTR() on failure.
 128  */
 129 void *memdup_user(const void __user *src, size_t len)
 130 {
 131         void *p;
 132
 133         /*
 134          * Always use GFP_KERNEL, since copy_from_user() can sleep and
 135          * cause pagefault, which makes it pointless to use GFP_NOFS
 136          * or GFP_ATOMIC.
 137          */
 138         p = kmalloc_track_caller(len, GFP_KERNEL);
 139         if (!p)
 140                 return ERR_PTR(-ENOMEM);
 141
 142         if (copy_from_user(p, src, len)) {
 143                 kfree(p);
 144                 return ERR_PTR(-EFAULT);
 145         }
 146
 147         return p;
 148 }
 149 EXPORT_SYMBOL(memdup_user);
 150
 151 /*
 152  * strndup_user - duplicate an existing string from user space
 153  * @s: The string to duplicate
 154  * @n: Maximum number of bytes to copy, including the trailing NUL.
 155  */
 156 char *strndup_user(const char __user *s, long n)
 157 {
 158         char *p;
 159         long length;
 160
 161         length = strnlen_user(s, n);
 162
 163         if (!length)
 164                 return ERR_PTR(-EFAULT);
 165
 166         if (length > n)
 167                 return ERR_PTR(-EINVAL);
 168
 169         p = memdup_user(s, length);
 170
 171         if (IS_ERR(p))
 172                 return p;
 173
 174         p[length - 1] = '\0';
 175
 176         return p;
 177 }
 178 EXPORT_SYMBOL(strndup_user);
 179
 180 /**
 181  * memdup_user_nul - duplicate memory region from user space and NUL-terminate
 182  *
 183  * @src: source address in user space
 184  * @len: number of bytes to copy
 185  *
 186  * Returns an ERR_PTR() on failure.
 187  */
 188 void *memdup_user_nul(const void __user *src, size_t len)
 189 {
 190         char *p;
 191
 192         /*
 193          * Always use GFP_KERNEL, since copy_from_user() can sleep and
 194          * cause pagefault, which makes it pointless to use GFP_NOFS
 195          * or GFP_ATOMIC.
 196          */
 197         p = kmalloc_track_caller(len + 1, GFP_KERNEL);
 198         if (!p)
 199                 return ERR_PTR(-ENOMEM);
 200
 201         if (copy_from_user(p, src, len)) {
 202                 kfree(p);
 203                 return ERR_PTR(-EFAULT);
 204         }
 205         p[len] = '\0';
 206
 207         return p;
 208 }
 209 EXPORT_SYMBOL(memdup_user_nul);
 210
 211 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
 212                 struct vm_area_struct *prev, struct rb_node *rb_parent)
 213 {
 214         struct vm_area_struct *next;
 215
 216         vma->vm_prev = prev;
 217         if (prev) {
 218                 next = prev->vm_next;
 219                 prev->vm_next = vma;
 220         } else {
 221                 mm->mmap = vma;
 222                 if (rb_parent)
 223                         next = rb_entry(rb_parent,
 224                                         struct vm_area_struct, vm_rb);
 225                 else
 226                         next = NULL;
 227         }
 228         vma->vm_next = next;
 229         if (next)
 230                 next->vm_prev = vma;
 231 }
 232
 233 /* Check if the vma is being used as a stack by this task */
 234 int vma_is_stack_for_current(struct vm_area_struct *vma)
 235 {
 236         struct task_struct * __maybe_unused t = current;
 237
 238         return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 239 }
 240
 241 #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 242 void arch_pick_mmap_layout(struct mm_struct *mm)
 243 {
 244         mm->mmap_base = TASK_UNMAPPED_BASE;
 245         mm->get_unmapped_area = arch_get_unmapped_area;
 246 }
 247 #endif
 248
 249 /*
 250  * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
 251  * back to the regular GUP.
 252  * If the architecture not support this function, simply return with no
 253  * page pinned
 254  */
 255 int __weak __get_user_pages_fast(unsigned long start,
 256                                  int nr_pages, int write, struct page **pages)
 257 {
 258         return 0;
 259 }
 260 EXPORT_SYMBOL_GPL(__get_user_pages_fast);
 261
 262 /**
 263  * get_user_pages_fast() - pin user pages in memory
 264  * @start:      starting user address
 265  * @nr_pages:   number of pages from start to pin
 266  * @write:      whether pages will be written to
 267  * @pages:      array that receives pointers to the pages pinned.
 268  *              Should be at least nr_pages long.
 269  *
 270  * Returns number of pages pinned. This may be fewer than the number
 271  * requested. If nr_pages is 0 or negative, returns 0. If no pages
 272  * were pinned, returns -errno.
 273  *
 274  * get_user_pages_fast provides equivalent functionality to get_user_pages,
 275  * operating on current and current->mm, with force=0 and vma=NULL. However
 276  * unlike get_user_pages, it must be called without mmap_sem held.
 277  *
 278  * get_user_pages_fast may take mmap_sem and page table locks, so no
 279  * assumptions can be made about lack of locking. get_user_pages_fast is to be
 280  * implemented in a way that is advantageous (vs get_user_pages()) when the
 281  * user memory area is already faulted in and present in ptes. However if the
 282  * pages have to be faulted in, it may turn out to be slightly slower so
 283  * callers need to carefully consider what to use. On many architectures,
 284  * get_user_pages_fast simply falls back to get_user_pages.
 285  */
 286 int __weak get_user_pages_fast(unsigned long start,
 287                                 int nr_pages, int write, struct page **pages)
 288 {
 289         return get_user_pages_unlocked(start, nr_pages, pages,
 290                                        write ? FOLL_WRITE : 0);
 291 }
 292 EXPORT_SYMBOL_GPL(get_user_pages_fast);
 293
 294 unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
 295         unsigned long len, unsigned long prot,
 296         unsigned long flag, unsigned long pgoff)
 297 {
 298         unsigned long ret;
 299         struct mm_struct *mm = current->mm;
 300         unsigned long populate;
 301         LIST_HEAD(uf);
 302
 303         ret = security_mmap_file(file, prot, flag);
 304         if (!ret) {
 305                 if (down_write_killable(&mm->mmap_sem))
 306                         return -EINTR;
 307                 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
 308                                     &populate, &uf);
 309                 up_write(&mm->mmap_sem);
 310                 userfaultfd_unmap_complete(mm, &uf);
 311                 if (populate)
 312                         mm_populate(ret, populate);
 313         }
 314         return ret;
 315 }
 316
 317 unsigned long vm_mmap(struct file *file, unsigned long addr,
 318         unsigned long len, unsigned long prot,
 319         unsigned long flag, unsigned long offset)
 320 {
 321         if (unlikely(offset + PAGE_ALIGN(len) < offset))
 322                 return -EINVAL;
 323         if (unlikely(offset_in_page(offset)))
 324                 return -EINVAL;
 325
 326         return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
 327 }
 328 EXPORT_SYMBOL(vm_mmap);
 329
 330 void kvfree(const void *addr)
 331 {
 332         if (is_vmalloc_addr(addr))
 333                 vfree(addr);
 334         else
 335                 kfree(addr);
 336 }
 337 EXPORT_SYMBOL(kvfree);
 338
 339 static inline void *__page_rmapping(struct page *page)
 340 {
 341         unsigned long mapping;
 342
 343         mapping = (unsigned long)page->mapping;
 344         mapping &= ~PAGE_MAPPING_FLAGS;
 345
 346         return (void *)mapping;
 347 }
 348
 349 /* Neutral page->mapping pointer to address_space or anon_vma or other */
 350 void *page_rmapping(struct page *page)
 351 {
 352         page = compound_head(page);
 353         return __page_rmapping(page);
 354 }
 355
 356 /*
 357  * Return true if this page is mapped into pagetables.
 358  * For compound page it returns true if any subpage of compound page is mapped.
 359  */
 360 bool page_mapped(struct page *page)
 361 {
 362         int i;
 363
 364         if (likely(!PageCompound(page)))
 365                 return atomic_read(&page->_mapcount) >= 0;
 366         page = compound_head(page);
 367         if (atomic_read(compound_mapcount_ptr(page)) >= 0)
 368                 return true;
 369         if (PageHuge(page))
 370                 return false;
 371         for (i = 0; i < hpage_nr_pages(page); i++) {
 372                 if (atomic_read(&page[i]._mapcount) >= 0)
 373                         return true;
 374         }
 375         return false;
 376 }
 377 EXPORT_SYMBOL(page_mapped);
 378
 379 struct anon_vma *page_anon_vma(struct page *page)
 380 {
 381         unsigned long mapping;
 382
 383         page = compound_head(page);
 384         mapping = (unsigned long)page->mapping;
 385         if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
 386                 return NULL;
 387         return __page_rmapping(page);
 388 }
 389
 390 struct address_space *page_mapping(struct page *page)
 391 {
 392         struct address_space *mapping;
 393
 394         page = compound_head(page);
 395
 396         /* This happens if someone calls flush_dcache_page on slab page */
 397         if (unlikely(PageSlab(page)))
 398                 return NULL;
 399
 400         if (unlikely(PageSwapCache(page))) {
 401                 swp_entry_t entry;
 402
 403                 entry.val = page_private(page);
 404                 return swap_address_space(entry);
 405         }
 406
 407         mapping = page->mapping;
 408         if ((unsigned long)mapping & PAGE_MAPPING_ANON)
 409                 return NULL;
 410
 411         return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
 412 }
 413 EXPORT_SYMBOL(page_mapping);
 414
 415 /* Slow path of page_mapcount() for compound pages */
 416 int __page_mapcount(struct page *page)
 417 {
 418         int ret;
 419
 420         ret = atomic_read(&page->_mapcount) + 1;
 421         /*
 422          * For file THP page->_mapcount contains total number of mapping
 423          * of the page: no need to look into compound_mapcount.
 424          */
 425         if (!PageAnon(page) && !PageHuge(page))
 426                 return ret;
 427         page = compound_head(page);
 428         ret += atomic_read(compound_mapcount_ptr(page)) + 1;
 429         if (PageDoubleMap(page))
 430                 ret--;
 431         return ret;
 432 }
 433 EXPORT_SYMBOL_GPL(__page_mapcount);
 434
 435 int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
 436 int sysctl_overcommit_ratio __read_mostly = 50;
 437 unsigned long sysctl_overcommit_kbytes __read_mostly;
 438 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
 439 unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
 440 unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
 441
 442 int overcommit_ratio_handler(struct ctl_table *table, int write,
 443                              void __user *buffer, size_t *lenp,
 444                              loff_t *ppos)
 445 {
 446         int ret;
 447
 448         ret = proc_dointvec(table, write, buffer, lenp, ppos);
 449         if (ret == 0 && write)
 450                 sysctl_overcommit_kbytes = 0;
 451         return ret;
 452 }
 453
 454 int overcommit_kbytes_handler(struct ctl_table *table, int write,
 455                              void __user *buffer, size_t *lenp,
 456                              loff_t *ppos)
 457 {
 458         int ret;
 459
 460         ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 461         if (ret == 0 && write)
 462                 sysctl_overcommit_ratio = 0;
 463         return ret;
 464 }
 465
 466 /*
 467  * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
 468  */
 469 unsigned long vm_commit_limit(void)
 470 {
 471         unsigned long allowed;
 472
 473         if (sysctl_overcommit_kbytes)
 474                 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
 475         else
 476                 allowed = ((totalram_pages - hugetlb_total_pages())
 477                            * sysctl_overcommit_ratio / 100);
 478         allowed += total_swap_pages;
 479
 480         return allowed;
 481 }
 482
 483 /*
 484  * Make sure vm_committed_as in one cacheline and not cacheline shared with
 485  * other variables. It can be updated by several CPUs frequently.
 486  */
 487 struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
 488
 489 /*
 490  * The global memory commitment made in the system can be a metric
 491  * that can be used to drive ballooning decisions when Linux is hosted
 492  * as a guest. On Hyper-V, the host implements a policy engine for dynamically
 493  * balancing memory across competing virtual machines that are hosted.
 494  * Several metrics drive this policy engine including the guest reported
 495  * memory commitment.
 496  */
 497 unsigned long vm_memory_committed(void)
 498 {
 499         return percpu_counter_read_positive(&vm_committed_as);
 500 }
 501 EXPORT_SYMBOL_GPL(vm_memory_committed);
 502
 503 /*
 504  * Check that a process has enough memory to allocate a new virtual
 505  * mapping. 0 means there is enough memory for the allocation to
 506  * succeed and -ENOMEM implies there is not.
 507  *
 508  * We currently support three overcommit policies, which are set via the
 509  * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
 510  *
 511  * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 512  * Additional code 2002 Jul 20 by Robert Love.
 513  *
 514  * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
 515  *
 516  * Note this is a helper function intended to be used by LSMs which
 517  * wish to use this logic.
 518  */
 519 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
 520 {
 521         long free, allowed, reserve;
 522
 523         VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
 524                         -(s64)vm_committed_as_batch * num_online_cpus(),
 525                         "memory commitment underflow");
 526
 527         vm_acct_memory(pages);
 528
 529         /*
 530          * Sometimes we want to use more memory than we have
 531          */
 532         if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
 533                 return 0;
 534
 535         if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
 536                 free = global_page_state(NR_FREE_PAGES);
 537                 free += global_node_page_state(NR_FILE_PAGES);
 538
 539                 /*
 540                  * shmem pages shouldn't be counted as free in this
 541                  * case, they can't be purged, only swapped out, and
 542                  * that won't affect the overall amount of available
 543                  * memory in the system.
 544                  */
 545                 free -= global_node_page_state(NR_SHMEM);
 546
 547                 free += get_nr_swap_pages();
 548
 549                 /*
 550                  * Any slabs which are created with the
 551                  * SLAB_RECLAIM_ACCOUNT flag claim to have contents
 552                  * which are reclaimable, under pressure.  The dentry
 553                  * cache and most inode caches should fall into this
 554                  */
 555                 free += global_page_state(NR_SLAB_RECLAIMABLE);
 556
 557                 /*
 558                  * Leave reserved pages. The pages are not for anonymous pages.
 559                  */
 560                 if (free <= totalreserve_pages)
 561                         goto error;
 562                 else
 563                         free -= totalreserve_pages;
 564
 565                 /*
 566                  * Reserve some for root
 567                  */
 568                 if (!cap_sys_admin)
 569                         free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
 570
 571                 if (free > pages)
 572                         return 0;
 573
 574                 goto error;
 575         }
 576
 577         allowed = vm_commit_limit();
 578         /*
 579          * Reserve some for root
 580          */
 581         if (!cap_sys_admin)
 582                 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
 583
 584         /*
 585          * Don't let a single process grow so big a user can't recover
 586          */
 587         if (mm) {
 588                 reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
 589                 allowed -= min_t(long, mm->total_vm / 32, reserve);
 590         }
 591
 592         if (percpu_counter_read_positive(&vm_committed_as) < allowed)
 593                 return 0;
 594 error:
 595         vm_unacct_memory(pages);
 596
 597         return -ENOMEM;
 598 }
 599
 600 /**
 601  * get_cmdline() - copy the cmdline value to a buffer.
 602  * @task:     the task whose cmdline value to copy.
 603  * @buffer:   the buffer to copy to.
 604  * @buflen:   the length of the buffer. Larger cmdline values are truncated
 605  *            to this length.
 606  * Returns the size of the cmdline field copied. Note that the copy does
 607  * not guarantee an ending NULL byte.
 608  */
 609 int get_cmdline(struct task_struct *task, char *buffer, int buflen)
 610 {
 611         int res = 0;
 612         unsigned int len;
 613         struct mm_struct *mm = get_task_mm(task);
 614         unsigned long arg_start, arg_end, env_start, env_end;
 615         if (!mm)
 616                 goto out;
 617         if (!mm->arg_end)
 618                 goto out_mm;    /* Shh! No looking before we're done */
 619
 620         down_read(&mm->mmap_sem);
 621         arg_start = mm->arg_start;
 622         arg_end = mm->arg_end;
 623         env_start = mm->env_start;
 624         env_end = mm->env_end;
 625         up_read(&mm->mmap_sem);
 626
 627         len = arg_end - arg_start;
 628
 629         if (len > buflen)
 630                 len = buflen;
 631
 632         res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
 633
 634         /*
 635          * If the nul at the end of args has been overwritten, then
 636          * assume application is using setproctitle(3).
 637          */
 638         if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
 639                 len = strnlen(buffer, res);
 640                 if (len < res) {
 641                         res = len;
 642                 } else {
 643                         len = env_end - env_start;
 644                         if (len > buflen - res)
 645                                 len = buflen - res;
 646                         res += access_process_vm(task, env_start,
 647                                                  buffer+res, len,
 648                                                  FOLL_FORCE);
 649                         res = strnlen(buffer, res);
 650                 }
 651         }
 652 out_mm:
 653         mmput(mm);
 654 out:
 655         return res;
 656 }