8331731: ubsan: relocInfo.cpp:155:30: runtime error: applying non-zer…

…o offset to null pointer

Co-authored-by: Axel Boldt-Christmas <aboldtch@openjdk.org>
Co-authored-by: Dean Long <dlong@openjdk.org>
Reviewed-by: mdoerr, thartmann, mbaesken

src/hotspot/share/asm/codeBuffer.cpp

@@ -525,7 +525,7 @@ void CodeBuffer::finalize_oop_references(const methodHandle& mh) {
   for (int n = (int) SECT_FIRST; n < (int) SECT_LIMIT; n++) {
     // pull code out of each section
     CodeSection* cs = code_section(n);
-    if (cs->is_empty() || !cs->has_locs()) continue;  // skip trivial section
+    if (cs->is_empty() || (cs->locs_count() == 0)) continue;  // skip trivial section
     RelocIterator iter(cs);
     while (iter.next()) {
       if (iter.type() == relocInfo::metadata_type) {
@@ -791,10 +791,8 @@ void CodeBuffer::relocate_code_to(CodeBuffer* dest) const {
   // call) is relocated. Stubs are placed behind the main code
   // section, so that section has to be copied before relocating.
   for (int n = (int) SECT_FIRST; n < (int)SECT_LIMIT; n++) {
-    // pull code out of each section
-    const CodeSection* cs = code_section(n);
-    if (cs->is_empty() || !cs->has_locs()) continue;  // skip trivial section
     CodeSection* dest_cs = dest->code_section(n);
+    if (dest_cs->is_empty() || (dest_cs->locs_count() == 0)) continue;  // skip trivial section
     { // Repair the pc relative information in the code after the move
       RelocIterator iter(dest_cs);
       while (iter.next()) {
@@ -1057,7 +1055,7 @@ void CodeSection::print(const char* name) {
                 name, p2i(start()), p2i(end()), p2i(limit()), size(), capacity());
   tty->print_cr(" %7s.locs = " PTR_FORMAT " : " PTR_FORMAT " : " PTR_FORMAT " (%d of %d) point=%d",
                 name, p2i(locs_start()), p2i(locs_end()), p2i(locs_limit()), locs_size, locs_capacity(), locs_point_off());
-  if (PrintRelocations) {
+  if (PrintRelocations && (locs_size != 0)) {
     RelocIterator iter(this);
     iter.print();
   }

src/hotspot/share/code/relocInfo.cpp

@@ -150,8 +150,7 @@ 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)) ||
-         ((cs->locs_start() == nullptr) && (cs->locs_end() == nullptr)), "valid start and end pointer");
+  assert(((cs->locs_start() != nullptr) && (cs->locs_end() != nullptr)), "valid start and end pointer");
   _current = cs->locs_start()-1;
   _end     = cs->locs_end();
   _addr    = cs->start();