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 #include <asm/word-at-a-time.h>
  11 #include <linux/sched.h>
  12
  13 /*
  14  * best effort, GUP based copy_from_user() that is NMI-safe
  15  */
  16 unsigned long
  17 copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
  18 {
  19         unsigned long offset, addr = (unsigned long)from;
  20         unsigned long size, len = 0;
  21         struct page *page;
  22         void *map;
  23         int ret;
  24
  25         if (__range_not_ok(from, n, TASK_SIZE))
  26                 return len;
  27
  28         do {
  29                 ret = __get_user_pages_fast(addr, 1, 0, &page);
  30                 if (!ret)
  31                         break;
  32
  33                 offset = addr & (PAGE_SIZE - 1);
  34                 size = min(PAGE_SIZE - offset, n - len);
  35
  36                 map = kmap_atomic(page);
  37                 memcpy(to, map+offset, size);
  38                 kunmap_atomic(map);
  39                 put_page(page);
  40
  41                 len  += size;
  42                 to   += size;
  43                 addr += size;
  44
  45         } while (len < n);
  46
  47         return len;
  48 }
  49 EXPORT_SYMBOL_GPL(copy_from_user_nmi);