8352426: RelocIterator should correctly handle nullptr address of relocation data

Reviewed-by: dlong, vlivanov, kvn

Author: Boris Ulasevich

src/hotspot/share/code/relocInfo.cpp

@@ -116,6 +116,9 @@ void relocInfo::change_reloc_info_for_address(RelocIterator *itr, address pc, re
 // ----------------------------------------------------------------------------------------------------
 // Implementation of RelocIterator
 
+// A static dummy to serve as a safe pointer when there is no relocation info.
+static relocInfo dummy_relocInfo = relocInfo(relocInfo::none, 0);
+
 void RelocIterator::initialize(nmethod* nm, address begin, address limit) {
   initialize_misc();
 
@@ -127,8 +130,14 @@ void RelocIterator::initialize(nmethod* nm, address begin, address limit) {
   guarantee(nm != nullptr, "must be able to deduce nmethod from other arguments");
 
   _code    = nm;
-  _current = nm->relocation_begin() - 1;
-  _end     = nm->relocation_end();
+  if (nm->relocation_size() == 0) {
+    _current = &dummy_relocInfo - 1;
+    _end = &dummy_relocInfo;
+  } else {
+    assert(((nm->relocation_begin() != nullptr) && (nm->relocation_end() != nullptr)), "valid start and end pointer");
+    _current = nm->relocation_begin() - 1;
+    _end     = nm->relocation_end();
+  }
   _addr    = nm->content_begin();
 
   // Initialize code sections.
@@ -150,7 +159,7 @@ void RelocIterator::initialize(nmethod* nm, address begin, address limit) {
 RelocIterator::RelocIterator(CodeSection* cs, address begin, address limit) {
   initialize_misc();
   assert(((cs->locs_start() != nullptr) && (cs->locs_end() != nullptr)), "valid start and end pointer");
-  _current = cs->locs_start()-1;
+  _current = cs->locs_start() - 1;
   _end     = cs->locs_end();
   _addr    = cs->start();
   _code    = nullptr; // Not cb->blob();