1 files changed, 59 insertions, 0 deletions
diff --git a/CryptoPkg/Library/BaseCryptLib/SysCall/Ia32/Alloca.S b/CryptoPkg/Library/BaseCryptLib/SysCall/Ia32/Alloca.S
new file mode 100644
index 0000000000..8496833ac8
--- /dev/null
+++ b/CryptoPkg/Library/BaseCryptLib/SysCall/Ia32/Alloca.S
@@ -0,0 +1,59 @@
+#------------------------------------------------------------------------------
+#
+# Copyright (c) 2009 - 2010, Intel Corporation. All rights reserved.<BR>
+# This program and the accompanying materials
+# are licensed and made available under the terms and conditions of the BSD License
+# which accompanies this distribution.  The full text of the license may be found at
+# http://opensource.org/licenses/bsd-license.php.
+#
+# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+# WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+#
+# Module Name:
+#
+#   Alloca.S
+#
+# Abstract:
+#
+#   Implementation for allocation of automatically reclaimed memory, which is
+#   used to allocate space off the runtime stack.
+#   (NOTE: There is a assumption in this code that the page size equal to 4K)
+#
+#------------------------------------------------------------------------------
+
+
+    .686:
+    .code:
+
+ASM_GLOBAL ASM_PFX(_alloca)
+
+#------------------------------------------------------------------------------
+#
+# void __cdecl _alloca (unsigned size)
+#
+#------------------------------------------------------------------------------
+ASM_PFX(_alloca):
+
+    pushl   %ecx
+    cmpl    $0x1000, %eax
+    leal    8(%esp), %ecx
+    jb      LastPage
+
+ProbePages:
+    subl    $0x1000, %ecx
+    subl    $0x1000, %eax
+    testl   %eax, 0(%ecx)
+    cmpl    $0x1000, %eax
+    jae     ProbePages
+
+LastPage:
+    subl    %eax, %ecx
+    movl    %esp, %eax
+    testl   %eax, 0(%ecx)
+
+    movl    %ecx, %esp
+    movl    0(%eax), %ecx
+    movl    4(%eax), %eax
+    pushl   %eax
+
+    ret