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 <asm/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         asm volatile(
  22                 "       testq  %[size8],%[size8]\n"
  23                 "       jz     4f\n"
  24                 "0:     movq %[zero],(%[dst])\n"
  25                 "       addq   %[eight],%[dst]\n"
  26                 "       decl %%ecx ; jnz   0b\n"
  27                 "4:     movq  %[size1],%%rcx\n"
  28                 "       testl %%ecx,%%ecx\n"
  29                 "       jz     2f\n"
  30                 "1:     movb   %b[zero],(%[dst])\n"
  31                 "       incq   %[dst]\n"
  32                 "       decl %%ecx ; jnz  1b\n"
  33                 "2:\n"
  34                 ".section .fixup,\"ax\"\n"
  35                 "3:     lea 0(%[size1],%[size8],8),%[size8]\n"
  36                 "       jmp 2b\n"
  37                 ".previous\n"
  38                 _ASM_EXTABLE(0b,3b)
  39                 _ASM_EXTABLE(1b,2b)
  40                 : [size8] "=&c"(size), [dst] "=&D" (__d0)
  41                 : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr),
  42                   [zero] "r" (0UL), [eight] "r" (8UL));
  43         return size;
  44 }
  45 EXPORT_SYMBOL(__clear_user);
  46
  47 unsigned long clear_user(void __user *to, unsigned long n)
  48 {
  49         if (access_ok(VERIFY_WRITE, to, n))
  50                 return __clear_user(to, n);
  51         return n;
  52 }
  53 EXPORT_SYMBOL(clear_user);
  54
  55 unsigned long copy_in_user(void __user *to, const void __user *from, unsigned len)
  56 {
  57         if (access_ok(VERIFY_WRITE, to, len) && access_ok(VERIFY_READ, from, len)) {
  58                 return copy_user_generic((__force void *)to, (__force void *)from, len);
  59         }
  60         return len;
  61 }
  62 EXPORT_SYMBOL(copy_in_user);
  63
  64 /*
  65  * Try to copy last bytes and clear the rest if needed.
  66  * Since protection fault in copy_from/to_user is not a normal situation,
  67  * it is not necessary to optimize tail handling.
  68  */
  69 unsigned long
  70 copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest)
  71 {
  72         char c;
  73         unsigned zero_len;
  74
  75         for (; len; --len) {
  76                 if (__get_user_nocheck(c, from++, sizeof(char)))
  77                         break;
  78                 if (__put_user_nocheck(c, to++, sizeof(char)))
  79                         break;
  80         }
  81
  82         for (c = 0, zero_len = len; zerorest && zero_len; --zero_len)
  83                 if (__put_user_nocheck(c, to++, sizeof(char)))
  84                         break;
  85         return len;
  86 }