arch/x86/lib/getuser.S

   1 /*
   2  * __get_user functions.
   3  *
   4  * (C) Copyright 1998 Linus Torvalds
   5  * (C) Copyright 2005 Andi Kleen
   6  * (C) Copyright 2008 Glauber Costa
   7  *
   8  * These functions have a non-standard call interface
   9  * to make them more efficient, especially as they
  10  * return an error value in addition to the "real"
  11  * return value.
  12  */
  13
  14 /*
  15  * __get_user_X
  16  *
  17  * Inputs:      %[r|e]ax contains the address.
  18  *
  19  * Outputs:     %[r|e]ax is error code (0 or -EFAULT)
  20  *              %[r|e]dx contains zero-extended value
  21  *              %ecx contains the high half for 32-bit __get_user_8
  22  *
  23  *
  24  * These functions should not modify any other registers,
  25  * as they get called from within inline assembly.
  26  */
  27
  28 #include <linux/linkage.h>
  29 #include <asm/page_types.h>
  30 #include <asm/errno.h>
  31 #include <asm/asm-offsets.h>
  32 #include <asm/thread_info.h>
  33 #include <asm/asm.h>
  34 #include <asm/smap.h>
  35
  36         .text
  37 ENTRY(__get_user_1)
  38         GET_THREAD_INFO(%_ASM_DX)
  39         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  40         jae bad_get_user
  41         ASM_STAC
  42 1:      movzbl (%_ASM_AX),%edx
  43         xor %eax,%eax
  44         ASM_CLAC
  45         ret
  46 ENDPROC(__get_user_1)
  47
  48 ENTRY(__get_user_2)
  49         add $1,%_ASM_AX
  50         jc bad_get_user
  51         GET_THREAD_INFO(%_ASM_DX)
  52         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  53         jae bad_get_user
  54         ASM_STAC
  55 2:      movzwl -1(%_ASM_AX),%edx
  56         xor %eax,%eax
  57         ASM_CLAC
  58         ret
  59 ENDPROC(__get_user_2)
  60
  61 ENTRY(__get_user_4)
  62         add $3,%_ASM_AX
  63         jc bad_get_user
  64         GET_THREAD_INFO(%_ASM_DX)
  65         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  66         jae bad_get_user
  67         ASM_STAC
  68 3:      movl -3(%_ASM_AX),%edx
  69         xor %eax,%eax
  70         ASM_CLAC
  71         ret
  72 ENDPROC(__get_user_4)
  73
  74 ENTRY(__get_user_8)
  75 #ifdef CONFIG_X86_64
  76         add $7,%_ASM_AX
  77         jc bad_get_user
  78         GET_THREAD_INFO(%_ASM_DX)
  79         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  80         jae bad_get_user
  81         ASM_STAC
  82 4:      movq -7(%_ASM_AX),%rdx
  83         xor %eax,%eax
  84         ASM_CLAC
  85         ret
  86 #else
  87         add $7,%_ASM_AX
  88         jc bad_get_user_8
  89         GET_THREAD_INFO(%_ASM_DX)
  90         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  91         jae bad_get_user_8
  92         ASM_STAC
  93 4:      movl -7(%_ASM_AX),%edx
  94 5:      movl -3(%_ASM_AX),%ecx
  95         xor %eax,%eax
  96         ASM_CLAC
  97         ret
  98 #endif
  99 ENDPROC(__get_user_8)
 100
 101
 102 bad_get_user:
 103         xor %edx,%edx
 104         mov $(-EFAULT),%_ASM_AX
 105         ASM_CLAC
 106         ret
 107 END(bad_get_user)
 108
 109 #ifdef CONFIG_X86_32
 110 bad_get_user_8:
 111         xor %edx,%edx
 112         xor %ecx,%ecx
 113         mov $(-EFAULT),%_ASM_AX
 114         ASM_CLAC
 115         ret
 116 END(bad_get_user_8)
 117 #endif
 118
 119         _ASM_EXTABLE(1b,bad_get_user)
 120         _ASM_EXTABLE(2b,bad_get_user)
 121         _ASM_EXTABLE(3b,bad_get_user)
 122 #ifdef CONFIG_X86_64
 123         _ASM_EXTABLE(4b,bad_get_user)
 124 #else
 125         _ASM_EXTABLE(4b,bad_get_user_8)
 126         _ASM_EXTABLE(5b,bad_get_user_8)
 127 #endif