[LNT] Fixed possible crash or junk data in cPerf

[kpdev42]

Summary

The return value of the first call of Dump.next() was not checked. Dump.getText() returned an uninitialized string (a junk string) if the objdump did not return an usable data for the specified address range. It caused a crash or inconsistent profile data.

OS Laboratory. Huawei Russian Research Institute. Saint-Petersburg

[thopre]

LGTM

lnt/testing/profile/cPerf.cpp

if (Stream) {
       wait(NULL);
     }
     if (Line)
       free(Line);
   }
 
   void reset(Map *M, uint64_t Start, uint64_t Stop) {
     ThisAddress = 0;
+    ThisText = "";
     if (Stream) {
       fclose(Stream);
       wait(NULL);
     }
 
     char buf1[32], buf2[32];
     sprintf(buf1, "%#llx", Start);
     sprintf(buf2, "%#llx", Stop + 4);
uint64_t next() {
     return ThisAddress;
   }
 
   void getLine() {
     while (true) {
       ssize_t Len = getline(&Line, &LineLen, Stream);
       if (Len == -1) {
         ThisAddress = EndAddress;
+        ThisText = "";
         return;
       }
       char *TokBuf;
       char *One = strtok_r(Line, ":", &TokBuf);
       char *Two = strtok_r(NULL, "\n", &TokBuf);
       if (!One || !Two)
         continue;
       char *EndPtr = NULL;

 
 void PerfReader::emitSymbol(
     Symbol &Sym, Map &M,
     std::map<uint64_t, std::map<const char *, uint64_t>>::iterator Event,
     std::map<const char *, uint64_t> &SymEvents,
     uint64_t Adjust) {
   ObjdumpOutput Dump(Objdump, BinaryCacheRoot);
   Dump.reset(&M, Sym.Start, Sym.End);
-  Dump.next();
 
   emitFunctionStart(Sym.Name);
-  for (uint64_t I = Sym.Start; I < Sym.End; I = Dump.next()) {
+  for (uint64_t I = Dump.next(); I < Sym.End; I = Dump.next()) {
     auto PC = Event->first - Adjust;
 
     auto Text = Dump.getText();
     if (PC == I) {
       emitLine(I, &Event->second, Text);
       ++Event;
     } else {
       emitLine(I, nullptr, Text);