Zsim-tlb: bug

bug

zsim-tlb simulate in icarus0

pinbin: build/opt/zsim.cpp:816: LEVEL_BASE::VOID VdsoCallPoint(LEVEL_VM::THREADID): Assertion `vdsoPatchData[tid].level' failed.
Pin app terminated abnormally due to signal 6.

locate error

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
}

• vDSO (virtual dynamic shared object) is a kernel machanism for exporting a carefully set kernel space routines (eg. not secret api, gettid() and gettimeofday()) to user spapce to eliminate the performance penalty of user-kernel mode switch according to wiki. vDSO
• You can use some __vdso_getcpu() C library, and kernel will auto move it to user-space
• vDSO overcome vsyscall(first linux-kernel machanism to accelerate syscall) drawback.
• In zsim, vDSO have only four function enum VdsoFunc {VF_CLOCK_GETTIME, VF_GETTIMEOFDAY, VF_TIME, VF_GETCPU};

vDSO simulate part

// 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;
    }
}

INS_Address is from pin-kit, but INS_InsertCall is pin api.

try:

.level is just show the level of nested vsyscall. I think comment the assert which trigerd when callfunc before entryfunc is just fun.

需要进一步的研究学习

暂无

遇到的问题

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开题缘由、总结、反思、吐槽~~

参考文献

上面回答部分来自ChatGPT-3.5，没有进行正确性的交叉校验。

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