arch/x86_64/lib/putuser.S

   1 /*
   2  * __put_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  * __put_user_X
  15  *
  16  * Inputs:      %rcx contains the address
  17  *              %rdx contains new value
  18  *
  19  * Outputs:     %rax is error code (0 or -EFAULT)
  20  *
  21  * %r8 is destroyed.
  22  *
  23  * These functions should not modify any other registers,
  24  * as they get called from within inline assembly.
  25  */
  26
  27 #include <linux/linkage.h>
  28 #include <asm/dwarf2.h>
  29 #include <asm/page.h>
  30 #include <asm/errno.h>
  31 #include <asm/asm-offsets.h>
  32 #include <asm/thread_info.h>
  33
  34         .text
  35 ENTRY(__put_user_1)
  36         CFI_STARTPROC
  37         GET_THREAD_INFO(%r8)
  38         cmpq threadinfo_addr_limit(%r8),%rcx
  39         jae bad_put_user
  40 1:      movb %dl,(%rcx)
  41         xorl %eax,%eax
  42         ret
  43         CFI_ENDPROC
  44 ENDPROC(__put_user_1)
  45
  46 ENTRY(__put_user_2)
  47         CFI_STARTPROC
  48         GET_THREAD_INFO(%r8)
  49         addq $1,%rcx
  50         jc 20f
  51         cmpq threadinfo_addr_limit(%r8),%rcx
  52         jae 20f
  53         decq %rcx
  54 2:      movw %dx,(%rcx)
  55         xorl %eax,%eax
  56         ret
  57 20:     decq %rcx
  58         jmp bad_put_user
  59         CFI_ENDPROC
  60 ENDPROC(__put_user_2)
  61
  62 ENTRY(__put_user_4)
  63         CFI_STARTPROC
  64         GET_THREAD_INFO(%r8)
  65         addq $3,%rcx
  66         jc 30f
  67         cmpq threadinfo_addr_limit(%r8),%rcx
  68         jae 30f
  69         subq $3,%rcx
  70 3:      movl %edx,(%rcx)
  71         xorl %eax,%eax
  72         ret
  73 30:     subq $3,%rcx
  74         jmp bad_put_user
  75         CFI_ENDPROC
  76 ENDPROC(__put_user_4)
  77
  78 ENTRY(__put_user_8)
  79         CFI_STARTPROC
  80         GET_THREAD_INFO(%r8)
  81         addq $7,%rcx
  82         jc 40f
  83         cmpq threadinfo_addr_limit(%r8),%rcx
  84         jae 40f
  85         subq $7,%rcx
  86 4:      movq %rdx,(%rcx)
  87         xorl %eax,%eax
  88         ret
  89 40:     subq $7,%rcx
  90         jmp bad_put_user
  91         CFI_ENDPROC
  92 ENDPROC(__put_user_8)
  93
  94 bad_put_user:
  95         CFI_STARTPROC
  96         movq $(-EFAULT),%rax
  97         ret
  98         CFI_ENDPROC
  99 END(bad_put_user)
 100
 101 .section __ex_table,"a"
 102         .quad 1b,bad_put_user
 103         .quad 2b,bad_put_user
 104         .quad 3b,bad_put_user
 105         .quad 4b,bad_put_user
 106 .previous