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TOMOYO Linux Cross Reference
Linux/mm/util.c

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  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 void __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 */
202 static 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  */
214 struct 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)
233 void 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  */
246 int __weak __get_user_pages_fast(unsigned long start,
247                                  int nr_pages, int write, struct page **pages)
248 {
249         return 0;
250 }
251 EXPORT_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  */
277 int __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 }
284 EXPORT_SYMBOL_GPL(get_user_pages_fast);
285 
286 unsigned 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 
306 unsigned 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 }
317 EXPORT_SYMBOL(vm_mmap);
318 
319 void kvfree(const void *addr)
320 {
321         if (is_vmalloc_addr(addr))
322                 vfree(addr);
323         else
324                 kfree(addr);
325 }
326 EXPORT_SYMBOL(kvfree);
327 
328 static 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 */
339 void *page_rmapping(struct page *page)
340 {
341         page = compound_head(page);
342         return __page_rmapping(page);
343 }
344 
345 struct 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 
356 struct 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 
377 int 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 
389 int 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  */
404 unsigned 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  */
427 int 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         }
461 out_mm:
462         mmput(mm);
463 out:
464         return res;
465 }
466 

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