Snap for 7508253 from 2218a7229a48b3fe97a4054e0875327f768ab64a to s-keystone-qcom-release

Change-Id: I31e87662f49ec0ed9b8b82276d8e986b7208e002

13 files changed, 678 insertions, 226 deletions

diff --git a/aosp/update_attempter_android.cc b/aosp/update_attempter_android.cc
index ba61f255..4636c430 100644
--- a/aosp/update_attempter_android.cc
+++ b/aosp/update_attempter_android.cc
@@ -364,6 +364,12 @@ bool UpdateAttempterAndroid::ResetStatus(brillo::ErrorPtr* error) {
   LOG(INFO) << "Attempting to reset state from "
             << UpdateStatusToString(status_) << " to UpdateStatus::IDLE";
 
+  if (apex_handler_android_ != nullptr) {
+    LOG(INFO) << "Cleaning up reserved space for compressed APEX (if any)";
+    std::vector<ApexInfo> apex_infos_blank;
+    apex_handler_android_->AllocateSpace(apex_infos_blank);
+  }
+
   switch (status_) {
     case UpdateStatus::IDLE: {
       if (!boot_control_->GetDynamicPartitionControl()->ResetUpdate(prefs_)) {
@@ -884,20 +890,25 @@ void UpdateAttempterAndroid::UpdatePrefsAndReportUpdateMetricsOnReboot() {
   string current_version =
       android::base::GetProperty("ro.build.version.incremental", "");
   TEST_AND_RETURN(!current_version.empty());
+  const auto current_slot = boot_control_->GetCurrentSlot();
 
   // If there's no record of previous version (e.g. due to a data wipe), we
   // save the info of current boot and skip the metrics report.
   if (!prefs_->Exists(kPrefsPreviousVersion)) {
     prefs_->SetString(kPrefsBootId, current_boot_id);
     prefs_->SetString(kPrefsPreviousVersion, current_version);
+    prefs_->SetInt64(std::string{kPrefsPreviousSlot},
+                     boot_control_->GetCurrentSlot());
     ClearMetricsPrefs();
     return;
   }
+  int64_t previous_slot = -1;
+  prefs_->GetInt64(kPrefsPreviousSlot, &previous_slot);
   string previous_version;
-  // update_engine restarted under the same build.
+  // update_engine restarted under the same build and same slot.
   // TODO(xunchang) identify and report rollback by checking UpdateMarker.
   if (prefs_->GetString(kPrefsPreviousVersion, &previous_version) &&
-      previous_version == current_version) {
+      previous_version == current_version && previous_slot == current_slot) {
     string last_boot_id;
     bool is_reboot = prefs_->Exists(kPrefsBootId) &&
                      (prefs_->GetString(kPrefsBootId, &last_boot_id) &&
@@ -917,6 +928,8 @@ void UpdateAttempterAndroid::UpdatePrefsAndReportUpdateMetricsOnReboot() {
   // TODO(xunchang) check the build version is larger than the previous one.
   prefs_->SetString(kPrefsBootId, current_boot_id);
   prefs_->SetString(kPrefsPreviousVersion, current_version);
+  prefs_->SetInt64(std::string{kPrefsPreviousSlot},
+                   boot_control_->GetCurrentSlot());
 
   bool previous_attempt_exists = prefs_->Exists(kPrefsPayloadAttemptNumber);
   // |kPrefsPayloadAttemptNumber| should be cleared upon successful update.
diff --git a/aosp/update_attempter_android_unittest.cc b/aosp/update_attempter_android_unittest.cc
index f799df3e..f73df168 100644
--- a/aosp/update_attempter_android_unittest.cc
+++ b/aosp/update_attempter_android_unittest.cc
@@ -24,6 +24,7 @@
 #include <base/time/time.h>
 #include <gtest/gtest.h>
 
+#include "common/constants.h"
 #include "update_engine/aosp/daemon_state_android.h"
 #include "update_engine/common/fake_boot_control.h"
 #include "update_engine/common/fake_clock.h"
@@ -81,6 +82,8 @@ TEST_F(UpdateAttempterAndroidTest, UpdatePrefsSameBuildVersionOnInit) {
   prefs_.SetString(kPrefsPreviousVersion, build_version);
   prefs_.SetString(kPrefsBootId, "oldboot");
   prefs_.SetInt64(kPrefsNumReboots, 1);
+  prefs_.SetInt64(kPrefsPreviousSlot, 1);
+  boot_control_.SetCurrentSlot(1);
 
   EXPECT_CALL(*metrics_reporter_, ReportTimeToReboot(_)).Times(0);
   update_attempter_android_.Init();
@@ -88,15 +91,15 @@ TEST_F(UpdateAttempterAndroidTest, UpdatePrefsSameBuildVersionOnInit) {
   // Check that the boot_id and reboot_count are updated.
   std::string boot_id;
   utils::GetBootId(&boot_id);
-  EXPECT_TRUE(prefs_.Exists(kPrefsBootId));
+  ASSERT_TRUE(prefs_.Exists(kPrefsBootId));
   std::string prefs_boot_id;
-  EXPECT_TRUE(prefs_.GetString(kPrefsBootId, &prefs_boot_id));
-  EXPECT_EQ(boot_id, prefs_boot_id);
+  ASSERT_TRUE(prefs_.GetString(kPrefsBootId, &prefs_boot_id));
+  ASSERT_EQ(boot_id, prefs_boot_id);
 
-  EXPECT_TRUE(prefs_.Exists(kPrefsNumReboots));
+  ASSERT_TRUE(prefs_.Exists(kPrefsNumReboots));
   int64_t reboot_count;
-  EXPECT_TRUE(prefs_.GetInt64(kPrefsNumReboots, &reboot_count));
-  EXPECT_EQ(2, reboot_count);
+  ASSERT_TRUE(prefs_.GetInt64(kPrefsNumReboots, &reboot_count));
+  ASSERT_EQ(2, reboot_count);
 }
 
 TEST_F(UpdateAttempterAndroidTest, UpdatePrefsBuildVersionChangeOnInit) {
diff --git a/common/constants.cc b/common/constants.cc
index a9cf238d..0677e663 100644
--- a/common/constants.cc
+++ b/common/constants.cc
@@ -112,6 +112,7 @@ const char kPrefsWallClockScatteringWaitPeriod[] = "wall-clock-wait-period";
 const char kPrefsWallClockStagingWaitPeriod[] =
     "wall-clock-staging-wait-period";
 const char kPrefsManifestBytes[] = "manifest-bytes";
+const char kPrefsPreviousSlot[] = "previous-slot";
 
 // These four fields are generated by scripts/brillo_update_payload.
 const char kPayloadPropertyFileSize[] = "FILE_SIZE";
diff --git a/common/constants.h b/common/constants.h
index 64447cea..68f720db 100644
--- a/common/constants.h
+++ b/common/constants.h
@@ -76,6 +76,7 @@ extern const char kPrefsPingLastRollcall[];
 extern const char kPrefsLastFp[];
 extern const char kPrefsPostInstallSucceeded[];
 extern const char kPrefsPreviousVersion[];
+extern const char kPrefsPreviousSlot[];
 extern const char kPrefsResumedUpdateFailures[];
 extern const char kPrefsRollbackHappened[];
 extern const char kPrefsRollbackVersion[];
diff --git a/common/scoped_task_id.h b/common/scoped_task_id.h
new file mode 100644
index 00000000..91a29860
--- /dev/null
+++ b/common/scoped_task_id.h
@@ -0,0 +1,123 @@
+//
+// Copyright (C) 2021 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.
+//
+
+#ifndef UPDATE_ENGINE_SCOPED_TASK_ID_H_
+#define UPDATE_ENGINE_SCOPED_TASK_ID_H_
+
+#include <type_traits>
+#include <utility>
+
+#include <base/bind.h>
+#include <brillo/message_loops/message_loop.h>
+
+namespace chromeos_update_engine {
+
+// This class provides unique_ptr like semantic for |MessageLoop::TaskId|, when
+// instance of this class goes out of scope, underlying task will be cancelled.
+class ScopedTaskId {
+  using MessageLoop = brillo::MessageLoop;
+
+ public:
+  // Move only type similar to unique_ptr.
+  ScopedTaskId(const ScopedTaskId&) = delete;
+  ScopedTaskId& operator=(const ScopedTaskId&) = delete;
+
+  constexpr ScopedTaskId() = default;
+
+  constexpr ScopedTaskId(ScopedTaskId&& other) noexcept {
+    *this = std::move(other);
+  }
+
+  constexpr ScopedTaskId& operator=(ScopedTaskId&& other) noexcept {
+    std::swap(task_id_, other.task_id_);
+    return *this;
+  }
+
+  // Post a callback on current message loop, return true if succeeded, false if
+  // the previous callback hasn't run yet, or scheduling failed at MessageLoop
+  // side.
+  [[nodiscard]] bool PostTask(const base::Location& from_here,
+                              base::OnceClosure&& callback,
+                              base::TimeDelta delay = {}) noexcept {
+    return PostTask<decltype(callback)>(from_here, std::move(callback), delay);
+  }
+  [[nodiscard]] bool PostTask(const base::Location& from_here,
+                              std::function<void()>&& callback,
+                              base::TimeDelta delay = {}) noexcept {
+    return PostTask<decltype(callback)>(from_here, std::move(callback), delay);
+  }
+
+  ~ScopedTaskId() noexcept { Cancel(); }
+
+  // Cancel the underlying managed task, true if cancel successful. False if no
+  // task scheduled or task cancellation failed
+  bool Cancel() noexcept {
+    if (task_id_ != MessageLoop::kTaskIdNull) {
+      if (MessageLoop::current()->CancelTask(task_id_)) {
+        LOG(INFO) << "Cancelled task id " << task_id_;
+        task_id_ = MessageLoop::kTaskIdNull;
+        return true;
+      }
+    }
+    return false;
+  }
+
+  [[nodiscard]] constexpr bool IsScheduled() const noexcept {
+    return task_id_ != MessageLoop::kTaskIdNull;
+  }
+
+  [[nodiscard]] constexpr bool operator==(const ScopedTaskId& other) const
+      noexcept {
+    return other.task_id_ == task_id_;
+  }
+
+  [[nodiscard]] constexpr bool operator<(const ScopedTaskId& other) const
+      noexcept {
+    return task_id_ < other.task_id_;
+  }
+
+ private:
+  template <typename Callable>
+  [[nodiscard]] bool PostTask(const base::Location& from_here,
+                              Callable&& callback,
+                              base::TimeDelta delay) noexcept {
+    if (task_id_ != MessageLoop::kTaskIdNull) {
+      LOG(ERROR) << "Scheduling another task but task id " << task_id_
+                 << " isn't executed yet! This can cause the old task to leak.";
+      return false;
+    }
+    task_id_ = MessageLoop::current()->PostDelayedTask(
+        from_here,
+        base::BindOnce(&ScopedTaskId::ExecuteTask<decltype(callback)>,
+                       base::Unretained(this),
+                       std::move(callback)),
+        delay);
+    return task_id_ != MessageLoop::kTaskIdNull;
+  }
+  template <typename Callable>
+  void ExecuteTask(Callable&& callback) {
+    task_id_ = MessageLoop::kTaskIdNull;
+    if constexpr (std::is_same_v<Callable&&, base::OnceClosure&&>) {
+      std::move(callback).Run();
+    } else {
+      std::move(callback)();
+    }
+  }
+  MessageLoop::TaskId task_id_{MessageLoop::kTaskIdNull};
+};
+}  // namespace chromeos_update_engine
+
+#endif
diff --git a/payload_consumer/file_descriptor.cc b/payload_consumer/file_descriptor.cc
index 7c69c1b4..da76327c 100644
--- a/payload_consumer/file_descriptor.cc
+++ b/payload_consumer/file_descriptor.cc
@@ -139,7 +139,9 @@ bool EintrSafeFileDescriptor::Flush() {
 }
 
 bool EintrSafeFileDescriptor::Close() {
-  CHECK_GE(fd_, 0);
+  if (fd_ < 0) {
+    return false;
+  }
   // https://stackoverflow.com/questions/705454/does-linux-guarantee-the-contents-of-a-file-is-flushed-to-disc-after-close
   // |close()| doesn't imply |fsync()|, we need to do it manually.
   fsync(fd_);
diff --git a/payload_consumer/filesystem_verifier_action.cc b/payload_consumer/filesystem_verifier_action.cc
index b14cbc8d..22c8e0bd 100644
--- a/payload_consumer/filesystem_verifier_action.cc
+++ b/payload_consumer/filesystem_verifier_action.cc
@@ -35,6 +35,7 @@
 #include <brillo/secure_blob.h>
 #include <brillo/streams/file_stream.h>
 
+#include "common/error_code.h"
 #include "payload_generator/delta_diff_generator.h"
 #include "update_engine/common/utils.h"
 #include "update_engine/payload_consumer/file_descriptor.h"
@@ -77,6 +78,7 @@ namespace chromeos_update_engine {
 
 namespace {
 const off_t kReadFileBufferSize = 128 * 1024;
+constexpr float kVerityProgressPercent = 0.6;
 }  // namespace
 
 void FilesystemVerifierAction::PerformAction() {
@@ -102,7 +104,6 @@ void FilesystemVerifierAction::PerformAction() {
 }
 
 void FilesystemVerifierAction::TerminateProcessing() {
-  brillo::MessageLoop::current()->CancelTask(pending_task_id_);
   cancelled_ = true;
   Cleanup(ErrorCode::kSuccess);  // error code is ignored if canceled_ is true.
 }
@@ -134,11 +135,29 @@ void FilesystemVerifierAction::UpdateProgress(double progress) {
   }
 }
 
-bool FilesystemVerifierAction::InitializeFdVABC() {
+void FilesystemVerifierAction::UpdatePartitionProgress(double progress) {
+  // We don't consider sizes of each partition. Every partition
+  // has the same length on progress bar.
+  // TODO(b/186087589): Take sizes of each partition into account.
+  UpdateProgress((progress + partition_index_) /
+                 install_plan_.partitions.size());
+}
+
+bool FilesystemVerifierAction::InitializeFdVABC(bool should_write_verity) {
   const InstallPlan::Partition& partition =
       install_plan_.partitions[partition_index_];
 
-  if (!ShouldWriteVerity()) {
+  if (!should_write_verity) {
+    // In VABC, we cannot map/unmap partitions w/o first closing ALL fds first.
+    // Since this function might be called inside a ScheduledTask, the closure
+    // might have a copy of partition_fd_ when executing this function. Which
+    // means even if we do |partition_fd_.reset()| here, there's a chance that
+    // underlying fd isn't closed until we return. This is unacceptable, we need
+    // to close |partition_fd| right away.
+    if (partition_fd_) {
+      partition_fd_->Close();
+      partition_fd_.reset();
+    }
     // In VABC, if we are not writing verity, just map all partitions,
     // and read using regular fd on |postinstall_mount_device| .
     // All read will go through snapuserd, which provides a consistent
@@ -152,8 +171,6 @@ bool FilesystemVerifierAction::InitializeFdVABC() {
     dynamic_control_->MapAllPartitions();
     return InitializeFd(partition.readonly_target_path);
   }
-
-  // FilesystemVerifierAction need the read_fd_.
   partition_fd_ =
       dynamic_control_->OpenCowFd(partition.name, partition.source_path, true);
   if (!partition_fd_) {
@@ -180,6 +197,112 @@ bool FilesystemVerifierAction::InitializeFd(const std::string& part_path) {
   return true;
 }
 
+void FilesystemVerifierAction::WriteVerityAndHashPartition(
+    FileDescriptorPtr fd,
+    const off64_t start_offset,
+    const off64_t end_offset,
+    void* buffer,
+    const size_t buffer_size) {
+  if (start_offset >= end_offset) {
+    LOG_IF(WARNING, start_offset > end_offset)
+        << "start_offset is greater than end_offset : " << start_offset << " > "
+        << end_offset;
+    if (!verity_writer_->Finalize(fd, fd)) {
+      LOG(ERROR) << "Failed to write verity data";
+      Cleanup(ErrorCode::kVerityCalculationError);
+      return;
+    }
+    if (dynamic_control_->UpdateUsesSnapshotCompression()) {
+      // Spin up snapuserd to read fs.
+      if (!InitializeFdVABC(false)) {
+        LOG(ERROR) << "Failed to map all partitions";
+        Cleanup(ErrorCode::kFilesystemVerifierError);
+        return;
+      }
+    }
+    HashPartition(partition_fd_, 0, partition_size_, buffer, buffer_size);
+    return;
+  }
+  const auto cur_offset = fd->Seek(start_offset, SEEK_SET);
+  if (cur_offset != start_offset) {
+    PLOG(ERROR) << "Failed to seek to offset: " << start_offset;
+    Cleanup(ErrorCode::kVerityCalculationError);
+    return;
+  }
+  const auto read_size =
+      std::min<size_t>(buffer_size, end_offset - start_offset);
+  const auto bytes_read = fd->Read(buffer, read_size);
+  if (bytes_read < 0 || static_cast<size_t>(bytes_read) != read_size) {
+    PLOG(ERROR) << "Failed to read offset " << start_offset << " expected "
+                << read_size << " bytes, actual: " << bytes_read;
+    Cleanup(ErrorCode::kVerityCalculationError);
+    return;
+  }
+  if (!verity_writer_->Update(
+          start_offset, static_cast<const uint8_t*>(buffer), read_size)) {
+    LOG(ERROR) << "VerityWriter::Update() failed";
+    Cleanup(ErrorCode::kVerityCalculationError);
+    return;
+  }
+  UpdatePartitionProgress((start_offset + bytes_read) * 1.0f / partition_size_ *
+                          kVerityProgressPercent);
+  CHECK(pending_task_id_.PostTask(
+      FROM_HERE,
+      base::BindOnce(&FilesystemVerifierAction::WriteVerityAndHashPartition,
+                     base::Unretained(this),
+                     fd,
+                     start_offset + bytes_read,
+                     end_offset,
+                     buffer,
+                     buffer_size)));
+}
+
+void FilesystemVerifierAction::HashPartition(FileDescriptorPtr fd,
+                                             const off64_t start_offset,
+                                             const off64_t end_offset,
+                                             void* buffer,
+                                             const size_t buffer_size) {
+  if (start_offset >= end_offset) {
+    LOG_IF(WARNING, start_offset > end_offset)
+        << "start_offset is greater than end_offset : " << start_offset << " > "
+        << end_offset;
+    FinishPartitionHashing();
+    return;
+  }
+  const auto cur_offset = fd->Seek(start_offset, SEEK_SET);
+  if (cur_offset != start_offset) {
+    PLOG(ERROR) << "Failed to seek to offset: " << start_offset;
+    Cleanup(ErrorCode::kFilesystemVerifierError);
+    return;
+  }
+  const auto read_size =
+      std::min<size_t>(buffer_size, end_offset - start_offset);
+  const auto bytes_read = fd->Read(buffer, read_size);
+  if (bytes_read < 0 || static_cast<size_t>(bytes_read) != read_size) {
+    PLOG(ERROR) << "Failed to read offset " << start_offset << " expected "
+                << read_size << " bytes, actual: " << bytes_read;
+    Cleanup(ErrorCode::kFilesystemVerifierError);
+    return;
+  }
+  if (!hasher_->Update(buffer, read_size)) {
+    LOG(ERROR) << "Hasher updated failed on offset" << start_offset;
+    Cleanup(ErrorCode::kFilesystemVerifierError);
+    return;
+  }
+  const auto progress = (start_offset + bytes_read) * 1.0f / partition_size_;
+  UpdatePartitionProgress(progress * (1 - kVerityProgressPercent) +
+                          kVerityProgressPercent);
+  CHECK(pending_task_id_.PostTask(
+      FROM_HERE,
+      base::BindOnce(&FilesystemVerifierAction::HashPartition,
+                     base::Unretained(this),
+                     fd,
+                     start_offset + bytes_read,
+                     end_offset,
+                     buffer,
+                     buffer_size)));
+}
+
 void FilesystemVerifierAction::StartPartitionHashing() {
   if (partition_index_ == install_plan_.partitions.size()) {
     if (!install_plan_.untouched_dynamic_partitions.empty()) {
@@ -201,26 +324,14 @@ void FilesystemVerifierAction::StartPartitionHashing() {
   }
   const InstallPlan::Partition& partition =
       install_plan_.partitions[partition_index_];
-  string part_path;
-  switch (verifier_step_) {
-    case VerifierStep::kVerifySourceHash:
-      part_path = partition.source_path;
-      partition_size_ = partition.source_size;
-      break;
-    case VerifierStep::kVerifyTargetHash:
-      part_path = partition.target_path;
-      partition_size_ = partition.target_size;
-      break;
-  }
+  const auto& part_path = GetPartitionPath();
+  partition_size_ = GetPartitionSize();
 
   LOG(INFO) << "Hashing partition " << partition_index_ << " ("
             << partition.name << ") on device " << part_path;
   auto success = false;
-  if (dynamic_control_->UpdateUsesSnapshotCompression() &&
-      verifier_step_ == VerifierStep::kVerifyTargetHash &&
-      dynamic_control_->IsDynamicPartition(partition.name,
-                                           install_plan_.target_slot)) {
-    success = InitializeFdVABC();
+  if (IsVABC(partition)) {
+    success = InitializeFdVABC(ShouldWriteVerity());
   } else {
     if (part_path.empty()) {
       if (partition_size_ == 0) {
@@ -255,125 +366,61 @@ void FilesystemVerifierAction::StartPartitionHashing() {
     filesystem_data_end_ = partition.fec_offset;
   }
   if (ShouldWriteVerity()) {
+    LOG(INFO) << "Verity writes enabled on partition " << partition.name;
     if (!verity_writer_->Init(partition)) {
       LOG(INFO) << "Verity writes enabled on partition " << partition.name;
       Cleanup(ErrorCode::kVerityCalculationError);
       return;
     }
+    WriteVerityAndHashPartition(
+        partition_fd_, 0, filesystem_data_end_, buffer_.data(), buffer_.size());
   } else {
     LOG(INFO) << "Verity writes disabled on partition " << partition.name;
+    HashPartition(
+        partition_fd_, 0, partition_size_, buffer_.data(), buffer_.size());
   }
+}
 
-  // Start the first read.
-  ScheduleFileSystemRead();
+bool FilesystemVerifierAction::IsVABC(
+    const InstallPlan::Partition& partition) const {
+  return dynamic_control_->UpdateUsesSnapshotCompression() &&
+         verifier_step_ == VerifierStep::kVerifyTargetHash &&
+         dynamic_control_->IsDynamicPartition(partition.name,
+                                              install_plan_.target_slot);
 }
 
-bool FilesystemVerifierAction::ShouldWriteVerity() {
+const std::string& FilesystemVerifierAction::GetPartitionPath() const {
   const InstallPlan::Partition& partition =
       install_plan_.partitions[partition_index_];
-  return verifier_step_ == VerifierStep::kVerifyTargetHash &&
-         install_plan_.write_verity &&
-         (partition.hash_tree_size > 0 || partition.fec_size > 0);
-}
-
-void FilesystemVerifierAction::ReadVerityAndFooter() {
-  if (ShouldWriteVerity()) {
-    if (!verity_writer_->Finalize(partition_fd_, partition_fd_)) {
-      LOG(ERROR) << "Failed to write hashtree/FEC data.";
-      Cleanup(ErrorCode::kFilesystemVerifierError);
-      return;
-    }
-  }
-  // Since we handed our |read_fd_| to verity_writer_ during |Finalize()|
-  // call, fd's position could have been changed. Re-seek.
-  partition_fd_->Seek(filesystem_data_end_, SEEK_SET);
-  auto bytes_to_read = partition_size_ - filesystem_data_end_;
-  while (bytes_to_read > 0) {
-    const auto read_size = std::min<size_t>(buffer_.size(), bytes_to_read);
-    auto bytes_read = partition_fd_->Read(buffer_.data(), read_size);
-    if (bytes_read <= 0) {
-      PLOG(ERROR) << "Failed to read hash tree " << bytes_read;
-      Cleanup(ErrorCode::kFilesystemVerifierError);
-      return;
-    }
-    if (!hasher_->Update(buffer_.data(), bytes_read)) {
-      LOG(ERROR) << "Unable to update the hash.";
-      Cleanup(ErrorCode::kError);
-      return;
-    }
-    bytes_to_read -= bytes_read;
+  switch (verifier_step_) {
+    case VerifierStep::kVerifySourceHash:
+      return partition.source_path;
+    case VerifierStep::kVerifyTargetHash:
+      if (IsVABC(partition)) {
+        return partition.readonly_target_path;
+      } else {
+        return partition.target_path;
+      }
   }
-  FinishPartitionHashing();
 }
 
-void FilesystemVerifierAction::ScheduleFileSystemRead() {
-  // We can only start reading anything past |hash_tree_offset| after we have
-  // already read all the data blocks that the hash tree covers. The same
-  // applies to FEC.
-
-  size_t bytes_to_read = std::min(static_cast<uint64_t>(buffer_.size()),
-                                  filesystem_data_end_ - offset_);
-  if (!bytes_to_read) {
-    ReadVerityAndFooter();
-    return;
-  }
-  partition_fd_->Seek(offset_, SEEK_SET);
-  auto bytes_read = partition_fd_->Read(buffer_.data(), bytes_to_read);
-  if (bytes_read < 0) {
-    LOG(ERROR) << "Unable to schedule an asynchronous read from the stream. "
-               << bytes_read;
-    Cleanup(ErrorCode::kError);
-  } else {
-    // We could just invoke |OnReadDoneCallback()|, it works. But |PostTask|
-    // is used so that users can cancel updates.
-    pending_task_id_ = brillo::MessageLoop::current()->PostTask(
-        base::Bind(&FilesystemVerifierAction::OnReadDone,
-                   base::Unretained(this),
-                   bytes_read));
+size_t FilesystemVerifierAction::GetPartitionSize() const {
+  const InstallPlan::Partition& partition =
+      install_plan_.partitions[partition_index_];
+  switch (verifier_step_) {
+    case VerifierStep::kVerifySourceHash:
+      return partition.source_size;
+    case VerifierStep::kVerifyTargetHash:
+      return partition.target_size;
   }
 }
 
-void FilesystemVerifierAction::OnReadDone(size_t bytes_read) {
-  if (cancelled_) {
-    Cleanup(ErrorCode::kError);
-    return;
-  }
-  if (bytes_read == 0) {
-    LOG(ERROR) << "Failed to read the remaining " << partition_size_ - offset_
-               << " bytes from partition "
-               << install_plan_.partitions[partition_index_].name;
-    Cleanup(ErrorCode::kFilesystemVerifierError);
-    return;
-  }
-
-  if (!hasher_->Update(buffer_.data(), bytes_read)) {
-    LOG(ERROR) << "Unable to update the hash.";
-    Cleanup(ErrorCode::kError);
-    return;
-  }
-
-  // WE don't consider sizes of each partition. Every partition
-  // has the same length on progress bar.
-  // TODO(zhangkelvin) Take sizes of each partition into account
-
-  UpdateProgress(
-      (static_cast<double>(offset_) / partition_size_ + partition_index_) /
-      install_plan_.partitions.size());
-  if (ShouldWriteVerity()) {
-    if (!verity_writer_->Update(offset_, buffer_.data(), bytes_read)) {
-      LOG(ERROR) << "Unable to update verity";
-      Cleanup(ErrorCode::kVerityCalculationError);
-      return;
-    }
-  }
-
-  offset_ += bytes_read;
-  if (offset_ == filesystem_data_end_) {
-    ReadVerityAndFooter();
-    return;
-  }
-
-  ScheduleFileSystemRead();
+bool FilesystemVerifierAction::ShouldWriteVerity() {
+  const InstallPlan::Partition& partition =
+      install_plan_.partitions[partition_index_];
+  return verifier_step_ == VerifierStep::kVerifyTargetHash &&
+         install_plan_.write_verity &&
+         (partition.hash_tree_size > 0 || partition.fec_size > 0);
 }
 
 void FilesystemVerifierAction::FinishPartitionHashing() {
@@ -447,6 +494,7 @@ void FilesystemVerifierAction::FinishPartitionHashing() {
   hasher_.reset();
   buffer_.clear();
   if (partition_fd_) {
+    partition_fd_->Close();
     partition_fd_.reset();
   }
   StartPartitionHashing();
diff --git a/payload_consumer/filesystem_verifier_action.h b/payload_consumer/filesystem_verifier_action.h
index 78634cb3..850abdad 100644
--- a/payload_consumer/filesystem_verifier_action.h
+++ b/payload_consumer/filesystem_verifier_action.h
@@ -22,12 +22,14 @@
 
 #include <memory>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include <brillo/message_loops/message_loop.h>
 
 #include "update_engine/common/action.h"
 #include "update_engine/common/hash_calculator.h"
+#include "update_engine/common/scoped_task_id.h"
 #include "update_engine/payload_consumer/file_descriptor.h"
 #include "update_engine/payload_consumer/install_plan.h"
 #include "update_engine/payload_consumer/verity_writer_interface.h"
@@ -84,6 +86,16 @@ class FilesystemVerifierAction : public InstallPlanAction {
 
  private:
   friend class FilesystemVerifierActionTestDelegate;
+  void WriteVerityAndHashPartition(FileDescriptorPtr fd,
+                                   const off64_t start_offset,
+                                   const off64_t end_offset,
+                                   void* buffer,
+                                   const size_t buffer_size);
+  void HashPartition(FileDescriptorPtr fd,
+                     const off64_t start_offset,
+                     const off64_t end_offset,
+                     void* buffer,
+                     const size_t buffer_size);
 
   // Return true if we need to write verity bytes.
   bool ShouldWriteVerity();
@@ -91,16 +103,11 @@ class FilesystemVerifierAction : public InstallPlanAction {
   // remaining to be hashed, it finishes the action.
   void StartPartitionHashing();
 
-  // Schedules the asynchronous read of the filesystem part of this
-  // partition(not including hashtree/verity).
-  void ScheduleFileSystemRead();
+  const std::string& GetPartitionPath() const;
 
-  // Read the verity part of this partition.(hash tree and FEC)
-  void ReadVerityAndFooter();
+  bool IsVABC(const InstallPlan::Partition& partition) const;
 
-  // Called from the main loop when a single read from |src_stream_| succeeds or
-  // fails, calling OnReadDoneCallback() and OnReadErrorCallback() respectively.
-  void OnReadDone(size_t bytes_read);
+  size_t GetPartitionSize() const;
 
   // When the read is done, finalize the hash checking of the current partition
   // and continue checking the next one.
@@ -114,9 +121,13 @@ class FilesystemVerifierAction : public InstallPlanAction {
   // Invoke delegate callback to report progress, if delegate is not null
   void UpdateProgress(double progress);
 
+  // Updates progress of current partition. |progress| should be in range [0,
+  // 1], and it will be scaled appropriately with # of partitions.
+  void UpdatePartitionProgress(double progress);
+
   // Initialize read_fd_ and write_fd_
   bool InitializeFd(const std::string& part_path);
-  bool InitializeFdVABC();
+  bool InitializeFdVABC(bool should_write_verity);
 
   // The type of the partition that we are verifying.
   VerifierStep verifier_step_ = VerifierStep::kVerifyTargetHash;
@@ -161,8 +172,7 @@ class FilesystemVerifierAction : public InstallPlanAction {
 
   // Callback that should be cancelled on |TerminateProcessing|. Usually this
   // points to pending read callbacks from async stream.
-  brillo::MessageLoop::TaskId pending_task_id_{
-      brillo::MessageLoop::kTaskIdNull};
+  ScopedTaskId pending_task_id_;
 
   DISALLOW_COPY_AND_ASSIGN(FilesystemVerifierAction);
 };
diff --git a/payload_consumer/filesystem_verifier_action_unittest.cc b/payload_consumer/filesystem_verifier_action_unittest.cc
index 586662d9..f2f29547 100644
--- a/payload_consumer/filesystem_verifier_action_unittest.cc
+++ b/payload_consumer/filesystem_verifier_action_unittest.cc
@@ -16,6 +16,8 @@
 
 #include "update_engine/payload_consumer/filesystem_verifier_action.h"
 
+#include <algorithm>
+#include <cstring>
 #include <memory>
 #include <string>
 #include <utility>
@@ -25,8 +27,10 @@
 #include <brillo/message_loops/fake_message_loop.h>
 #include <brillo/message_loops/message_loop_utils.h>
 #include <brillo/secure_blob.h>
+#include <fec/ecc.h>
 #include <gtest/gtest.h>
 #include <libsnapshot/snapshot_writer.h>
+#include <sys/stat.h>
 
 #include "update_engine/common/dynamic_partition_control_stub.h"
 #include "update_engine/common/hash_calculator.h"
@@ -35,6 +39,7 @@
 #include "update_engine/common/utils.h"
 #include "update_engine/payload_consumer/fake_file_descriptor.h"
 #include "update_engine/payload_consumer/install_plan.h"
+#include "update_engine/payload_consumer/verity_writer_android.h"
 
 using brillo::MessageLoop;
 using std::string;
@@ -50,19 +55,46 @@ namespace chromeos_update_engine {
 class FilesystemVerifierActionTest : public ::testing::Test {
  public:
   static constexpr size_t BLOCK_SIZE = 4096;
+  // We use SHA256 for testing, so hash size is 256bits / 8
+  static constexpr size_t HASH_SIZE = 256 / 8;
   static constexpr size_t PARTITION_SIZE = BLOCK_SIZE * 1024;
+  static constexpr size_t HASH_TREE_START_OFFSET = 800 * BLOCK_SIZE;
+  size_t hash_tree_size = 0;
+  size_t fec_start_offset = 0;
+  size_t fec_data_size = 0;
+  static constexpr size_t FEC_ROOTS = 2;
+  size_t fec_rounds = 0;
+  size_t fec_size = 0;
 
  protected:
   void SetUp() override {
+    hash_tree_size = HashTreeBuilder::CalculateSize(
+        HASH_TREE_START_OFFSET, BLOCK_SIZE, HASH_SIZE);
+    fec_start_offset = HASH_TREE_START_OFFSET + hash_tree_size;
+    fec_data_size = fec_start_offset;
+    static constexpr size_t FEC_ROOTS = 2;
+    fec_rounds =
+        utils::DivRoundUp(fec_data_size / BLOCK_SIZE, FEC_RSM - FEC_ROOTS);
+    fec_size = fec_rounds * FEC_ROOTS * BLOCK_SIZE;
+
+    fec_data_.resize(fec_size);
+    hash_tree_data_.resize(hash_tree_size);
+    // Globally readable writable, as we want to write data
+    ASSERT_EQ(0, fchmod(source_part_.fd(), 0666))
+        << " Failed to set " << source_part_.path() << " as writable "
+        << strerror(errno);
+    ASSERT_EQ(0, fchmod(target_part_.fd(), 0666))
+        << " Failed to set " << target_part_.path() << " as writable "
+        << strerror(errno);
     brillo::Blob part_data(PARTITION_SIZE);
     test_utils::FillWithData(&part_data);
     ASSERT_TRUE(utils::WriteFile(
-        source_part.path().c_str(), part_data.data(), part_data.size()));
-    // FillWithData() will will with different data next call. We want
+        source_part_.path().c_str(), part_data.data(), part_data.size()));
+    // FillWithData() will fill with different data next call. We want
     // source/target partitions to contain different data for testing.
     test_utils::FillWithData(&part_data);
     ASSERT_TRUE(utils::WriteFile(
-        target_part.path().c_str(), part_data.data(), part_data.size()));
+        target_part_.path().c_str(), part_data.data(), part_data.size()));
     loop_.SetAsCurrent();
   }
 
@@ -70,6 +102,8 @@ class FilesystemVerifierActionTest : public ::testing::Test {
     EXPECT_EQ(0, brillo::MessageLoopRunMaxIterations(&loop_, 1));
   }
 
+  void DoTestVABC(bool clear_target_hash, bool enable_verity);
+
   // Returns true iff test has completed successfully.
   bool DoTest(bool terminate_early, bool hash_fail);
 
@@ -81,29 +115,105 @@ class FilesystemVerifierActionTest : public ::testing::Test {
                                            std::string name = "fake_part") {
     InstallPlan::Partition& part = install_plan->partitions.emplace_back();
     part.name = name;
-    part.target_path = target_part.path();
+    part.target_path = target_part_.path();
     part.readonly_target_path = part.target_path;
     part.target_size = PARTITION_SIZE;
     part.block_size = BLOCK_SIZE;
-    part.source_path = source_part.path();
+    part.source_path = source_part_.path();
+    part.source_size = PARTITION_SIZE;
     EXPECT_TRUE(
-        HashCalculator::RawHashOfFile(source_part.path(), &part.source_hash));
+        HashCalculator::RawHashOfFile(source_part_.path(), &part.source_hash));
     EXPECT_TRUE(
-        HashCalculator::RawHashOfFile(target_part.path(), &part.target_hash));
+        HashCalculator::RawHashOfFile(target_part_.path(), &part.target_hash));
     return &part;
   }
+  static void ZeroRange(FileDescriptorPtr fd,
+                        size_t start_block,
+                        size_t num_blocks) {
+    std::vector<unsigned char> buffer(BLOCK_SIZE);
+    ASSERT_EQ((ssize_t)(start_block * BLOCK_SIZE),
+              fd->Seek(start_block * BLOCK_SIZE, SEEK_SET));
+    for (size_t i = 0; i < num_blocks; i++) {
+      ASSERT_TRUE(utils::WriteAll(fd, buffer.data(), buffer.size()));
+    }
+  }
+
+  void SetHashWithVerity(InstallPlan::Partition* partition) {
+    partition->hash_tree_algorithm = "sha256";
+    partition->hash_tree_size = hash_tree_size;
+    partition->hash_tree_offset = HASH_TREE_START_OFFSET;
+    partition->hash_tree_data_offset = 0;
+    partition->hash_tree_data_size = HASH_TREE_START_OFFSET;
+    partition->fec_size = fec_size;
+    partition->fec_offset = fec_start_offset;
+    partition->fec_data_offset = 0;
+    partition->fec_data_size = fec_data_size;
+    partition->fec_roots = FEC_ROOTS;
+    VerityWriterAndroid verity_writer;
+    ASSERT_TRUE(verity_writer.Init(*partition));
+    LOG(INFO) << "Opening " << partition->readonly_target_path;
+    auto fd = std::make_shared<EintrSafeFileDescriptor>();
+    ASSERT_TRUE(fd->Open(partition->readonly_target_path.c_str(), O_RDWR))
+        << "Failed to open " << partition->target_path.c_str() << " "
+        << strerror(errno);
+    std::vector<unsigned char> buffer(BLOCK_SIZE);
+    // Only need to read up to hash tree
+    auto bytes_to_read = HASH_TREE_START_OFFSET;
+    auto offset = 0;
+    while (bytes_to_read > 0) {
+      const auto bytes_read = fd->Read(
+          buffer.data(), std::min<size_t>(buffer.size(), bytes_to_read));
+      ASSERT_GT(bytes_read, 0)
+          << "offset: " << offset << " bytes to read: " << bytes_to_read
+          << " error: " << strerror(errno);
+      ASSERT_TRUE(verity_writer.Update(offset, buffer.data(), bytes_read));
+      bytes_to_read -= bytes_read;
+      offset += bytes_read;
+    }
+    ASSERT_TRUE(verity_writer.Finalize(fd, fd));
+    ASSERT_TRUE(fd->IsOpen());
+    ASSERT_TRUE(HashCalculator::RawHashOfFile(target_part_.path(),
+                                              &partition->target_hash));
+
+    ASSERT_TRUE(fd->Seek(HASH_TREE_START_OFFSET, SEEK_SET));
+    ASSERT_EQ(fd->Read(hash_tree_data_.data(), hash_tree_data_.size()),
+              static_cast<ssize_t>(hash_tree_data_.size()))
+        << "Failed to read hashtree " << strerror(errno);
+    ASSERT_TRUE(fd->Seek(fec_start_offset, SEEK_SET));
+    ASSERT_EQ(fd->Read(fec_data_.data(), fec_data_.size()),
+              static_cast<ssize_t>(fec_data_.size()))
+        << "Failed to read FEC " << strerror(errno);
+    // Fs verification action is expected to write them, so clear verity data to
+    // ensure that they are re-created correctly.
+    ZeroRange(
+        fd, HASH_TREE_START_OFFSET / BLOCK_SIZE, hash_tree_size / BLOCK_SIZE);
+    ZeroRange(fd, fec_start_offset / BLOCK_SIZE, fec_size / BLOCK_SIZE);
+  }
 
   brillo::FakeMessageLoop loop_{nullptr};
   ActionProcessor processor_;
   DynamicPartitionControlStub dynamic_control_stub_;
-  static ScopedTempFile source_part;
-  static ScopedTempFile target_part;
+  std::vector<unsigned char> fec_data_;
+  std::vector<unsigned char> hash_tree_data_;
+  static ScopedTempFile source_part_;
+  static ScopedTempFile target_part_;
+  InstallPlan install_plan_;
 };
 
-ScopedTempFile FilesystemVerifierActionTest::source_part{
-    "source_part.XXXXXX", false, PARTITION_SIZE};
-ScopedTempFile FilesystemVerifierActionTest::target_part{
-    "target_part.XXXXXX", false, PARTITION_SIZE};
+ScopedTempFile FilesystemVerifierActionTest::source_part_{
+    "source_part.XXXXXX", true, PARTITION_SIZE};
+ScopedTempFile FilesystemVerifierActionTest::target_part_{
+    "target_part.XXXXXX", true, PARTITION_SIZE};
+
+static void EnableVABC(MockDynamicPartitionControl* dynamic_control,
+                       const std::string& part_name) {
+  ON_CALL(*dynamic_control, GetDynamicPartitionsFeatureFlag())
+      .WillByDefault(Return(FeatureFlag(FeatureFlag::Value::LAUNCH)));
+  ON_CALL(*dynamic_control, UpdateUsesSnapshotCompression())
+      .WillByDefault(Return(true));
+  ON_CALL(*dynamic_control, IsDynamicPartition(part_name, _))
+      .WillByDefault(Return(true));
+}
 
 class FilesystemVerifierActionTestDelegate : public ActionProcessorDelegate {
  public:
@@ -170,9 +280,8 @@ bool FilesystemVerifierActionTest::DoTest(bool terminate_early,
   bool success = true;
 
   // Set up the action objects
-  InstallPlan install_plan;
-  install_plan.source_slot = 0;
-  install_plan.target_slot = 1;
+  install_plan_.source_slot = 0;
+  install_plan_.target_slot = 1;
   InstallPlan::Partition part;
   part.name = "part";
   part.target_size = kLoopFileSize - (hash_fail ? 1 : 0);
@@ -187,23 +296,19 @@ bool FilesystemVerifierActionTest::DoTest(bool terminate_early,
     ADD_FAILURE();
     success = false;
   }
-  install_plan.partitions = {part};
+  install_plan_.partitions = {part};
 
-  BuildActions(install_plan);
+  BuildActions(install_plan_);
 
   FilesystemVerifierActionTestDelegate delegate;
   processor_.set_delegate(&delegate);
 
-  loop_.PostTask(FROM_HERE,
-                 base::Bind(
-                     [](ActionProcessor* processor, bool terminate_early) {
-                       processor->StartProcessing();
-                       if (terminate_early) {
-                         processor->StopProcessing();
-                       }
-                     },
-                     base::Unretained(&processor_),
-                     terminate_early));
+  loop_.PostTask(base::Bind(&ActionProcessor::StartProcessing,
+                            base::Unretained(&processor_)));
+  if (terminate_early) {
+    loop_.PostTask(base::Bind(&ActionProcessor::StopProcessing,
+                              base::Unretained(&processor_)));
+  }
   loop_.Run();
 
   if (!terminate_early) {
@@ -232,7 +337,7 @@ bool FilesystemVerifierActionTest::DoTest(bool terminate_early,
   EXPECT_TRUE(is_a_file_reading_eq);
   success = success && is_a_file_reading_eq;
 
-  bool is_install_plan_eq = (*delegate.install_plan_ == install_plan);
+  bool is_install_plan_eq = (*delegate.install_plan_ == install_plan_);
   EXPECT_TRUE(is_install_plan_eq);
   success = success && is_install_plan_eq;
   return success;
@@ -297,14 +402,13 @@ TEST_F(FilesystemVerifierActionTest, MissingInputObjectTest) {
 }
 
 TEST_F(FilesystemVerifierActionTest, NonExistentDriveTest) {
-  InstallPlan install_plan;
   InstallPlan::Partition part;
   part.name = "nope";
   part.source_path = "/no/such/file";
   part.target_path = "/no/such/file";
-  install_plan.partitions = {part};
+  install_plan_.partitions = {part};
 
-  BuildActions(install_plan);
+  BuildActions(install_plan_);
 
   FilesystemVerifierActionTest2Delegate delegate;
   processor_.set_delegate(&delegate);
@@ -345,7 +449,6 @@ TEST_F(FilesystemVerifierActionTest, RunAsRootWriteVerityTest) {
   test_utils::ScopedLoopbackDeviceBinder target_device(
       part_file.path(), true, &target_path);
 
-  InstallPlan install_plan;
   InstallPlan::Partition part;
   part.name = "part";
   part.target_path = target_path;
@@ -376,9 +479,9 @@ TEST_F(FilesystemVerifierActionTest, RunAsRootWriteVerityTest) {
   part.hash_tree_salt = {0x9e, 0xcb, 0xf8, 0xd5, 0x0b, 0xb4, 0x43,
                          0x0a, 0x7a, 0x10, 0xad, 0x96, 0xd7, 0x15,
                          0x70, 0xba, 0xed, 0x27, 0xe2, 0xae};
-  install_plan.partitions = {part};
+  install_plan_.partitions = {part};
 
-  BuildActions(install_plan);
+  BuildActions(install_plan_);
 
   FilesystemVerifierActionTestDelegate delegate;
   processor_.set_delegate(&delegate);
@@ -407,8 +510,7 @@ TEST_F(FilesystemVerifierActionTest, RunAsRootSkipWriteVerityTest) {
   test_utils::ScopedLoopbackDeviceBinder target_device(
       part_file.path(), true, &target_path);
 
-  InstallPlan install_plan;
-  install_plan.write_verity = false;
+  install_plan_.write_verity = false;
   InstallPlan::Partition part;
   part.name = "part";
   part.target_path = target_path;
@@ -423,9 +525,9 @@ TEST_F(FilesystemVerifierActionTest, RunAsRootSkipWriteVerityTest) {
   part.fec_offset = part.fec_data_size;
   part.fec_size = 2 * 4096;
   EXPECT_TRUE(HashCalculator::RawHashOfData(part_data, &part.target_hash));
-  install_plan.partitions = {part};
+  install_plan_.partitions = {part};
 
-  BuildActions(install_plan);
+  BuildActions(install_plan_);
 
   FilesystemVerifierActionTestDelegate delegate;
   processor_.set_delegate(&delegate);
@@ -442,76 +544,146 @@ TEST_F(FilesystemVerifierActionTest, RunAsRootSkipWriteVerityTest) {
   ASSERT_EQ(ErrorCode::kSuccess, delegate.code());
 }
 
-TEST_F(FilesystemVerifierActionTest, RunWithVABCNoVerity) {
-  InstallPlan install_plan;
-  auto part_ptr = AddFakePartition(&install_plan);
+void FilesystemVerifierActionTest::DoTestVABC(bool clear_target_hash,
+                                              bool enable_verity) {
+  auto part_ptr = AddFakePartition(&install_plan_);
+  if (::testing::Test::HasFailure()) {
+    return;
+  }
   ASSERT_NE(part_ptr, nullptr);
   InstallPlan::Partition& part = *part_ptr;
   part.target_path = "Shouldn't attempt to open this path";
+  if (enable_verity) {
+    install_plan_.write_verity = true;
+    ASSERT_NO_FATAL_FAILURE(SetHashWithVerity(&part));
+  }
+  if (clear_target_hash) {
+    part.target_hash.clear();
+  }
 
   NiceMock<MockDynamicPartitionControl> dynamic_control;
 
-  ON_CALL(dynamic_control, GetDynamicPartitionsFeatureFlag())
-      .WillByDefault(Return(FeatureFlag(FeatureFlag::Value::LAUNCH)));
-  ON_CALL(dynamic_control, UpdateUsesSnapshotCompression())
-      .WillByDefault(Return(true));
-  ON_CALL(dynamic_control, IsDynamicPartition(part.name, _))
-      .WillByDefault(Return(true));
+  EnableVABC(&dynamic_control, part.name);
+  auto open_cow = [part]() {
+    auto cow_fd = std::make_shared<EintrSafeFileDescriptor>();
+    EXPECT_TRUE(cow_fd->Open(part.readonly_target_path.c_str(), O_RDWR))
+        << "Failed to open part " << part.readonly_target_path
+        << strerror(errno);
+    return cow_fd;
+  };
 
   EXPECT_CALL(dynamic_control, UpdateUsesSnapshotCompression())
       .Times(AtLeast(1));
-  // Since we are not writing verity, we should not attempt to OpenCowFd()
-  // reads should go through regular file descriptors on mapped partitions.
-  EXPECT_CALL(dynamic_control, OpenCowFd(part.name, {part.source_path}, _))
-      .Times(0);
-  EXPECT_CALL(dynamic_control, MapAllPartitions()).Times(AtLeast(1));
+  auto cow_fd = open_cow();
+  if (HasFailure()) {
+    return;
+  }
+
+  if (enable_verity) {
+    ON_CALL(dynamic_control, OpenCowFd(part.name, {part.source_path}, _))
+        .WillByDefault(open_cow);
+    EXPECT_CALL(dynamic_control, OpenCowFd(part.name, {part.source_path}, _))
+        .Times(AtLeast(1));
+
+    // fs verification isn't supposed to write to |readonly_target_path|. All
+    // writes should go through fd returned by |OpenCowFd|. Therefore we set
+    // target part as read-only to make sure.
+    ASSERT_EQ(0, chmod(part.readonly_target_path.c_str(), 0444))
+        << " Failed to set " << part.readonly_target_path << " as read-only "
+        << strerror(errno);
+  } else {
+    // Since we are not writing verity, we should not attempt to OpenCowFd()
+    // reads should go through regular file descriptors on mapped partitions.
+    EXPECT_CALL(dynamic_control, OpenCowFd(part.name, {part.source_path}, _))
+        .Times(0);
+    EXPECT_CALL(dynamic_control, MapAllPartitions()).Times(AtLeast(1));
+  }
   EXPECT_CALL(dynamic_control, ListDynamicPartitionsForSlot(_, _, _))
       .WillRepeatedly(
           DoAll(SetArgPointee<2, std::vector<std::string>>({part.name}),
                 Return(true)));
 
-  BuildActions(install_plan, &dynamic_control);
+  BuildActions(install_plan_, &dynamic_control);
 
   FilesystemVerifierActionTestDelegate delegate;
   processor_.set_delegate(&delegate);
 
-  loop_.PostTask(
-      FROM_HERE,
-      base::Bind(
-          [](ActionProcessor* processor) { processor->StartProcessing(); },
-          base::Unretained(&processor_)));
+  loop_.PostTask(FROM_HERE,
+                 base::Bind(&ActionProcessor::StartProcessing,
+                            base::Unretained(&processor_)));
   loop_.Run();
 
   ASSERT_FALSE(processor_.IsRunning());
   ASSERT_TRUE(delegate.ran());
-  ASSERT_EQ(ErrorCode::kSuccess, delegate.code());
+  if (enable_verity) {
+    std::vector<unsigned char> actual_fec(fec_size);
+    ssize_t bytes_read = 0;
+    ASSERT_TRUE(utils::PReadAll(cow_fd,
+                                actual_fec.data(),
+                                actual_fec.size(),
+                                fec_start_offset,
+                                &bytes_read));
+    ASSERT_EQ(actual_fec, fec_data_);
+    std::vector<unsigned char> actual_hash_tree(hash_tree_size);
+    ASSERT_TRUE(utils::PReadAll(cow_fd,
+                                actual_hash_tree.data(),
+                                actual_hash_tree.size(),
+                                HASH_TREE_START_OFFSET,
+                                &bytes_read));
+    ASSERT_EQ(actual_hash_tree, hash_tree_data_);
+  }
+  if (clear_target_hash) {
+    ASSERT_EQ(ErrorCode::kNewRootfsVerificationError, delegate.code());
+  } else {
+    ASSERT_EQ(ErrorCode::kSuccess, delegate.code());
+  }
+}
+
+TEST_F(FilesystemVerifierActionTest, VABC_NoVerity_Success) {
+  DoTestVABC(false, false);
+}
+
+TEST_F(FilesystemVerifierActionTest, VABC_NoVerity_Target_Mismatch) {
+  DoTestVABC(true, false);
+}
+
+TEST_F(FilesystemVerifierActionTest, VABC_Verity_Success) {
+  DoTestVABC(false, true);
+}
+
+TEST_F(FilesystemVerifierActionTest, VABC_Verity_ReadAfterWrite) {
+  ASSERT_NO_FATAL_FAILURE(DoTestVABC(false, true));
+  // Run FS verification again, w/o writing verity. We have seen a bug where
+  // attempting to run fs again will cause previously written verity data to be
+  // dropped, so cover this scenario.
+  ASSERT_GE(install_plan_.partitions.size(), 1UL);
+  auto& part = install_plan_.partitions[0];
+  install_plan_.write_verity = false;
+  part.readonly_target_path = target_part_.path();
+  NiceMock<MockDynamicPartitionControl> dynamic_control;
+  EnableVABC(&dynamic_control, part.name);
+
+  // b/186196758 is only visible if we repeatedely run FS verification w/o
+  // writing verity
+  for (int i = 0; i < 3; i++) {
+    BuildActions(install_plan_, &dynamic_control);
+
+    FilesystemVerifierActionTestDelegate delegate;
+    processor_.set_delegate(&delegate);
+    loop_.PostTask(
+        FROM_HERE,
+        base::Bind(
+            [](ActionProcessor* processor) { processor->StartProcessing(); },
+            base::Unretained(&processor_)));
+    loop_.Run();
+    ASSERT_FALSE(processor_.IsRunning());
+    ASSERT_TRUE(delegate.ran());
+    ASSERT_EQ(ErrorCode::kSuccess, delegate.code());
+  }
 }
 
-TEST_F(FilesystemVerifierActionTest, ReadAfterWrite) {
-  ScopedTempFile cow_device_file("cow_device.XXXXXX", true);
-  android::snapshot::CompressedSnapshotWriter snapshot_writer{
-      {.block_size = BLOCK_SIZE}};
-  snapshot_writer.SetCowDevice(android::base::unique_fd{cow_device_file.fd()});
-  snapshot_writer.Initialize();
-  std::vector<unsigned char> buffer;
-  buffer.resize(BLOCK_SIZE);
-  std::fill(buffer.begin(), buffer.end(), 123);
-
-  ASSERT_TRUE(snapshot_writer.AddRawBlocks(0, buffer.data(), buffer.size()));
-  ASSERT_TRUE(snapshot_writer.Finalize());
-  auto cow_reader = snapshot_writer.OpenReader();
-  ASSERT_NE(cow_reader, nullptr);
-  ASSERT_TRUE(snapshot_writer.AddRawBlocks(1, buffer.data(), buffer.size()));
-  ASSERT_TRUE(snapshot_writer.AddRawBlocks(2, buffer.data(), buffer.size()));
-  ASSERT_TRUE(snapshot_writer.Finalize());
-  cow_reader = snapshot_writer.OpenReader();
-  ASSERT_NE(cow_reader, nullptr);
-  std::vector<unsigned char> read_back;
-  read_back.resize(buffer.size());
-  cow_reader->Seek(BLOCK_SIZE, SEEK_SET);
-  const auto bytes_read = cow_reader->Read(read_back.data(), read_back.size());
-  ASSERT_EQ((size_t)(bytes_read), BLOCK_SIZE);
-  ASSERT_EQ(read_back, buffer);
+TEST_F(FilesystemVerifierActionTest, VABC_Verity_Target_Mismatch) {
+  DoTestVABC(true, true);
 }
 
 }  // namespace chromeos_update_engine
diff --git a/stable/Android.bp b/stable/Android.bp
index 5e54e9a0..1573ebd2 100644
--- a/stable/Android.bp
+++ b/stable/Android.bp
@@ -49,6 +49,7 @@ aidl_interface {
             ],
         },
     },
+    versions: ["1"],
 }
 
 // update_engine_stable_client (type: executable)
diff --git a/stable/aidl_api/libupdate_engine_stable/1/.hash b/stable/aidl_api/libupdate_engine_stable/1/.hash
new file mode 100644
index 00000000..f21562a4
--- /dev/null
+++ b/stable/aidl_api/libupdate_engine_stable/1/.hash
@@ -0,0 +1 @@
+526043ea6cb098d53a9c3e778420e64c4e864d8c
diff --git a/stable/aidl_api/libupdate_engine_stable/1/android/os/IUpdateEngineStable.aidl b/stable/aidl_api/libupdate_engine_stable/1/android/os/IUpdateEngineStable.aidl
new file mode 100644
index 00000000..67db18e9
--- /dev/null
+++ b/stable/aidl_api/libupdate_engine_stable/1/android/os/IUpdateEngineStable.aidl
@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+///////////////////////////////////////////////////////////////////////////////
+// THIS FILE IS IMMUTABLE. DO NOT EDIT IN ANY CASE.                          //
+///////////////////////////////////////////////////////////////////////////////
+
+// This file is a snapshot of an AIDL file. Do not edit it manually. There are
+// two cases:
+// 1). this is a frozen version file - do not edit this in any case.
+// 2). this is a 'current' file. If you make a backwards compatible change to
+//     the interface (from the latest frozen version), the build system will
+//     prompt you to update this file with `m <name>-update-api`.
+//
+// You must not make a backward incompatible change to any AIDL file built
+// with the aidl_interface module type with versions property set. The module
+// type is used to build AIDL files in a way that they can be used across
+// independently updatable components of the system. If a device is shipped
+// with such a backward incompatible change, it has a high risk of breaking
+// later when a module using the interface is updated, e.g., Mainline modules.
+
+package android.os;
+interface IUpdateEngineStable {
+  void applyPayloadFd(in ParcelFileDescriptor pfd, in long payload_offset, in long payload_size, in String[] headerKeyValuePairs);
+  boolean bind(android.os.IUpdateEngineStableCallback callback);
+  boolean unbind(android.os.IUpdateEngineStableCallback callback);
+}
diff --git a/stable/aidl_api/libupdate_engine_stable/1/android/os/IUpdateEngineStableCallback.aidl b/stable/aidl_api/libupdate_engine_stable/1/android/os/IUpdateEngineStableCallback.aidl
new file mode 100644
index 00000000..dbca127c
--- /dev/null
+++ b/stable/aidl_api/libupdate_engine_stable/1/android/os/IUpdateEngineStableCallback.aidl
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+///////////////////////////////////////////////////////////////////////////////
+// THIS FILE IS IMMUTABLE. DO NOT EDIT IN ANY CASE.                          //
+///////////////////////////////////////////////////////////////////////////////
+
+// This file is a snapshot of an AIDL file. Do not edit it manually. There are
+// two cases:
+// 1). this is a frozen version file - do not edit this in any case.
+// 2). this is a 'current' file. If you make a backwards compatible change to
+//     the interface (from the latest frozen version), the build system will
+//     prompt you to update this file with `m <name>-update-api`.
+//
+// You must not make a backward incompatible change to any AIDL file built
+// with the aidl_interface module type with versions property set. The module
+// type is used to build AIDL files in a way that they can be used across
+// independently updatable components of the system. If a device is shipped
+// with such a backward incompatible change, it has a high risk of breaking
+// later when a module using the interface is updated, e.g., Mainline modules.
+
+package android.os;
+interface IUpdateEngineStableCallback {
+  oneway void onStatusUpdate(int status_code, float percentage);
+  oneway void onPayloadApplicationComplete(int error_code);
+}