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/dwarf2.h>
  30 #include <asm/page_types.h>
  31 #include <asm/errno.h>
  32 #include <asm/asm-offsets.h>
  33 #include <asm/thread_info.h>
  34 #include <asm/asm.h>
  35 #include <asm/smap.h>
  36
  37         .text
  38 ENTRY(__get_user_1)
  39         CFI_STARTPROC
  40         GET_THREAD_INFO(%_ASM_DX)
  41         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  42         jae bad_get_user
  43         ASM_STAC
  44 1:      movzbl (%_ASM_AX),%edx
  45         xor %eax,%eax
  46         ASM_CLAC
  47         ret
  48         CFI_ENDPROC
  49 ENDPROC(__get_user_1)
  50
  51 ENTRY(__get_user_2)
  52         CFI_STARTPROC
  53         add $1,%_ASM_AX
  54         jc bad_get_user
  55         GET_THREAD_INFO(%_ASM_DX)
  56         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  57         jae bad_get_user
  58         ASM_STAC
  59 2:      movzwl -1(%_ASM_AX),%edx
  60         xor %eax,%eax
  61         ASM_CLAC
  62         ret
  63         CFI_ENDPROC
  64 ENDPROC(__get_user_2)
  65
  66 ENTRY(__get_user_4)
  67         CFI_STARTPROC
  68         add $3,%_ASM_AX
  69         jc bad_get_user
  70         GET_THREAD_INFO(%_ASM_DX)
  71         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  72         jae bad_get_user
  73         ASM_STAC
  74 3:      movl -3(%_ASM_AX),%edx
  75         xor %eax,%eax
  76         ASM_CLAC
  77         ret
  78         CFI_ENDPROC
  79 ENDPROC(__get_user_4)
  80
  81 ENTRY(__get_user_8)
  82         CFI_STARTPROC
  83 #ifdef CONFIG_X86_64
  84         add $7,%_ASM_AX
  85         jc bad_get_user
  86         GET_THREAD_INFO(%_ASM_DX)
  87         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  88         jae bad_get_user
  89         ASM_STAC
  90 4:      movq -7(%_ASM_AX),%rdx
  91         xor %eax,%eax
  92         ASM_CLAC
  93         ret
  94 #else
  95         add $7,%_ASM_AX
  96         jc bad_get_user_8
  97         GET_THREAD_INFO(%_ASM_DX)
  98         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  99         jae bad_get_user_8
 100         ASM_STAC
 101 4:      movl -7(%_ASM_AX),%edx
 102 5:      movl -3(%_ASM_AX),%ecx
 103         xor %eax,%eax
 104         ASM_CLAC
 105         ret
 106 #endif
 107         CFI_ENDPROC
 108 ENDPROC(__get_user_8)
 109
 110
 111 bad_get_user:
 112         CFI_STARTPROC
 113         xor %edx,%edx
 114         mov $(-EFAULT),%_ASM_AX
 115         ASM_CLAC
 116         ret
 117         CFI_ENDPROC
 118 END(bad_get_user)
 119
 120 #ifdef CONFIG_X86_32
 121 bad_get_user_8:
 122         CFI_STARTPROC
 123         xor %edx,%edx
 124         xor %ecx,%ecx
 125         mov $(-EFAULT),%_ASM_AX
 126         ASM_CLAC
 127         ret
 128         CFI_ENDPROC
 129 END(bad_get_user_8)
 130 #endif
 131
 132         _ASM_EXTABLE(1b,bad_get_user)
 133         _ASM_EXTABLE(2b,bad_get_user)
 134         _ASM_EXTABLE(3b,bad_get_user)
 135 #ifdef CONFIG_X86_64
 136         _ASM_EXTABLE(4b,bad_get_user)
 137 #else
 138         _ASM_EXTABLE(4b,bad_get_user_8)
 139         _ASM_EXTABLE(5b,bad_get_user_8)
 140 #endif