arch/x86/lib/usercopy_64.c

   1 /*
   2  * User address space access functions.
   3  *
   4  * Copyright 1997 Andi Kleen <ak@muc.de>
   5  * Copyright 1997 Linus Torvalds
   6  * Copyright 2002 Andi Kleen <ak@suse.de>
   7  */
   8 #include <linux/module.h>
   9 #include <linux/uaccess.h>
  10
  11 /*
  12  * Zero Userspace
  13  */
  14
  15 unsigned long __clear_user(void __user *addr, unsigned long size)
  16 {
  17         long __d0;
  18         might_fault();
  19         /* no memory constraint because it doesn't change any memory gcc knows
  20            about */
  21         stac();
  22         asm volatile(
  23                 "       testq  %[size8],%[size8]\n"
  24                 "       jz     4f\n"
  25                 "0:     movq %[zero],(%[dst])\n"
  26                 "       addq   %[eight],%[dst]\n"
  27                 "       decl %%ecx ; jnz   0b\n"
  28                 "4:     movq  %[size1],%%rcx\n"
  29                 "       testl %%ecx,%%ecx\n"
  30                 "       jz     2f\n"
  31                 "1:     movb   %b[zero],(%[dst])\n"
  32                 "       incq   %[dst]\n"
  33                 "       decl %%ecx ; jnz  1b\n"
  34                 "2:\n"
  35                 ".section .fixup,\"ax\"\n"
  36                 "3:     lea 0(%[size1],%[size8],8),%[size8]\n"
  37                 "       jmp 2b\n"
  38                 ".previous\n"
  39                 _ASM_EXTABLE(0b,3b)
  40                 _ASM_EXTABLE(1b,2b)
  41                 : [size8] "=&c"(size), [dst] "=&D" (__d0)
  42                 : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr),
  43                   [zero] "r" (0UL), [eight] "r" (8UL));
  44         clac();
  45         return size;
  46 }
  47 EXPORT_SYMBOL(__clear_user);
  48
  49 unsigned long clear_user(void __user *to, unsigned long n)
  50 {
  51         if (access_ok(VERIFY_WRITE, to, n))
  52                 return __clear_user(to, n);
  53         return n;
  54 }
  55 EXPORT_SYMBOL(clear_user);
  56
  57 unsigned long copy_in_user(void __user *to, const void __user *from, unsigned len)
  58 {
  59         if (access_ok(VERIFY_WRITE, to, len) && access_ok(VERIFY_READ, from, len)) {
  60                 return copy_user_generic((__force void *)to, (__force void *)from, len);
  61         }
  62         return len;
  63 }
  64 EXPORT_SYMBOL(copy_in_user);
  65
  66 /*
  67  * Try to copy last bytes and clear the rest if needed.
  68  * Since protection fault in copy_from/to_user is not a normal situation,
  69  * it is not necessary to optimize tail handling.
  70  */
  71 __visible unsigned long
  72 copy_user_handle_tail(char *to, char *from, unsigned len)
  73 {
  74         for (; len; --len, to++) {
  75                 char c;
  76
  77                 if (__get_user_nocheck(c, from++, sizeof(char)))
  78                         break;
  79                 if (__put_user_nocheck(c, to, sizeof(char)))
  80                         break;
  81         }
  82         clac();
  83
  84         /* If the destination is a kernel buffer, we always clear the end */
  85         if (!__addr_ok(to))
  86                 memset(to, 0, len);
  87         return len;
  88 }