summaryrefslogtreecommitdiff
path: root/mm/util.c (plain)
blob: 07f46720618678acbc038a44be488be0ee8c23c0
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
20static 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 */
32void kfree_const(const void *x)
33{
34 if (!is_kernel_rodata((unsigned long)x))
35 kfree(x);
36}
37EXPORT_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 */
44char *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}
58EXPORT_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 */
69const 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}
76EXPORT_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 * Note: Use kmemdup_nul() instead if the size is known exactly.
85 */
86char *kstrndup(const char *s, size_t max, gfp_t gfp)
87{
88 size_t len;
89 char *buf;
90
91 if (!s)
92 return NULL;
93
94 len = strnlen(s, max);
95 buf = kmalloc_track_caller(len+1, gfp);
96 if (buf) {
97 memcpy(buf, s, len);
98 buf[len] = '\0';
99 }
100 return buf;
101}
102EXPORT_SYMBOL(kstrndup);
103
104/**
105 * kmemdup - duplicate region of memory
106 *
107 * @src: memory region to duplicate
108 * @len: memory region length
109 * @gfp: GFP mask to use
110 */
111void *kmemdup(const void *src, size_t len, gfp_t gfp)
112{
113 void *p;
114
115 p = kmalloc_track_caller(len, gfp);
116 if (p)
117 memcpy(p, src, len);
118 return p;
119}
120EXPORT_SYMBOL(kmemdup);
121
122/**
123 * kmemdup_nul - Create a NUL-terminated string from unterminated data
124 * @s: The data to stringify
125 * @len: The size of the data
126 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
127 */
128char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
129{
130 char *buf;
131
132 if (!s)
133 return NULL;
134
135 buf = kmalloc_track_caller(len + 1, gfp);
136 if (buf) {
137 memcpy(buf, s, len);
138 buf[len] = '\0';
139 }
140 return buf;
141}
142EXPORT_SYMBOL(kmemdup_nul);
143
144/**
145 * memdup_user - duplicate memory region from user space
146 *
147 * @src: source address in user space
148 * @len: number of bytes to copy
149 *
150 * Returns an ERR_PTR() on failure.
151 */
152void *memdup_user(const void __user *src, size_t len)
153{
154 void *p;
155
156 /*
157 * Always use GFP_KERNEL, since copy_from_user() can sleep and
158 * cause pagefault, which makes it pointless to use GFP_NOFS
159 * or GFP_ATOMIC.
160 */
161 p = kmalloc_track_caller(len, GFP_KERNEL);
162 if (!p)
163 return ERR_PTR(-ENOMEM);
164
165 if (copy_from_user(p, src, len)) {
166 kfree(p);
167 return ERR_PTR(-EFAULT);
168 }
169
170 return p;
171}
172EXPORT_SYMBOL(memdup_user);
173
174/*
175 * strndup_user - duplicate an existing string from user space
176 * @s: The string to duplicate
177 * @n: Maximum number of bytes to copy, including the trailing NUL.
178 */
179char *strndup_user(const char __user *s, long n)
180{
181 char *p;
182 long length;
183
184 length = strnlen_user(s, n);
185
186 if (!length)
187 return ERR_PTR(-EFAULT);
188
189 if (length > n)
190 return ERR_PTR(-EINVAL);
191
192 p = memdup_user(s, length);
193
194 if (IS_ERR(p))
195 return p;
196
197 p[length - 1] = '\0';
198
199 return p;
200}
201EXPORT_SYMBOL(strndup_user);
202
203/**
204 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
205 *
206 * @src: source address in user space
207 * @len: number of bytes to copy
208 *
209 * Returns an ERR_PTR() on failure.
210 */
211void *memdup_user_nul(const void __user *src, size_t len)
212{
213 char *p;
214
215 /*
216 * Always use GFP_KERNEL, since copy_from_user() can sleep and
217 * cause pagefault, which makes it pointless to use GFP_NOFS
218 * or GFP_ATOMIC.
219 */
220 p = kmalloc_track_caller(len + 1, GFP_KERNEL);
221 if (!p)
222 return ERR_PTR(-ENOMEM);
223
224 if (copy_from_user(p, src, len)) {
225 kfree(p);
226 return ERR_PTR(-EFAULT);
227 }
228 p[len] = '\0';
229
230 return p;
231}
232EXPORT_SYMBOL(memdup_user_nul);
233
234void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
235 struct vm_area_struct *prev, struct rb_node *rb_parent)
236{
237 struct vm_area_struct *next;
238
239 vma->vm_prev = prev;
240 if (prev) {
241 next = prev->vm_next;
242 prev->vm_next = vma;
243 } else {
244 mm->mmap = vma;
245 if (rb_parent)
246 next = rb_entry(rb_parent,
247 struct vm_area_struct, vm_rb);
248 else
249 next = NULL;
250 }
251 vma->vm_next = next;
252 if (next)
253 next->vm_prev = vma;
254}
255
256/* Check if the vma is being used as a stack by this task */
257int vma_is_stack_for_current(struct vm_area_struct *vma)
258{
259 struct task_struct * __maybe_unused t = current;
260
261 return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
262}
263
264#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
265void arch_pick_mmap_layout(struct mm_struct *mm)
266{
267 mm->mmap_base = TASK_UNMAPPED_BASE;
268 mm->get_unmapped_area = arch_get_unmapped_area;
269}
270#endif
271
272/*
273 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
274 * back to the regular GUP.
275 * If the architecture not support this function, simply return with no
276 * page pinned
277 */
278int __weak __get_user_pages_fast(unsigned long start,
279 int nr_pages, int write, struct page **pages)
280{
281 return 0;
282}
283EXPORT_SYMBOL_GPL(__get_user_pages_fast);
284
285/**
286 * get_user_pages_fast() - pin user pages in memory
287 * @start: starting user address
288 * @nr_pages: number of pages from start to pin
289 * @write: whether pages will be written to
290 * @pages: array that receives pointers to the pages pinned.
291 * Should be at least nr_pages long.
292 *
293 * Returns number of pages pinned. This may be fewer than the number
294 * requested. If nr_pages is 0 or negative, returns 0. If no pages
295 * were pinned, returns -errno.
296 *
297 * get_user_pages_fast provides equivalent functionality to get_user_pages,
298 * operating on current and current->mm, with force=0 and vma=NULL. However
299 * unlike get_user_pages, it must be called without mmap_sem held.
300 *
301 * get_user_pages_fast may take mmap_sem and page table locks, so no
302 * assumptions can be made about lack of locking. get_user_pages_fast is to be
303 * implemented in a way that is advantageous (vs get_user_pages()) when the
304 * user memory area is already faulted in and present in ptes. However if the
305 * pages have to be faulted in, it may turn out to be slightly slower so
306 * callers need to carefully consider what to use. On many architectures,
307 * get_user_pages_fast simply falls back to get_user_pages.
308 */
309int __weak get_user_pages_fast(unsigned long start,
310 int nr_pages, int write, struct page **pages)
311{
312 return get_user_pages_unlocked(start, nr_pages, pages,
313 write ? FOLL_WRITE : 0);
314}
315EXPORT_SYMBOL_GPL(get_user_pages_fast);
316
317unsigned 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 if (down_write_killable(&mm->mmap_sem))
328 return -EINTR;
329 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
330 &populate);
331 up_write(&mm->mmap_sem);
332 if (populate)
333 mm_populate(ret, populate);
334 }
335 return ret;
336}
337
338unsigned long vm_mmap(struct file *file, unsigned long addr,
339 unsigned long len, unsigned long prot,
340 unsigned long flag, unsigned long offset)
341{
342 if (unlikely(offset + PAGE_ALIGN(len) < offset))
343 return -EINVAL;
344 if (unlikely(offset_in_page(offset)))
345 return -EINVAL;
346
347 return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
348}
349EXPORT_SYMBOL(vm_mmap);
350
351void kvfree(const void *addr)
352{
353 if (is_vmalloc_addr(addr))
354 vfree(addr);
355 else
356 kfree(addr);
357}
358EXPORT_SYMBOL(kvfree);
359
360static inline void *__page_rmapping(struct page *page)
361{
362 unsigned long mapping;
363
364 mapping = (unsigned long)page->mapping;
365 mapping &= ~PAGE_MAPPING_FLAGS;
366
367 return (void *)mapping;
368}
369
370/* Neutral page->mapping pointer to address_space or anon_vma or other */
371void *page_rmapping(struct page *page)
372{
373 page = compound_head(page);
374 return __page_rmapping(page);
375}
376
377/*
378 * Return true if this page is mapped into pagetables.
379 * For compound page it returns true if any subpage of compound page is mapped.
380 */
381bool page_mapped(struct page *page)
382{
383 int i;
384
385 if (likely(!PageCompound(page)))
386 return atomic_read(&page->_mapcount) >= 0;
387 page = compound_head(page);
388 if (atomic_read(compound_mapcount_ptr(page)) >= 0)
389 return true;
390 if (PageHuge(page))
391 return false;
392 for (i = 0; i < (1 << compound_order(page)); i++) {
393 if (atomic_read(&page[i]._mapcount) >= 0)
394 return true;
395 }
396 return false;
397}
398EXPORT_SYMBOL(page_mapped);
399
400struct anon_vma *page_anon_vma(struct page *page)
401{
402 unsigned long mapping;
403
404 page = compound_head(page);
405 mapping = (unsigned long)page->mapping;
406 if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
407 return NULL;
408 return __page_rmapping(page);
409}
410
411struct address_space *page_mapping(struct page *page)
412{
413 struct address_space *mapping;
414
415 page = compound_head(page);
416
417 /* This happens if someone calls flush_dcache_page on slab page */
418 if (unlikely(PageSlab(page)))
419 return NULL;
420
421 if (unlikely(PageSwapCache(page))) {
422 swp_entry_t entry;
423
424 entry.val = page_private(page);
425 return swap_address_space(entry);
426 }
427
428 mapping = page->mapping;
429 if ((unsigned long)mapping & PAGE_MAPPING_ANON)
430 return NULL;
431
432 return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
433}
434EXPORT_SYMBOL(page_mapping);
435
436/* Slow path of page_mapcount() for compound pages */
437int __page_mapcount(struct page *page)
438{
439 int ret;
440
441 ret = atomic_read(&page->_mapcount) + 1;
442 /*
443 * For file THP page->_mapcount contains total number of mapping
444 * of the page: no need to look into compound_mapcount.
445 */
446 if (!PageAnon(page) && !PageHuge(page))
447 return ret;
448 page = compound_head(page);
449 ret += atomic_read(compound_mapcount_ptr(page)) + 1;
450 if (PageDoubleMap(page))
451 ret--;
452 return ret;
453}
454EXPORT_SYMBOL_GPL(__page_mapcount);
455
456int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
457int sysctl_overcommit_ratio __read_mostly = 50;
458unsigned long sysctl_overcommit_kbytes __read_mostly;
459int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
460unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
461unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
462
463int overcommit_ratio_handler(struct ctl_table *table, int write,
464 void __user *buffer, size_t *lenp,
465 loff_t *ppos)
466{
467 int ret;
468
469 ret = proc_dointvec(table, write, buffer, lenp, ppos);
470 if (ret == 0 && write)
471 sysctl_overcommit_kbytes = 0;
472 return ret;
473}
474
475int overcommit_kbytes_handler(struct ctl_table *table, int write,
476 void __user *buffer, size_t *lenp,
477 loff_t *ppos)
478{
479 int ret;
480
481 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
482 if (ret == 0 && write)
483 sysctl_overcommit_ratio = 0;
484 return ret;
485}
486
487/*
488 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
489 */
490unsigned long vm_commit_limit(void)
491{
492 unsigned long allowed;
493
494 if (sysctl_overcommit_kbytes)
495 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
496 else
497 allowed = ((totalram_pages - hugetlb_total_pages())
498 * sysctl_overcommit_ratio / 100);
499 allowed += total_swap_pages;
500
501 return allowed;
502}
503
504/*
505 * Make sure vm_committed_as in one cacheline and not cacheline shared with
506 * other variables. It can be updated by several CPUs frequently.
507 */
508struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
509
510/*
511 * The global memory commitment made in the system can be a metric
512 * that can be used to drive ballooning decisions when Linux is hosted
513 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
514 * balancing memory across competing virtual machines that are hosted.
515 * Several metrics drive this policy engine including the guest reported
516 * memory commitment.
517 */
518unsigned long vm_memory_committed(void)
519{
520 return percpu_counter_read_positive(&vm_committed_as);
521}
522EXPORT_SYMBOL_GPL(vm_memory_committed);
523
524/*
525 * Check that a process has enough memory to allocate a new virtual
526 * mapping. 0 means there is enough memory for the allocation to
527 * succeed and -ENOMEM implies there is not.
528 *
529 * We currently support three overcommit policies, which are set via the
530 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting
531 *
532 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
533 * Additional code 2002 Jul 20 by Robert Love.
534 *
535 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
536 *
537 * Note this is a helper function intended to be used by LSMs which
538 * wish to use this logic.
539 */
540int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
541{
542 long free, allowed, reserve;
543
544 VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
545 -(s64)vm_committed_as_batch * num_online_cpus(),
546 "memory commitment underflow");
547
548 vm_acct_memory(pages);
549
550 /*
551 * Sometimes we want to use more memory than we have
552 */
553 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
554 return 0;
555
556 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
557 free = global_page_state(NR_FREE_PAGES);
558 free += global_node_page_state(NR_FILE_PAGES);
559
560 /*
561 * shmem pages shouldn't be counted as free in this
562 * case, they can't be purged, only swapped out, and
563 * that won't affect the overall amount of available
564 * memory in the system.
565 */
566 free -= global_node_page_state(NR_SHMEM);
567
568 free += get_nr_swap_pages();
569
570 /*
571 * Any slabs which are created with the
572 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
573 * which are reclaimable, under pressure. The dentry
574 * cache and most inode caches should fall into this
575 */
576 free += global_page_state(NR_SLAB_RECLAIMABLE);
577
578 /*
579 * Leave reserved pages. The pages are not for anonymous pages.
580 */
581 if (free <= totalreserve_pages)
582 goto error;
583 else
584 free -= totalreserve_pages;
585
586 /*
587 * Reserve some for root
588 */
589 if (!cap_sys_admin)
590 free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
591
592 if (free > pages)
593 return 0;
594
595 goto error;
596 }
597
598 allowed = vm_commit_limit();
599 /*
600 * Reserve some for root
601 */
602 if (!cap_sys_admin)
603 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
604
605 /*
606 * Don't let a single process grow so big a user can't recover
607 */
608 if (mm) {
609 reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
610 allowed -= min_t(long, mm->total_vm / 32, reserve);
611 }
612
613 if (percpu_counter_read_positive(&vm_committed_as) < allowed)
614 return 0;
615error:
616 vm_unacct_memory(pages);
617
618 return -ENOMEM;
619}
620
621/**
622 * get_cmdline() - copy the cmdline value to a buffer.
623 * @task: the task whose cmdline value to copy.
624 * @buffer: the buffer to copy to.
625 * @buflen: the length of the buffer. Larger cmdline values are truncated
626 * to this length.
627 * Returns the size of the cmdline field copied. Note that the copy does
628 * not guarantee an ending NULL byte.
629 */
630int get_cmdline(struct task_struct *task, char *buffer, int buflen)
631{
632 int res = 0;
633 unsigned int len;
634 struct mm_struct *mm = get_task_mm(task);
635 unsigned long arg_start, arg_end, env_start, env_end;
636 if (!mm)
637 goto out;
638 if (!mm->arg_end)
639 goto out_mm; /* Shh! No looking before we're done */
640
641 down_read(&mm->mmap_sem);
642 arg_start = mm->arg_start;
643 arg_end = mm->arg_end;
644 env_start = mm->env_start;
645 env_end = mm->env_end;
646 up_read(&mm->mmap_sem);
647
648 len = arg_end - arg_start;
649
650 if (len > buflen)
651 len = buflen;
652
653 res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
654
655 /*
656 * If the nul at the end of args has been overwritten, then
657 * assume application is using setproctitle(3).
658 */
659 if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
660 len = strnlen(buffer, res);
661 if (len < res) {
662 res = len;
663 } else {
664 len = env_end - env_start;
665 if (len > buflen - res)
666 len = buflen - res;
667 res += access_process_vm(task, env_start,
668 buffer+res, len,
669 FOLL_FORCE);
670 res = strnlen(buffer, res);
671 }
672 }
673out_mm:
674 mmput(mm);
675out:
676 return res;
677}
678
generated by cgit at 2024-05-18 17:31:23 (GMT)