arch/x86/lib/cmpxchg8b_emu.S

   1 /*
   2  *      This program is free software; you can redistribute it and/or
   3  *      modify it under the terms of the GNU General Public License
   4  *      as published by the Free Software Foundation; version 2
   5  *      of the License.
   6  *
   7  */
   8
   9 #include <linux/linkage.h>
  10 #include <asm/alternative-asm.h>
  11 #include <asm/frame.h>
  12 #include <asm/dwarf2.h>
  13
  14
  15 .text
  16
  17 /*
  18  * Inputs:
  19  * %esi : memory location to compare
  20  * %eax : low 32 bits of old value
  21  * %edx : high 32 bits of old value
  22  * %ebx : low 32 bits of new value
  23  * %ecx : high 32 bits of new value
  24  */
  25 ENTRY(cmpxchg8b_emu)
  26 CFI_STARTPROC
  27
  28 #
  29 # Emulate 'cmpxchg8b (%esi)' on UP except we don't
  30 # set the whole ZF thing (caller will just compare
  31 # eax:edx with the expected value)
  32 #
  33 cmpxchg8b_emu:
  34         pushfl
  35         cli
  36
  37         cmpl  (%esi), %eax
  38         jne not_same
  39         cmpl 4(%esi), %edx
  40         jne half_same
  41
  42         movl %ebx,  (%esi)
  43         movl %ecx, 4(%esi)
  44
  45         popfl
  46         ret
  47
  48  not_same:
  49         movl  (%esi), %eax
  50  half_same:
  51         movl 4(%esi), %edx
  52
  53         popfl
  54         ret
  55
  56 CFI_ENDPROC
  57 ENDPROC(cmpxchg8b_emu)