arch/i386/lib/getuser.S

   1 /*
   2  * __get_user functions.
   3  *
   4  * (C) Copyright 1998 Linus Torvalds
   5  *
   6  * These functions have a non-standard call interface
   7  * to make them more efficient, especially as they
   8  * return an error value in addition to the "real"
   9  * return value.
  10  */
  11 #include <asm/thread_info.h>
  12
  13
  14 /*
  15  * __get_user_X
  16  *
  17  * Inputs:      %eax contains the address
  18  *
  19  * Outputs:     %eax is error code (0 or -EFAULT)
  20  *              %edx contains zero-extended value
  21  *
  22  * These functions should not modify any other registers,
  23  * as they get called from within inline assembly.
  24  */
  25
  26 .text
  27 .align 4
  28 .globl __get_user_1
  29 __get_user_1:
  30         GET_THREAD_INFO(%edx)
  31         cmpl TI_addr_limit(%edx),%eax
  32         jae bad_get_user
  33 1:      movzbl (%eax),%edx
  34         xorl %eax,%eax
  35         ret
  36
  37 .align 4
  38 .globl __get_user_2
  39 __get_user_2:
  40         addl $1,%eax
  41         jc bad_get_user
  42         GET_THREAD_INFO(%edx)
  43         cmpl TI_addr_limit(%edx),%eax
  44         jae bad_get_user
  45 2:      movzwl -1(%eax),%edx
  46         xorl %eax,%eax
  47         ret
  48
  49 .align 4
  50 .globl __get_user_4
  51 __get_user_4:
  52         addl $3,%eax
  53         jc bad_get_user
  54         GET_THREAD_INFO(%edx)
  55         cmpl TI_addr_limit(%edx),%eax
  56         jae bad_get_user
  57 3:      movl -3(%eax),%edx
  58         xorl %eax,%eax
  59         ret
  60
  61 bad_get_user:
  62         xorl %edx,%edx
  63         movl $-14,%eax
  64         ret
  65
  66 .section __ex_table,"a"
  67         .long 1b,bad_get_user
  68         .long 2b,bad_get_user
  69         .long 3b,bad_get_user
  70 .previous