blob: 6cc81e7b870523342cb8882ba222149644d894ac [file] [log] [blame]
Andrew Morton16d69262008-07-25 19:44:36 -07001#include <linux/mm.h>
Matt Mackall30992c92006-01-08 01:01:43 -08002#include <linux/slab.h>
3#include <linux/string.h>
Gideon Israel Dsouza3b321232014-04-07 15:37:26 -07004#include <linux/compiler.h>
Paul Gortmakerb95f1b312011-10-16 02:01:52 -04005#include <linux/export.h>
Davi Arnaut96840aa2006-03-24 03:18:42 -08006#include <linux/err.h>
Adrian Bunk3b8f14b2008-07-26 15:22:28 -07007#include <linux/sched.h>
Al Viroeb36c582012-05-30 20:17:35 -04008#include <linux/security.h>
Shaohua Li98003392013-02-22 16:34:35 -08009#include <linux/swap.h>
Shaohua Li33806f02013-02-22 16:34:37 -080010#include <linux/swapops.h>
Jerome Marchand00619bc2013-11-12 15:08:31 -080011#include <linux/mman.h>
12#include <linux/hugetlb.h>
Al Viro39f1f782014-05-06 14:02:53 -040013#include <linux/vmalloc.h>
Jerome Marchand00619bc2013-11-12 15:08:31 -080014
Andrzej Hajdaa4bb1e42015-02-13 14:36:24 -080015#include <asm/sections.h>
Davi Arnaut96840aa2006-03-24 03:18:42 -080016#include <asm/uaccess.h>
Matt Mackall30992c92006-01-08 01:01:43 -080017
Namhyung Kim6038def2011-05-24 17:11:22 -070018#include "internal.h"
19
Andrzej Hajdaa4bb1e42015-02-13 14:36:24 -080020static 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
Matt Mackall30992c92006-01-08 01:01:43 -080039/**
Matt Mackall30992c92006-01-08 01:01:43 -080040 * kstrdup - allocate space for and copy an existing string
Matt Mackall30992c92006-01-08 01:01:43 -080041 * @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;
Christoph Hellwig1d2c8ee2006-10-04 02:15:25 -070053 buf = kmalloc_track_caller(len, gfp);
Matt Mackall30992c92006-01-08 01:01:43 -080054 if (buf)
55 memcpy(buf, s, len);
56 return buf;
57}
58EXPORT_SYMBOL(kstrdup);
Davi Arnaut96840aa2006-03-24 03:18:42 -080059
Alexey Dobriyan1a2f67b2006-09-30 23:27:20 -070060/**
Andrzej Hajdaa4bb1e42015-02-13 14:36:24 -080061 * 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/**
Jeremy Fitzhardinge1e66df32007-07-17 18:37:02 -070079 * 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 */
84char *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}
100EXPORT_SYMBOL(kstrndup);
101
102/**
Alexey Dobriyan1a2f67b2006-09-30 23:27:20 -0700103 * kmemdup - duplicate region of memory
104 *
105 * @src: memory region to duplicate
106 * @len: memory region length
107 * @gfp: GFP mask to use
108 */
109void *kmemdup(const void *src, size_t len, gfp_t gfp)
110{
111 void *p;
112
Christoph Hellwig1d2c8ee2006-10-04 02:15:25 -0700113 p = kmalloc_track_caller(len, gfp);
Alexey Dobriyan1a2f67b2006-09-30 23:27:20 -0700114 if (p)
115 memcpy(p, src, len);
116 return p;
117}
118EXPORT_SYMBOL(kmemdup);
119
Christoph Lameteref2ad802007-07-17 04:03:21 -0700120/**
Li Zefan610a77e2009-03-31 15:23:16 -0700121 * 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 */
128void *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}
148EXPORT_SYMBOL(memdup_user);
149
Davi Arnaut96840aa2006-03-24 03:18:42 -0800150/*
151 * strndup_user - duplicate an existing string from user space
Davi Arnaut96840aa2006-03-24 03:18:42 -0800152 * @s: The string to duplicate
153 * @n: Maximum number of bytes to copy, including the trailing NUL.
154 */
155char *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
Julia Lawall90d74042010-08-09 17:18:26 -0700168 p = memdup_user(s, length);
Davi Arnaut96840aa2006-03-24 03:18:42 -0800169
Julia Lawall90d74042010-08-09 17:18:26 -0700170 if (IS_ERR(p))
171 return p;
Davi Arnaut96840aa2006-03-24 03:18:42 -0800172
173 p[length - 1] = '\0';
174
175 return p;
176}
177EXPORT_SYMBOL(strndup_user);
Andrew Morton16d69262008-07-25 19:44:36 -0700178
Al Viroe9d408e2015-12-24 00:06:05 -0500179/**
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 */
187void *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}
208EXPORT_SYMBOL(memdup_user_nul);
209
Namhyung Kim6038def2011-05-24 17:11:22 -0700210void __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
Siddhesh Poyarekarb7643752012-03-21 16:34:04 -0700232/* Check if the vma is being used as a stack by this task */
Johannes Weiner65376df2016-02-02 16:57:29 -0800233int vma_is_stack_for_task(struct vm_area_struct *vma, struct task_struct *t)
Siddhesh Poyarekarb7643752012-03-21 16:34:04 -0700234{
235 return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
236}
237
David Howellsefc1a3b2010-01-15 17:01:35 -0800238#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
Andrew Morton16d69262008-07-25 19:44:36 -0700239void 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;
Andrew Morton16d69262008-07-25 19:44:36 -0700243}
244#endif
Rusty Russell912985d2008-08-12 17:52:52 -0500245
Xiao Guangrong45888a02010-08-22 19:08:57 +0800246/*
247 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
248 * back to the regular GUP.
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300249 * If the architecture not support this function, simply return with no
Xiao Guangrong45888a02010-08-22 19:08:57 +0800250 * page pinned
251 */
Gideon Israel Dsouza3b321232014-04-07 15:37:26 -0700252int __weak __get_user_pages_fast(unsigned long start,
Xiao Guangrong45888a02010-08-22 19:08:57 +0800253 int nr_pages, int write, struct page **pages)
254{
255 return 0;
256}
257EXPORT_SYMBOL_GPL(__get_user_pages_fast);
258
Andy Grover9de100d2009-04-13 14:40:05 -0700259/**
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 *
Andy Grover9de100d2009-04-13 14:40:05 -0700267 * 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.
Nick Piggind2bf6be2009-06-16 15:31:39 -0700270 *
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.
Andy Grover9de100d2009-04-13 14:40:05 -0700282 */
Gideon Israel Dsouza3b321232014-04-07 15:37:26 -0700283int __weak get_user_pages_fast(unsigned long start,
Rusty Russell912985d2008-08-12 17:52:52 -0500284 int nr_pages, int write, struct page **pages)
285{
Dave Hansencde70142016-02-12 13:01:55 -0800286 return get_user_pages_unlocked(start, nr_pages, write, 0, pages);
Rusty Russell912985d2008-08-12 17:52:52 -0500287}
288EXPORT_SYMBOL_GPL(get_user_pages_fast);
Eduard - Gabriel Munteanuca2b84cb2009-03-23 15:12:24 +0200289
Al Viroeb36c582012-05-30 20:17:35 -0400290unsigned 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;
Michel Lespinasse41badc12013-02-22 16:32:47 -0800296 unsigned long populate;
Al Viroeb36c582012-05-30 20:17:35 -0400297
298 ret = security_mmap_file(file, prot, flag);
299 if (!ret) {
300 down_write(&mm->mmap_sem);
Michel Lespinassebebeb3d2013-02-22 16:32:37 -0800301 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
302 &populate);
Al Viroeb36c582012-05-30 20:17:35 -0400303 up_write(&mm->mmap_sem);
Michel Lespinasse41badc12013-02-22 16:32:47 -0800304 if (populate)
305 mm_populate(ret, populate);
Al Viroeb36c582012-05-30 20:17:35 -0400306 }
307 return ret;
308}
309
310unsigned long vm_mmap(struct file *file, unsigned long addr,
311 unsigned long len, unsigned long prot,
312 unsigned long flag, unsigned long offset)
313{
314 if (unlikely(offset + PAGE_ALIGN(len) < offset))
315 return -EINVAL;
Alexander Kuleshovea53cde2015-11-05 18:46:46 -0800316 if (unlikely(offset_in_page(offset)))
Al Viroeb36c582012-05-30 20:17:35 -0400317 return -EINVAL;
318
319 return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
320}
321EXPORT_SYMBOL(vm_mmap);
322
Al Viro39f1f782014-05-06 14:02:53 -0400323void kvfree(const void *addr)
324{
325 if (is_vmalloc_addr(addr))
326 vfree(addr);
327 else
328 kfree(addr);
329}
330EXPORT_SYMBOL(kvfree);
331
Kirill A. Shutemove39155e2015-04-15 16:14:53 -0700332static inline void *__page_rmapping(struct page *page)
333{
334 unsigned long mapping;
335
336 mapping = (unsigned long)page->mapping;
337 mapping &= ~PAGE_MAPPING_FLAGS;
338
339 return (void *)mapping;
340}
341
342/* Neutral page->mapping pointer to address_space or anon_vma or other */
343void *page_rmapping(struct page *page)
344{
345 page = compound_head(page);
346 return __page_rmapping(page);
347}
348
349struct anon_vma *page_anon_vma(struct page *page)
350{
351 unsigned long mapping;
352
353 page = compound_head(page);
354 mapping = (unsigned long)page->mapping;
355 if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
356 return NULL;
357 return __page_rmapping(page);
358}
359
Shaohua Li98003392013-02-22 16:34:35 -0800360struct address_space *page_mapping(struct page *page)
361{
Kirill A. Shutemov1c290f62016-01-15 16:52:07 -0800362 struct address_space *mapping;
363
364 page = compound_head(page);
Shaohua Li98003392013-02-22 16:34:35 -0800365
Mikulas Patocka03e5ac22014-01-14 17:56:40 -0800366 /* This happens if someone calls flush_dcache_page on slab page */
367 if (unlikely(PageSlab(page)))
368 return NULL;
369
Shaohua Li33806f02013-02-22 16:34:37 -0800370 if (unlikely(PageSwapCache(page))) {
371 swp_entry_t entry;
372
373 entry.val = page_private(page);
Kirill A. Shutemove39155e2015-04-15 16:14:53 -0700374 return swap_address_space(entry);
375 }
376
Kirill A. Shutemov1c290f62016-01-15 16:52:07 -0800377 mapping = page->mapping;
378 if ((unsigned long)mapping & PAGE_MAPPING_FLAGS)
Kirill A. Shutemove39155e2015-04-15 16:14:53 -0700379 return NULL;
Kirill A. Shutemov1c290f62016-01-15 16:52:07 -0800380 return mapping;
Shaohua Li98003392013-02-22 16:34:35 -0800381}
382
Kirill A. Shutemovb20ce5e2016-01-15 16:54:37 -0800383/* Slow path of page_mapcount() for compound pages */
384int __page_mapcount(struct page *page)
385{
386 int ret;
387
388 ret = atomic_read(&page->_mapcount) + 1;
389 page = compound_head(page);
390 ret += atomic_read(compound_mapcount_ptr(page)) + 1;
391 if (PageDoubleMap(page))
392 ret--;
393 return ret;
394}
395EXPORT_SYMBOL_GPL(__page_mapcount);
396
Andrey Ryabinin39a1aa82016-03-17 14:18:50 -0700397int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
398int sysctl_overcommit_ratio __read_mostly = 50;
399unsigned long sysctl_overcommit_kbytes __read_mostly;
400int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
401unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
402unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
403
Jerome Marchand49f0ce52014-01-21 15:49:14 -0800404int overcommit_ratio_handler(struct ctl_table *table, int write,
405 void __user *buffer, size_t *lenp,
406 loff_t *ppos)
407{
408 int ret;
409
410 ret = proc_dointvec(table, write, buffer, lenp, ppos);
411 if (ret == 0 && write)
412 sysctl_overcommit_kbytes = 0;
413 return ret;
414}
415
416int overcommit_kbytes_handler(struct ctl_table *table, int write,
417 void __user *buffer, size_t *lenp,
418 loff_t *ppos)
419{
420 int ret;
421
422 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
423 if (ret == 0 && write)
424 sysctl_overcommit_ratio = 0;
425 return ret;
426}
427
Jerome Marchand00619bc2013-11-12 15:08:31 -0800428/*
429 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
430 */
431unsigned long vm_commit_limit(void)
432{
Jerome Marchand49f0ce52014-01-21 15:49:14 -0800433 unsigned long allowed;
434
435 if (sysctl_overcommit_kbytes)
436 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
437 else
438 allowed = ((totalram_pages - hugetlb_total_pages())
439 * sysctl_overcommit_ratio / 100);
440 allowed += total_swap_pages;
441
442 return allowed;
Jerome Marchand00619bc2013-11-12 15:08:31 -0800443}
444
Andrey Ryabinin39a1aa82016-03-17 14:18:50 -0700445/*
446 * Make sure vm_committed_as in one cacheline and not cacheline shared with
447 * other variables. It can be updated by several CPUs frequently.
448 */
449struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
450
451/*
452 * The global memory commitment made in the system can be a metric
453 * that can be used to drive ballooning decisions when Linux is hosted
454 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
455 * balancing memory across competing virtual machines that are hosted.
456 * Several metrics drive this policy engine including the guest reported
457 * memory commitment.
458 */
459unsigned long vm_memory_committed(void)
460{
461 return percpu_counter_read_positive(&vm_committed_as);
462}
463EXPORT_SYMBOL_GPL(vm_memory_committed);
464
465/*
466 * Check that a process has enough memory to allocate a new virtual
467 * mapping. 0 means there is enough memory for the allocation to
468 * succeed and -ENOMEM implies there is not.
469 *
470 * We currently support three overcommit policies, which are set via the
471 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting
472 *
473 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
474 * Additional code 2002 Jul 20 by Robert Love.
475 *
476 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
477 *
478 * Note this is a helper function intended to be used by LSMs which
479 * wish to use this logic.
480 */
481int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
482{
483 long free, allowed, reserve;
484
485 VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
486 -(s64)vm_committed_as_batch * num_online_cpus(),
487 "memory commitment underflow");
488
489 vm_acct_memory(pages);
490
491 /*
492 * Sometimes we want to use more memory than we have
493 */
494 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
495 return 0;
496
497 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
498 free = global_page_state(NR_FREE_PAGES);
499 free += global_page_state(NR_FILE_PAGES);
500
501 /*
502 * shmem pages shouldn't be counted as free in this
503 * case, they can't be purged, only swapped out, and
504 * that won't affect the overall amount of available
505 * memory in the system.
506 */
507 free -= global_page_state(NR_SHMEM);
508
509 free += get_nr_swap_pages();
510
511 /*
512 * Any slabs which are created with the
513 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
514 * which are reclaimable, under pressure. The dentry
515 * cache and most inode caches should fall into this
516 */
517 free += global_page_state(NR_SLAB_RECLAIMABLE);
518
519 /*
520 * Leave reserved pages. The pages are not for anonymous pages.
521 */
522 if (free <= totalreserve_pages)
523 goto error;
524 else
525 free -= totalreserve_pages;
526
527 /*
528 * Reserve some for root
529 */
530 if (!cap_sys_admin)
531 free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
532
533 if (free > pages)
534 return 0;
535
536 goto error;
537 }
538
539 allowed = vm_commit_limit();
540 /*
541 * Reserve some for root
542 */
543 if (!cap_sys_admin)
544 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
545
546 /*
547 * Don't let a single process grow so big a user can't recover
548 */
549 if (mm) {
550 reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
551 allowed -= min_t(long, mm->total_vm / 32, reserve);
552 }
553
554 if (percpu_counter_read_positive(&vm_committed_as) < allowed)
555 return 0;
556error:
557 vm_unacct_memory(pages);
558
559 return -ENOMEM;
560}
561
William Robertsa9090252014-02-11 10:11:59 -0800562/**
563 * get_cmdline() - copy the cmdline value to a buffer.
564 * @task: the task whose cmdline value to copy.
565 * @buffer: the buffer to copy to.
566 * @buflen: the length of the buffer. Larger cmdline values are truncated
567 * to this length.
568 * Returns the size of the cmdline field copied. Note that the copy does
569 * not guarantee an ending NULL byte.
570 */
571int get_cmdline(struct task_struct *task, char *buffer, int buflen)
572{
573 int res = 0;
574 unsigned int len;
575 struct mm_struct *mm = get_task_mm(task);
Mateusz Guzika3b609e2016-01-20 15:01:05 -0800576 unsigned long arg_start, arg_end, env_start, env_end;
William Robertsa9090252014-02-11 10:11:59 -0800577 if (!mm)
578 goto out;
579 if (!mm->arg_end)
580 goto out_mm; /* Shh! No looking before we're done */
581
Mateusz Guzika3b609e2016-01-20 15:01:05 -0800582 down_read(&mm->mmap_sem);
583 arg_start = mm->arg_start;
584 arg_end = mm->arg_end;
585 env_start = mm->env_start;
586 env_end = mm->env_end;
587 up_read(&mm->mmap_sem);
588
589 len = arg_end - arg_start;
William Robertsa9090252014-02-11 10:11:59 -0800590
591 if (len > buflen)
592 len = buflen;
593
Mateusz Guzika3b609e2016-01-20 15:01:05 -0800594 res = access_process_vm(task, arg_start, buffer, len, 0);
William Robertsa9090252014-02-11 10:11:59 -0800595
596 /*
597 * If the nul at the end of args has been overwritten, then
598 * assume application is using setproctitle(3).
599 */
600 if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
601 len = strnlen(buffer, res);
602 if (len < res) {
603 res = len;
604 } else {
Mateusz Guzika3b609e2016-01-20 15:01:05 -0800605 len = env_end - env_start;
William Robertsa9090252014-02-11 10:11:59 -0800606 if (len > buflen - res)
607 len = buflen - res;
Mateusz Guzika3b609e2016-01-20 15:01:05 -0800608 res += access_process_vm(task, env_start,
William Robertsa9090252014-02-11 10:11:59 -0800609 buffer+res, len, 0);
610 res = strnlen(buffer, res);
611 }
612 }
613out_mm:
614 mmput(mm);
615out:
616 return res;
617}