Add JVMTI agent to dump/reset JaCoCo coverage information

This agent can be attached to an arbitrary Android process with
arguments that cause it to either reset or dump the JaCoCo information
to a provided directory.

Test: manual, used examples in README to test whether it works on a
userdebug_coverage build on cuttlefish

Change-Id: If6cee20046f790676b8085e1ca84652c063295fa

3 files changed, 318 insertions, 0 deletions

diff --git a/tools/dump-coverage/Android.bp b/tools/dump-coverage/Android.bp
new file mode 100644
index 000000000000..4519ce3636bf
--- /dev/null
+++ b/tools/dump-coverage/Android.bp
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+//
+// 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.
+//
+
+// Build variants {target,host} x {32,64}
+cc_library {
+    name: "libdumpcoverage",
+    srcs: ["dump_coverage.cc"],
+    header_libs: [
+        "libopenjdkjvmti_headers",
+    ],
+
+    host_supported: true,
+    shared_libs: [
+        "libbase",
+    ],
+}
diff --git a/tools/dump-coverage/README.md b/tools/dump-coverage/README.md
new file mode 100644
index 000000000000..2bab4bc8c984
--- /dev/null
+++ b/tools/dump-coverage/README.md
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+# dumpcoverage
+
+libdumpcoverage.so is a JVMTI agent designed to dump coverage information for a process, where the binaries have been instrumented by JaCoCo. JaCoCo automatically starts recording data on process start, and we need a way to trigger the resetting or dumping of this data.
+
+The JVMTI agent is used to make the calls to JaCoCo in its process.
+
+# Usage
+
+Note that these examples assume you have an instrumented build (userdebug_coverage). Here is, for example, how to dump coverage information regarding the default clock app. First some setup is necessary:
+
+```
+adb root # necessary to copy files in/out of the /data/data/{package} folder
+adb shell 'mkdir /data/data/com.android.deskclock/folder-to-use'
+```
+
+Then we can run the command to dump the data:
+
+```
+adb shell 'am attach-agent com.android.deskclock /system/lib/libdumpcoverage.so=dump:/data/data/com.android.deskclock/folder-to-use'
+```
+
+We can also reset the coverage information with
+
+```
+adb shell 'am attach-agent com.android.deskclock /system/lib/libdumpcoverage.so=reset'
+```
+
+then perform more actions, then dump the data again. To get the files, we can get
+
+```
+adb pull /data/data/com.android.deskclock/folder-to-use ~/path-on-your-computer
+```
+
+And you should have timestamped `.exec` files on your machine under the folder `~/path-on-your-computer`
+
+# Details
+
+In dump mode, the agent makes JNI calls equivalent to
+
+```
+Agent.getInstance().getExecutionData(/*reset = */ false);
+```
+
+and then saves the result to a file specified by the passed in directory
+
+In reset mode, it makes a JNI call equivalent to
+
+```
+Agent.getInstance().reset();
+```
diff --git a/tools/dump-coverage/dump_coverage.cc b/tools/dump-coverage/dump_coverage.cc
new file mode 100644
index 000000000000..3de1865b8018
--- /dev/null
+++ b/tools/dump-coverage/dump_coverage.cc
@@ -0,0 +1,239 @@
+// Copyright (C) 2018 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 <android-base/logging.h>
+#include <jni.h>
+#include <jvmti.h>
+#include <string.h>
+
+#include <atomic>
+#include <ctime>
+#include <fstream>
+#include <iomanip>
+#include <iostream>
+#include <istream>
+#include <memory>
+#include <sstream>
+#include <string>
+#include <vector>
+
+using std::get;
+using std::tuple;
+using std::chrono::system_clock;
+
+namespace dump_coverage {
+
+#define CHECK_JVMTI(x) CHECK_EQ((x), JVMTI_ERROR_NONE)
+#define CHECK_NOTNULL(x) CHECK((x) != nullptr)
+#define CHECK_NO_EXCEPTION(env) CHECK(!(env)->ExceptionCheck());
+
+static JavaVM* java_vm = nullptr;
+
+// Get the current JNI environment.
+static JNIEnv* GetJNIEnv() {
+  JNIEnv* env = nullptr;
+  CHECK_EQ(java_vm->GetEnv(reinterpret_cast<void**>(&env), JNI_VERSION_1_6),
+           JNI_OK);
+  return env;
+}
+
+// Get the JaCoCo Agent class and an instance of the class, given a JNI
+// environment.
+// Will crash if the Agent isn't found or if any Java Exception occurs.
+static tuple<jclass, jobject> GetJavaAgent(JNIEnv* env) {
+  jclass java_agent_class =
+      env->FindClass("org/jacoco/agent/rt/internal/Agent");
+  CHECK_NOTNULL(java_agent_class);
+
+  jmethodID java_agent_get_instance =
+      env->GetStaticMethodID(java_agent_class, "getInstance",
+                             "()Lorg/jacoco/agent/rt/internal/Agent;");
+  CHECK_NOTNULL(java_agent_get_instance);
+
+  jobject java_agent_instance =
+      env->CallStaticObjectMethod(java_agent_class, java_agent_get_instance);
+  CHECK_NO_EXCEPTION(env);
+  CHECK_NOTNULL(java_agent_instance);
+
+  return tuple(java_agent_class, java_agent_instance);
+}
+
+// Runs equivalent of Agent.getInstance().getExecutionData(false) and returns
+// the result.
+// Will crash if the Agent isn't found or if any Java Exception occurs.
+static jbyteArray GetExecutionData(JNIEnv* env) {
+  auto java_agent = GetJavaAgent(env);
+  jmethodID java_agent_get_execution_data =
+      env->GetMethodID(get<0>(java_agent), "getExecutionData", "(Z)[B");
+  CHECK_NO_EXCEPTION(env);
+  CHECK_NOTNULL(java_agent_get_execution_data);
+
+  jbyteArray java_result_array = (jbyteArray)env->CallObjectMethod(
+      get<1>(java_agent), java_agent_get_execution_data, false);
+  CHECK_NO_EXCEPTION(env);
+
+  return java_result_array;
+}
+
+// Gets the filename to write execution data to
+//  dirname: the directory in which to place the file
+//  outputs <dirname>/YYYY-MM-DD-HH-MM-SS.SSS.exec
+static std::string GetFilename(const std::string& dirname) {
+  system_clock::time_point time_point = system_clock::now();
+  auto seconds = std::chrono::time_point_cast<std::chrono::seconds>(time_point);
+  auto fractional_time = time_point - seconds;
+  auto millis = std::chrono::duration_cast<std::chrono::milliseconds>(fractional_time);
+
+  std::time_t time = system_clock::to_time_t(time_point);
+  auto tm = *std::gmtime(&time);
+
+  std::ostringstream oss;
+  oss
+    << dirname
+    << "/"
+    << std::put_time(&tm, "%Y-%m-%d-%H-%M-%S.")
+    << std::setfill('0') << std::setw(3) << millis.count()
+    << ".ec";
+  return oss.str();
+}
+
+// Writes the execution data to a file
+//  data, length: represent the data, as a sequence of bytes
+//  dirname: directory name to contain the file
+//  returns JNI_ERR if there is an error in writing the file, otherwise JNI_OK.
+static jint WriteFile(const char* data, int length, const std::string& dirname) {
+  auto filename = GetFilename(dirname);
+
+  LOG(INFO) << "Writing file of length " << length << " to '" << filename
+            << "'";
+  std::ofstream file(filename, std::ios::binary);
+
+  if (!file.is_open()) {
+    LOG(ERROR) << "Could not open file: '" << filename << "'";
+    return JNI_ERR;
+  }
+  file.write(data, length);
+  file.close();
+
+  if (!file) {
+    LOG(ERROR) << "I/O error in reading file";
+    return JNI_ERR;
+  }
+
+  LOG(INFO) << "Done writing file";
+  return JNI_OK;
+}
+
+// Grabs execution data and writes it to a file
+//  dirname: directory name to contain the file
+//  returns JNI_ERR if there is an error writing the file.
+// Will crash if the Agent isn't found or if any Java Exception occurs.
+static jint Dump(const std::string& dirname) {
+  LOG(INFO) << "Dumping file";
+
+  JNIEnv* env = GetJNIEnv();
+  jbyteArray java_result_array = GetExecutionData(env);
+  CHECK_NOTNULL(java_result_array);
+
+  jbyte* result_ptr = env->GetByteArrayElements(java_result_array, 0);
+  CHECK_NOTNULL(result_ptr);
+
+  int result_len = env->GetArrayLength(java_result_array);
+
+  return WriteFile((const char*) result_ptr, result_len, dirname);
+}
+
+// Resets execution data, performing the equivalent of
+//  Agent.getInstance().reset();
+//  args: should be empty
+//  returns JNI_ERR if the arguments are invalid.
+// Will crash if the Agent isn't found or if any Java Exception occurs.
+static jint Reset(const std::string& args) {
+  if (args != "") {
+    LOG(ERROR) << "reset takes no arguments, but received '" << args << "'";
+    return JNI_ERR;
+  }
+
+  JNIEnv* env = GetJNIEnv();
+  auto java_agent = GetJavaAgent(env);
+
+  jmethodID java_agent_reset =
+      env->GetMethodID(get<0>(java_agent), "reset", "()V");
+  CHECK_NOTNULL(java_agent_reset);
+
+  env->CallVoidMethod(get<1>(java_agent), java_agent_reset);
+  CHECK_NO_EXCEPTION(env);
+  return JNI_OK;
+}
+
+// Given a string of the form "<a>:<b>" returns (<a>, <b>).
+// Given a string <a> that doesn't contain a colon, returns (<a>, "").
+static tuple<std::string, std::string> SplitOnColon(const std::string& options) {
+  size_t loc_delim = options.find(':');
+  std::string command, args;
+
+  if (loc_delim == std::string::npos) {
+    command = options;
+  } else {
+    command = options.substr(0, loc_delim);
+    args = options.substr(loc_delim + 1, options.length());
+  }
+  return tuple(command, args);
+}
+
+// Parses and executes a command specified by options of the form
+// "<command>:<args>" where <command> is either "dump" or "reset".
+static jint ParseOptionsAndExecuteCommand(const std::string& options) {
+  auto split = SplitOnColon(options);
+  auto command = get<0>(split), args = get<1>(split);
+
+  LOG(INFO) << "command: '" << command << "' args: '" << args << "'";
+
+  if (command == "dump") {
+    return Dump(args);
+  }
+
+  if (command == "reset") {
+    return Reset(args);
+  }
+
+  LOG(ERROR) << "Invalid command: expected 'dump' or 'reset' but was '"
+             << command << "'";
+  return JNI_ERR;
+}
+
+static jint AgentStart(JavaVM* vm, char* options) {
+  android::base::InitLogging(/* argv= */ nullptr);
+  java_vm = vm;
+
+  return ParseOptionsAndExecuteCommand(options);
+}
+
+// Late attachment (e.g. 'am attach-agent').
+extern "C" JNIEXPORT jint JNICALL
+Agent_OnAttach(JavaVM* vm, char* options, void* reserved ATTRIBUTE_UNUSED) {
+  return AgentStart(vm, options);
+}
+
+// Early attachment.
+extern "C" JNIEXPORT jint JNICALL
+Agent_OnLoad(JavaVM* jvm ATTRIBUTE_UNUSED, char* options ATTRIBUTE_UNUSED, void* reserved ATTRIBUTE_UNUSED) {
+  LOG(ERROR)
+    << "The dumpcoverage agent will not work on load,"
+    << " as it does not have access to the runtime.";
+  return JNI_ERR;
+}
+
+}  // namespace dump_coverage