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  *              The register is modified, but all changes are undone
  19  *              before returning because the C code doesn't know about it.
  20  *
  21  * Outputs:     %[r|e]ax is error code (0 or -EFAULT)
  22  *              %[r|e]dx contains zero-extended value
  23  *
  24  *
  25  * These functions should not modify any other registers,
  26  * as they get called from within inline assembly.
  27  */
  28
  29 #include <linux/linkage.h>
  30 #include <asm/dwarf2.h>
  31 #include <asm/page_types.h>
  32 #include <asm/errno.h>
  33 #include <asm/asm-offsets.h>
  34 #include <asm/thread_info.h>
  35 #include <asm/asm.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 1:      movzb (%_ASM_AX),%edx
  44         xor %eax,%eax
  45         ret
  46         CFI_ENDPROC
  47 ENDPROC(__get_user_1)
  48
  49 ENTRY(__get_user_2)
  50         CFI_STARTPROC
  51         add $1,%_ASM_AX
  52         jc bad_get_user
  53         GET_THREAD_INFO(%_ASM_DX)
  54         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  55         jae bad_get_user
  56 2:      movzwl -1(%_ASM_AX),%edx
  57         xor %eax,%eax
  58         ret
  59         CFI_ENDPROC
  60 ENDPROC(__get_user_2)
  61
  62 ENTRY(__get_user_4)
  63         CFI_STARTPROC
  64         add $3,%_ASM_AX
  65         jc bad_get_user
  66         GET_THREAD_INFO(%_ASM_DX)
  67         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  68         jae bad_get_user
  69 3:      mov -3(%_ASM_AX),%edx
  70         xor %eax,%eax
  71         ret
  72         CFI_ENDPROC
  73 ENDPROC(__get_user_4)
  74
  75 #ifdef CONFIG_X86_64
  76 ENTRY(__get_user_8)
  77         CFI_STARTPROC
  78         add $7,%_ASM_AX
  79         jc bad_get_user
  80         GET_THREAD_INFO(%_ASM_DX)
  81         cmp TI_addr_limit(%_ASM_DX),%_ASM_AX
  82         jae     bad_get_user
  83 4:      movq -7(%_ASM_AX),%_ASM_DX
  84         xor %eax,%eax
  85         ret
  86         CFI_ENDPROC
  87 ENDPROC(__get_user_8)
  88 #endif
  89
  90 bad_get_user:
  91         CFI_STARTPROC
  92         xor %edx,%edx
  93         mov $(-EFAULT),%_ASM_AX
  94         ret
  95         CFI_ENDPROC
  96 END(bad_get_user)
  97
  98 .section __ex_table,"a"
  99         _ASM_PTR 1b,bad_get_user
 100         _ASM_PTR 2b,bad_get_user
 101         _ASM_PTR 3b,bad_get_user
 102 #ifdef CONFIG_X86_64
 103         _ASM_PTR 4b,bad_get_user
 104 #endif