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

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