Function dmtcpPrepareForExec

src/execwrappers.cpp:390–462

FIXME: Unify this code with code prior to execvp in dmtcp_launch.cpp Can use argument to dmtcpPrepareForExec() or getenv("DMTCP_...") from DmtcpWorker constructor, to distinguish the two cases.

// Can use argument to dmtcpPrepareForExec() or getenv("DMTCP_...")
// from DmtcpWorker constructor, to distinguish the two cases.
static void
dmtcpPrepareForExec(const char *path,
                    const char *argv[],
                    const char **filename,
                    const char ***newArgv)
{
  JTRACE("Preparing for Exec") (path);

  const char *libPrefix = "/lib/lib";
  const char *lib64Prefix = "/lib64/lib";
  if (path != NULL && Util::strStartsWith(path, libPrefix)) {
    execShortLivedProcessAndExit(path, argv);
  }
  if (path != NULL && Util::strStartsWith(path, lib64Prefix)) {
    execShortLivedProcessAndExit(path, argv);
  }

  // Needed for /usr/libexec/utempter/utempter and other short-lived
  // setuid/setgid processes.
  // FIXME:  USE THIS FOR ALL setuid/setgid PROCESSES EXCEPT ONES THAT
  // WE DIRECTLY HANDLE, LIKE 'screen'.  (Need to name special routine,
  // execScreenProcess() ??)
  if (path != NULL && Util::strEndsWith(path, "/utempter")) {
    JTRACE("Trying to exec: utempter")(path)(argv[0])(argv[1]);
    string realPtsNameStr;

    // utempter takes a pts slave name as an argument. Since we virtualize
    // ptys, the slave name points to a virtual slave name, thus we need to
    // replace it with the real one.
    for (size_t i = 0; argv[i] != NULL; i++) {
      if (Util::strStartsWith(argv[i], VIRT_PTS_PREFIX_STR)) {
        // FIXME: Potential memory leak if exec() fails.
        char *realPtsNameStr = (char *)JALLOC_HELPER_MALLOC(PTS_PATH_MAX);
        SharedData::getRealPtyName(argv[i], realPtsNameStr,
                                   PTS_PATH_MAX);

        // Override const restriction
        argv[i] = realPtsNameStr;
      }
    }
    execShortLivedProcessAndExit(path, argv);
  }

  // FIXME:  SEE COMMENTS IN dmtcp_launch.cpp, rev. 1087; AND CHANGE THIS.
  if (path != NULL && Util::isSetuid(path)) {
    if (Util::isScreen(path)) {
      Util::setScreenDir();
    }

    // THIS NEXT LINE IS DANGEROUS.  MOST setuid PROGRAMS CAN'T RUN UNPRIVILEGED
    Util::patchArgvIfSetuid(path, argv, newArgv);

    // BUG:  Util::patchArgvIfSetuid() DOES NOT SET newArgv WHEN COPYING
    // BINARY IN CODE RE-FACTORING FROM REVISION 911.
    *filename = (*newArgv)[0];
  } else {
    *filename = (char *)path;
    *newArgv = argv;