Add caching of build id in MapInfo object.

Change the GetBuildID function to return a std::string.
Added benchmark to check how long it takes to get the build id from
a file versus an elf object.
Added a way to get an elf without passing in a valid process_memory and
added tests for this.

Test: New unit tests.
Change-Id: I3029019767e0181c758d611fe635bc1bf72d6e8e

5 files changed, 200 insertions, 16 deletions

diff --git a/libunwindstack/tests/ElfFake.h b/libunwindstack/tests/ElfFake.h
index c2bd0f6c6..946bc3c21 100644
--- a/libunwindstack/tests/ElfFake.h
+++ b/libunwindstack/tests/ElfFake.h
@@ -72,9 +72,7 @@ class ElfInterfaceFake : public ElfInterface {
 
   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 @@ class ElfInterfaceFake : public ElfInterface {
     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 @@ class ElfInterfaceFake : public ElfInterface {
 
  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 6023dc4b8..7239749c6 100644
--- a/libunwindstack/tests/ElfInterfaceTest.cpp
+++ b/libunwindstack/tests/ElfInterfaceTest.cpp
@@ -1228,9 +1228,7 @@ void ElfInterfaceTest::BuildID() {
 
   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 @@ void ElfInterfaceTest::BuildIDTwoNotes() {
 
   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 @@ void ElfInterfaceTest::BuildIDSectionTooSmallForName () {
 
   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 @@ void ElfInterfaceTest::BuildIDSectionTooSmallForDesc () {
 
   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 @@ void ElfInterfaceTest::BuildIDSectionTooSmallForHeader () {
 
   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 f7689ceb7..1ff23064f 100644
--- a/libunwindstack/tests/ElfTest.cpp
+++ b/libunwindstack/tests/ElfTest.cpp
@@ -311,7 +311,7 @@ class ElfInterfaceMock : public ElfInterface {
   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 000000000..3b89c5961
--- /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 99f8fa3b0..d7b848544 100644
--- a/libunwindstack/tests/MapInfoGetElfTest.cpp
+++ b/libunwindstack/tests/MapInfoGetElfTest.cpp
@@ -88,6 +88,12 @@ TEST_F(MapInfoGetElfTest, valid32) {
   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) {