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 */
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/**
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 */
109void *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}
118EXPORT_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 */
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
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 */
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
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}
177EXPORT_SYMBOL(strndup_user);
178
179void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
180		struct vm_area_struct *prev, struct rb_node *rb_parent)
181{
182	struct vm_area_struct *next;
183
184	vma->vm_prev = prev;
185	if (prev) {
186		next = prev->vm_next;
187		prev->vm_next = vma;
188	} else {
189		mm->mmap = vma;
190		if (rb_parent)
191			next = rb_entry(rb_parent,
192					struct vm_area_struct, vm_rb);
193		else
194			next = NULL;
195	}
196	vma->vm_next = next;
197	if (next)
198		next->vm_prev = vma;
199}
200
201/* Check if the vma is being used as a stack by this task */
202static int vm_is_stack_for_task(struct task_struct *t,
203				struct vm_area_struct *vma)
204{
205	return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
206}
207
208/*
209 * Check if the vma is being used as a stack.
210 * If is_group is non-zero, check in the entire thread group or else
211 * just check in the current task. Returns the task_struct of the task
212 * that the vma is stack for. Must be called under rcu_read_lock().
213 */
214struct task_struct *task_of_stack(struct task_struct *task,
215				struct vm_area_struct *vma, bool in_group)
216{
217	if (vm_is_stack_for_task(task, vma))
218		return task;
219
220	if (in_group) {
221		struct task_struct *t;
222
223		for_each_thread(task, t) {
224			if (vm_is_stack_for_task(t, vma))
225				return t;
226		}
227	}
228
229	return NULL;
230}
231
232#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
233void arch_pick_mmap_layout(struct mm_struct *mm)
234{
235	mm->mmap_base = TASK_UNMAPPED_BASE;
236	mm->get_unmapped_area = arch_get_unmapped_area;
237}
238#endif
239
240/*
241 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
242 * back to the regular GUP.
243 * If the architecture not support this function, simply return with no
244 * page pinned
245 */
246int __weak __get_user_pages_fast(unsigned long start,
247				 int nr_pages, int write, struct page **pages)
248{
249	return 0;
250}
251EXPORT_SYMBOL_GPL(__get_user_pages_fast);
252
253/**
254 * get_user_pages_fast() - pin user pages in memory
255 * @start:	starting user address
256 * @nr_pages:	number of pages from start to pin
257 * @write:	whether pages will be written to
258 * @pages:	array that receives pointers to the pages pinned.
259 *		Should be at least nr_pages long.
260 *
261 * Returns number of pages pinned. This may be fewer than the number
262 * requested. If nr_pages is 0 or negative, returns 0. If no pages
263 * were pinned, returns -errno.
264 *
265 * get_user_pages_fast provides equivalent functionality to get_user_pages,
266 * operating on current and current->mm, with force=0 and vma=NULL. However
267 * unlike get_user_pages, it must be called without mmap_sem held.
268 *
269 * get_user_pages_fast may take mmap_sem and page table locks, so no
270 * assumptions can be made about lack of locking. get_user_pages_fast is to be
271 * implemented in a way that is advantageous (vs get_user_pages()) when the
272 * user memory area is already faulted in and present in ptes. However if the
273 * pages have to be faulted in, it may turn out to be slightly slower so
274 * callers need to carefully consider what to use. On many architectures,
275 * get_user_pages_fast simply falls back to get_user_pages.
276 */
277int __weak get_user_pages_fast(unsigned long start,
278				int nr_pages, int write, struct page **pages)
279{
280	struct mm_struct *mm = current->mm;
281	return get_user_pages_unlocked(current, mm, start, nr_pages,
282				       write, 0, pages);
283}
284EXPORT_SYMBOL_GPL(get_user_pages_fast);
285
286unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
287	unsigned long len, unsigned long prot,
288	unsigned long flag, unsigned long pgoff)
289{
290	unsigned long ret;
291	struct mm_struct *mm = current->mm;
292	unsigned long populate;
293
294	ret = security_mmap_file(file, prot, flag);
295	if (!ret) {
296		down_write(&mm->mmap_sem);
297		ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
298				    &populate);
299		up_write(&mm->mmap_sem);
300		if (populate)
301			mm_populate(ret, populate);
302	}
303	return ret;
304}
305
306unsigned long vm_mmap(struct file *file, unsigned long addr,
307	unsigned long len, unsigned long prot,
308	unsigned long flag, unsigned long offset)
309{
310	if (unlikely(offset + PAGE_ALIGN(len) < offset))
311		return -EINVAL;
312	if (unlikely(offset & ~PAGE_MASK))
313		return -EINVAL;
314
315	return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
316}
317EXPORT_SYMBOL(vm_mmap);
318
319void kvfree(const void *addr)
320{
321	if (is_vmalloc_addr(addr))
322		vfree(addr);
323	else
324		kfree(addr);
325}
326EXPORT_SYMBOL(kvfree);
327
328static inline void *__page_rmapping(struct page *page)
329{
330	unsigned long mapping;
331
332	mapping = (unsigned long)page->mapping;
333	mapping &= ~PAGE_MAPPING_FLAGS;
334
335	return (void *)mapping;
336}
337
338/* Neutral page->mapping pointer to address_space or anon_vma or other */
339void *page_rmapping(struct page *page)
340{
341	page = compound_head(page);
342	return __page_rmapping(page);
343}
344
345struct anon_vma *page_anon_vma(struct page *page)
346{
347	unsigned long mapping;
348
349	page = compound_head(page);
350	mapping = (unsigned long)page->mapping;
351	if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
352		return NULL;
353	return __page_rmapping(page);
354}
355
356struct address_space *page_mapping(struct page *page)
357{
358	unsigned long mapping;
359
360	/* This happens if someone calls flush_dcache_page on slab page */
361	if (unlikely(PageSlab(page)))
362		return NULL;
363
364	if (unlikely(PageSwapCache(page))) {
365		swp_entry_t entry;
366
367		entry.val = page_private(page);
368		return swap_address_space(entry);
369	}
370
371	mapping = (unsigned long)page->mapping;
372	if (mapping & PAGE_MAPPING_FLAGS)
373		return NULL;
374	return page->mapping;
375}
376
377int overcommit_ratio_handler(struct ctl_table *table, int write,
378			     void __user *buffer, size_t *lenp,
379			     loff_t *ppos)
380{
381	int ret;
382
383	ret = proc_dointvec(table, write, buffer, lenp, ppos);
384	if (ret == 0 && write)
385		sysctl_overcommit_kbytes = 0;
386	return ret;
387}
388
389int overcommit_kbytes_handler(struct ctl_table *table, int write,
390			     void __user *buffer, size_t *lenp,
391			     loff_t *ppos)
392{
393	int ret;
394
395	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
396	if (ret == 0 && write)
397		sysctl_overcommit_ratio = 0;
398	return ret;
399}
400
401/*
402 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
403 */
404unsigned long vm_commit_limit(void)
405{
406	unsigned long allowed;
407
408	if (sysctl_overcommit_kbytes)
409		allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
410	else
411		allowed = ((totalram_pages - hugetlb_total_pages())
412			   * sysctl_overcommit_ratio / 100);
413	allowed += total_swap_pages;
414
415	return allowed;
416}
417
418/**
419 * get_cmdline() - copy the cmdline value to a buffer.
420 * @task:     the task whose cmdline value to copy.
421 * @buffer:   the buffer to copy to.
422 * @buflen:   the length of the buffer. Larger cmdline values are truncated
423 *            to this length.
424 * Returns the size of the cmdline field copied. Note that the copy does
425 * not guarantee an ending NULL byte.
426 */
427int get_cmdline(struct task_struct *task, char *buffer, int buflen)
428{
429	int res = 0;
430	unsigned int len;
431	struct mm_struct *mm = get_task_mm(task);
432	if (!mm)
433		goto out;
434	if (!mm->arg_end)
435		goto out_mm;	/* Shh! No looking before we're done */
436
437	len = mm->arg_end - mm->arg_start;
438
439	if (len > buflen)
440		len = buflen;
441
442	res = access_process_vm(task, mm->arg_start, buffer, len, 0);
443
444	/*
445	 * If the nul at the end of args has been overwritten, then
446	 * assume application is using setproctitle(3).
447	 */
448	if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
449		len = strnlen(buffer, res);
450		if (len < res) {
451			res = len;
452		} else {
453			len = mm->env_end - mm->env_start;
454			if (len > buflen - res)
455				len = buflen - res;
456			res += access_process_vm(task, mm->env_start,
457						 buffer+res, len, 0);
458			res = strnlen(buffer, res);
459		}
460	}
461out_mm:
462	mmput(mm);
463out:
464	return res;
465}
466