[13/20] symtab_reader: add support for ppc64 ELFv1 binaries

diff --git a/src/abg-symtab-reader.cc b/src/abg-symtab-reader.cc
index 4576be2a0b42..7318fdfce52e 100644
--- a/src/abg-symtab-reader.cc
+++ b/src/abg-symtab-reader.cc
@@ -100,9 +100,15 @@  const elf_symbol_sptr&
 symtab::lookup_symbol(GElf_Addr symbol_addr) const
 {
   static const elf_symbol_sptr empty_result;
-  const auto it = addr_symbol_map_.find(symbol_addr);
-  if (it != addr_symbol_map_.end())
-      return it->second;
+  const auto addr_it = addr_symbol_map_.find(symbol_addr);
+  if (addr_it != addr_symbol_map_.end())
+    return addr_it->second;
+  else
+    {
+      const auto entry_it = entry_addr_symbol_map_.find(symbol_addr);
+      if (entry_it != entry_addr_symbol_map_.end())
+	return entry_it->second;
+    }
   return empty_result;
 }
 
@@ -197,6 +203,8 @@  symtab::load_(Elf*	       elf_handle,
   const bool is_kernel = elf_helpers::is_linux_kernel(elf_handle);
   std::unordered_set<std::string> exported_kernel_symbols;
 
+  const bool is_ppc64 = elf_helpers::architecture_is_ppc64(elf_handle);
+
   for (size_t i = 0; i < number_syms; ++i)
     {
       GElf_Sym *sym, sym_mem;
@@ -304,6 +312,10 @@  symtab::load_(Elf*	       elf_handle,
 	      elf_helpers::maybe_adjust_et_rel_sym_addr_to_abs_addr(elf_handle,
 								    sym);
 
+	  if (is_ppc64 && symbol_sptr->is_function())
+	    update_function_entry_address_symbol_map(elf_handle, sym,
+						     symbol_sptr);
+
 	  const auto result =
 	    addr_symbol_map_.emplace(symbol_value, symbol_sptr);
 	  if (!result.second)
@@ -364,5 +376,80 @@  symtab::load_(string_elf_symbols_map_sptr function_symbol_map,
   return true;
 }
 
+void
+symtab::update_function_entry_address_symbol_map(
+    Elf*		   elf_handle,
+    GElf_Sym*		   native_symbol,
+    const elf_symbol_sptr& symbol_sptr)
+{
+
+  // For ppc64 ELFv1 binaries, we need to build a function entry point address
+  // -> function symbol map. This is in addition to the function pointer ->
+  // symbol map.  This is because on ppc64 ELFv1, a function pointer is
+  // different from a function entry point address.
+  //
+  // On ppc64 ELFv1, the DWARF DIE of a function references the address of the
+  // entry point of the function symbol; whereas the value of the function
+  // symbol is the function pointer. As these addresses are different, if I we
+  // want to get to the symbol of a function from its entry point address (as
+  // referenced by DWARF function DIEs) we must have the two maps I mentionned
+  // right above.
+  //
+  // In other words, we need a map that associates a function entry point
+  // address with the symbol of that function, to be able to get the function
+  // symbol that corresponds to a given function DIE, on ppc64.
+  //
+  // The value of the function pointer (the value of the symbol) usually refers
+  // to the offset of a table in the .opd section.  But sometimes, for a symbol
+  // named "foo", the corresponding symbol named ".foo" (note the dot before
+  // foo) which value is the entry point address of the function; that entry
+  // point address refers to a region in the .text section.
+  //
+  // So we are only interested in values of the symbol that are in the .opd
+  // section.
+  const GElf_Addr fn_desc_addr = native_symbol->st_value;
+  const GElf_Addr fn_entry_point_addr =
+    elf_helpers::lookup_ppc64_elf_fn_entry_point_address(elf_handle,
+							 fn_desc_addr);
+
+  const std::pair<addr_symbol_map_type::const_iterator, bool>& result =
+    entry_addr_symbol_map_.emplace(fn_entry_point_addr, symbol_sptr);
+
+  const addr_symbol_map_type::const_iterator it = result.first;
+  const bool was_inserted = result.second;
+  if (!was_inserted
+      && elf_helpers::address_is_in_opd_section(elf_handle, fn_desc_addr))
+    {
+      // Either
+      //
+      // 'symbol' must have been registered as an alias for
+      // it->second->get_main_symbol()
+      //
+      // Or
+      //
+      // if the name of 'symbol' is foo, then the name of it2->second is
+      // ".foo". That is, foo is the name of the symbol when it refers to the
+      // function descriptor in the .opd section and ".foo" is an internal name
+      // for the address of the entry point of foo.
+      //
+      // In the latter case, we just want to keep a reference to "foo" as .foo
+      // is an internal name.
+
+      const bool two_symbols_alias =
+	it->second->get_main_symbol()->does_alias(*symbol_sptr);
+      const bool symbol_is_foo_and_prev_symbol_is_dot_foo =
+	(it->second->get_name() == std::string(".") + symbol_sptr->get_name());
+
+      ABG_ASSERT(two_symbols_alias
+		 || symbol_is_foo_and_prev_symbol_is_dot_foo);
+
+      if (symbol_is_foo_and_prev_symbol_is_dot_foo)
+	// Let's just keep a reference of the symbol that the user sees in the
+	// source code (the one named foo). The symbol which name is prefixed
+	// with a "dot" is an artificial one.
+	entry_addr_symbol_map_[fn_entry_point_addr] = symbol_sptr;
+    }
+}
+
 } // end namespace symtab_reader
 } // end namespace abigail
diff --git a/src/abg-symtab-reader.h b/src/abg-symtab-reader.h
index 4c5e3b85c22d..2906bab818b0 100644
--- a/src/abg-symtab-reader.h
+++ b/src/abg-symtab-reader.h
@@ -251,12 +251,20 @@  private:
   typedef std::unordered_map<GElf_Addr, elf_symbol_sptr> addr_symbol_map_type;
   addr_symbol_map_type addr_symbol_map_;
 
+  /// Lookup map function entry address -> symbol
+  addr_symbol_map_type entry_addr_symbol_map_;
+
   bool
   load_(Elf* elf_handle, ir::environment* env, symbol_predicate is_suppressed);
 
   bool
   load_(string_elf_symbols_map_sptr function_symbol_map,
        string_elf_symbols_map_sptr variables_symbol_map);
+
+  void
+  update_function_entry_address_symbol_map(Elf*	     elf_handle,
+					   GElf_Sym* native_symbol,
+					   const elf_symbol_sptr& symbol_sptr);
 };
 
 /// Helper class to allow range-for loops on symtabs for C++11 and later code.