Add error handling for common failure case seen processing debug symbols

Propagates error from ProcessDIEs to the top level where it can be
handled.

Change-Id: Ib6ba171ff642a898c75233a3f70995837c6c0552
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/5564423
Reviewed-by: Joshua Peraza <jperaza@chromium.org>

src/common/dwarf/dwarf2reader.cc

@@ -463,7 +463,11 @@ uint64_t CompilationUnit::Start() {
   }
 
   // Now that we have our abbreviations, start processing DIE's.
-  ProcessDIEs();
+  if (!ProcessDIEs()) {
+    // If ProcessDIEs fails return 0, ourlength must be non-zero
+    // as it is equal to header_.length + (12 or 4)
+    return 0;
+  }
 
   // If this is a skeleton compilation unit generated with split DWARF,
   // and the client needs the full debug info, we need to find the full
@@ -922,7 +926,7 @@ const uint8_t* CompilationUnit::ProcessDIE(uint64_t dieoffset,
   return start;
 }
 
-void CompilationUnit::ProcessDIEs() {
+bool CompilationUnit::ProcessDIEs() {
   const uint8_t* dieptr = after_header_;
   size_t len;
 
@@ -953,13 +957,22 @@ void CompilationUnit::ProcessDIEs() {
     if (abbrev_num == 0) {
       if (die_stack.size() == 0)
         // If it is padding, then we are done with the compilation unit's DIEs.
-        return;
+        return true;
       const uint64_t offset = die_stack.top();
       die_stack.pop();
       handler_->EndDIE(offset);
       continue;
     }
 
+    // Abbrev > abbrev_.size() indicates a corruption in the dwarf file
+    // We attempt to recover
+    if (abbrev_num > abbrevs_->size()) {
+      fprintf(stderr, "An invalid abbrev was referenced %d / %d. Stopped "
+              "procesing following DIEs in this CU.", abbrev_num,
+              abbrevs_->size());
+      return false;
+    }
+
     const Abbrev& abbrev = abbrevs_->at(static_cast<size_t>(abbrev_num));
     const enum DwarfTag tag = abbrev.tag;
     if (!handler_->StartDIE(absolute_offset, tag)) {
@@ -989,6 +1002,7 @@ void CompilationUnit::ProcessDIEs() {
       handler_->EndDIE(absolute_offset);
     }
   }
+  return true;
 }
 
 // Check for a valid ELF file and return the Address size.

src/common/dwarf/dwarf2reader.h

@@ -664,7 +664,7 @@ class CompilationUnit {
   }
 
   // Processes all DIEs for this compilation unit
-  void ProcessDIEs();
+  bool ProcessDIEs();
 
   // Skips the die with attributes specified in ABBREV starting at
   // START, and return the new place to position the stream to.

src/common/linux/dump_symbols.cc

@@ -498,7 +498,11 @@ bool LoadDwarf(const string& dwarf_filename,
                                          &byte_reader,
                                          &die_dispatcher);
     // Process the entire compilation unit; get the offset of the next.
-    offset += reader.Start();
+    uint64_t result = reader.Start();
+    if (result == 0) {
+      return false;
+    }
+    offset += result;
     // Start to process split dwarf file.
     if (reader.ShouldProcessSplitDwarf()) {
       StartProcessSplitDwarf(&reader, module, endianness, handle_inter_cu_refs,
@@ -878,6 +882,7 @@ bool LoadSymbols(const string& obj_file,
   const char* names_end = names + section_names->sh_size;
   bool found_debug_info_section = false;
   bool found_usable_info = false;
+  bool usable_info_parsed = false;
 
   if ((options.symbol_data & SYMBOLS_AND_FILES) ||
       (options.symbol_data & INLINES)) {
@@ -893,8 +898,10 @@ bool LoadSymbols(const string& obj_file,
         found_debug_info_section = true;
         found_usable_info = true;
         info->LoadedSection(".stab");
-        if (!LoadStabs<ElfClass>(elf_header, stab_section, stabstr_section,
-                                 big_endian, module)) {
+        bool result = LoadStabs<ElfClass>(elf_header, stab_section, stabstr_section,
+                                 big_endian, module);
+        usable_info_parsed = usable_info_parsed || result;
+        if (!result) {
           fprintf(stderr, "%s: \".stab\" section found, but failed to load"
                   " STABS debugging information\n", obj_file.c_str());
         }
@@ -981,9 +988,11 @@ bool LoadSymbols(const string& obj_file,
       found_debug_info_section = true;
       found_usable_info = true;
       info->LoadedSection(".debug_info");
-      if (!LoadDwarf<ElfClass>(obj_file, elf_header, big_endian,
+      bool result = LoadDwarf<ElfClass>(obj_file, elf_header, big_endian,
                                options.handle_inter_cu_refs,
-                               options.symbol_data & INLINES, module)) {
+                               options.symbol_data & INLINES, module);
+      usable_info_parsed = usable_info_parsed || result;
+      if (!result){
         fprintf(stderr, "%s: \".debug_info\" section found, but failed to load "
                 "DWARF debugging information\n", obj_file.c_str());
       }
@@ -1088,7 +1097,7 @@ bool LoadSymbols(const string& obj_file,
     return false;
   }
 
-  return true;
+  return usable_info_parsed;
 }
 
 // Return the breakpad symbol file identifier for the architecture of