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