From cc7abac08b0c52e6581b9c9c4226816b17a4c26d Mon Sep 17 00:00:00 2001
From: Leonard Grey <lgrey@chromium.org>
Date: Thu, 8 Dec 2022 18:27:40 +0000
Subject: [PATCH] Add option to enable multiple symbol field in Linux tool

Bug: google-breakpad:751
Change-Id: I63a4d652413ef7311da7494fbd8fb816445eb353
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/4089183
Reviewed-by: Mark Mentovai <mark@chromium.org>
---
 src/common/linux/dump_symbols.cc       | 14 ++++++++------
 src/common/linux/dump_symbols.h        |  9 ++++++---
 src/tools/linux/dump_syms/dump_syms.cc |  9 ++++++++-
 3 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/src/common/linux/dump_symbols.cc b/src/common/linux/dump_symbols.cc
index 7e639b0a..4915e6ff 100644
--- a/src/common/linux/dump_symbols.cc
+++ b/src/common/linux/dump_symbols.cc
@@ -1024,7 +1024,8 @@ template<typename ElfClass>
 bool InitModuleForElfClass(const typename ElfClass::Ehdr* elf_header,
                            const string& obj_filename,
                            const string& obj_os,
-                           scoped_ptr<Module>& module) {
+                           scoped_ptr<Module>& module,
+                           bool enable_multiple_field) {
   PageAllocator allocator;
   wasteful_vector<uint8_t> identifier(&allocator, kDefaultBuildIdSize);
   if (!FileID::ElfFileIdentifierFromMappedFile(elf_header, identifier)) {
@@ -1053,7 +1054,8 @@ bool InitModuleForElfClass(const typename ElfClass::Ehdr* elf_header,
   // This is just the raw Build ID in hex.
   string code_id = FileID::ConvertIdentifierToString(identifier);
 
-  module.reset(new Module(name, obj_os, architecture, id, code_id));
+  module.reset(new Module(name, obj_os, architecture, id, code_id,
+                          enable_multiple_field));
 
   return true;
 }
@@ -1070,8 +1072,8 @@ bool ReadSymbolDataElfClass(const typename ElfClass::Ehdr* elf_header,
   *out_module = NULL;
 
   scoped_ptr<Module> module;
-  if (!InitModuleForElfClass<ElfClass>(elf_header, obj_filename, obj_os,
-                                       module)) {
+  if (!InitModuleForElfClass<ElfClass>(elf_header, obj_filename, obj_os, module,
+                                       options.enable_multiple_field)) {
     return false;
   }
 
@@ -1183,14 +1185,14 @@ bool WriteSymbolFileHeader(const string& load_path,
   if (elfclass == ELFCLASS32) {
     if (!InitModuleForElfClass<ElfClass32>(
         reinterpret_cast<const Elf32_Ehdr*>(elf_header), obj_file, obj_os,
-        module)) {
+        module, /*enable_multiple_field=*/false)) {
       fprintf(stderr, "Failed to load ELF module: %s\n", obj_file.c_str());
       return false;
     }
   } else if (elfclass == ELFCLASS64) {
     if (!InitModuleForElfClass<ElfClass64>(
         reinterpret_cast<const Elf64_Ehdr*>(elf_header), obj_file, obj_os,
-        module)) {
+        module, /*enable_multiple_field=*/false)) {
       fprintf(stderr, "Failed to load ELF module: %s\n", obj_file.c_str());
       return false;
     }
diff --git a/src/common/linux/dump_symbols.h b/src/common/linux/dump_symbols.h
index 8ac169c9..f1802ecc 100644
--- a/src/common/linux/dump_symbols.h
+++ b/src/common/linux/dump_symbols.h
@@ -46,13 +46,16 @@ namespace google_breakpad {
 class Module;
 
 struct DumpOptions {
-  DumpOptions(SymbolData symbol_data, bool handle_inter_cu_refs)
+  DumpOptions(SymbolData symbol_data,
+              bool handle_inter_cu_refs,
+              bool enable_multiple_field)
       : symbol_data(symbol_data),
-        handle_inter_cu_refs(handle_inter_cu_refs) {
-  }
+        handle_inter_cu_refs(handle_inter_cu_refs),
+        enable_multiple_field(enable_multiple_field) {}
 
   SymbolData symbol_data;
   bool handle_inter_cu_refs;
+  bool enable_multiple_field;
 };
 
 // Find all the debugging information in OBJ_FILE, an ELF executable
diff --git a/src/tools/linux/dump_syms/dump_syms.cc b/src/tools/linux/dump_syms/dump_syms.cc
index 6e6a6424..8998b3b3 100644
--- a/src/tools/linux/dump_syms/dump_syms.cc
+++ b/src/tools/linux/dump_syms/dump_syms.cc
@@ -56,6 +56,9 @@ int usage(const char* self) {
   fprintf(stderr, "  -n <name>   Use specified name for name of the object\n");
   fprintf(stderr, "  -o <os>     Use specified name for the "
                                  "operating system\n");
+  fprintf(stderr, "  -m          Enable writing the optional 'm' field on FUNC"
+                                 "and PUBLIC, denoting multiple symbols for "
+                                 "the address.\n");
   return 1;
 }
 
@@ -67,6 +70,7 @@ int main(int argc, char** argv) {
   bool handle_inlines = false;
   bool handle_inter_cu_refs = true;
   bool log_to_stderr = false;
+  bool enable_multiple_field = false;
   std::string obj_name;
   const char* obj_os = "Linux";
   int arg_index = 1;
@@ -96,6 +100,8 @@ int main(int argc, char** argv) {
       }
       obj_os = argv[arg_index + 1];
       ++arg_index;
+    } else if (strcmp("-m", argv[arg_index]) == 0) {
+      enable_multiple_field = true;
     } else {
       printf("2.4 %s\n", argv[arg_index]);
       return usage(argv[0]);
@@ -132,7 +138,8 @@ int main(int argc, char** argv) {
   } else {
     SymbolData symbol_data = (handle_inlines ? INLINES : NO_DATA) |
                              (cfi ? CFI : NO_DATA) | SYMBOLS_AND_FILES;
-    google_breakpad::DumpOptions options(symbol_data, handle_inter_cu_refs);
+    google_breakpad::DumpOptions options(symbol_data, handle_inter_cu_refs,
+                                         enable_multiple_field);
     if (!WriteSymbolFile(binary, obj_name, obj_os, debug_dirs, options,
                          std::cout)) {
       fprintf(saved_stderr, "Failed to write symbol file.\n");