Root/mm/util.c

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

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