CryptoPkg/Library/BaseCryptLib/SysCall/Ia32/Alloca.S

   1 #------------------------------------------------------------------------------
   2 #
   3 # Copyright (c) 2009 - 2010, Intel Corporation. All rights reserved.<BR>
   4 # This program and the accompanying materials
   5 # are licensed and made available under the terms and conditions of the BSD License
   6 # which accompanies this distribution.  The full text of the license may be found at
   7 # http://opensource.org/licenses/bsd-license.php.
   8 #
   9 # THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 # WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11 #
  12 # Module Name:
  13 #
  14 #   Alloca.S
  15 #
  16 # Abstract:
  17 #
  18 #   Implementation for allocation of automatically reclaimed memory, which is
  19 #   used to allocate space off the runtime stack.
  20 #   (NOTE: There is a assumption in this code that the page size equal to 4K)
  21 #
  22 #------------------------------------------------------------------------------
  23
  24
  25     .686:
  26     .code:
  27
  28 ASM_GLOBAL ASM_PFX(_alloca)
  29
  30 #------------------------------------------------------------------------------
  31 #
  32 # void __cdecl _alloca (unsigned size)
  33 #
  34 #------------------------------------------------------------------------------
  35 ASM_PFX(_alloca):
  36
  37     pushl   %ecx
  38     cmpl    $0x1000, %eax
  39     leal    8(%esp), %ecx
  40     jb      LastPage
  41
  42 ProbePages:
  43     subl    $0x1000, %ecx
  44     subl    $0x1000, %eax
  45     testl   %eax, 0(%ecx)
  46     cmpl    $0x1000, %eax
  47     jae     ProbePages
  48
  49 LastPage:
  50     subl    %eax, %ecx
  51     movl    %esp, %eax
  52     testl   %eax, 0(%ecx)
  53
  54     movl    %ecx, %esp
  55     movl    0(%eax), %ecx
  56     movl    4(%eax), %eax
  57     pushl   %eax
  58
  59     ret