Root/mm/util.c

1#include <linux/mm.h>
2#include <linux/slab.h>
3#include <linux/string.h>
4#include <linux/export.h>
5#include <linux/err.h>
6#include <linux/sched.h>
7#include <linux/security.h>
8#include <asm/uaccess.h>
9
10#include "internal.h"
11
12#define CREATE_TRACE_POINTS
13#include <trace/events/kmem.h>
14
15/**
16 * kstrdup - allocate space for and copy an existing string
17 * @s: the string to duplicate
18 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
19 */
20char *kstrdup(const char *s, gfp_t gfp)
21{
22    size_t len;
23    char *buf;
24
25    if (!s)
26        return NULL;
27
28    len = strlen(s) + 1;
29    buf = kmalloc_track_caller(len, gfp);
30    if (buf)
31        memcpy(buf, s, len);
32    return buf;
33}
34EXPORT_SYMBOL(kstrdup);
35
36/**
37 * kstrndup - allocate space for and copy an existing string
38 * @s: the string to duplicate
39 * @max: read at most @max chars from @s
40 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
41 */
42char *kstrndup(const char *s, size_t max, gfp_t gfp)
43{
44    size_t len;
45    char *buf;
46
47    if (!s)
48        return NULL;
49
50    len = strnlen(s, max);
51    buf = kmalloc_track_caller(len+1, gfp);
52    if (buf) {
53        memcpy(buf, s, len);
54        buf[len] = '\0';
55    }
56    return buf;
57}
58EXPORT_SYMBOL(kstrndup);
59
60/**
61 * kmemdup - duplicate region of memory
62 *
63 * @src: memory region to duplicate
64 * @len: memory region length
65 * @gfp: GFP mask to use
66 */
67void *kmemdup(const void *src, size_t len, gfp_t gfp)
68{
69    void *p;
70
71    p = kmalloc_track_caller(len, gfp);
72    if (p)
73        memcpy(p, src, len);
74    return p;
75}
76EXPORT_SYMBOL(kmemdup);
77
78/**
79 * memdup_user - duplicate memory region from user space
80 *
81 * @src: source address in user space
82 * @len: number of bytes to copy
83 *
84 * Returns an ERR_PTR() on failure.
85 */
86void *memdup_user(const void __user *src, size_t len)
87{
88    void *p;
89
90    /*
91     * Always use GFP_KERNEL, since copy_from_user() can sleep and
92     * cause pagefault, which makes it pointless to use GFP_NOFS
93     * or GFP_ATOMIC.
94     */
95    p = kmalloc_track_caller(len, GFP_KERNEL);
96    if (!p)
97        return ERR_PTR(-ENOMEM);
98
99    if (copy_from_user(p, src, len)) {
100        kfree(p);
101        return ERR_PTR(-EFAULT);
102    }
103
104    return p;
105}
106EXPORT_SYMBOL(memdup_user);
107
108/**
109 * __krealloc - like krealloc() but don't free @p.
110 * @p: object to reallocate memory for.
111 * @new_size: how many bytes of memory are required.
112 * @flags: the type of memory to allocate.
113 *
114 * This function is like krealloc() except it never frees the originally
115 * allocated buffer. Use this if you don't want to free the buffer immediately
116 * like, for example, with RCU.
117 */
118void *__krealloc(const void *p, size_t new_size, gfp_t flags)
119{
120    void *ret;
121    size_t ks = 0;
122
123    if (unlikely(!new_size))
124        return ZERO_SIZE_PTR;
125
126    if (p)
127        ks = ksize(p);
128
129    if (ks >= new_size)
130        return (void *)p;
131
132    ret = kmalloc_track_caller(new_size, flags);
133    if (ret && p)
134        memcpy(ret, p, ks);
135
136    return ret;
137}
138EXPORT_SYMBOL(__krealloc);
139
140/**
141 * krealloc - reallocate memory. The contents will remain unchanged.
142 * @p: object to reallocate memory for.
143 * @new_size: how many bytes of memory are required.
144 * @flags: the type of memory to allocate.
145 *
146 * The contents of the object pointed to are preserved up to the
147 * lesser of the new and old sizes. If @p is %NULL, krealloc()
148 * behaves exactly like kmalloc(). If @size is 0 and @p is not a
149 * %NULL pointer, the object pointed to is freed.
150 */
151void *krealloc(const void *p, size_t new_size, gfp_t flags)
152{
153    void *ret;
154
155    if (unlikely(!new_size)) {
156        kfree(p);
157        return ZERO_SIZE_PTR;
158    }
159
160    ret = __krealloc(p, new_size, flags);
161    if (ret && p != ret)
162        kfree(p);
163
164    return ret;
165}
166EXPORT_SYMBOL(krealloc);
167
168/**
169 * kzfree - like kfree but zero memory
170 * @p: object to free memory of
171 *
172 * The memory of the object @p points to is zeroed before freed.
173 * If @p is %NULL, kzfree() does nothing.
174 *
175 * Note: this function zeroes the whole allocated buffer which can be a good
176 * deal bigger than the requested buffer size passed to kmalloc(). So be
177 * careful when using this function in performance sensitive code.
178 */
179void kzfree(const void *p)
180{
181    size_t ks;
182    void *mem = (void *)p;
183
184    if (unlikely(ZERO_OR_NULL_PTR(mem)))
185        return;
186    ks = ksize(mem);
187    memset(mem, 0, ks);
188    kfree(mem);
189}
190EXPORT_SYMBOL(kzfree);
191
192/*
193 * strndup_user - duplicate an existing string from user space
194 * @s: The string to duplicate
195 * @n: Maximum number of bytes to copy, including the trailing NUL.
196 */
197char *strndup_user(const char __user *s, long n)
198{
199    char *p;
200    long length;
201
202    length = strnlen_user(s, n);
203
204    if (!length)
205        return ERR_PTR(-EFAULT);
206
207    if (length > n)
208        return ERR_PTR(-EINVAL);
209
210    p = memdup_user(s, length);
211
212    if (IS_ERR(p))
213        return p;
214
215    p[length - 1] = '\0';
216
217    return p;
218}
219EXPORT_SYMBOL(strndup_user);
220
221void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
222        struct vm_area_struct *prev, struct rb_node *rb_parent)
223{
224    struct vm_area_struct *next;
225
226    vma->vm_prev = prev;
227    if (prev) {
228        next = prev->vm_next;
229        prev->vm_next = vma;
230    } else {
231        mm->mmap = vma;
232        if (rb_parent)
233            next = rb_entry(rb_parent,
234                    struct vm_area_struct, vm_rb);
235        else
236            next = NULL;
237    }
238    vma->vm_next = next;
239    if (next)
240        next->vm_prev = vma;
241}
242
243/* Check if the vma is being used as a stack by this task */
244static int vm_is_stack_for_task(struct task_struct *t,
245                struct vm_area_struct *vma)
246{
247    return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
248}
249
250/*
251 * Check if the vma is being used as a stack.
252 * If is_group is non-zero, check in the entire thread group or else
253 * just check in the current task. Returns the pid of the task that
254 * the vma is stack for.
255 */
256pid_t vm_is_stack(struct task_struct *task,
257          struct vm_area_struct *vma, int in_group)
258{
259    pid_t ret = 0;
260
261    if (vm_is_stack_for_task(task, vma))
262        return task->pid;
263
264    if (in_group) {
265        struct task_struct *t;
266        rcu_read_lock();
267        if (!pid_alive(task))
268            goto done;
269
270        t = task;
271        do {
272            if (vm_is_stack_for_task(t, vma)) {
273                ret = t->pid;
274                goto done;
275            }
276        } while_each_thread(task, t);
277done:
278        rcu_read_unlock();
279    }
280
281    return ret;
282}
283
284#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
285void arch_pick_mmap_layout(struct mm_struct *mm)
286{
287    mm->mmap_base = TASK_UNMAPPED_BASE;
288    mm->get_unmapped_area = arch_get_unmapped_area;
289    mm->unmap_area = arch_unmap_area;
290}
291#endif
292
293/*
294 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
295 * back to the regular GUP.
296 * If the architecture not support this function, simply return with no
297 * page pinned
298 */
299int __attribute__((weak)) __get_user_pages_fast(unsigned long start,
300                 int nr_pages, int write, struct page **pages)
301{
302    return 0;
303}
304EXPORT_SYMBOL_GPL(__get_user_pages_fast);
305
306/**
307 * get_user_pages_fast() - pin user pages in memory
308 * @start: starting user address
309 * @nr_pages: number of pages from start to pin
310 * @write: whether pages will be written to
311 * @pages: array that receives pointers to the pages pinned.
312 * Should be at least nr_pages long.
313 *
314 * Returns number of pages pinned. This may be fewer than the number
315 * requested. If nr_pages is 0 or negative, returns 0. If no pages
316 * were pinned, returns -errno.
317 *
318 * get_user_pages_fast provides equivalent functionality to get_user_pages,
319 * operating on current and current->mm, with force=0 and vma=NULL. However
320 * unlike get_user_pages, it must be called without mmap_sem held.
321 *
322 * get_user_pages_fast may take mmap_sem and page table locks, so no
323 * assumptions can be made about lack of locking. get_user_pages_fast is to be
324 * implemented in a way that is advantageous (vs get_user_pages()) when the
325 * user memory area is already faulted in and present in ptes. However if the
326 * pages have to be faulted in, it may turn out to be slightly slower so
327 * callers need to carefully consider what to use. On many architectures,
328 * get_user_pages_fast simply falls back to get_user_pages.
329 */
330int __attribute__((weak)) get_user_pages_fast(unsigned long start,
331                int nr_pages, int write, struct page **pages)
332{
333    struct mm_struct *mm = current->mm;
334    int ret;
335
336    down_read(&mm->mmap_sem);
337    ret = get_user_pages(current, mm, start, nr_pages,
338                    write, 0, pages, NULL);
339    up_read(&mm->mmap_sem);
340
341    return ret;
342}
343EXPORT_SYMBOL_GPL(get_user_pages_fast);
344
345unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
346    unsigned long len, unsigned long prot,
347    unsigned long flag, unsigned long pgoff)
348{
349    unsigned long ret;
350    struct mm_struct *mm = current->mm;
351
352    ret = security_mmap_file(file, prot, flag);
353    if (!ret) {
354        down_write(&mm->mmap_sem);
355        ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff);
356        up_write(&mm->mmap_sem);
357    }
358    return ret;
359}
360
361unsigned long vm_mmap(struct file *file, unsigned long addr,
362    unsigned long len, unsigned long prot,
363    unsigned long flag, unsigned long offset)
364{
365    if (unlikely(offset + PAGE_ALIGN(len) < offset))
366        return -EINVAL;
367    if (unlikely(offset & ~PAGE_MASK))
368        return -EINVAL;
369
370    return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
371}
372EXPORT_SYMBOL(vm_mmap);
373
374/* Tracepoints definitions. */
375EXPORT_TRACEPOINT_SYMBOL(kmalloc);
376EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
377EXPORT_TRACEPOINT_SYMBOL(kmalloc_node);
378EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc_node);
379EXPORT_TRACEPOINT_SYMBOL(kfree);
380EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);
381

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