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- Always copy (almost) the whole stack space over to the 16bit stack

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instead of calculating some potentially bogus parameter count.
- Add some comments.
This commit is contained in:
Andreas Mohr 2002-07-08 19:40:29 +00:00 committed by Alexandre Julliard
parent 421660e894
commit 22ffa982ec
1 changed files with 33 additions and 2 deletions
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35
dlls/kernel/thunk.c
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@ -299,9 +299,24 @@ UINT WINAPI ThunkConnect32(
* QT_Thunk (KERNEL32.@)
*
* The target address is in EDX.
* The 16 bit arguments start at ESP.
* The 16bit arguments start at ESP.
* The number of 16bit argument bytes is EBP-ESP-0x40 (64 Byte thunksetup).
* So the stack layout is 16bit argument bytes and then the 64 byte
* scratch buffer.
* The scratch buffer is used as work space by Windows' QT_Thunk
* function.
* As the programs unfortunately don't always provide a fixed size
* scratch buffer (danger, stack corruption ahead !!), we simply resort
* to copying over the whole EBP-ESP range to the 16bit stack
* (as there's no way to safely figure out the param count
* due to this misbehaviour of some programs).
* [ok]
*
* See DDJ article 9614c for a very good description of QT_Thunk (also
* available online !).
*
* FIXME: DDJ talks of certain register usage rules; I'm not sure
* whether we cover this 100%.
*/
void WINAPI QT_Thunk( CONTEXT86 *context )
{
@ -312,19 +327,35 @@ void WINAPI QT_Thunk( CONTEXT86 *context )
context16.SegCs = HIWORD(context->Edx);
context16.Eip = LOWORD(context->Edx);
/* point EBP to the STACK16FRAME on the stack
* for the call_to_16 to set up the register content on calling */
context16.Ebp = OFFSETOF( NtCurrentTeb()->cur_stack )
+ (WORD)&((STACK16FRAME*)0)->bp;
argsize = context->Ebp-context->Esp-0x40;
/*
* used to be (problematic):
* argsize = context->Ebp - context->Esp - 0x40;
* due to some programs abusing the API, we better assume the full
* EBP - ESP range for copying instead: */
argsize = context->Ebp - context->Esp;
/* ok, too much is insane; let's limit param count a bit again */
if (argsize > 64)
argsize = 64; /* 32 WORDs */
memcpy( (LPBYTE)CURRENT_STACK16 - argsize,
(LPBYTE)context->Esp, argsize );
/* let's hope call_to_16 won't mind getting called with such a
* potentially bogus large number of arguments */
wine_call_to_16_regs_short( &context16, argsize );
context->Eax = context16.Eax;
context->Edx = context16.Edx;
context->Ecx = context16.Ecx;
/* make sure to update the Win32 ESP, too, in order to throw away
* the number of parameters that the Win16 function
* accepted (that it popped from the corresponding Win16 stack) */
context->Esp += LOWORD(context16.Esp) -
( OFFSETOF( NtCurrentTeb()->cur_stack ) - argsize );
}