arch/x86_64/lib/getuser.S

   1 /*
   2  * __get_user functions.
   3  *
   4  * (C) Copyright 1998 Linus Torvalds
   5  * (C) Copyright 2005 Andi Kleen
   6  *
   7  * These functions have a non-standard call interface
   8  * to make them more efficient, especially as they
   9  * return an error value in addition to the "real"
  10  * return value.
  11  */
  12
  13 /*
  14  * __get_user_X
  15  *
  16  * Inputs:      %rcx contains the address.
  17  *              The register is modified, but all changes are undone
  18  *              before returning because the C code doesn't know about it.
  19  *
  20  * Outputs:     %rax is error code (0 or -EFAULT)
  21  *              %rdx contains zero-extended value
  22  *
  23  * %r8 is destroyed.
  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.h>
  32 #include <asm/errno.h>
  33 #include <asm/asm-offsets.h>
  34 #include <asm/thread_info.h>
  35
  36         .text
  37 ENTRY(__get_user_1)
  38         CFI_STARTPROC
  39         GET_THREAD_INFO(%r8)
  40         cmpq threadinfo_addr_limit(%r8),%rcx
  41         jae bad_get_user
  42 1:      movzb (%rcx),%edx
  43         xorl %eax,%eax
  44         ret
  45         CFI_ENDPROC
  46 ENDPROC(__get_user_1)
  47
  48 ENTRY(__get_user_2)
  49         CFI_STARTPROC
  50         GET_THREAD_INFO(%r8)
  51         addq $1,%rcx
  52         jc 20f
  53         cmpq threadinfo_addr_limit(%r8),%rcx
  54         jae 20f
  55         decq   %rcx
  56 2:      movzwl (%rcx),%edx
  57         xorl %eax,%eax
  58         ret
  59 20:     decq    %rcx
  60         jmp     bad_get_user
  61         CFI_ENDPROC
  62 ENDPROC(__get_user_2)
  63
  64 ENTRY(__get_user_4)
  65         CFI_STARTPROC
  66         GET_THREAD_INFO(%r8)
  67         addq $3,%rcx
  68         jc 30f
  69         cmpq threadinfo_addr_limit(%r8),%rcx
  70         jae 30f
  71         subq $3,%rcx
  72 3:      movl (%rcx),%edx
  73         xorl %eax,%eax
  74         ret
  75 30:     subq $3,%rcx
  76         jmp bad_get_user
  77         CFI_ENDPROC
  78 ENDPROC(__get_user_4)
  79
  80 ENTRY(__get_user_8)
  81         CFI_STARTPROC
  82         GET_THREAD_INFO(%r8)
  83         addq $7,%rcx
  84         jc 40f
  85         cmpq threadinfo_addr_limit(%r8),%rcx
  86         jae     40f
  87         subq    $7,%rcx
  88 4:      movq (%rcx),%rdx
  89         xorl %eax,%eax
  90         ret
  91 40:     subq $7,%rcx
  92         jmp bad_get_user
  93         CFI_ENDPROC
  94 ENDPROC(__get_user_8)
  95
  96 bad_get_user:
  97         CFI_STARTPROC
  98         xorl %edx,%edx
  99         movq $(-EFAULT),%rax
 100         ret
 101         CFI_ENDPROC
 102 END(bad_get_user)
 103
 104 .section __ex_table,"a"
 105         .quad 1b,bad_get_user
 106         .quad 2b,bad_get_user
 107         .quad 3b,bad_get_user
 108         .quad 4b,bad_get_user
 109 .previous