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/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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