extern "C" void __declspec(naked) __cdecl _chkesp()
{
#ifndefPAGESIZE    #definePAGESIZE1000h
#endif /PAGESIZE
    __asm
    {
        push    ecx                     // save ecx
        cmp     eax,PAGESIZE        // more than one page requested?
        lea     ecx, [esp] + 8          // compute new stack pointer in ecx
                                        // correct for return address and
                                        // saved ecx
        jb      short lastpage          // no


probepages:

        sub     ecx,PAGESIZE        // yes, move down a page
        sub     eax,PAGESIZE        // adjust request and...

        test    dword ptr [ecx], eax    // ...probe it

        cmp     eax,PAGESIZE        // more than one page requested?
        jae     short probepages        // no


lastpage:

        sub     ecx, eax                // move stack down by eax
        mov     eax, esp                // save current tos and do a...

        test    dword ptr [ecx], eax    // ...probe in case a page was crossed

        mov     esp, ecx                // set the new stack pointer

        mov     ecx, dword ptr [eax]    // recover ecx
        mov     eax, dword ptr [eax + 4]// recover return address

        push    eax                     // prepare return address
                                        // ...probe in case a page was crossed
        ret
    }
}