arch/x86/lib/usercopy.c

   1 /*
   2  * User address space access functions.
   3  *
   4  *  For licencing details see kernel-base/COPYING
   5  */
   6
   7 #include <linux/highmem.h>
   8 #include <linux/module.h>
   9
  10 /*
  11  * best effort, GUP based copy_from_user() that is NMI-safe
  12  */
  13 unsigned long
  14 copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
  15 {
  16         unsigned long offset, addr = (unsigned long)from;
  17         unsigned long size, len = 0;
  18         struct page *page;
  19         void *map;
  20         int ret;
  21
  22         do {
  23                 ret = __get_user_pages_fast(addr, 1, 0, &page);
  24                 if (!ret)
  25                         break;
  26
  27                 offset = addr & (PAGE_SIZE - 1);
  28                 size = min(PAGE_SIZE - offset, n - len);
  29
  30                 map = kmap_atomic(page);
  31                 memcpy(to, map+offset, size);
  32                 kunmap_atomic(map);
  33                 put_page(page);
  34
  35                 len  += size;
  36                 to   += size;
  37                 addr += size;
  38
  39         } while (len < n);
  40
  41         return len;
  42 }
  43 EXPORT_SYMBOL_GPL(copy_from_user_nmi);