VOID VdsoCallPoint(THREADID tid) {
	//level=0,invalid
    assert(vdsoPatchData[tid].level);
    vdsoPatchData[tid].level++;
    // info("vDSO internal callpoint, now level %d", vdsoPatchData[tid].level); //common
}

// Instrumentation function, called for EVERY instruction
VOID VdsoInstrument(INS ins) {
    ADDRINT insAddr = INS_Address(ins);	//get ins addr
    if (unlikely(insAddr >= vdsoStart && insAddr < vdsoEnd)) {
		//INS is vdso syscall
        if (vdsoEntryMap.find(insAddr) != vdsoEntryMap.end()) {
            VdsoFunc func = vdsoEntryMap[insAddr];
			//call VdsoEntryPoint function
			//argv are: tid ,func(IARG_UINT32),arg0(LEVEL_BASE::REG_RDI),arg1(LEVEL_BASE::REG_RSI) 
            INS_InsertCall(ins, IPOINT_BEFORE, (AFUNPTR) VdsoEntryPoint, IARG_THREAD_ID, IARG_UINT32, (uint32_t)func, IARG_REG_VALUE, LEVEL_BASE::REG_RDI, IARG_REG_VALUE, LEVEL_BASE::REG_RSI, IARG_END);
        } else if (INS_IsCall(ins)) {	//call instruction
            INS_InsertCall(ins, IPOINT_BEFORE, (AFUNPTR) VdsoCallPoint, IARG_THREAD_ID, IARG_END);
        } else if (INS_IsRet(ins)) {	//Ret instruction
            INS_InsertCall(ins, IPOINT_BEFORE, (AFUNPTR) VdsoRetPoint, IARG_THREAD_ID, IARG_REG_REFERENCE, LEVEL_BASE::REG_RAX /* return val */, IARG_END);
        }
    }

    //Warn on the first vsyscall code translation
    if (unlikely(insAddr >= vsyscallStart && insAddr < vsyscallEnd && !vsyscallWarned)) {
        warn("Instrumenting vsyscall page code --- this process executes vsyscalls, which zsim does not virtualize!");
        vsyscallWarned = true;
    }
}