release/src-rt-6.x.4708/linux/linux-2.6.36/arch/sparc/lib/user_fixup.c

   1 /* user_fixup.c: Fix up user copy faults.
   2  *
   3  * Copyright (C) 2004 David S. Miller <davem@redhat.com>
   4  */
   5
   6 #include <linux/compiler.h>
   7 #include <linux/kernel.h>
   8 #include <linux/string.h>
   9 #include <linux/errno.h>
  10 #include <linux/module.h>
  11
  12 #include <asm/uaccess.h>
  13
  14 /* Calculating the exact fault address when using
  15  * block loads and stores can be very complicated.
  16  *
  17  * Instead of trying to be clever and handling all
  18  * of the cases, just fix things up simply here.
  19  */
  20
  21 static unsigned long compute_size(unsigned long start, unsigned long size, unsigned long *offset)
  22 {
  23         unsigned long fault_addr = current_thread_info()->fault_address;
  24         unsigned long end = start + size;
  25
  26         if (fault_addr < start || fault_addr >= end) {
  27                 *offset = 0;
  28         } else {
  29                 *offset = fault_addr - start;
  30                 size = end - fault_addr;
  31         }
  32         return size;
  33 }
  34
  35 unsigned long copy_from_user_fixup(void *to, const void __user *from, unsigned long size)
  36 {
  37         unsigned long offset;
  38
  39         size = compute_size((unsigned long) from, size, &offset);
  40         if (likely(size))
  41                 memset(to + offset, 0, size);
  42
  43         return size;
  44 }
  45 EXPORT_SYMBOL(copy_from_user_fixup);
  46
  47 unsigned long copy_to_user_fixup(void __user *to, const void *from, unsigned long size)
  48 {
  49         unsigned long offset;
  50
  51         return compute_size((unsigned long) to, size, &offset);
  52 }
  53 EXPORT_SYMBOL(copy_to_user_fixup);
  54
  55 unsigned long copy_in_user_fixup(void __user *to, void __user *from, unsigned long size)
  56 {
  57         unsigned long fault_addr = current_thread_info()->fault_address;
  58         unsigned long start = (unsigned long) to;
  59         unsigned long end = start + size;
  60
  61         if (fault_addr >= start && fault_addr < end)
  62                 return end - fault_addr;
  63
  64         start = (unsigned long) from;
  65         end = start + size;
  66         if (fault_addr >= start && fault_addr < end)
  67                 return end - fault_addr;
  68
  69         return size;
  70 }
  71 EXPORT_SYMBOL(copy_in_user_fixup);