Speed up map creation.

- Rewrite the Maps::Parse to use open, and a buffer on the stack.
- Rewrite the line parser away from sscanf. The current way sscanf
  is used does not catch many malformed lines. In addition, this
  new version improves performance by 50% over sscanf on sailfish.
- Add a lot of unit tests for the parser to make sure there are
  no problems. In addition, add a special line that was not rejected
  with the previous version of the code.
- Add new accessor to get the map at a particular index.
- Add a backtrace benchmark for map creation for both new and old.

This cl results in ~5% speedup and makes the new unwinder map creation
about the same for 64 bit. It's still a bit slower, but not by much.
On 32 bit, we are still about 5% slower than the old creation method,
though.

Bug: 23762183

Test: libunwindstack unit tests pass. Ran the new benchmarks.
Change-Id: Id4431e539f400984e6fad62153fdf4152d518322

libbacktrace/Android.bp

@@ -240,3 +240,17 @@ cc_test {
         },
     },
 }
+
+cc_benchmark {
+    name: "backtrace_benchmarks",
+    defaults: ["libbacktrace_common"],
+
+    srcs: [
+        "backtrace_benchmarks.cpp",
+    ],
+
+    shared_libs: [
+        "libbacktrace",
+        "libbase",
+    ],
+}

libbacktrace/backtrace_benchmarks.cpp

@@ -0,0 +1,162 @@
+/*
+ * Copyright (C) 2017 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 <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <string>
+
+#include <android-base/file.h>
+
+#include <benchmark/benchmark.h>
+
+#include <backtrace/Backtrace.h>
+#include <backtrace/BacktraceMap.h>
+
+// Definitions of prctl arguments to set a vma name in Android kernels.
+#define ANDROID_PR_SET_VMA 0x53564d41
+#define ANDROID_PR_SET_VMA_ANON_NAME 0
+
+constexpr size_t kNumMaps = 2000;
+constexpr size_t kNumIterations = 1000;
+
+static bool CountMaps(pid_t pid, size_t* num_maps) {
+  // Minimize the calls that might allocate memory. If too much memory
+  // gets allocated, then this routine will add extra maps and the next
+  // call will fail to get the same number of maps as before.
+  int fd =
+      open((std::string("/proc/") + std::to_string(pid) + "/maps").c_str(), O_RDONLY | O_CLOEXEC);
+  if (fd == -1) {
+    fprintf(stderr, "Cannot open map file for pid %d: %s\n", pid, strerror(errno));
+    return false;
+  }
+  *num_maps = 0;
+  while (true) {
+    char buffer[2048];
+    ssize_t bytes = read(fd, buffer, sizeof(buffer));
+    if (bytes <= 0) {
+      break;
+    }
+    // Count the '\n'.
+    for (size_t i = 0; i < static_cast<size_t>(bytes); i++) {
+      if (buffer[i] == '\n') {
+        ++*num_maps;
+      }
+    }
+  }
+
+  close(fd);
+  return true;
+}
+
+static void CreateMap(benchmark::State& state, BacktraceMap* (*map_func)(pid_t, bool)) {
+  state.PauseTiming();
+  // Create a remote process so that the map data is exactly the same.
+  // Also, so that we can create a set number of maps.
+  pid_t pid;
+  if ((pid = fork()) == 0) {
+    size_t num_maps;
+    if (!CountMaps(getpid(), &num_maps)) {
+      exit(1);
+    }
+    // Create uniquely named maps.
+    std::vector<void*> maps;
+    for (size_t i = num_maps; i < kNumMaps; i++) {
+      int flags = PROT_READ | PROT_WRITE;
+      // Alternate page type to make sure a map entry is added for each call.
+      if ((i % 2) == 0) {
+        flags |= PROT_EXEC;
+      }
+      void* memory = mmap(nullptr, PAGE_SIZE, flags, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+      if (memory == MAP_FAILED) {
+        fprintf(stderr, "Failed to create map: %s\n", strerror(errno));
+        exit(1);
+      }
+      memset(memory, 0x1, PAGE_SIZE);
+      if (prctl(ANDROID_PR_SET_VMA, ANDROID_PR_SET_VMA_ANON_NAME, memory, PAGE_SIZE, "test_map") ==
+          -1) {
+        fprintf(stderr, "Failed: %s\n", strerror(errno));
+      }
+      maps.push_back(memory);
+    }
+
+    if (!CountMaps(getpid(), &num_maps)) {
+      exit(1);
+    }
+
+    if (num_maps != kNumMaps) {
+      fprintf(stderr, "Maps set incorrectly: %zu found, %zu expected.\n", num_maps, kNumMaps);
+      std::string str;
+      android::base::ReadFileToString("/proc/self/maps", &str);
+      fprintf(stderr, "%s\n", str.c_str());
+      exit(1);
+    }
+
+    // Wait for an hour at most.
+    sleep(3600);
+    exit(1);
+  } else if (pid < 0) {
+    fprintf(stderr, "Fork failed: %s\n", strerror(errno));
+    return;
+  }
+
+  size_t num_maps = 0;
+  for (size_t i = 0; i < 2000; i++) {
+    if (CountMaps(pid, &num_maps) && num_maps == kNumMaps) {
+      break;
+    }
+    usleep(1000);
+  }
+  if (num_maps != kNumMaps) {
+    fprintf(stderr, "Timed out waiting for the number of maps available: %zu\n", num_maps);
+    return;
+  }
+
+  state.ResumeTiming();
+  while (state.KeepRunning()) {
+    for (size_t i = 0; i < static_cast<size_t>(state.range(0)); i++) {
+      BacktraceMap* map = map_func(pid, false);
+      if (map == nullptr) {
+        fprintf(stderr, "Failed to create map\n");
+        return;
+      }
+      delete map;
+    }
+  }
+  state.PauseTiming();
+
+  kill(pid, SIGKILL);
+  waitpid(pid, nullptr, 0);
+}
+
+static void BM_create_map(benchmark::State& state) {
+  CreateMap(state, BacktraceMap::Create);
+}
+BENCHMARK(BM_create_map)->Arg(kNumIterations);
+
+static void BM_create_map_new(benchmark::State& state) {
+  CreateMap(state, BacktraceMap::CreateNew);
+}
+BENCHMARK(BM_create_map_new)->Arg(kNumIterations);
+
+BENCHMARK_MAIN();

libunwindstack/Maps.cpp

@@ -25,6 +25,7 @@
 
 #include <android-base/unique_fd.h>
 
+#include <cctype>
 #include <memory>
 #include <string>
 #include <vector>
@@ -55,63 +56,151 @@ MapInfo* Maps::Find(uint64_t pc) {
   return nullptr;
 }
 
-bool Maps::ParseLine(const char* line, MapInfo* map_info) {
-  char permissions[5];
-  int name_pos;
-  // Linux /proc/<pid>/maps lines:
+// Assumes that line does not end in '\n'.
+static bool InternalParseLine(const char* line, MapInfo* map_info) {
+  // Do not use a sscanf implementation since it is not performant.
+
+  // Example linux /proc/<pid>/maps lines:
   // 6f000000-6f01e000 rwxp 00000000 00:0c 16389419   /system/lib/libcomposer.so
-  if (sscanf(line, "%" SCNx64 "-%" SCNx64 " %4s %" SCNx64 " %*x:%*x %*d %n", &map_info->start,
-             &map_info->end, permissions, &map_info->offset, &name_pos) != 4) {
+  char* str;
+  const char* old_str = line;
+  map_info->start = strtoul(old_str, &str, 16);
+  if (old_str == str || *str++ != '-') {
     return false;
   }
-  map_info->flags = PROT_NONE;
-  if (permissions[0] == 'r') {
+
+  old_str = str;
+  map_info->end = strtoul(old_str, &str, 16);
+  if (old_str == str || !std::isspace(*str++)) {
+    return false;
+  }
+
+  while (std::isspace(*str)) {
+    str++;
+  }
+
+  // Parse permissions data.
+  if (*str == '\0') {
+    return false;
+  }
+  map_info->flags = 0;
+  if (*str == 'r') {
     map_info->flags |= PROT_READ;
+  } else if (*str != '-') {
+    return false;
   }
-  if (permissions[1] == 'w') {
+  str++;
+  if (*str == 'w') {
     map_info->flags |= PROT_WRITE;
+  } else if (*str != '-') {
+    return false;
   }
-  if (permissions[2] == 'x') {
+  str++;
+  if (*str == 'x') {
     map_info->flags |= PROT_EXEC;
+  } else if (*str != '-') {
+    return false;
+  }
+  str++;
+  if (*str != 'p' && *str != 's') {
+    return false;
+  }
+  str++;
+
+  if (!std::isspace(*str++)) {
+    return false;
   }
 
-  if (line[name_pos] != '\0') {
-    map_info->name = &line[name_pos];
-    size_t length = map_info->name.length() - 1;
-    if (map_info->name[length] == '\n') {
-      map_info->name.erase(length);
-    }
-
-    // Mark a device map in /dev/and not in /dev/ashmem/ specially.
-    if (map_info->name.substr(0, 5) == "/dev/" && map_info->name.substr(5, 7) != "ashmem/") {
-      map_info->flags |= MAPS_FLAGS_DEVICE_MAP;
-    }
+  old_str = str;
+  map_info->offset = strtoul(old_str, &str, 16);
+  if (old_str == str || !std::isspace(*str)) {
+    return false;
   }
 
+  // Ignore the 00:00 values.
+  old_str = str;
+  (void)strtoul(old_str, &str, 16);
+  if (old_str == str || *str++ != ':') {
+    return false;
+  }
+  if (std::isspace(*str)) {
+    return false;
+  }
+
+  // Skip the inode.
+  old_str = str;
+  (void)strtoul(str, &str, 16);
+  if (old_str == str || !std::isspace(*str++)) {
+    return false;
+  }
+
+  // Skip decimal digit.
+  old_str = str;
+  (void)strtoul(old_str, &str, 10);
+  if (old_str == str || (!std::isspace(*str) && *str != '\0')) {
+    return false;
+  }
+
+  while (std::isspace(*str)) {
+    str++;
+  }
+  if (*str == '\0') {
+    map_info->name = str;
+    return true;
+  }
+
+  // Save the name data.
+  map_info->name = str;
+
+  // Mark a device map in /dev/ and not in /dev/ashmem/ specially.
+  if (map_info->name.substr(0, 5) == "/dev/" && map_info->name.substr(5, 7) != "ashmem/") {
+    map_info->flags |= MAPS_FLAGS_DEVICE_MAP;
+  }
   return true;
 }
 
 bool Maps::Parse() {
-  std::unique_ptr<FILE, decltype(&fclose)> fp(fopen(GetMapsFile().c_str(), "re"), fclose);
-  if (!fp) {
+  int fd = open(GetMapsFile().c_str(), O_RDONLY | O_CLOEXEC);
+  if (fd == -1) {
     return false;
   }
 
-  bool valid = true;
-  char* line = nullptr;
-  size_t line_len;
-  while (getline(&line, &line_len, fp.get()) > 0) {
-    MapInfo map_info;
-    if (!ParseLine(line, &map_info)) {
-      valid = false;
+  bool return_value = true;
+  char buffer[2048];
+  size_t leftover = 0;
+  while (true) {
+    ssize_t bytes = read(fd, &buffer[leftover], 2048 - leftover);
+    if (bytes == -1) {
+      return_value = false;
       break;
     }
+    if (bytes == 0) {
+      break;
+    }
+    bytes += leftover;
+    char* line = buffer;
+    while (bytes > 0) {
+      char* newline = static_cast<char*>(memchr(line, '\n', bytes));
+      if (newline == nullptr) {
+        memmove(buffer, line, bytes);
+        break;
+      }
+      *newline = '\0';
 
-    maps_.push_back(map_info);
+      MapInfo map_info;
+      if (!InternalParseLine(line, &map_info)) {
+        return_value = false;
+        break;
+      }
+      maps_.push_back(map_info);
+
+      bytes -= newline - line + 1;
+      line = newline + 1;
+    }
+    leftover = bytes;
   }
-  free(line);
-
-  return valid;
+  close(fd);
+  return return_value;
 }
 
 Maps::~Maps() {
@@ -129,12 +218,12 @@ bool BufferMaps::Parse() {
     if (end_of_line == nullptr) {
       line = start_of_line;
     } else {
-      end_of_line++;
       line = std::string(start_of_line, end_of_line - start_of_line);
+      end_of_line++;
     }
 
     MapInfo map_info;
-    if (!ParseLine(line.c_str(), &map_info)) {
+    if (!InternalParseLine(line.c_str(), &map_info)) {
       return false;
     }
     maps_.push_back(map_info);

libunwindstack/include/unwindstack/Maps.h

@@ -38,8 +38,6 @@ class Maps {
 
   MapInfo* Find(uint64_t pc);
 
-  bool ParseLine(const char* line, MapInfo* map_info);
-
   virtual bool Parse();
 
   virtual const std::string GetMapsFile() const { return ""; }
@@ -54,6 +52,11 @@ class Maps {
 
   size_t Total() { return maps_.size(); }
 
+  MapInfo* Get(size_t index) {
+    if (index >= maps_.size()) return nullptr;
+    return &maps_[index];
+  }
+
  protected:
   std::vector<MapInfo> maps_;
 };

libunwindstack/tests/MapsTest.cpp

@@ -14,9 +14,11 @@
  * limitations under the License.
  */
 
+#include <inttypes.h>
 #include <sys/mman.h>
 
 #include <android-base/file.h>
+#include <android-base/stringprintf.h>
 #include <android-base/test_utils.h>
 #include <gtest/gtest.h>
 
@@ -24,13 +26,116 @@
 
 namespace unwindstack {
 
+static void VerifyLine(std::string line, MapInfo* info) {
+  BufferMaps maps(line.c_str());
+
+  if (info == nullptr) {
+    ASSERT_FALSE(maps.Parse()) << "Failed on: " + line;
+  } else {
+    ASSERT_TRUE(maps.Parse()) << "Failed on: " + line;
+    MapInfo* element = maps.Get(0);
+    ASSERT_TRUE(element != nullptr) << "Failed on: " + line;
+    *info = *element;
+  }
+}
+
+TEST(MapsTest, verify_parse_line) {
+  MapInfo info;
+
+  VerifyLine("01-02 rwxp 03 04:05 06\n", &info);
+  EXPECT_EQ(1U, info.start);
+  EXPECT_EQ(2U, info.end);
+  EXPECT_EQ(PROT_READ | PROT_WRITE | PROT_EXEC, info.flags);
+  EXPECT_EQ(3U, info.offset);
+  EXPECT_EQ("", info.name);
+
+  VerifyLine("0a-0b ---s 0c 0d:0e 06 /fake/name\n", &info);
+  EXPECT_EQ(0xaU, info.start);
+  EXPECT_EQ(0xbU, info.end);
+  EXPECT_EQ(0U, info.flags);
+  EXPECT_EQ(0xcU, info.offset);
+  EXPECT_EQ("/fake/name", info.name);
+
+  VerifyLine("01-02   rwxp   03    04:05    06    /fake/name/again\n", &info);
+  EXPECT_EQ(1U, info.start);
+  EXPECT_EQ(2U, info.end);
+  EXPECT_EQ(PROT_READ | PROT_WRITE | PROT_EXEC, info.flags);
+  EXPECT_EQ(3U, info.offset);
+  EXPECT_EQ("/fake/name/again", info.name);
+
+  VerifyLine("-00 rwxp 00 00:00 0\n", nullptr);
+  VerifyLine("00- rwxp 00 00:00 0\n", nullptr);
+  VerifyLine("00-00 rwxp 00 :00 0\n", nullptr);
+  VerifyLine("00-00 rwxp 00 00:00 \n", nullptr);
+  VerifyLine("x-00 rwxp 00 00:00 0\n", nullptr);
+  VerifyLine("00 -00 rwxp 00 00:00 0\n", nullptr);
+  VerifyLine("00-x rwxp 00 00:00 0\n", nullptr);
+  VerifyLine("00-x rwxp 00 00:00 0\n", nullptr);
+  VerifyLine("00-00x rwxp 00 00:00 0\n", nullptr);
+  VerifyLine("00-00 rwxp0 00 00:00 0\n", nullptr);
+  VerifyLine("00-00 rwxp0 00 00:00 0\n", nullptr);
+  VerifyLine("00-00 rwp 00 00:00 0\n", nullptr);
+  VerifyLine("00-00 rwxp 0000:00 0\n", nullptr);
+  VerifyLine("00-00 rwxp 00 00 :00 0\n", nullptr);
+  VerifyLine("00-00 rwxp 00 00: 00 0\n", nullptr);
+  VerifyLine("00-00 rwxp 00 00:000\n", nullptr);
+  VerifyLine("00-00 rwxp 00 00:00 0/fake\n", nullptr);
+  VerifyLine("00-00 xxxx 00 00:00 0 /fake\n", nullptr);
+  VerifyLine("00-00 ywxp 00 00:00 0 /fake\n", nullptr);
+  VerifyLine("00-00 ryxp 00 00:00 0 /fake\n", nullptr);
+  VerifyLine("00-00 rwyp 00 00:00 0 /fake\n", nullptr);
+  VerifyLine("00-00 rwx- 00 00:00 0 /fake\n", nullptr);
+  VerifyLine("0\n", nullptr);
+  VerifyLine("00\n", nullptr);
+  VerifyLine("00-\n", nullptr);
+  VerifyLine("00-0\n", nullptr);
+  VerifyLine("00-00\n", nullptr);
+  VerifyLine("00-00 \n", nullptr);
+  VerifyLine("00-00 -\n", nullptr);
+  VerifyLine("00-00 r\n", nullptr);
+  VerifyLine("00-00 --\n", nullptr);
+  VerifyLine("00-00 rw\n", nullptr);
+  VerifyLine("00-00 ---\n", nullptr);
+  VerifyLine("00-00 rwx\n", nullptr);
+  VerifyLine("00-00 ---s\n", nullptr);
+  VerifyLine("00-00 ---p\n", nullptr);
+  VerifyLine("00-00 ---s 0\n", nullptr);
+  VerifyLine("00-00 ---p 0 \n", nullptr);
+  VerifyLine("00-00 ---p 0 0\n", nullptr);
+  VerifyLine("00-00 ---p 0 0:\n", nullptr);
+  VerifyLine("00-00 ---p 0 0:0\n", nullptr);
+  VerifyLine("00-00 ---p 0 0:0 \n", nullptr);
+
+  // Line to verify that the parser will detect a completely malformed line
+  // properly.
+  VerifyLine("7ffff7dda000-7ffff7dfd7ffff7ff3000-7ffff7ff4000 ---p 0000f000 fc:02 44171565\n",
+             nullptr);
+}
+
+TEST(MapsTest, verify_large_values) {
+  MapInfo info;
+#if defined(__LP64__)
+  VerifyLine("fabcdef012345678-f12345678abcdef8 rwxp f0b0d0f010305070 00:00 0\n", &info);
+  EXPECT_EQ(0xfabcdef012345678UL, info.start);
+  EXPECT_EQ(0xf12345678abcdef8UL, info.end);
+  EXPECT_EQ(PROT_READ | PROT_WRITE | PROT_EXEC, info.flags);
+  EXPECT_EQ(0xf0b0d0f010305070UL, info.offset);
+#else
+  VerifyLine("f2345678-fabcdef8 rwxp f0305070 00:00 0\n", &info);
+  EXPECT_EQ(0xf2345678UL, info.start);
+  EXPECT_EQ(0xfabcdef8UL, info.end);
+  EXPECT_EQ(PROT_READ | PROT_WRITE | PROT_EXEC, info.flags);
+  EXPECT_EQ(0xf0305070UL, info.offset);
+#endif
+}
+
 TEST(MapsTest, parse_permissions) {
   BufferMaps maps(
-      "1000-2000 ---- 00000000 00:00 0\n"
-      "2000-3000 r--- 00000000 00:00 0\n"
-      "3000-4000 -w-- 00000000 00:00 0\n"
-      "4000-5000 --x- 00000000 00:00 0\n"
-      "5000-6000 rwx- 00000000 00:00 0\n");
+      "1000-2000 ---s 00000000 00:00 0\n"
+      "2000-3000 r--s 00000000 00:00 0\n"
+      "3000-4000 -w-s 00000000 00:00 0\n"
+      "4000-5000 --xp 00000000 00:00 0\n"
+      "5000-6000 rwxp 00000000 00:00 0\n");
 
   ASSERT_TRUE(maps.Parse());
   ASSERT_EQ(5U, maps.Total());
@@ -70,28 +175,28 @@ TEST(MapsTest, parse_permissions) {
 
 TEST(MapsTest, parse_name) {
   BufferMaps maps(
-      "720b29b000-720b29e000 rw-p 00000000 00:00 0\n"
-      "720b29e000-720b29f000 rw-p 00000000 00:00 0 /system/lib/fake.so\n"
-      "720b29f000-720b2a0000 rw-p 00000000 00:00 0");
+      "7b29b000-7b29e000 rw-p 00000000 00:00 0\n"
+      "7b29e000-7b29f000 rw-p 00000000 00:00 0 /system/lib/fake.so\n"
+      "7b29f000-7b2a0000 rw-p 00000000 00:00 0");
 
   ASSERT_TRUE(maps.Parse());
   ASSERT_EQ(3U, maps.Total());
   auto it = maps.begin();
   ASSERT_EQ("", it->name);
-  ASSERT_EQ(0x720b29b000U, it->start);
-  ASSERT_EQ(0x720b29e000U, it->end);
+  ASSERT_EQ(0x7b29b000U, it->start);
+  ASSERT_EQ(0x7b29e000U, it->end);
   ASSERT_EQ(0U, it->offset);
   ASSERT_EQ(PROT_READ | PROT_WRITE, it->flags);
   ++it;
   ASSERT_EQ("/system/lib/fake.so", it->name);
-  ASSERT_EQ(0x720b29e000U, it->start);
-  ASSERT_EQ(0x720b29f000U, it->end);
+  ASSERT_EQ(0x7b29e000U, it->start);
+  ASSERT_EQ(0x7b29f000U, it->end);
   ASSERT_EQ(0U, it->offset);
   ASSERT_EQ(PROT_READ | PROT_WRITE, it->flags);
   ++it;
   ASSERT_EQ("", it->name);
-  ASSERT_EQ(0x720b29f000U, it->start);
-  ASSERT_EQ(0x720b2a0000U, it->end);
+  ASSERT_EQ(0x7b29f000U, it->start);
+  ASSERT_EQ(0x7b2a0000U, it->end);
   ASSERT_EQ(0U, it->offset);
   ASSERT_EQ(PROT_READ | PROT_WRITE, it->flags);
   ++it;
@@ -149,9 +254,9 @@ TEST(MapsTest, file_smoke) {
   ASSERT_TRUE(tf.fd != -1);
 
   ASSERT_TRUE(
-      android::base::WriteStringToFile("720b29b000-720b29e000 r-xp a0000000 00:00 0   /fake.so\n"
-                                       "720b2b0000-720b2e0000 r-xp b0000000 00:00 0   /fake2.so\n"
-                                       "720b2e0000-720b2f0000 r-xp c0000000 00:00 0   /fake3.so\n",
+      android::base::WriteStringToFile("7b29b000-7b29e000 r-xp a0000000 00:00 0   /fake.so\n"
+                                       "7b2b0000-7b2e0000 r-xp b0000000 00:00 0   /fake2.so\n"
+                                       "7b2e0000-7b2f0000 r-xp c0000000 00:00 0   /fake3.so\n",
                                        tf.path, 0660, getuid(), getgid()));
 
   FileMaps maps(tf.path);
@@ -159,20 +264,20 @@ TEST(MapsTest, file_smoke) {
   ASSERT_TRUE(maps.Parse());
   ASSERT_EQ(3U, maps.Total());
   auto it = maps.begin();
-  ASSERT_EQ(0x720b29b000U, it->start);
-  ASSERT_EQ(0x720b29e000U, it->end);
+  ASSERT_EQ(0x7b29b000U, it->start);
+  ASSERT_EQ(0x7b29e000U, it->end);
   ASSERT_EQ(0xa0000000U, it->offset);
   ASSERT_EQ(PROT_READ | PROT_EXEC, it->flags);
   ASSERT_EQ("/fake.so", it->name);
   ++it;
-  ASSERT_EQ(0x720b2b0000U, it->start);
-  ASSERT_EQ(0x720b2e0000U, it->end);
+  ASSERT_EQ(0x7b2b0000U, it->start);
+  ASSERT_EQ(0x7b2e0000U, it->end);
   ASSERT_EQ(0xb0000000U, it->offset);
   ASSERT_EQ(PROT_READ | PROT_EXEC, it->flags);
   ASSERT_EQ("/fake2.so", it->name);
   ++it;
-  ASSERT_EQ(0x720b2e0000U, it->start);
-  ASSERT_EQ(0x720b2f0000U, it->end);
+  ASSERT_EQ(0x7b2e0000U, it->start);
+  ASSERT_EQ(0x7b2f0000U, it->end);
   ASSERT_EQ(0xc0000000U, it->offset);
   ASSERT_EQ(PROT_READ | PROT_EXEC, it->flags);
   ASSERT_EQ("/fake3.so", it->name);
@@ -180,6 +285,163 @@ TEST(MapsTest, file_smoke) {
   ASSERT_EQ(it, maps.end());
 }
 
+TEST(MapsTest, file_no_map_name) {
+  TemporaryFile tf;
+  ASSERT_TRUE(tf.fd != -1);
+
+  ASSERT_TRUE(
+      android::base::WriteStringToFile("7b29b000-7b29e000 r-xp a0000000 00:00 0\n"
+                                       "7b2b0000-7b2e0000 r-xp b0000000 00:00 0   /fake2.so\n"
+                                       "7b2e0000-7b2f0000 r-xp c0000000 00:00 0 \n",
+                                       tf.path, 0660, getuid(), getgid()));
+
+  FileMaps maps(tf.path);
+
+  ASSERT_TRUE(maps.Parse());
+  ASSERT_EQ(3U, maps.Total());
+  auto it = maps.begin();
+  ASSERT_EQ(0x7b29b000U, it->start);
+  ASSERT_EQ(0x7b29e000U, it->end);
+  ASSERT_EQ(0xa0000000U, it->offset);
+  ASSERT_EQ(PROT_READ | PROT_EXEC, it->flags);
+  ASSERT_EQ("", it->name);
+  ++it;
+  ASSERT_EQ(0x7b2b0000U, it->start);
+  ASSERT_EQ(0x7b2e0000U, it->end);
+  ASSERT_EQ(0xb0000000U, it->offset);
+  ASSERT_EQ(PROT_READ | PROT_EXEC, it->flags);
+  ASSERT_EQ("/fake2.so", it->name);
+  ++it;
+  ASSERT_EQ(0x7b2e0000U, it->start);
+  ASSERT_EQ(0x7b2f0000U, it->end);
+  ASSERT_EQ(0xc0000000U, it->offset);
+  ASSERT_EQ(PROT_READ | PROT_EXEC, it->flags);
+  ASSERT_EQ("", it->name);
+  ++it;
+  ASSERT_EQ(it, maps.end());
+}
+
+// Verify that a file that crosses a buffer is parsed correctly.
+static std::string CreateEntry(size_t index) {
+  return android::base::StringPrintf("%08zx-%08zx rwxp 0000 00:00 0\n", index * 4096,
+                                     (index + 1) * 4096);
+}
+
+TEST(MapsTest, file_buffer_cross) {
+  constexpr size_t kBufferSize = 2048;
+  TemporaryFile tf;
+  ASSERT_TRUE(tf.fd != -1);
+
+  // Compute how many to add in the first buffer.
+  size_t entry_len = CreateEntry(0).size();
+  size_t index;
+  std::string file_data;
+  for (index = 0; index < kBufferSize / entry_len; index++) {
+    file_data += CreateEntry(index);
+  }
+  // Add a long name to make sure that the first buffer does not contain a
+  // complete line.
+  // Remove the last newline.
+  size_t extra = 0;
+  size_t leftover = kBufferSize % entry_len;
+  size_t overlap1_index = 0;
+  std::string overlap1_name;
+  if (leftover == 0) {
+    // Exact match, add a long name to cross over the value.
+    overlap1_name = "/fake/name/is/long/on/purpose";
+    file_data.erase(file_data.size() - 1);
+    file_data += ' ' + overlap1_name + '\n';
+    extra = entry_len + overlap1_name.size() + 1;
+    overlap1_index = index;
+  }
+
+  // Compute how many need to go in to hit the buffer boundary exactly.
+  size_t bytes_left_in_buffer = kBufferSize - extra;
+  size_t entries_to_add = bytes_left_in_buffer / entry_len + index;
+  for (; index < entries_to_add; index++) {
+    file_data += CreateEntry(index);
+  }
+
+  // Now figure out how many bytes to add to get exactly to the buffer boundary.
+  leftover = bytes_left_in_buffer % entry_len;
+  std::string overlap2_name;
+  size_t overlap2_index = 0;
+  if (leftover != 0) {
+    file_data.erase(file_data.size() - 1);
+    file_data += ' ';
+    overlap2_name = std::string(leftover - 1, 'x');
+    file_data += overlap2_name + '\n';
+    overlap2_index = index - 1;
+  }
+
+  // Now add a few entries on the next page.
+  for (size_t start = index; index < start + 10; index++) {
+    file_data += CreateEntry(index);
+  }
+
+  ASSERT_TRUE(android::base::WriteStringToFile(file_data, tf.path, 0660, getuid(), getgid()));
+
+  FileMaps maps(tf.path);
+  ASSERT_TRUE(maps.Parse());
+  EXPECT_EQ(index, maps.Total());
+  // Verify all of the maps.
+  for (size_t i = 0; i < index; i++) {
+    MapInfo* info = maps.Get(i);
+    ASSERT_TRUE(info != nullptr) << "Failed verifying index " + std::to_string(i);
+    EXPECT_EQ(i * 4096, info->start) << "Failed verifying index " + std::to_string(i);
+    EXPECT_EQ((i + 1) * 4096, info->end) << "Failed verifying index " + std::to_string(i);
+    EXPECT_EQ(0U, info->offset) << "Failed verifying index " + std::to_string(i);
+    if (overlap1_index != 0 && i == overlap1_index) {
+      EXPECT_EQ(overlap1_name, info->name) << "Failed verifying overlap1 name " + std::to_string(i);
+    } else if (overlap2_index != 0 && i == overlap2_index) {
+      EXPECT_EQ(overlap2_name, info->name) << "Failed verifying overlap2 name " + std::to_string(i);
+    } else {
+      EXPECT_EQ("", info->name) << "Failed verifying index " + std::to_string(i);
+    }
+  }
+}
+
+TEST(MapsTest, file_should_fail) {
+  TemporaryFile tf;
+  ASSERT_TRUE(tf.fd != -1);
+
+  ASSERT_TRUE(android::base::WriteStringToFile(
+      "7ffff7dda000-7ffff7dfd7ffff7ff3000-7ffff7ff4000 ---p 0000f000 fc:02 44171565\n", tf.path,
+      0660, getuid(), getgid()));
+
+  FileMaps maps(tf.path);
+
+  ASSERT_FALSE(maps.Parse());
+}
+
+// Create a maps file that is extremely large.
+TEST(MapsTest, large_file) {
+  TemporaryFile tf;
+  ASSERT_TRUE(tf.fd != -1);
+
+  std::string file_data;
+  uint64_t start = 0x700000;
+  for (size_t i = 0; i < 5000; i++) {
+    file_data +=
+        android::base::StringPrintf("%" PRIx64 "-%" PRIx64 " r-xp 1000 00:0 0 /fake%zu.so\n",
+                                    start + i * 4096, start + (i + 1) * 4096, i);
+  }
+
+  ASSERT_TRUE(android::base::WriteStringToFile(file_data, tf.path, 0660, getuid(), getgid()));
+
+  FileMaps maps(tf.path);
+
+  ASSERT_TRUE(maps.Parse());
+  ASSERT_EQ(5000U, maps.Total());
+  for (size_t i = 0; i < 5000; i++) {
+    MapInfo* info = maps.Get(i);
+    ASSERT_EQ(start + i * 4096, info->start) << "Failed at map " + std::to_string(i);
+    ASSERT_EQ(start + (i + 1) * 4096, info->end) << "Failed at map " + std::to_string(i);
+    std::string name = "/fake" + std::to_string(i) + ".so";
+    ASSERT_EQ(name, info->name) << "Failed at map " + std::to_string(i);
+  }
+}
+
 TEST(MapsTest, find) {
   BufferMaps maps(
       "1000-2000 r--p 00000010 00:00 0 /system/lib/fake1.so\n"