Source code of Windows XP (NT5)
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//*****************************************************************************
//
// SUBCLASSING -
//
// Support for subclassing of 32bit standard (predefined) classes by
// WOW apps.
//
//
// 01-10-92 NanduriR Created.
//
//*****************************************************************************
#include "precomp.h"
#pragma hdrstop
MODNAME(wsubcls.c);
VPVOID vptwpFirst = (VPVOID)NULL;
BOOL ConstructThunkWindowProc(
LPTWPLIST lptwp,
VPVOID vptwp
) {
/*
** This is the code which would build a thunk window proc but since we already
** have code like this laying around (button window proc thunk) we can just
** copy it. This also saves us from having to know things like the DGROUP
** of USER16, or the address of the 16-bit CallWindowProc function.
**
** lptwp->Code[0x00] = 0x45; inc bp
** lptwp->Code[0x01] = 0x55; push bp
** lptwp->Code[0x02] = 0x8B; mov bp,sp
** lptwp->Code[0x03] = 0xEC;
** lptwp->Code[0x04] = 0x1E; push ds
** lptwp->Code[0x05] = 0xB8; mov ax,DGROUP
** lptwp->Code[0x06] = LOBYTE(USER_DGROUP);
** lptwp->Code[0x07] = HIBYTE(USER_DGROUP);
** lptwp->Code[0x08] = 0x8E; mov ds,ax
** lptwp->Code[0x09] = 0xD8;
** lptwp->Code[0x0A] = 0xB8; mov ax,OFFSET BUTTONWNDPROC
** lptwp->Code[0x0B] = LOBYTE(LOWORD(ThunkProc16));
** lptwp->Code[0x0C] = HIBYTE(LOWORD(ThunkProc16));
** lptwp->Code[0x0D] = 0xBA; mov dx,SEG BUTTONWNDPROC
** lptwp->Code[0x0E] = LOBYTE(HIWORD(ThunkProc16));
** lptwp->Code[0x0F] = HIBYTE(HIWORD(ThunkProc16));
** lptwp->Code[0x10] = 0x52; push dx
** lptwp->Code[0x11] = 0x50; push ax
** lptwp->Code[0x12] = 0xFF; push WORD PTR [bp+14] ;hwnd
** lptwp->Code[0x13] = 0x76;
** lptwp->Code[0x14] = 0x0E;
** lptwp->Code[0x15] = 0xFF; push WORD PTR [bp+12] ;messag
** lptwp->Code[0x16] = 0x76;
** lptwp->Code[0x17] = 0x0C;
** lptwp->Code[0x18] = 0xFF; push WORD PTR [bp+10] ;wParam
** lptwp->Code[0x19] = 0x76;
** lptwp->Code[0x1A] = 0x0A;
** lptwp->Code[0x1B] = 0xFF; push WORD PTR [bp+8]
** lptwp->Code[0x1C] = 0x76;
** lptwp->Code[0x1D] = 0x08;
** lptwp->Code[0x1E] = 0xFF; push WORD PTR [bp+6] ;lParam
** lptwp->Code[0x1F] = 0x76;
** lptwp->Code[0x20] = 0x06;
** lptwp->Code[0x21] = 0x9A; call FAR PTR CALLWINDOWPROC
** lptwp->Code[0x22] = LOBYTE(LOWORD(CallWindowProc16));
** lptwp->Code[0x23] = HIBYTE(LOWORD(CallWindowProc16));
** lptwp->Code[0x24] = LOBYTE(HIWORD(CallWindowProc16));
** lptwp->Code[0x25] = HIBYTE(HIWORD(CallWindowProc16));
** lptwp->Code[0x26] = 0x4D; dec bp
** lptwp->Code[0x27] = 0x4D; dec bp
** lptwp->Code[0x28] = 0x8B; mov sp,bp
** lptwp->Code[0x29] = 0xE5; dec bp
** lptwp->Code[0x2A] = 0x1F; pop ds
** lptwp->Code[0x2B] = 0x5D; pop bp
** lptwp->Code[0x2C] = 0x4D; dec bp
** lptwp->Code[0x2D] = 0xCA; ret 10
** lptwp->Code[0x2E] = 0x0A;
** lptwp->Code[0x2F] = 0x00;
*/
VPVOID vpfn;
LPVOID lpfn;
VPVOID vpProc16;
/*
** Get the proc address of the Button Window Proc thunk
*/
vpfn = GetStdClassThunkProc( WOWCLASS_BUTTON );
if ( vpfn == (VPVOID)NULL ) {
return( FALSE );
}
/*
** Now copy it into our thunk
*/
GETVDMPTR( vpfn, THUNKWP_SIZE, lpfn);
RtlCopyMemory( lptwp->Code, lpfn, THUNKWP_SIZE );
FREEVDMPTR( lpfn );
/*
** Patch the "our address" pointer
*/
vpProc16 = (VPVOID)((DWORD)vptwp + FIELD_OFFSET(TWPLIST,Code[0]));
lptwp->Code[0x0B] = LOBYTE(LOWORD(vpProc16));
lptwp->Code[0x0C] = HIBYTE(LOWORD(vpProc16));
lptwp->Code[0x0E] = LOBYTE(HIWORD(vpProc16));
lptwp->Code[0x0F] = HIBYTE(HIWORD(vpProc16));
/*
** Initialize the rest of the TWPLIST structure
*/
lptwp->lpfn32 = 0;
lptwp->vpfn16 = vpProc16;
lptwp->vptwpNext = (VPVOID)NULL;
lptwp->hwnd32 = (HWND)0;
lptwp->dwMagic = SUBCLASS_MAGIC;
return( TRUE );
}
DWORD GetThunkWindowProc(
DWORD lpfn32,
LPSTR lpszClass,
PWW pww,
HWND hwnd32
) {
VPVOID vptwp;
LPTWPLIST lptwp;
INT count;
DWORD dwResult;
BOOL fOk;
VPVOID vpAvail = (VPVOID)NULL;
INT iClass;
// Dont try to thunk a NULL 32-bit proc.
if (!lpfn32) {
LOGDEBUG(2, ("WOW:GetThunkWindowProc: attempt to thunk NULL proc\n"));
return 0;
}
// the input is either lpstrClass or pww. One of them is always NULL.
if (lpszClass != NULL) {
iClass = GetStdClassNumber(lpszClass);
}
else {
iClass = GETICLASS(pww, hwnd32);
}
if ( iClass == WOWCLASS_WIN16 ) {
DWORD dwpid;
// iClass == WOWCLASS_WIN16 implies that hwnd could either be a 32bit
// window belonging to a WOW process (like Ole windows) or a window of
// a different process. If it is the former return a stub proc
// else return 0;
if (!(GetWindowThreadProcessId(hwnd32,&dwpid) &&
(dwpid == GetCurrentProcessId()))){
LOGDEBUG(LOG_ALWAYS, ("WOW:GetThunkWindowProc: class unknown\n"));
return 0;
}
} else {
//
// If they are subclassing one of the standard classes, and they
// are doing it for the 1st time, then return the address of the
// hardcoded thunk in USER16.
//
if ( lpfn32 == (DWORD)GetStdClassWndProc(iClass) ) {
dwResult = GetStdClassThunkProc(iClass);
return( dwResult );
}
}
/*
** Scan the list for available TWPLIST entries or duplicates
*/
vptwp = vptwpFirst;
while ( vptwp != (VPVOID)NULL ) {
GETVDMPTR( vptwp, sizeof(TWPLIST), lptwp );
if ( lptwp->lpfn32 == 0 && vpAvail == (VPVOID)NULL ) {
vpAvail = vptwp;
}
//
// If we find that we've already subclassed this proc32
// then return that thunk proc again.
//
if ( lptwp->lpfn32 == lpfn32 ) {
dwResult = (DWORD)lptwp->vpfn16;
FREEVDMPTR( lptwp );
return( dwResult );
}
vptwp = lptwp->vptwpNext;
FREEVDMPTR( lptwp );
}
// Obviously we didn't find any duplicate if we got here.
// If we didn't find a slot to reuse, then allocate more.
if ( vpAvail == (VPVOID)NULL ) {
/*
** No more available slots, allocate some more
*/
vptwp = GlobalAllocLock16( GMEM_MOVEABLE,
THUNKWP_BLOCK * sizeof(TWPLIST),
NULL );
if ( vptwp == (VPVOID)NULL ) {
LOGDEBUG( 1, ("GetThunkWindowProc: GlobalAllocLock16 failed to allocate memory\n"));
return( (DWORD)NULL );
}
count = THUNKWP_BLOCK;
while ( count ) {
GETVDMPTR( vptwp, sizeof(TWPLIST), lptwp );
fOk = ConstructThunkWindowProc( lptwp, vptwp );
if ( fOk ) {
/*
** Insert this thunk window proc into the list
*/
lptwp->vptwpNext = vptwpFirst;
vptwpFirst = vptwp;
vpAvail = vptwp;
}
FLUSHVDMPTR( vptwp, sizeof(TWPLIST), lptwp );
FREEVDMPTR( lptwp );
vptwp = (VPVOID)((DWORD)vptwp + sizeof(TWPLIST));
--count;
}
ChangeSelector16( HIWORD(vptwp) ); // Change into a code selector
}
if ( vpAvail != (VPVOID)NULL ) {
/*
** Use that available slot
*/
GETVDMPTR( vpAvail, sizeof(TWPLIST), lptwp );
lptwp->lpfn32 = lpfn32;
lptwp->hwnd32 = hwnd32;
lptwp->iClass = iClass;
dwResult = (DWORD)lptwp->vpfn16;
FLUSHVDMCODEPTR(vpAvail, sizeof(TWPLIST), lptwp);
FREEVDMPTR( lptwp );
return( dwResult );
}
return( (DWORD)NULL );
}
#if 0 // Currently unused
BOOL FreeThunkWindowProc(
DWORD vpProc16
) {
VPVOID vptwp;
LPTWPLIST lptwp;
/*
** Scan the list for available TWPLIST entries
*/
vptwp = vptwpFirst;
while ( vptwp != (VPVOID)NULL ) {
GETVDMPTR( vptwp, sizeof(TWPLIST), lptwp );
if ( lptwp->vpfn16 == vpProc16 ) {
/*
** Found slot to free
*/
lptwp->lpfn32 = 0;
lptwp->hwnd32 = (HWND)0;
lptwp->iClass = WOWCLASS_UNKNOWN;
FREEVDMPTR( lptwp );
return( TRUE );
}
vptwp = lptwp->vptwpNext;
FREEVDMPTR( lptwp );
}
return( FALSE );
}
void W32FreeThunkWindowProc(
DWORD lpfn32,
DWORD lpfn16
) {
VPVOID vptwp;
LPTWPLIST lptwp;
/*
** Scan the list for available TWPLIST entries
*/
vptwp = vptwpFirst;
while ( vptwp != (VPVOID)NULL ) {
GETVDMPTR( vptwp, sizeof(TWPLIST), lptwp );
if ( lptwp->lpfn32 == lpfn32 ) {
/*
** Found slot to free
*/
lptwp->lpfn32 = 0;
lptwp->hwnd32 = (HWND)0;
lptwp->iClass = WOWCLASS_UNKNOWN;
FREEVDMPTR( lptwp );
}
vptwp = lptwp->vptwpNext;
FREEVDMPTR( lptwp );
}
}
#endif
DWORD IsThunkWindowProc(
DWORD vpProc16, // IN
PINT piClass // OUT OPTIONAL
) {
VPVOID vpdw;
DWORD UNALIGNED * lpdw;
DWORD dwResult;
INT iClass;
/* Screen for valid addresses... */
if ( (HIWORD(vpProc16) == 0) || (LOWORD(vpProc16) < (sizeof(DWORD)*3)) ) {
return( 0 );
}
/*
** If it is a valid sub-class thunk, then it should be preceeded by
** three dword values. The first is the subclassing magic number,
** the second is the WOWCLASS_*, the 3rd is the 32-bit proc address.
*/
vpdw = (VPVOID)((DWORD)vpProc16 - sizeof(DWORD)*3);
GETVDMPTR( vpdw, sizeof(DWORD)*3, lpdw );
iClass = (INT)*(lpdw+1);
dwResult = *(lpdw+2); // Get the lpfn32 value
if ( *lpdw != SUBCLASS_MAGIC ) {
dwResult = 0; // Zero it if it wasn't valid
iClass = WOWCLASS_WIN16;
} else {
if ( dwResult == 0 ) {
// They cheated and looked up the export from USER.EXE
dwResult = (DWORD) GetStdClassWndProc( iClass );
}
}
if (piClass) {
*piClass = iClass;
}
FREEVDMPTR( lpdw );
return( dwResult );
}