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#include <windows.h> 
#include <stdio.h> 
#include <assert.h> 

//=======================================================================
// This is the application for testing the syscall_std tool.
// It uses two different system call standards on ia32: INT2E and sysenter.
// On intel64 it always uses syscall instruction to invoke system call.
//=======================================================================

typedef BOOL WINAPI IsWow64Process_T(HANDLE, PBOOL);
typedef LONG NTSTATUS, *PNTSTATUS;
typedef NTSTATUS __stdcall NtAllocateVirtualMemory_T(HANDLE processHandle, 
                                           PVOID      *baseAddress, 
                                           ULONG_PTR  zeroBits, 
                                           PSIZE_T    regionSize, 
                                           ULONG      allocationType, 
                                           ULONG      protect);

NtAllocateVirtualMemory_T * pfnNtAllocateVirtualMemory = 0;
UINT32 ntAllocateNumber = 0;

//=======================================================================
// Return TRUE for native 32-bit OS
BOOL IsNativeOs32()
{
    BOOL isNativeOs32 = FALSE;
    if (sizeof(void *) == 4)
    {
        static IsWow64Process_T * fnIsWow64Process = 
            (IsWow64Process_T *)GetProcAddress(GetModuleHandle("kernel32"),"IsWow64Process");

        BOOL isWow64 = FALSE;
        if (fnIsWow64Process != 0)
        {
            fnIsWow64Process(GetCurrentProcess(),&isWow64);
        }
        isNativeOs32 =!isWow64;
    }

    return isNativeOs32;
}

BOOL isNativeOs32 = IsNativeOs32();

//=======================================================================
// Allocate memory region using FAST or ALT system call standard
// If syscallNum is non-zero and we are running on ia32 - use ALT system call
// Otherwise - use FAST system call
extern "C" __declspec(dllexport)
PVOID My_AllocateVirtualMemory(  HANDLE  processHandle,
                                 SIZE_T size,
                                 ULONG protect,
                                 UINT32 syscallNum)
{
    PVOID  baseAddress = 0;
    PVOID * pBaseAddress = &baseAddress;
    SIZE_T regionSize = size;
    SIZE_T *pRegionSize = &regionSize;
    ULONG allocationType = MEM_RESERVE | MEM_COMMIT;

    BOOL done = FALSE;
    if (isNativeOs32 && (syscallNum != 0))
    {
        #ifndef  _WIN64
            _asm
            {
                push    protect;
                push    allocationType;
                push    pRegionSize;
                push    0;
                push    pBaseAddress;
                push    processHandle;
                mov     edx, esp
                mov     eax, syscallNum;
                // change ESP arbitrarily to check that it is not used to retrieve 
                // ALT syscall arguments
                sub     esp, 0x10; 
                int     0x2e;
                add     esp, 0x10;

                add     esp, 0x18;
            }
            done = TRUE;
        #endif

    }
    if (!done)
    {
        pfnNtAllocateVirtualMemory(processHandle, pBaseAddress, 0, 
                           pRegionSize, allocationType, protect);
    }
    return baseAddress;
}

//=======================================================================
// Set syscall number for ALT syscall to NtAllocateVirtualMemory.
// To be called by a tool
extern "C" __declspec(dllexport)
void My_SetNtAllocateNumber(UINT32 num)
{
    ntAllocateNumber = num;
}

//=======================================================================

int main()
{
    pfnNtAllocateVirtualMemory = (NtAllocateVirtualMemory_T *)GetProcAddress(
        GetModuleHandle("ntdll.dll"), "NtAllocateVirtualMemory");
    assert(pfnNtAllocateVirtualMemory != 0);

    printf( "Before FAST call to NtAllocateVirtualMemory\n" ); fflush( stdout );
    My_AllocateVirtualMemory( GetCurrentProcess(), 777 ,PAGE_READWRITE, 0);
    printf( "After FAST call to NtAllocateVirtualMemory\n" ); fflush( stdout );

    printf( "Before ALT call to NtAllocateVirtualMemory\n" ); fflush( stdout );
    My_AllocateVirtualMemory( GetCurrentProcess(), 777,PAGE_READWRITE, ntAllocateNumber);
    printf( "After ALT call to NtAllocateVirtualMemory\n" ); fflush( stdout );

    return 0;
}

