diff --git a/libunwindstack/Android.bp b/libunwindstack/Android.bp
index 73dc921..d1b8271 100644
--- a/libunwindstack/Android.bp
+++ b/libunwindstack/Android.bp
@@ -191,6 +191,7 @@
         "tests/LocalUnwinderTest.cpp",
         "tests/LogFake.cpp",
         "tests/MapInfoCreateMemoryTest.cpp",
+        "tests/MapInfoGetBuildIDTest.cpp",
         "tests/MapInfoGetElfTest.cpp",
         "tests/MapInfoGetLoadBiasTest.cpp",
         "tests/MapInfoTest.cpp",
@@ -343,6 +344,7 @@
     ],
 
     shared_libs: [
+        "libbase",
         "libunwindstack",
     ],
 }
diff --git a/libunwindstack/Elf.cpp b/libunwindstack/Elf.cpp
index 5b586a2..2f5eed9 100644
--- a/libunwindstack/Elf.cpp
+++ b/libunwindstack/Elf.cpp
@@ -140,8 +140,11 @@
   return true;
 }
 
-bool Elf::GetBuildID(std::string* build_id) {
-  return valid_ && interface_->GetBuildID(build_id);
+std::string Elf::GetBuildID() {
+  if (!valid_) {
+    return "";
+  }
+  return interface_->GetBuildID();
 }
 
 void Elf::GetLastError(ErrorData* data) {
@@ -384,4 +387,22 @@
   return false;
 }
 
+std::string Elf::GetBuildID(Memory* memory) {
+  if (!IsValidElf(memory)) {
+    return "";
+  }
+
+  uint8_t class_type;
+  if (!memory->Read(EI_CLASS, &class_type, 1)) {
+    return "";
+  }
+
+  if (class_type == ELFCLASS32) {
+    return ElfInterface::ReadBuildIDFromMemory<Elf32_Ehdr, Elf32_Shdr, Elf32_Nhdr>(memory);
+  } else if (class_type == ELFCLASS64) {
+    return ElfInterface::ReadBuildIDFromMemory<Elf64_Ehdr, Elf64_Shdr, Elf64_Nhdr>(memory);
+  }
+  return "";
+}
+
 }  // namespace unwindstack
diff --git a/libunwindstack/ElfInterface.cpp b/libunwindstack/ElfInterface.cpp
index 709e6c9..c1b98d9 100644
--- a/libunwindstack/ElfInterface.cpp
+++ b/libunwindstack/ElfInterface.cpp
@@ -238,31 +238,31 @@
 }
 
 template <typename NhdrType>
-bool ElfInterface::ReadBuildID(std::string* build_id) {
+std::string ElfInterface::ReadBuildID() {
   // Ensure there is no overflow in any of the calulations below.
   uint64_t tmp;
   if (__builtin_add_overflow(gnu_build_id_offset_, gnu_build_id_size_, &tmp)) {
-    return false;
+    return "";
   }
 
   uint64_t offset = 0;
   while (offset < gnu_build_id_size_) {
     if (gnu_build_id_size_ - offset < sizeof(NhdrType)) {
-      return false;
+      return "";
     }
     NhdrType hdr;
     if (!memory_->ReadFully(gnu_build_id_offset_ + offset, &hdr, sizeof(hdr))) {
-      return false;
+      return "";
     }
     offset += sizeof(hdr);
 
     if (gnu_build_id_size_ - offset < hdr.n_namesz) {
-      return false;
+      return "";
     }
     if (hdr.n_namesz > 0) {
       std::string name(hdr.n_namesz, '\0');
       if (!memory_->ReadFully(gnu_build_id_offset_ + offset, &(name[0]), hdr.n_namesz)) {
-        return false;
+        return "";
       }
 
       // Trim trailing \0 as GNU is stored as a C string in the ELF file.
@@ -273,18 +273,20 @@
       offset += (hdr.n_namesz + 3) & ~3;
 
       if (name == "GNU" && hdr.n_type == NT_GNU_BUILD_ID) {
-        if (gnu_build_id_size_ - offset < hdr.n_descsz) {
-          return false;
+        if (gnu_build_id_size_ - offset < hdr.n_descsz || hdr.n_descsz == 0) {
+          return "";
         }
-        build_id->resize(hdr.n_descsz);
-        return memory_->ReadFully(gnu_build_id_offset_ + offset, &(*build_id)[0],
-                                  hdr.n_descsz);
+        std::string build_id(hdr.n_descsz - 1, '\0');
+        if (memory_->ReadFully(gnu_build_id_offset_ + offset, &build_id[0], hdr.n_descsz)) {
+          return build_id;
+        }
+        return "";
       }
     }
     // Align hdr.n_descsz to next power multiple of 4. See man 5 elf.
     offset += (hdr.n_descsz + 3) & ~3;
   }
-  return false;
+  return "";
 }
 
 template <typename EhdrType, typename ShdrType>
@@ -536,6 +538,103 @@
   *size = ehdr.e_shoff + ehdr.e_shentsize * ehdr.e_shnum;
 }
 
+template <typename EhdrType, typename ShdrType>
+bool GetBuildIDInfo(Memory* memory, uint64_t* build_id_offset, uint64_t* build_id_size) {
+  EhdrType ehdr;
+  if (!memory->ReadFully(0, &ehdr, sizeof(ehdr))) {
+    return false;
+  }
+
+  uint64_t offset = ehdr.e_shoff;
+  uint64_t sec_offset;
+  uint64_t sec_size;
+  ShdrType shdr;
+  if (ehdr.e_shstrndx >= ehdr.e_shnum) {
+    return false;
+  }
+
+  uint64_t sh_offset = offset + ehdr.e_shstrndx * ehdr.e_shentsize;
+  if (!memory->ReadFully(sh_offset, &shdr, sizeof(shdr))) {
+    return false;
+  }
+  sec_offset = shdr.sh_offset;
+  sec_size = shdr.sh_size;
+
+  // Skip the first header, it's always going to be NULL.
+  offset += ehdr.e_shentsize;
+  for (size_t i = 1; i < ehdr.e_shnum; i++, offset += ehdr.e_shentsize) {
+    if (!memory->ReadFully(offset, &shdr, sizeof(shdr))) {
+      return false;
+    }
+    std::string name;
+    if (shdr.sh_type == SHT_NOTE && shdr.sh_name < sec_size &&
+        memory->ReadString(sec_offset + shdr.sh_name, &name) && name == ".note.gnu.build-id") {
+      *build_id_offset = shdr.sh_offset;
+      *build_id_size = shdr.sh_size;
+      return true;
+    }
+  }
+
+  return false;
+}
+
+template <typename EhdrType, typename ShdrType, typename NhdrType>
+std::string ElfInterface::ReadBuildIDFromMemory(Memory* memory) {
+  uint64_t note_offset;
+  uint64_t note_size;
+  if (!GetBuildIDInfo<EhdrType, ShdrType>(memory, &note_offset, &note_size)) {
+    return "";
+  }
+
+  // Ensure there is no overflow in any of the calculations below.
+  uint64_t tmp;
+  if (__builtin_add_overflow(note_offset, note_size, &tmp)) {
+    return "";
+  }
+
+  uint64_t offset = 0;
+  while (offset < note_size) {
+    if (note_size - offset < sizeof(NhdrType)) {
+      return "";
+    }
+    NhdrType hdr;
+    if (!memory->ReadFully(note_offset + offset, &hdr, sizeof(hdr))) {
+      return "";
+    }
+    offset += sizeof(hdr);
+
+    if (note_size - offset < hdr.n_namesz) {
+      return "";
+    }
+    if (hdr.n_namesz > 0) {
+      std::string name(hdr.n_namesz, '\0');
+      if (!memory->ReadFully(note_offset + offset, &(name[0]), hdr.n_namesz)) {
+        return "";
+      }
+
+      // Trim trailing \0 as GNU is stored as a C string in the ELF file.
+      if (name.back() == '\0') name.resize(name.size() - 1);
+
+      // Align hdr.n_namesz to next power multiple of 4. See man 5 elf.
+      offset += (hdr.n_namesz + 3) & ~3;
+
+      if (name == "GNU" && hdr.n_type == NT_GNU_BUILD_ID) {
+        if (note_size - offset < hdr.n_descsz || hdr.n_descsz == 0) {
+          return "";
+        }
+        std::string build_id(hdr.n_descsz - 1, '\0');
+        if (memory->ReadFully(note_offset + offset, &build_id[0], hdr.n_descsz)) {
+          return build_id;
+        }
+        return "";
+      }
+    }
+    // Align hdr.n_descsz to next power multiple of 4. See man 5 elf.
+    offset += (hdr.n_descsz + 3) & ~3;
+  }
+  return "";
+}
+
 // Instantiate all of the needed template functions.
 template void ElfInterface::InitHeadersWithTemplate<uint32_t>(uint64_t);
 template void ElfInterface::InitHeadersWithTemplate<uint64_t>(uint64_t);
@@ -551,8 +650,8 @@
 template void ElfInterface::ReadSectionHeaders<Elf32_Ehdr, Elf32_Shdr>(const Elf32_Ehdr&);
 template void ElfInterface::ReadSectionHeaders<Elf64_Ehdr, Elf64_Shdr>(const Elf64_Ehdr&);
 
-template bool ElfInterface::ReadBuildID<Elf32_Nhdr>(std::string*);
-template bool ElfInterface::ReadBuildID<Elf64_Nhdr>(std::string*);
+template std::string ElfInterface::ReadBuildID<Elf32_Nhdr>();
+template std::string ElfInterface::ReadBuildID<Elf64_Nhdr>();
 
 template bool ElfInterface::GetSonameWithTemplate<Elf32_Dyn>(std::string*);
 template bool ElfInterface::GetSonameWithTemplate<Elf64_Dyn>(std::string*);
@@ -571,4 +670,9 @@
 template uint64_t ElfInterface::GetLoadBias<Elf32_Ehdr, Elf32_Phdr>(Memory*);
 template uint64_t ElfInterface::GetLoadBias<Elf64_Ehdr, Elf64_Phdr>(Memory*);
 
+template std::string ElfInterface::ReadBuildIDFromMemory<Elf32_Ehdr, Elf32_Shdr, Elf32_Nhdr>(
+    Memory*);
+template std::string ElfInterface::ReadBuildIDFromMemory<Elf64_Ehdr, Elf64_Shdr, Elf64_Nhdr>(
+    Memory*);
+
 }  // namespace unwindstack
diff --git a/libunwindstack/MapInfo.cpp b/libunwindstack/MapInfo.cpp
index b9d8b3d..f319971 100644
--- a/libunwindstack/MapInfo.cpp
+++ b/libunwindstack/MapInfo.cpp
@@ -146,6 +146,10 @@
     }
   }
 
+  if (process_memory == nullptr) {
+    return nullptr;
+  }
+
   // Need to verify that this elf is valid. It's possible that
   // only part of the elf file to be mapped into memory is in the executable
   // map. In this case, there will be another read-only map that includes the
@@ -263,4 +267,48 @@
   return cur_load_bias;
 }
 
+MapInfo::~MapInfo() {
+  uintptr_t id = build_id.load();
+  if (id != 0) {
+    delete reinterpret_cast<std::string*>(id);
+  }
+}
+
+std::string MapInfo::GetBuildID() {
+  uintptr_t id = build_id.load();
+  if (build_id != 0) {
+    return *reinterpret_cast<std::string*>(id);
+  }
+
+  // No need to lock, at worst if multiple threads do this at the same
+  // time it should be detected and only one thread should win and
+  // save the data.
+  std::unique_ptr<std::string> cur_build_id(new std::string);
+
+  // Now need to see if the elf object exists.
+  // Make sure no other thread is trying to add the elf to this map.
+  mutex_.lock();
+  Elf* elf_obj = elf.get();
+  mutex_.unlock();
+  if (elf_obj != nullptr) {
+    *cur_build_id = elf_obj->GetBuildID();
+  } else {
+    // This will only work if we can get the file associated with this memory.
+    // If this is only available in memory, then the section name information
+    // is not present and we will not be able to find the build id info.
+    std::unique_ptr<Memory> memory(GetFileMemory());
+    if (memory != nullptr) {
+      *cur_build_id = Elf::GetBuildID(memory.get());
+    }
+  }
+
+  id = reinterpret_cast<uintptr_t>(cur_build_id.get());
+  uintptr_t expected_id = 0;
+  if (build_id.compare_exchange_weak(expected_id, id)) {
+    // Value saved, so make sure the memory is not freed.
+    cur_build_id.release();
+  }
+  return *reinterpret_cast<std::string*>(id);
+}
+
 }  // namespace unwindstack
diff --git a/libunwindstack/benchmarks/unwind_benchmarks.cpp b/libunwindstack/benchmarks/unwind_benchmarks.cpp
index db0fb54..8caecc7 100644
--- a/libunwindstack/benchmarks/unwind_benchmarks.cpp
+++ b/libunwindstack/benchmarks/unwind_benchmarks.cpp
@@ -20,6 +20,9 @@
 
 #include <benchmark/benchmark.h>
 
+#include <android-base/strings.h>
+
+#include <unwindstack/Elf.h>
 #include <unwindstack/Maps.h>
 #include <unwindstack/Memory.h>
 #include <unwindstack/Regs.h>
@@ -80,4 +83,63 @@
 }
 BENCHMARK(BM_cached_unwind);
 
+static void Initialize(benchmark::State& state, unwindstack::Maps& maps,
+                       unwindstack::MapInfo** build_id_map_info) {
+  if (!maps.Parse()) {
+    state.SkipWithError("Failed to parse local maps.");
+    return;
+  }
+
+  // Find the libc.so share library and use that for benchmark purposes.
+  *build_id_map_info = nullptr;
+  for (unwindstack::MapInfo* map_info : maps) {
+    if (map_info->offset == 0 && map_info->GetBuildID() != "") {
+      *build_id_map_info = map_info;
+      break;
+    }
+  }
+
+  if (*build_id_map_info == nullptr) {
+    state.SkipWithError("Failed to find a map with a BuildID.");
+  }
+}
+
+static void BM_get_build_id_from_elf(benchmark::State& state) {
+  unwindstack::LocalMaps maps;
+  unwindstack::MapInfo* build_id_map_info;
+  Initialize(state, maps, &build_id_map_info);
+
+  unwindstack::Elf* elf = build_id_map_info->GetElf(std::shared_ptr<unwindstack::Memory>(),
+                                                    unwindstack::Regs::CurrentArch());
+  if (!elf->valid()) {
+    state.SkipWithError("Cannot get valid elf from map.");
+  }
+
+  for (auto _ : state) {
+    uintptr_t id = build_id_map_info->build_id;
+    if (id != 0) {
+      delete reinterpret_cast<std::string*>(id);
+      build_id_map_info->build_id = 0;
+    }
+    benchmark::DoNotOptimize(build_id_map_info->GetBuildID());
+  }
+}
+BENCHMARK(BM_get_build_id_from_elf);
+
+static void BM_get_build_id_from_file(benchmark::State& state) {
+  unwindstack::LocalMaps maps;
+  unwindstack::MapInfo* build_id_map_info;
+  Initialize(state, maps, &build_id_map_info);
+
+  for (auto _ : state) {
+    uintptr_t id = build_id_map_info->build_id;
+    if (id != 0) {
+      delete reinterpret_cast<std::string*>(id);
+      build_id_map_info->build_id = 0;
+    }
+    benchmark::DoNotOptimize(build_id_map_info->GetBuildID());
+  }
+}
+BENCHMARK(BM_get_build_id_from_file);
+
 BENCHMARK_MAIN();
diff --git a/libunwindstack/include/unwindstack/Elf.h b/libunwindstack/include/unwindstack/Elf.h
index 27f7201..00a249f 100644
--- a/libunwindstack/include/unwindstack/Elf.h
+++ b/libunwindstack/include/unwindstack/Elf.h
@@ -65,8 +65,6 @@
 
   bool GetGlobalVariable(const std::string& name, uint64_t* memory_address);
 
-  bool GetBuildID(std::string* build_id);
-
   uint64_t GetRelPc(uint64_t pc, const MapInfo* map_info);
 
   bool Step(uint64_t rel_pc, uint64_t adjusted_rel_pc, Regs* regs, Memory* process_memory,
@@ -74,6 +72,8 @@
 
   ElfInterface* CreateInterfaceFromMemory(Memory* memory);
 
+  std::string GetBuildID();
+
   uint64_t GetLoadBias() { return load_bias_; }
 
   bool IsValidPc(uint64_t pc);
@@ -102,6 +102,8 @@
 
   static uint64_t GetLoadBias(Memory* memory);
 
+  static std::string GetBuildID(Memory* memory);
+
   static void SetCachingEnabled(bool enable);
   static bool CachingEnabled() { return cache_enabled_; }
 
diff --git a/libunwindstack/include/unwindstack/ElfInterface.h b/libunwindstack/include/unwindstack/ElfInterface.h
index 52992d9..d41bb13 100644
--- a/libunwindstack/include/unwindstack/ElfInterface.h
+++ b/libunwindstack/include/unwindstack/ElfInterface.h
@@ -62,7 +62,7 @@
 
   virtual bool GetGlobalVariable(const std::string& name, uint64_t* memory_address) = 0;
 
-  virtual bool GetBuildID(std::string* build_id) = 0;
+  virtual std::string GetBuildID() = 0;
 
   virtual bool Step(uint64_t rel_pc, Regs* regs, Memory* process_memory, bool* finished);
 
@@ -100,6 +100,9 @@
   template <typename EhdrType, typename PhdrType>
   static uint64_t GetLoadBias(Memory* memory);
 
+  template <typename EhdrType, typename ShdrType, typename NhdrType>
+  static std::string ReadBuildIDFromMemory(Memory* memory);
+
  protected:
   template <typename AddressType>
   void InitHeadersWithTemplate(uint64_t load_bias);
@@ -128,7 +131,7 @@
   static void GetMaxSizeWithTemplate(Memory* memory, uint64_t* size);
 
   template <typename NhdrType>
-  bool ReadBuildID(std::string* build_id);
+  std::string ReadBuildID();
 
   Memory* memory_;
   std::unordered_map<uint64_t, LoadInfo> pt_loads_;
@@ -192,9 +195,7 @@
     return ElfInterface::GetGlobalVariableWithTemplate<Elf32_Sym>(name, memory_address);
   }
 
-  bool GetBuildID(std::string* build_id) {
-    return ElfInterface::ReadBuildID<Elf32_Nhdr>(build_id);
-  }
+  std::string GetBuildID() override { return ElfInterface::ReadBuildID<Elf32_Nhdr>(); }
 
   static void GetMaxSize(Memory* memory, uint64_t* size) {
     GetMaxSizeWithTemplate<Elf32_Ehdr>(memory, size);
@@ -226,9 +227,7 @@
     return ElfInterface::GetGlobalVariableWithTemplate<Elf64_Sym>(name, memory_address);
   }
 
-  bool GetBuildID(std::string* build_id) {
-    return ElfInterface::ReadBuildID<Elf64_Nhdr>(build_id);
-  }
+  std::string GetBuildID() override { return ElfInterface::ReadBuildID<Elf64_Nhdr>(); }
 
   static void GetMaxSize(Memory* memory, uint64_t* size) {
     GetMaxSizeWithTemplate<Elf64_Ehdr>(memory, size);
diff --git a/libunwindstack/include/unwindstack/MapInfo.h b/libunwindstack/include/unwindstack/MapInfo.h
index a9febd1..5143ff1 100644
--- a/libunwindstack/include/unwindstack/MapInfo.h
+++ b/libunwindstack/include/unwindstack/MapInfo.h
@@ -38,7 +38,8 @@
         flags(flags),
         name(name),
         prev_map(map_info),
-        load_bias(static_cast<uint64_t>(-1)) {}
+        load_bias(static_cast<uint64_t>(-1)),
+        build_id(0) {}
   MapInfo(MapInfo* map_info, uint64_t start, uint64_t end, uint64_t offset, uint64_t flags,
           const std::string& name)
       : start(start),
@@ -47,8 +48,9 @@
         flags(flags),
         name(name),
         prev_map(map_info),
-        load_bias(static_cast<uint64_t>(-1)) {}
-  ~MapInfo() = default;
+        load_bias(static_cast<uint64_t>(-1)),
+        build_id(0) {}
+  ~MapInfo();
 
   uint64_t start = 0;
   uint64_t end = 0;
@@ -68,6 +70,11 @@
 
   std::atomic_uint64_t load_bias;
 
+  // This is a pointer to a new'd std::string.
+  // Using an atomic value means that we don't need to lock and will
+  // make it easier to move to a fine grained lock in the future.
+  std::atomic_uintptr_t build_id;
+
   // This function guarantees it will never return nullptr.
   Elf* GetElf(const std::shared_ptr<Memory>& process_memory, ArchEnum expected_arch);
 
@@ -77,6 +84,8 @@
 
   bool GetFunctionName(uint64_t addr, std::string* name, uint64_t* func_offset);
 
+  std::string GetBuildID();
+
  private:
   MapInfo(const MapInfo&) = delete;
   void operator=(const MapInfo&) = delete;
diff --git a/libunwindstack/tests/ElfFake.h b/libunwindstack/tests/ElfFake.h
index c2bd0f6..946bc3c 100644
--- a/libunwindstack/tests/ElfFake.h
+++ b/libunwindstack/tests/ElfFake.h
@@ -72,9 +72,7 @@
 
   bool GetFunctionName(uint64_t, std::string*, uint64_t*) override;
   bool GetGlobalVariable(const std::string&, uint64_t*) override;
-  bool GetBuildID(std::string*) override {
-    return false;
-  }
+  std::string GetBuildID() override { return fake_build_id_; }
 
   bool Step(uint64_t, Regs*, Memory*, bool*) override;
 
@@ -82,6 +80,9 @@
     globals_[global] = offset;
   }
 
+  void FakeSetBuildID(std::string& build_id) { fake_build_id_ = build_id; }
+  void FakeSetBuildID(const char* build_id) { fake_build_id_ = build_id; }
+
   static void FakePushFunctionData(const FunctionData data) { functions_.push_back(data); }
   static void FakePushStepData(const StepData data) { steps_.push_back(data); }
 
@@ -96,6 +97,7 @@
 
  private:
   std::unordered_map<std::string, uint64_t> globals_;
+  std::string fake_build_id_;
 
   static std::deque<FunctionData> functions_;
   static std::deque<StepData> steps_;
diff --git a/libunwindstack/tests/ElfInterfaceTest.cpp b/libunwindstack/tests/ElfInterfaceTest.cpp
index 6023dc4..7239749 100644
--- a/libunwindstack/tests/ElfInterfaceTest.cpp
+++ b/libunwindstack/tests/ElfInterfaceTest.cpp
@@ -1228,9 +1228,7 @@
 
   uint64_t load_bias = 0;
   ASSERT_TRUE(elf->Init(&load_bias));
-  std::string build_id;
-  ASSERT_TRUE(elf->GetBuildID(&build_id));
-  EXPECT_STREQ(build_id.c_str(), "BUILDID");
+  ASSERT_EQ("BUILDID", elf->GetBuildID());
 }
 
 template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
@@ -1292,9 +1290,7 @@
 
   uint64_t load_bias = 0;
   ASSERT_TRUE(elf->Init(&load_bias));
-  std::string build_id;
-  ASSERT_TRUE(elf->GetBuildID(&build_id));
-  EXPECT_STREQ(build_id.c_str(), "BUILDID");
+  ASSERT_EQ("BUILDID", elf->GetBuildID());
 }
 
 template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
@@ -1346,8 +1342,7 @@
 
   uint64_t load_bias = 0;
   ASSERT_TRUE(elf->Init(&load_bias));
-  std::string build_id;
-  ASSERT_FALSE(elf->GetBuildID(&build_id));
+  ASSERT_EQ("", elf->GetBuildID());
 }
 
 template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
@@ -1399,8 +1394,7 @@
 
   uint64_t load_bias = 0;
   ASSERT_TRUE(elf->Init(&load_bias));
-  std::string build_id;
-  ASSERT_FALSE(elf->GetBuildID(&build_id));
+  ASSERT_EQ("", elf->GetBuildID());
 }
 
 template <typename Ehdr, typename Shdr, typename Nhdr, typename ElfInterfaceType>
@@ -1452,8 +1446,7 @@
 
   uint64_t load_bias = 0;
   ASSERT_TRUE(elf->Init(&load_bias));
-  std::string build_id;
-  ASSERT_FALSE(elf->GetBuildID(&build_id));
+  ASSERT_EQ("", elf->GetBuildID());
 }
 
 TEST_F(ElfInterfaceTest, build_id32) {
diff --git a/libunwindstack/tests/ElfTest.cpp b/libunwindstack/tests/ElfTest.cpp
index f7689ce..1ff2306 100644
--- a/libunwindstack/tests/ElfTest.cpp
+++ b/libunwindstack/tests/ElfTest.cpp
@@ -311,7 +311,7 @@
   void InitHeaders(uint64_t) override {}
   bool GetSoname(std::string*) override { return false; }
   bool GetFunctionName(uint64_t, std::string*, uint64_t*) override { return false; }
-  bool GetBuildID(std::string*) override { return false; }
+  std::string GetBuildID() override { return ""; }
 
   MOCK_METHOD4(Step, bool(uint64_t, Regs*, Memory*, bool*));
   MOCK_METHOD2(GetGlobalVariable, bool(const std::string&, uint64_t*));
diff --git a/libunwindstack/tests/MapInfoGetBuildIDTest.cpp b/libunwindstack/tests/MapInfoGetBuildIDTest.cpp
new file mode 100644
index 0000000..3b89c59
--- /dev/null
+++ b/libunwindstack/tests/MapInfoGetBuildIDTest.cpp
@@ -0,0 +1,183 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <elf.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <atomic>
+#include <memory>
+#include <string>
+#include <thread>
+#include <vector>
+
+#include <android-base/test_utils.h>
+
+#include <gtest/gtest.h>
+
+#include <unwindstack/Elf.h>
+#include <unwindstack/MapInfo.h>
+#include <unwindstack/Maps.h>
+#include <unwindstack/Memory.h>
+
+#include "ElfFake.h"
+#include "ElfTestUtils.h"
+#include "MemoryFake.h"
+
+namespace unwindstack {
+
+class MapInfoGetBuildIDTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    tf_.reset(new TemporaryFile);
+
+    memory_ = new MemoryFake;
+    elf_ = new ElfFake(new MemoryFake);
+    elf_interface_ = new ElfInterfaceFake(memory_);
+    elf_->FakeSetInterface(elf_interface_);
+    elf_container_.reset(elf_);
+    map_info_.reset(new MapInfo(nullptr, 0x1000, 0x20000, 0, PROT_READ | PROT_WRITE, tf_->path));
+  }
+
+  void MultipleThreadTest(std::string expected_build_id);
+
+  MemoryFake* memory_;
+  ElfFake* elf_;
+  ElfInterfaceFake* elf_interface_;
+  std::unique_ptr<ElfFake> elf_container_;
+  std::unique_ptr<MapInfo> map_info_;
+  std::unique_ptr<TemporaryFile> tf_;
+};
+
+TEST_F(MapInfoGetBuildIDTest, no_elf_and_no_valid_elf_in_memory) {
+  MapInfo info(nullptr, 0x1000, 0x2000, 0, PROT_READ, "");
+
+  EXPECT_EQ("", info.GetBuildID());
+}
+
+TEST_F(MapInfoGetBuildIDTest, from_elf) {
+  map_info_->elf.reset(elf_container_.release());
+  elf_interface_->FakeSetBuildID("FAKE_BUILD_ID");
+
+  EXPECT_EQ("FAKE_BUILD_ID", map_info_->GetBuildID());
+}
+
+void MapInfoGetBuildIDTest::MultipleThreadTest(std::string expected_build_id) {
+  static constexpr size_t kNumConcurrentThreads = 100;
+
+  std::string build_id_values[kNumConcurrentThreads];
+  std::vector<std::thread*> threads;
+
+  std::atomic_bool wait;
+  wait = true;
+  // Create all of the threads and have them do the GetLoadBias at the same time
+  // to make it likely that a race will occur.
+  for (size_t i = 0; i < kNumConcurrentThreads; i++) {
+    std::thread* thread = new std::thread([i, this, &wait, &build_id_values]() {
+      while (wait)
+        ;
+      build_id_values[i] = map_info_->GetBuildID();
+    });
+    threads.push_back(thread);
+  }
+
+  // Set them all going and wait for the threads to finish.
+  wait = false;
+  for (auto thread : threads) {
+    thread->join();
+    delete thread;
+  }
+
+  // Now verify that all of the elf files are exactly the same and valid.
+  for (size_t i = 0; i < kNumConcurrentThreads; i++) {
+    EXPECT_EQ(expected_build_id, build_id_values[i]) << "Thread " << i << " mismatched.";
+  }
+}
+
+TEST_F(MapInfoGetBuildIDTest, multiple_thread_elf_exists) {
+  map_info_->elf.reset(elf_container_.release());
+  elf_interface_->FakeSetBuildID("FAKE_BUILD_ID");
+
+  MultipleThreadTest("FAKE_BUILD_ID");
+}
+
+static void InitElfData(int fd) {
+  Elf32_Ehdr ehdr;
+  TestInitEhdr(&ehdr, ELFCLASS32, EM_ARM);
+  ehdr.e_shoff = 0x2000;
+  ehdr.e_shnum = 3;
+  ehdr.e_shentsize = sizeof(Elf32_Shdr);
+  ehdr.e_shstrndx = 2;
+  off_t offset = 0;
+  ASSERT_EQ(offset, lseek(fd, offset, SEEK_SET));
+  ASSERT_EQ(static_cast<ssize_t>(sizeof(ehdr)), write(fd, &ehdr, sizeof(ehdr)));
+
+  char note_section[128];
+  Elf32_Nhdr note_header = {};
+  note_header.n_namesz = 4;   // "GNU"
+  note_header.n_descsz = 12;  // "ELF_BUILDID"
+  note_header.n_type = NT_GNU_BUILD_ID;
+  memcpy(&note_section, &note_header, sizeof(note_header));
+  size_t note_offset = sizeof(note_header);
+  memcpy(&note_section[note_offset], "GNU", sizeof("GNU"));
+  note_offset += sizeof("GNU");
+  memcpy(&note_section[note_offset], "ELF_BUILDID", sizeof("ELF_BUILDID"));
+  note_offset += sizeof("ELF_BUILDID");
+
+  Elf32_Shdr shdr = {};
+  shdr.sh_type = SHT_NOTE;
+  shdr.sh_name = 0x500;
+  shdr.sh_offset = 0xb000;
+  shdr.sh_size = sizeof(note_section);
+  offset += ehdr.e_shoff + sizeof(shdr);
+  ASSERT_EQ(offset, lseek(fd, offset, SEEK_SET));
+  ASSERT_EQ(static_cast<ssize_t>(sizeof(shdr)), write(fd, &shdr, sizeof(shdr)));
+
+  // The string data for section header names.
+  memset(&shdr, 0, sizeof(shdr));
+  shdr.sh_type = SHT_STRTAB;
+  shdr.sh_name = 0x20000;
+  shdr.sh_offset = 0xf000;
+  shdr.sh_size = 0x1000;
+  offset += sizeof(shdr);
+  ASSERT_EQ(offset, lseek(fd, offset, SEEK_SET));
+  ASSERT_EQ(static_cast<ssize_t>(sizeof(shdr)), write(fd, &shdr, sizeof(shdr)));
+
+  offset = 0xf500;
+  ASSERT_EQ(offset, lseek(fd, offset, SEEK_SET));
+  ASSERT_EQ(static_cast<ssize_t>(sizeof(".note.gnu.build-id")),
+            write(fd, ".note.gnu.build-id", sizeof(".note.gnu.build-id")));
+
+  offset = 0xb000;
+  ASSERT_EQ(offset, lseek(fd, offset, SEEK_SET));
+  ASSERT_EQ(static_cast<ssize_t>(sizeof(note_section)),
+            write(fd, note_section, sizeof(note_section)));
+}
+
+TEST_F(MapInfoGetBuildIDTest, from_memory) {
+  InitElfData(tf_->fd);
+
+  EXPECT_EQ("ELF_BUILDID", map_info_->GetBuildID());
+}
+
+TEST_F(MapInfoGetBuildIDTest, multiple_thread_elf_exists_in_memory) {
+  InitElfData(tf_->fd);
+
+  MultipleThreadTest("ELF_BUILDID");
+}
+
+}  // namespace unwindstack
diff --git a/libunwindstack/tests/MapInfoGetElfTest.cpp b/libunwindstack/tests/MapInfoGetElfTest.cpp
index 99f8fa3..d7b8485 100644
--- a/libunwindstack/tests/MapInfoGetElfTest.cpp
+++ b/libunwindstack/tests/MapInfoGetElfTest.cpp
@@ -88,6 +88,12 @@
   ASSERT_TRUE(elf->valid());
   EXPECT_EQ(static_cast<uint32_t>(EM_ARM), elf->machine_type());
   EXPECT_EQ(ELFCLASS32, elf->class_type());
+
+  // Now verify that an empty process memory returns an invalid elf object.
+  info.elf.reset();
+  elf = info.GetElf(std::shared_ptr<Memory>(), ARCH_ARM);
+  ASSERT_TRUE(elf != nullptr);
+  ASSERT_FALSE(elf->valid());
 }
 
 TEST_F(MapInfoGetElfTest, valid64) {
diff --git a/libunwindstack/tools/unwind_info.cpp b/libunwindstack/tools/unwind_info.cpp
index 3f2dfb0..3f5b88b 100644
--- a/libunwindstack/tools/unwind_info.cpp
+++ b/libunwindstack/tools/unwind_info.cpp
@@ -123,8 +123,8 @@
     printf("Soname: %s\n", soname.c_str());
   }
 
-  std::string build_id;
-  if (elf.GetBuildID(&build_id)) {
+  std::string build_id = elf.GetBuildID();
+  if (!build_id.empty()) {
     printf("Build ID: ");
     for (size_t i = 0; i < build_id.size(); ++i) {
       printf("%02hhx", build_id[i]);