Merge pull request iovisor#1015 from goldshtn/perfmap-retry

cc: Retry symbol resolution using perfmap

src/cc/bcc_syms.cc

@@ -114,6 +114,7 @@ bool ProcSyms::resolve_addr(uint64_t addr, struct bcc_symbol *sym) {
  sym->demangle_name = nullptr;
  sym->offset = 0x0;
 
+ const char *original_module = nullptr;
  for (Module &mod : modules_) {
  if (addr >= mod.start_ && addr < mod.end_) {
  bool res = mod.find_addr(addr, sym);
@@ -122,7 +123,21 @@ bool ProcSyms::resolve_addr(uint64_t addr, struct bcc_symbol *sym) {
  if (!sym->demangle_name)
  sym->demangle_name = sym->name;
  }
- return res;
+ // If we have a match, return right away. But if we don't have a match in
+ // this module, we might have a match in the perf map (even though the
+ // module itself doesn't have symbols). Wait until we see the perf map if
+ // any, but keep the original module name for reporting.
+ if (res) {
+ // If we have already seen this module, report the original name rather
+ // than the perf map name:
+ if (original_module)
+ sym->module = original_module;
+ return res;
+ } else {
+ // Record the module to which this symbol belongs, so that even if it's
+ // later found using a perf map, we still report the right module name.
+ original_module = mod.name_.c_str();
+ }
  }
  }
  return false;