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
 108static __always_inline void *__do_krealloc(const void *p, size_t new_size,
 109                                           gfp_t flags)
 110{
 111        void *ret;
 112        size_t ks = 0;
 113
 114        if (p)
 115                ks = ksize(p);
 116
 117        if (ks >= new_size)
 118                return (void *)p;
 119
 120        ret = kmalloc_track_caller(new_size, flags);
 121        if (ret && p)
 122                memcpy(ret, p, ks);
 123
 124        return ret;
 125}
 126
 127/**
 128 * __krealloc - like krealloc() but don't free @p.
 129 * @p: object to reallocate memory for.
 130 * @new_size: how many bytes of memory are required.
 131 * @flags: the type of memory to allocate.
 132 *
 133 * This function is like krealloc() except it never frees the originally
 134 * allocated buffer. Use this if you don't want to free the buffer immediately
 135 * like, for example, with RCU.
 136 */
 137void *__krealloc(const void *p, size_t new_size, gfp_t flags)
 138{
 139        if (unlikely(!new_size))
 140                return ZERO_SIZE_PTR;
 141
 142        return __do_krealloc(p, new_size, flags);
 143
 144}
 145EXPORT_SYMBOL(__krealloc);
 146
 147/**
 148 * krealloc - reallocate memory. The contents will remain unchanged.
 149 * @p: object to reallocate memory for.
 150 * @new_size: how many bytes of memory are required.
 151 * @flags: the type of memory to allocate.
 152 *
 153 * The contents of the object pointed to are preserved up to the
 154 * lesser of the new and old sizes.  If @p is %NULL, krealloc()
 155 * behaves exactly like kmalloc().  If @new_size is 0 and @p is not a
 156 * %NULL pointer, the object pointed to is freed.
 157 */
 158void *krealloc(const void *p, size_t new_size, gfp_t flags)
 159{
 160        void *ret;
 161
 162        if (unlikely(!new_size)) {
 163                kfree(p);
 164                return ZERO_SIZE_PTR;
 165        }
 166
 167        ret = __do_krealloc(p, new_size, flags);
 168        if (ret && p != ret)
 169                kfree(p);
 170
 171        return ret;
 172}
 173EXPORT_SYMBOL(krealloc);
 174
 175/**
 176 * kzfree - like kfree but zero memory
 177 * @p: object to free memory of
 178 *
 179 * The memory of the object @p points to is zeroed before freed.
 180 * If @p is %NULL, kzfree() does nothing.
 181 *
 182 * Note: this function zeroes the whole allocated buffer which can be a good
 183 * deal bigger than the requested buffer size passed to kmalloc(). So be
 184 * careful when using this function in performance sensitive code.
 185 */
 186void kzfree(const void *p)
 187{
 188        size_t ks;
 189        void *mem = (void *)p;
 190
 191        if (unlikely(ZERO_OR_NULL_PTR(mem)))
 192                return;
 193        ks = ksize(mem);
 194        memset(mem, 0, ks);
 195        kfree(mem);
 196}
 197EXPORT_SYMBOL(kzfree);
 198
 199/*
 200 * strndup_user - duplicate an existing string from user space
 201 * @s: The string to duplicate
 202 * @n: Maximum number of bytes to copy, including the trailing NUL.
 203 */
 204char *strndup_user(const char __user *s, long n)
 205{
 206        char *p;
 207        long length;
 208
 209        length = strnlen_user(s, n);
 210
 211        if (!length)
 212                return ERR_PTR(-EFAULT);
 213
 214        if (length > n)
 215                return ERR_PTR(-EINVAL);
 216
 217        p = memdup_user(s, length);
 218
 219        if (IS_ERR(p))
 220                return p;
 221
 222        p[length - 1] = '\0';
 223
 224        return p;
 225}
 226EXPORT_SYMBOL(strndup_user);
 227
 228void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
 229                struct vm_area_struct *prev, struct rb_node *rb_parent)
 230{
 231        struct vm_area_struct *next;
 232
 233        vma->vm_prev = prev;
 234        if (prev) {
 235                next = prev->vm_next;
 236                prev->vm_next = vma;
 237        } else {
 238                mm->mmap = vma;
 239                if (rb_parent)
 240                        next = rb_entry(rb_parent,
 241                                        struct vm_area_struct, vm_rb);
 242                else
 243                        next = NULL;
 244        }
 245        vma->vm_next = next;
 246        if (next)
 247                next->vm_prev = vma;
 248}
 249
 250/* Check if the vma is being used as a stack by this task */
 251static int vm_is_stack_for_task(struct task_struct *t,
 252                                struct vm_area_struct *vma)
 253{
 254        return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 255}
 256
 257/*
 258 * Check if the vma is being used as a stack.
 259 * If is_group is non-zero, check in the entire thread group or else
 260 * just check in the current task. Returns the pid of the task that
 261 * the vma is stack for.
 262 */
 263pid_t vm_is_stack(struct task_struct *task,
 264                  struct vm_area_struct *vma, int in_group)
 265{
 266        pid_t ret = 0;
 267
 268        if (vm_is_stack_for_task(task, vma))
 269                return task->pid;
 270
 271        if (in_group) {
 272                struct task_struct *t;
 273                rcu_read_lock();
 274                if (!pid_alive(task))
 275                        goto done;
 276
 277                t = task;
 278                do {
 279                        if (vm_is_stack_for_task(t, vma)) {
 280                                ret = t->pid;
 281                                goto done;
 282                        }
 283                } while_each_thread(task, t);
 284done:
 285                rcu_read_unlock();
 286        }
 287
 288        return ret;
 289}
 290
 291#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 292void arch_pick_mmap_layout(struct mm_struct *mm)
 293{
 294        mm->mmap_base = TASK_UNMAPPED_BASE;
 295        mm->get_unmapped_area = arch_get_unmapped_area;
 296        mm->unmap_area = arch_unmap_area;
 297}
 298#endif
 299
 300/*
 301 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
 302 * back to the regular GUP.
 303 * If the architecture not support this function, simply return with no
 304 * page pinned
 305 */
 306int __attribute__((weak)) __get_user_pages_fast(unsigned long start,
 307                                 int nr_pages, int write, struct page **pages)
 308{
 309        return 0;
 310}
 311EXPORT_SYMBOL_GPL(__get_user_pages_fast);
 312
 313/**
 314 * get_user_pages_fast() - pin user pages in memory
 315 * @start:      starting user address
 316 * @nr_pages:   number of pages from start to pin
 317 * @write:      whether pages will be written to
 318 * @pages:      array that receives pointers to the pages pinned.
 319 *              Should be at least nr_pages long.
 320 *
 321 * Returns number of pages pinned. This may be fewer than the number
 322 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 323 * were pinned, returns -errno.
 324 *
 325 * get_user_pages_fast provides equivalent functionality to get_user_pages,
 326 * operating on current and current->mm, with force=0 and vma=NULL. However
 327 * unlike get_user_pages, it must be called without mmap_sem held.
 328 *
 329 * get_user_pages_fast may take mmap_sem and page table locks, so no
 330 * assumptions can be made about lack of locking. get_user_pages_fast is to be
 331 * implemented in a way that is advantageous (vs get_user_pages()) when the
 332 * user memory area is already faulted in and present in ptes. However if the
 333 * pages have to be faulted in, it may turn out to be slightly slower so
 334 * callers need to carefully consider what to use. On many architectures,
 335 * get_user_pages_fast simply falls back to get_user_pages.
 336 */
 337int __attribute__((weak)) get_user_pages_fast(unsigned long start,
 338                                int nr_pages, int write, struct page **pages)
 339{
 340        struct mm_struct *mm = current->mm;
 341        int ret;
 342
 343        down_read(&mm->mmap_sem);
 344        ret = get_user_pages(current, mm, start, nr_pages,
 345                                        write, 0, pages, NULL);
 346        up_read(&mm->mmap_sem);
 347
 348        return ret;
 349}
 350EXPORT_SYMBOL_GPL(get_user_pages_fast);
 351
 352unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
 353        unsigned long len, unsigned long prot,
 354        unsigned long flag, unsigned long pgoff)
 355{
 356        unsigned long ret;
 357        struct mm_struct *mm = current->mm;
 358
 359        ret = security_mmap_file(file, prot, flag);
 360        if (!ret) {
 361                down_write(&mm->mmap_sem);
 362                ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff);
 363                up_write(&mm->mmap_sem);
 364        }
 365        return ret;
 366}
 367
 368unsigned long vm_mmap(struct file *file, unsigned long addr,
 369        unsigned long len, unsigned long prot,
 370        unsigned long flag, unsigned long offset)
 371{
 372        if (unlikely(offset + PAGE_ALIGN(len) < offset))
 373                return -EINVAL;
 374        if (unlikely(offset & ~PAGE_MASK))
 375                return -EINVAL;
 376
 377        return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
 378}
 379EXPORT_SYMBOL(vm_mmap);
 380
 381/* Tracepoints definitions. */
 382EXPORT_TRACEPOINT_SYMBOL(kmalloc);
 383EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);
 384EXPORT_TRACEPOINT_SYMBOL(kmalloc_node);
 385EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc_node);
 386EXPORT_TRACEPOINT_SYMBOL(kfree);
 387EXPORT_TRACEPOINT_SYMBOL(kmem_cache_free);
 388
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