Instrumenting Before and After Forks

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>

#include "pin.H"

#include <iostream>
#include <fstream>

using namespace std;


INT32 Usage()
{
    cerr <<
        "This pin tool registers callbacks around fork().\n"
        "\n";
    cerr << KNOB_BASE::StringKnobSummary();
    cerr << endl;
    return -1;
}


pid_t parent_pid;
PIN_LOCK lock;

VOID BeforeFork(THREADID threadid, const CONTEXT* ctxt, VOID * arg)
{
    PIN_GetLock(&lock, threadid+1);
    cerr << "TOOL: Before fork." << endl;
    PIN_ReleaseLock(&lock);
    parent_pid = PIN_GetPid();
}

VOID AfterForkInParent(THREADID threadid, const CONTEXT* ctxt, VOID * arg)
{
    PIN_GetLock(&lock, threadid+1);
    cerr << "TOOL: After fork in parent." << endl;
    PIN_ReleaseLock(&lock);

    if (PIN_GetPid() != parent_pid)
    {
        cerr << "PIN_GetPid() fails in parent process" << endl;
        exit(-1);
    }
}

VOID AfterForkInChild(THREADID threadid, const CONTEXT* ctxt, VOID * arg)
{
    PIN_GetLock(&lock, threadid+1);
    cerr << "TOOL: After fork in child." << endl;
    PIN_ReleaseLock(&lock);
    
    if ((PIN_GetPid() == parent_pid) || (getppid() != parent_pid))
    {
        cerr << "PIN_GetPid() fails in child process" << endl;
        exit(-1);
    }
}

int main(INT32 argc, CHAR **argv)
{
    PIN_InitSymbols();
    if( PIN_Init(argc,argv) )
    {
        return Usage();
    }
    
    // Initialize the pin lock
    PIN_InitLock(&lock);
    
    // Register a notification handler that is called when the application
    // forks a new process.
    PIN_AddForkFunction(FPOINT_BEFORE, BeforeFork, 0);  
    PIN_AddForkFunction(FPOINT_AFTER_IN_PARENT, AfterForkInParent, 0);
    PIN_AddForkFunction(FPOINT_AFTER_IN_CHILD, AfterForkInChild, 0);
    
    // Never returns
    PIN_StartProgram();
    
    return 0;
}

fork라는 것은 유닉스 운영 체제에서 프로세스가 자기 자신을 복제하는 동작이다. 복제의 대상이 부모 프로세스, 복제의 결과가 자식 프로세스이다. 

PIN_AddForkFunction은 JIT mode에서 사용되는 것이고, PIN_AddFrokFunctionProbed()는 Probed mode에서 사용되는 것이다. fork()가 실패하면 FPOINT_AFTER_IN_PARENT callback이 이루어진다.