IntelFspPkg/FspSecCore/Ia32/Stacks.s

   1 #------------------------------------------------------------------------------
   2 #
   3 # Copyright (c) 2014 - 2015, Intel Corporation. All rights reserved.<BR>
   4 # SPDX-License-Identifier: BSD-2-Clause-Patent
   5 #
   6 # Abstract:
   7 #
   8 #   Switch the stack from temporary memory to permenent memory.
   9 #
  10 #------------------------------------------------------------------------------
  11
  12 ASM_GLOBAL ASM_PFX(SecSwitchStack)
  13
  14 #------------------------------------------------------------------------------
  15 # VOID
  16 # EFIAPI
  17 # SecSwitchStack (
  18 #   UINT32   TemporaryMemoryBase,
  19 #   UINT32   PermenentMemoryBase
  20 #   )
  21 #------------------------------------------------------------------------------
  22 ASM_GLOBAL ASM_PFX(SecSwitchStack)
  23 ASM_PFX(SecSwitchStack):
  24 #
  25 # Save four registers: eax, ebx, ecx, edx
  26 #
  27     pushl  %eax
  28     pushl  %ebx
  29     pushl  %ecx
  30     pushl  %edx
  31
  32 #
  33 # !!CAUTION!! this function address's is pushed into stack after
  34 # migration of whole temporary memory, so need save it to permenent
  35 # memory at first!
  36 #
  37
  38     movl  20(%esp), %ebx            # Save the first parameter
  39     movl  24(%esp), %ecx            # Save the second parameter
  40
  41 #
  42 # Save this function's return address into permenent memory at first.
  43 # Then, Fixup the esp point to permenent memory
  44 #
  45
  46     movl  %esp, %eax
  47     subl  %ebx, %eax
  48     addl  %ecx, %eax
  49     movl  (%esp), %edx                 # copy pushed register's value to permenent memory
  50     movl  %edx, (%eax)
  51     movl  4(%esp), %edx
  52     movl  %edx, 4(%eax)
  53     movl  8(%esp), %edx
  54     movl  %edx, 8(%eax)
  55     movl  12(%esp), %edx
  56     movl  %edx, 12(%eax)
  57     movl  16(%esp), %edx               # Update this function's return address into permenent memory
  58     movl  %edx, 16(%eax)
  59     movl  %eax, %esp                   # From now, esp is pointed to permenent memory
  60
  61 #
  62 # Fixup the ebp point to permenent memory
  63 #
  64     movl   %ebp, %eax
  65     subl   %ebx, %eax
  66     addl   %ecx, %eax
  67     movl   %eax, %ebp                  # From now, ebp is pointed to permenent memory
  68
  69 #
  70 # Fixup callee's ebp point for PeiDispatch
  71 #
  72 #    movl   %ebp, %eax
  73 #    subl   %ebx, %eax
  74 #    addl   %ecx, %eax
  75 #    movl   %eax, %ebp                #  From now, ebp is pointed to permenent memory
  76     popl   %edx
  77     popl   %ecx
  78     popl   %ebx
  79     popl   %eax
  80     ret