reactos/lib/sdk/crt/except/i386/seh_prolog.s

   1 /*
   2  * COPYRIGHT:       GNU GPL, see COPYING in the top level directory
   3  * PROJECT:         ReactOS CRT
   4  * FILE:            lib/crt/misc/i386/seh_prolog.S
   5  * PURPOSE:         SEH Support for MSVC
   6  * PROGRAMMERS:     Timo Kreuzer
   7  */
   8
   9 /* INCLUDES ******************************************************************/
  10
  11 #include <asm.inc>
  12
  13 EXTERN __except_handler3:PROC
  14
  15 /* The very first thing a function compiled with MSVC containing SEH
  16  * will do is call __SEH_prolog like this:
  17  *
  18  *  push <Number of stackbytes>
  19  *  push <Address of exception handler>
  20  *  call __SEH_prolog
  21  *
  22  * When entering the function the stack layout is like this:
  23  *
  24  *  esp + 08: OLDFRAME.StackBytes
  25  *  esp + 04: OLDFRAME.SEHTable
  26  *  esp + 00: OLDFRAME.ReturnAddress
  27  *
  28  * __SEH_prolog will now setup the stack to the following layout:
  29  *
  30  *  esp + N + 24: SEH_FRAME.OriginalEbp       OLDFRAME.StackBytes
  31  *  esp + N + 20: SEH_FRAME.Disable           OLDFRAME.SEHTable
  32  *  esp + N + 1C: SEH_FRAME.SEHTable          OLDFRAME.ReturnAddress
  33  *  esp + N + 18: SEH_FRAME.Handler
  34  *  esp + N + 14: SEH_FRAME.PreviousRecord
  35  *  esp + N + 10: SEH_FRAME.unused
  36  *  esp + N + 0c: SEH_FRAME.NewEsp
  37  *
  38  *           N bytes local variables
  39  *  ...
  40  *  esp +     08: SAFE_AREA.Ebx
  41  *  esp +     04: SAFE_AREA.Esi
  42  *  esp +     00: SAFE_AREA.Edi
  43  *
  44  * all this is documented here (with some minor errors):
  45  * http://reactos-blog.blogspot.com/2009/08/inside-mind-of-reactos-developer.html
  46  */
  47
  48 OLDFRAME_ReturnAddress   =  0 /* 0x00 */
  49 OLDFRAME_SEHTable        =  4 /* 0x04 */
  50 OLDFRAME_StackBytes      =  8 /* 0x08 */
  51 OLDFRAME_Size            = 12 /* 0x0c */
  52
  53 SEH_FRAME_NewEsp         =  0 /* 0x00 */
  54 SEH_FRAME_unused         =  4 /* 0x04 */
  55 SEH_FRAME_PreviousRecord =  8 /* 0x08 */
  56 SEH_FRAME_Handler        = 12 /* 0x0c */
  57 SEH_FRAME_SEHTable       = 16 /* 0x10 */
  58 SEH_FRAME_Disable        = 20 /* 0x14 */
  59 SEH_FRAME_OriginalEbp    = 24 /* 0x18 */
  60 SEH_FRAME_Size           = 28 /* 0x1c */
  61
  62 SAFE_AREA_Edi            =  0 /* 0x00 */
  63 SAFE_AREA_Esi            =  4 /* 0x04 */
  64 SAFE_AREA_Ebx            =  8 /* 0x08 */
  65 SAFE_AREA_Size           = 12 /* 0x0c */
  66
  67
  68 .code
  69
  70 PUBLIC __SEH_prolog
  71 __SEH_prolog:
  72
  73     /* Get the number of stack bytes to reserve */
  74     mov eax, [esp + OLDFRAME_StackBytes]
  75
  76     /* Push address of __except_handler3 on the stack */
  77     push offset __except_handler3
  78
  79     /* Push the old exception record on the stack */
  80     push dword ptr fs:0
  81
  82     /* Adjust stack allocation, add size of the stack frame minus 2 pushes */
  83     add eax, SEH_FRAME_Size + SAFE_AREA_Size - OLDFRAME_Size - 8
  84
  85     /* Save old ebp, overwriting OLDFRAME.StackBytes */
  86     mov [esp + 8 + OLDFRAME_StackBytes], ebp
  87
  88     /* Load new ebp, pointing to OLDFRAME.StackBytes */
  89     lea ebp, [esp + 8 + OLDFRAME_StackBytes]
  90
  91     /* Allocate stack space */
  92     sub esp, eax
  93
  94     /* Push the return address on the stack */
  95     push dword ptr [ebp - OLDFRAME_StackBytes + OLDFRAME_ReturnAddress]
  96
  97     /* Get address of the SEH table */
  98     mov eax, [ebp + OLDFRAME_SEHTable]
  99
 100     /* Save new esp */
 101     mov [ebp - SEH_FRAME_OriginalEbp + SEH_FRAME_NewEsp], esp
 102
 103     /* Safe SEH table, overwriting OLDFRAME.ReturnAddress */
 104     mov [ebp - SEH_FRAME_OriginalEbp + SEH_FRAME_SEHTable], eax
 105
 106     /* Safe the disable value, overwriting OLDFRAME.SEHTable */
 107     mov dword ptr [ebp - SEH_FRAME_OriginalEbp + SEH_FRAME_Disable], -1
 108
 109     /* Load the address of the new registration record */
 110     lea eax, [ebp - SEH_FRAME_OriginalEbp + SEH_FRAME_PreviousRecord]
 111
 112     /* Save registers */
 113     mov [esp + SAFE_AREA_Edi], edi
 114     mov [esp + SAFE_AREA_Esi], esi
 115     mov [esp + SAFE_AREA_Ebx], ebx
 116
 117     /* Enqueue the new record */
 118     mov fs:[0], eax
 119
 120     /* Return to the caller */
 121     ret
 122
 123
 124 PUBLIC __SEH_epilog
 125 __SEH_epilog:
 126
 127     /* Restore the previous exception registration record */
 128     mov ecx, [ebp - SEH_FRAME_OriginalEbp + SEH_FRAME_PreviousRecord]
 129     mov fs:[0], ecx
 130
 131     /* Restore saved registers */
 132     mov edi, [esp + 4 + SAFE_AREA_Edi]
 133     mov esi, [esp + 4 + SAFE_AREA_Esi]
 134     mov ebx, [esp + 4 + SAFE_AREA_Ebx]
 135
 136     /* Get the return address */
 137     mov ecx, [esp]
 138
 139     /* Clean up stack */
 140     mov esp, ebp
 141
 142     /* Get previous ebp */
 143     mov ebp, [esp]
 144
 145     /* Save return address */
 146     mov [esp], ecx
 147
 148     /* Return to the caller */
 149     ret
 150
 151
 152 END