diff --git a/linker/linker.h b/linker/linker.h
index 7482581..dae3972 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -40,6 +40,7 @@
 #include "linked_list.h"
 
 #include <string>
+#include <vector>
 
 #define DL_ERR(fmt, x...) \
     do { \
@@ -142,6 +143,32 @@
   DISALLOW_IMPLICIT_CONSTRUCTORS(SymbolName);
 };
 
+struct version_info {
+  version_info() : elf_hash(0), name(nullptr), target_si(nullptr) {}
+
+  uint32_t elf_hash;
+  const char* name;
+  const soinfo* target_si;
+};
+
+// Class used construct version dependency graph.
+class VersionTracker {
+ public:
+  VersionTracker() = default;
+  bool init(const soinfo* si_from);
+
+  const version_info* get_version_info(ElfW(Versym) source_symver) const;
+ private:
+  bool init_verneed(const soinfo* si_from);
+  bool init_verdef(const soinfo* si_from);
+  void add_version_info(size_t source_index, ElfW(Word) elf_hash,
+      const char* ver_name, const soinfo* target_si);
+
+  std::vector<version_info> version_infos;
+
+  DISALLOW_COPY_AND_ASSIGN(VersionTracker);
+};
+
 struct soinfo {
  public:
   typedef LinkedList<soinfo, SoinfoListAllocator> soinfo_list_t;
@@ -260,11 +287,16 @@
   void set_dt_flags_1(uint32_t dt_flags_1);
 
   soinfo_list_t& get_children();
+  const soinfo_list_t& get_children() const;
+
   soinfo_list_t& get_parents();
 
-  ElfW(Sym)* find_symbol_by_name(SymbolName& symbol_name);
+  bool find_symbol_by_name(SymbolName& symbol_name,
+                           const version_info* vi,
+                           const ElfW(Sym)** symbol) const;
+
   ElfW(Sym)* find_symbol_by_address(const void* addr);
-  ElfW(Addr) resolve_symbol_address(ElfW(Sym)* s);
+  ElfW(Addr) resolve_symbol_address(const ElfW(Sym)* s) const;
 
   const char* get_string(ElfW(Word) index) const;
   bool can_unload() const;
@@ -292,11 +324,18 @@
 
   const char* get_soname() const;
   const char* get_realpath() const;
+  const ElfW(Versym)* get_versym(size_t n) const;
+  ElfW(Addr) get_verneed_ptr() const;
+  size_t get_verneed_cnt() const;
+  ElfW(Addr) get_verdef_ptr() const;
+  size_t get_verdef_cnt() const;
+
+  bool find_verdef_version_index(const version_info* vi, ElfW(Versym)* versym) const;
 
  private:
-  ElfW(Sym)* elf_lookup(SymbolName& symbol_name);
+  bool elf_lookup(SymbolName& symbol_name, const version_info* vi, uint32_t* symbol_index) const;
   ElfW(Sym)* elf_addr_lookup(const void* addr);
-  ElfW(Sym)* gnu_lookup(SymbolName& symbol_name);
+  bool gnu_lookup(SymbolName& symbol_name, const version_info* vi, uint32_t* symbol_index) const;
   ElfW(Sym)* gnu_addr_lookup(const void* addr);
 
   void call_array(const char* array_name, linker_function_t* functions, size_t count, bool reverse);
@@ -341,11 +380,20 @@
   const char* soname_;
   std::string realpath_;
 
+  const ElfW(Versym)* versym_;
+
+  ElfW(Addr) verdef_ptr_;
+  size_t verdef_cnt_;
+
+  ElfW(Addr) verneed_ptr_;
+  size_t verneed_cnt_;
+
   friend soinfo* get_libdl_info();
 };
 
-ElfW(Sym)* soinfo_do_lookup(soinfo* si_from, const char* name, soinfo** si_found_in,
-    const soinfo::soinfo_list_t& global_group, const soinfo::soinfo_list_t& local_group);
+bool soinfo_do_lookup(soinfo* si_from, const char* name, const version_info* vi,
+                      soinfo** si_found_in, const soinfo::soinfo_list_t& global_group,
+                      const soinfo::soinfo_list_t& local_group, const ElfW(Sym)** symbol);
 
 enum RelocationKind {
   kRelocAbsolute = 0,
@@ -364,10 +412,10 @@
 soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo);
 void do_dlclose(soinfo* si);
 
-ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* caller, void* handle);
+const ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* caller, void* handle);
 soinfo* find_containing_library(const void* addr);
 
-ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name);
+const ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name);
 
 void debuggerd_init();
 extern "C" abort_msg_t* g_abort_message;