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 /**
  10  * kstrdup - allocate space for and copy an existing string
  11  * @s: the string to duplicate
  12  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  13  */
  14 char *kstrdup(const char *s, gfp_t gfp)
  15 {
  16         size_t len;
  17         char *buf;
  18
  19         if (!s)
  20                 return NULL;
  21
  22         len = strlen(s) + 1;
  23         buf = kmalloc_track_caller(len, gfp);
  24         if (buf)
  25                 memcpy(buf, s, len);
  26         return buf;
  27 }
  28 EXPORT_SYMBOL(kstrdup);
  29
  30 /**
  31  * kstrndup - allocate space for and copy an existing string
  32  * @s: the string to duplicate
  33  * @max: read at most @max chars from @s
  34  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  35  */
  36 char *kstrndup(const char *s, size_t max, gfp_t gfp)
  37 {
  38         size_t len;
  39         char *buf;
  40
  41         if (!s)
  42                 return NULL;
  43
  44         len = strnlen(s, max);
  45         buf = kmalloc_track_caller(len+1, gfp);
  46         if (buf) {
  47                 memcpy(buf, s, len);
  48                 buf[len] = '\0';
  49         }
  50         return buf;
  51 }
  52 EXPORT_SYMBOL(kstrndup);
  53
  54 /**
  55  * kmemdup - duplicate region of memory
  56  *
  57  * @src: memory region to duplicate
  58  * @len: memory region length
  59  * @gfp: GFP mask to use
  60  */
  61 void *kmemdup(const void *src, size_t len, gfp_t gfp)
  62 {
  63         void *p;
  64
  65         p = kmalloc_track_caller(len, gfp);
  66         if (p)
  67                 memcpy(p, src, len);
  68         return p;
  69 }
  70 EXPORT_SYMBOL(kmemdup);
  71
  72 /**
  73  * __krealloc - like krealloc() but don't free @p.
  74  * @p: object to reallocate memory for.
  75  * @new_size: how many bytes of memory are required.
  76  * @flags: the type of memory to allocate.
  77  *
  78  * This function is like krealloc() except it never frees the originally
  79  * allocated buffer. Use this if you don't want to free the buffer immediately
  80  * like, for example, with RCU.
  81  */
  82 void *__krealloc(const void *p, size_t new_size, gfp_t flags)
  83 {
  84         void *ret;
  85         size_t ks = 0;
  86
  87         if (unlikely(!new_size))
  88                 return ZERO_SIZE_PTR;
  89
  90         if (p)
  91                 ks = ksize(p);
  92
  93         if (ks >= new_size)
  94                 return (void *)p;
  95
  96         ret = kmalloc_track_caller(new_size, flags);
  97         if (ret && p)
  98                 memcpy(ret, p, ks);
  99
 100         return ret;
 101 }
 102 EXPORT_SYMBOL(__krealloc);
 103
 104 /**
 105  * krealloc - reallocate memory. The contents will remain unchanged.
 106  * @p: object to reallocate memory for.
 107  * @new_size: how many bytes of memory are required.
 108  * @flags: the type of memory to allocate.
 109  *
 110  * The contents of the object pointed to are preserved up to the
 111  * lesser of the new and old sizes.  If @p is %NULL, krealloc()
 112  * behaves exactly like kmalloc().  If @size is 0 and @p is not a
 113  * %NULL pointer, the object pointed to is freed.
 114  */
 115 void *krealloc(const void *p, size_t new_size, gfp_t flags)
 116 {
 117         void *ret;
 118
 119         if (unlikely(!new_size)) {
 120                 kfree(p);
 121                 return ZERO_SIZE_PTR;
 122         }
 123
 124         ret = __krealloc(p, new_size, flags);
 125         if (ret && p != ret)
 126                 kfree(p);
 127
 128         return ret;
 129 }
 130 EXPORT_SYMBOL(krealloc);
 131
 132 /*
 133  * strndup_user - duplicate an existing string from user space
 134  * @s: The string to duplicate
 135  * @n: Maximum number of bytes to copy, including the trailing NUL.
 136  */
 137 char *strndup_user(const char __user *s, long n)
 138 {
 139         char *p;
 140         long length;
 141
 142         length = strnlen_user(s, n);
 143
 144         if (!length)
 145                 return ERR_PTR(-EFAULT);
 146
 147         if (length > n)
 148                 return ERR_PTR(-EINVAL);
 149
 150         p = kmalloc(length, GFP_KERNEL);
 151
 152         if (!p)
 153                 return ERR_PTR(-ENOMEM);
 154
 155         if (copy_from_user(p, s, length)) {
 156                 kfree(p);
 157                 return ERR_PTR(-EFAULT);
 158         }
 159
 160         p[length - 1] = '\0';
 161
 162         return p;
 163 }
 164 EXPORT_SYMBOL(strndup_user);
 165
 166 #ifndef HAVE_ARCH_PICK_MMAP_LAYOUT
 167 void arch_pick_mmap_layout(struct mm_struct *mm)
 168 {
 169         mm->mmap_base = TASK_UNMAPPED_BASE;
 170         mm->get_unmapped_area = arch_get_unmapped_area;
 171         mm->unmap_area = arch_unmap_area;
 172 }
 173 #endif
 174
 175 int __attribute__((weak)) get_user_pages_fast(unsigned long start,
 176                                 int nr_pages, int write, struct page **pages)
 177 {
 178         struct mm_struct *mm = current->mm;
 179         int ret;
 180
 181         down_read(&mm->mmap_sem);
 182         ret = get_user_pages(current, mm, start, nr_pages,
 183                                         write, 0, pages, NULL);
 184         up_read(&mm->mmap_sem);
 185
 186         return ret;
 187 }
 188 EXPORT_SYMBOL_GPL(get_user_pages_fast);