Add FWU documentation
Adds documentation to describe FWU support. Gives an overall
design description and explains the platform configuration
model.
Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: Ib7b362ec645c7afca198f4b5138a249c17bc5056
diff --git a/docs/services/fwu-service-description.rst b/docs/services/fwu-service-description.rst
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+Firmware Update Service
+=======================
+Overview
+--------
+The ability to update device firmware and related resources is a key requirement for
+maintaining security over a device's lifetime. Keeping firmware up-to-date with security
+fixes and feature enhancements is important for defending against emerging threats.
+Because firmware forms the security foundation of a device, it is important to apply
+updates in a timely manner to minimize risks exposed by firmware vulnerabilities. Any
+remote firmware update mechanism carries a risk of failure. As firmware is critical to
+the operation of a device, failures during the update process that lead to corrupted
+firmware have the potential to be highly disruptive. Any update mechanism intended
+for use with a large population of devices must offer robustness guarantees sufficient
+to keep the risk of failure at an acceptable level.
+
+Firmware update support within the Trusted Services project consists of a set of reusable
+firmware components that can be deployed within different execution environments to enable
+platform integrators to create firmware update solutions, tailored for their platform.
+The components are intended to be integrated into platform firmware and will be used in
+conjunction with a third-party update client, such as mender, swupd or fwupd, to create
+an end-to-end solution. The features supported aim to meet requirements for robustness
+and security. These include:
+
+ - Banked A/B robust update support
+ - Transactional multi-component updates with ACID (Atomicity, Consistency, Isolation,
+ Durability) guarantees
+ - Partial updates where not all components are updated
+ - Trial of an update with bootloader or client initiated rollback
+ - Anti-rollback counter management
+ - Standardized signaling to bootloader via the FWU Metadata structure
+ - Flexible installer framework to support different image types
+ - Image directory for advertising updatable components
+ - Compatible with UEFI FMP capsule update model and ESRT
+
+To support test and development and to provide a useful reference, the Trusted Services
+project maintains a reference integration with the following characteristics:
+
+ - Dual flash system where firmware is loaded from a dedicated secure world flash device.
+ - Secure flash is formatted with UEFI MBR/GPT with separate partitions for FWU metadata
+ and firmware banks.
+ - TF-A is used as the bootloader with separate firmware components packaged in a FIP
+ image.
+ - The Update Agent runs within a secure partition and exposes an FF-A based ABI that
+ conforms to the Arm FWU-A specification.
+ - Test and development on FVP or QEMU platforms.
+
+Source Code Location
+--------------------
+Within the Trusted Services project, source code related to FWU can be found under the
+following subdirectories (relative to the project root).
+
+.. list-table::
+ :header-rows: 1
+
+ * - Directory
+ - Contains
+ * - components/service/fwu
+ - Service components for implementing the FWU service provider.
+ * - protocols/service/fwu
+ - Public service access protocol (ABI) definition.
+ * - media/volume
+ - Storage volume access.
+
+Testing is covered in more detail in a later section. However, if you want a simple way
+of building and testing FWU components, the component-test deployment may be built for a
+native PC environment. The built executable includes an extensive set of FWU related tests
+that exercise the core Update Agent in various configurations. To build and run these tests
+on a Linux PC, use the following (from TS root directory)::
+
+ cd deployments/component-test/linux-pc
+ cmake -B build
+ cd build
+ make
+ ./component-test -v -g Fwu
+
+ Output will look like this:
+ TEST(FwuCopyInstallerTests, installAndCopy) - 1 ms
+ TEST(FwuRawInstallerTests, normalInstallFlow) - 1 ms
+ TEST(FwuMetadataManagerTests, checkAndRepairInaccessibleStorage) - 0 ms
+ TEST(FwuMetadataManagerTests, checkAndRepairAccessibleStorage) - 1 ms
+ TEST(FwuRollbackTests, bootloaderFallback) - 0 ms
+ TEST(FwuRollbackTests, selectPreviousAfterActivation) - 0 ms
+ TEST(FwuRollbackTests, selectPreviousPriorToActivation) - 0 ms
+ TEST(FwuPowerFailureTests, powerFailureDuringTrial) - 0 ms
+ TEST(FwuPowerFailureTests, powerFailureDuringStaging) - 0 ms
+ TEST(FwuUpdateScenarioTests, partialFirmwareUpdateFlow) - 0 ms
+ TEST(FwuUpdateScenarioTests, wholeFirmwareUpdateFlow) - 0 ms
+ TEST(FwuInvalidBehaviourTests, invalidOperationsInTrial) - 0 ms
+ TEST(FwuInvalidBehaviourTests, invalidOperationsInStaging) - 0 ms
+ TEST(FwuInvalidBehaviourTests, invalidOperationsInRegular) - 0 ms
+ TEST(FwuImageDirectoryTests, zeroFwLocations) - 0 ms
+ TEST(FwuImageDirectoryTests, multipleFwLocations) - 0 ms
+ TEST(FwuImageDirectoryTests, singleFwLocation) - 1 ms
+ TEST(FwuImageDirectoryTests, streamRecycling) - 0 ms
+ TEST(FwuImageDirectoryTests, streamedReads) - 0 ms
+
+ OK (234 tests, 19 ran, 3452 checks, 0 ignored, 215 filtered out, 5 ms)
+
+Concepts and Assumptions
+------------------------
+Before describing details of the design, some important concepts and assumptions are
+introduced in this section.
+
+Update Packaging
+''''''''''''''''
+A set of firmware images that forms an update will be packaged in some way to enable
+it to be delivered to a device for installation. No particular packaging method is assumed
+by the FWU Update Agent. Any unpacking will be performed before individual images are
+presented to the FWU service for installation. The only assumption that the Update Agent
+relies on is that each image is identified by an image type UUID/GUID. The UEFI specification
+defines the FMP Capsule format that acts as a container for a set of arbitrary images. The
+reference integration maintained by the Trusted Services project uses UEFI FMP capsules
+but the FWU service can be used with any packaging method.
+
+Transactional Updates
+'''''''''''''''''''''
+A firmware update package may contain multiple images that all need to be installed as a
+set in order to successfully update a device's firmware. To avoid the hazard of booting
+a device using partially installed firmware, the FWU-A specification supports transactional
+updates where as set of separate image install operations are grouped together to form a
+single update transaction. The FWU-A specification defines a behavioral model where images
+are installed during the STAGING state. Entry to the STAGING state is triggered by the
+client making the fwu_begin_staging ABI call. This is followed a set of one or more install
+operations where images are written to the Update Agent. After committing the final image
+in the set, the client marks the end of the transaction by calling fwu_end_staging.
+
+Banked Firmware Store
+'''''''''''''''''''''
+To offer the guarantee that device firmware is never left in an unbootable state, a valid
+version of firmware is always held in flash. Flash storage is organized into A and B banks
+where one bank holds a valid set of images while updates are installed in the other bank.
+The bootloader is capable of booting from either bank, as instructed by the FWU metadata
+written by the Update Agent. Where firmware storage is distributed across multiple locations,
+A and B volumes must exist for each location.
+
+Update Agent
+''''''''''''
+The Update Agent is a logical component defined in the FWU-A specification reference model.
+The Update Agent handles requests from a client to install a set of images in preparation
+for activating the updated firmware. In the TS project, the role of the Update Agent is
+reflected by a firmware component with the same name.
+
+Firmware Directory
+''''''''''''''''''
+The FWU-A specification defines a stream endpoint that can be read by a client to obtain a
+listing of updatable firmware components. In the TS implementation, this is backed by the
+Firmware Directory component that is populated with information about the booted firmware.
+
+Storage Volumes
+''''''''''''''''
+All NV storage accessed by the Update Agent is represented by a set of volume objects. A
+volume presents a unit of storage as a seekable file with support for conventional file IO
+operations. The volume provides a uniform interface for all storage operations performed by
+the Update Agent. The volume uses and extends the io_dev driver model from the TF-A project.
+Concrete volume objects can access different types of storage such as:
+
+ - A raw flash device
+ - A disk partition
+ - Storage managed by a sub-processor
+
+Installers
+''''''''''
+Trusted Services FWU support provides a framework for updating arbitrary firmware images.
+From the framework's perspective, an image is just a binary blob, identified by an image
+type UUID. To allow for image format specific installation, a common installer interface is
+defined to allow for alternative concrete installers. Installers can update the entire
+contents of a volume or modify parts of a volume. Where a volume holds a container such
+as a FIP, a specialized installer with knowledge of the container format can provide finer
+grain updates of the container contents. An installer implements an enumerate method to
+return information about images that it can handle. The Firmware Directory is formed by
+aggregating the information returned by each installer's enumerate method.
+
+Firmware Locations
+''''''''''''''''''
+The Update Agent can manage firmware distributed across multiple locations e.g. different
+flash partitions, different flash devices or different subsystems. The concept of a firmware
+location is used in the TS implementation to provide a generalized model for handling
+distributed firmware. Each location is assigned an integer ID that is used to bind together:
+
+ - A pair of storage volumes (for A + B banks)
+ - A set of one or more installers. The set of installers configured for the location
+ determines which image types are updatable for the location.
+
+Installers are categorized as one of the following types:
+
+ - **Whole volume installer** - updates the entire contents of a volume. The whole volume
+ contents is presented as an entry in the firmware directory.
+ - **Sub-volume installer** - updates components contained within a volume. Each image
+ contained within the active volume is presented as an entry in the firmware directory.
+ - **Whole volume copy installer** - copies entire volume contents from one volume to
+ another. Contributes no entries to the firmware directory.
+
+A platform integrator is responsible for selecting which installers are configured for a
+location. Each location must be assigned at least one installer. Any combination of different
+types of installer could make sense in a platform configuration. Here are some example
+configurations:
+
+.. list-table::
+ :header-rows: 1
+
+ * - Location configuration
+ - Update capability for location
+ * - *WholeVolumeInstaller*
+ - A single entry appears in the firmware directory for the location that corresponds to
+ the entire volume contents. An incoming update package must include an image that
+ corresponds to the directory entry.
+ * - *WholeVolumeInstaller + SubVolumeInstaller*
+ - Firmware directory entries appear for the whole volume and for each updatable component
+ contained within the volume. An incoming update package must include either one or more
+ sub-volume images or a whole volume image for this location.
+ * - *WholeVolumeInstaller + SubVolumeInstaller + WholeVolumeCopyInstaller*
+ - Firmware directory entries appear for the whole volume and for each updatable component
+ contained within the volume. If no image for this location is included in an incoming
+ update package, the currently active volume contents is copied to the update volume.
+ * - *WholeVolumeCopyInstaller*
+ - This configuration can be used if it is necessary to prevent updates for a location.
+ For any update transaction, the currently active volume contents will always be copied
+ to the update volume for this location.
+
+Design Description
+------------------
+FWU components within the TS project are designed for reuse in alternative deployments. The
+project currently maintains two FWU deployments, both sharing many common components:
+
+ - **fwu/config/default-sp** - the Update Agent runs within a secure partition. The client
+ invokes ABI operations via FF-A based RPC. Updates are applied to a dedicated Swd flash device.
+ - **fwu/config/fwu-app-linux-pc** - the Update Agent runs within a command-line application.
+ Updates are applied to a disk image file residing in the host filesystem.
+
+There is clear separation between different classes of component making component-level reuse
+straight-forward. The following diagram illustrates the main FWU components. The direction of
+the arrows linking components shows the direction of a dependency between associated
+components (i.e. A→B means that A depends on B).
+
+.. image:: image/update-agent-components.svg
+
+Core Components
+''''''''''''''''
+Any FWU deployment that supports a banked firmware store is expected to use the core set of
+FWU components. Core components are partitioned between:
+
+ - **Generic Update Agent** - manages update transactions and streams used for transferring
+ image data. Also owns the FW Directory.
+ - **Banked FW Store** - manages banked access to storage and communication with the bootloader
+ via FWU metadata.
+
+Generic Update Agent Model
+""""""""""""""""""""""""""
+The following class diagram models the generic Update Agent:
+
+.. uml:: uml/UpdateAgentClassDiagram.puml
+
+Classes in the model perform the following roles:
+
+.. list-table::
+ :header-rows: 1
+
+ * - Class
+ - Description
+ - Source files
+ * - *update_agent*
+ - Coordinates update transactions from start to finish. Implements the FWU state machine that
+ enforces correct behaviour during an update. Provides functions that form the public interface
+ for an instance of the Update Agent.
+ - components/service/fwu/agent/update_agent.h, components/service/fwu/agent/update_agent.c
+ * - *stream_manager*
+ - Manages a pool of stream objects for client initiated stream read and write operations. Streams
+ are used for writing image data and reading FWU objects such as the image directory.
+ - components/service/fwu/agent/stream_manager.h, components/service/fwu/agent/stream_manager.c
+ * - *fw_directory*
+ - Holds information about the currently active firmware. The contents of the fw_directory is
+ updated by a fw_inspector at boot time. Forms the source of the information returned to a
+ client that reads the image directory object.
+ - components/service/fwu/agent/fw_directory.h, components/service/fwu/agent/fw_directory.c
+ * - *img_dir_serializer*
+ - Serializes information about currently active firmware in-line with the FWU-A specification.
+ - components/service/fwu/agent/img_dir_serializer.h, components/service/fwu/agent/img_dir_serializer.c
+ * - *fw_inspector*
+ - Called by the update_agent to inspect firmware and update the contents of the fw_directory to
+ provide a fresh view of active firmware. To allow for alternative inspection strategies, the
+ concrete fw_inspector to use is determined by deployment specific configuration code and passed
+ to the update_agent at initialization. The direct_fw_inspector is a concrete fw_inspector that
+ relies on direct access to the set of installers registered as part of the Update Agent configuration.
+ - components/service/fwu/inspector/fw_inspector.h, components/service/fwu/inspector/direct/direct_fw_inspector.h,
+ components/service/fwu/inspector/direct/direct_fw_inspector.c
+
+Banked FW Store Model
+""""""""""""""""""""""
+The update_agent interacts with the fw_store via a common interface. No details about the nature of the fw_store
+are exposed to the update_agent. The following class diagram models a particular realization of the fw_store
+interface that implements the A/B bank scheme:
+
+.. uml:: uml/FwStoreClassDiagram.puml
+
+Classes in the model perform the following roles:
+
+.. list-table::
+ :header-rows: 1
+
+ * - Class
+ - Description
+ - Source files
+ * - *fw_store*
+ - Manages updates to banked storage volumes.
+ - components/service/fwu/fw_store/fw_store.h,
+ components/service/fwu/fw_store/banked/banked_fw_store.h,
+ components/service/fwu/fw_store/banked/banked_fw_store.c
+ * - *bank_tracker*
+ - Tracks usage and accepted state of firmware banks.
+ - components/service/fwu/fw_store/banked/bank_tracker.h,
+ components/service/fwu/fw_store/banked/bank_tracker.c
+ * - *metadata_manager*
+ - Manages storage and updates to the FWU metadata used for signaling to the bootloader. Responsible for
+ detecting and repairing corrupted metadata.
+ - components/service/fwu/fw_store/banked/metadata_manager.h,
+ components/service/fwu/fw_store/banked/metadata_manager.c
+ * - *metadata_serializer*
+ - Serializes update bank state in a standard format for compatibility with the boot loader. To ensure
+ version compatibility through fw updates, alternative realizations of the metadata_serializer may be
+ selected at runtime. Currently support for V1 and V2 formats (as defined by the FWU-A specification).
+ - components/service/fwu/fw_store/banked/metadata_serializer/metadata_serializer.h
+ * - *installer*
+ - Base class for installers. Defines a common interface for installing images associated with a location.
+ - components/service/fwu/installer/installer.h,
+ components/service/fwu/installer/installer.c
+ * - *installer_index*
+ - Holds pointers to the set of concrete installers registered during platform configuration.
+ - components/service/fwu/installer/installer_index.h,
+ components/service/fwu/installer/installer_index.c
+ * - *volume*
+ - Presents a unit of storage is a seekable file. Supports byte-orient read and writes operation
+ to storage. All NV storage is accessed by the Update Agent using volumes. The set of volume objects
+ needed for a deployment are created as part of platform specific initialisation.
+ - components/media/volume/volume.h,
+ components/media/volume/volume.c
+ * - *volume_index*
+ - Holds pointers to the set of concrete volumes registered during platform configuration.
+ - components/media/volume/index/volume_index.h,
+ components/media/volume/index/volume_index.c
+
+Service Interface
+''''''''''''''''''
+For deployments where the Update Agent needs to be remotely callable, the fwu_provider implements an
+RPC interface that accepts call requests, de-serializes call parameters and calls the corresponding
+interface functions provided by the update_agent. In the reference deployment, where the Update
+Agent runs within an SP, the fwu_provider receives call requests, made via FF-A, and returns responses
+to the remote client. The fwu_provider may be used with any RPC layer where remote calling is required.
+
+Platform Configuration
+----------------------
+A platform specific configuration tells the Update Agent about storage for firmware and defines the
+policy for the way the firmware can be update. Configuration steps result in the creation of:
+
+ - A set of concrete installer objects registered with the installer_index. This defines the
+ type of images that can be updated.
+ - A set of concrete volume objects registered with the volume_index. This defines where images
+ can be installed.
+
+Each installer is assigned a location ID to bind the installer to a particular firmware location.
+Location IDs are integer values defined by the configuration code. For example, where firmware
+consists of AP firmware, SCP firmware and RSS firmware, location IDs could be assigned as follows:
+
+.. list-table::
+ :header-rows: 1
+
+ * - Location
+ - ID
+ * - AP firmware
+ - 0
+ * - SCP firmware
+ - 1
+ * - RSS firmware
+ - 2
+
+When volume objects are added to the volume index, each one is assigned a volume ID which is
+formed by combining the corresponding location ID with the bank index to which the volume
+provides access to.
+
+The types of installer and volume needed will depend on factors such as:
+
+ - How NV storage is accessed by the Update Agent.
+ - The type of images that need to be installed.
+ - How flash storage is partitioned e.g. is GPT used or some other partition description method.
+
+Source files related to FWU configuration:
+
+.. list-table::
+ :header-rows: 1
+
+ * - Directory
+ - Contains
+ * - components/service/fwu/config
+ - Configuration strategies for provisioning installers and volumes
+ * - components/service/fwu/installer/factory
+ - Factories for constructing different types of installer
+ * - components/media/volume/factory
+ - Factories for constructing different types of volume
+
+Update Agent Configuration using GPT
+''''''''''''''''''''''''''''''''''''
+The TS FWU service implementation includes a GPT based configurator that automatically discovers
+the set of installers and volumes to construct, based on the contents of the GPT that describes
+the flash layout. The following diagram illustrates a typical flash partition layout. Note that
+not all partitions contain firmware.
+
+.. image:: image/gpt-based-flash-layout.svg
+
+A deployment of the Update Agent is built with an installer factory that has the capability to
+construct a set of installers that are suitable for a family of platforms where common image
+types and update policy applies. An installer factory is capable of constructing a concrete set
+of installers for installing images into a particular set of partitions, identified by partition
+type GUID. A platform may not incorporate the complete set of partition types. The default
+installer factory (under components/service/fwu/installer/factory/default) includes rules for
+constructing installers for:
+
+ - **AP Firmware** - where application firmware is contained within a FIP
+ - **SCP Firmware** - binary boot image for SCP
+ - **RSS Firmware** - binary boot image for RSS
+
+The GPT based configurator relies on access to the GPT partition table. During initialization
+of the Update Agent, the configurator iterates over each partition entry. If no installers are
+registered for the partition, the partition type GUID is offered to the installer factory. If
+at least one installer is constructed, a volume object is constructed to provide access to the
+partition. This partition will hold one of the banked copies of the image identified by the
+partition type GUID. If one or more installers have already been constructed for the partition
+type GUID, an additional volume object is constructed to provide access to the second
+banked partition.
+
+The designation of bank index to partition is determined from the PartitionName field in the
+partition entry. The first UTF-16 character (0 or 1) is interpreted as the bank index assigned
+to the partition. Different conventions are possible if an alternative configurator is used.
+
+FWU Command Line Application
+----------------------------
+A build configuration of the fwu deployment integrates the Update Agent within a command-line
+application that can be run on a Linux PC. Instead of updating images stored in flash, the
+application operates on a GPT formatted disk image file residing in the host machine's filesystem.
+The core components of the application are identical to those used in embedded deployments.
+To build and run the fwu application, use the following commands from the root of the
+checked-out TS project::
+
+ cd deployments/fwu/config/fwu-app-linux-pc
+ cmake -B build
+ cd build
+ make
+ ./fwu -help
+ Usage: fwu disk-filename [-dir -meta] [-boot-index number -meta-ver number] [-img filename -img-type uuid]
+
+ disk-filename Disk image file to update
+ -dir Print image directory
+ -meta Print FWU metadata
+ -boot-index Override default boot index [0..n]
+ -meta-ver Specify FWU metadata to use
+ -img File containing image update
+ -img-type Canonical UUID of image to update
+
+Some sample disk image files can be found under::
+
+ components/media/disk/disk_images
+
+The sample disk image file multi_location_fw.img includes a GPT with entries for the firmware
+and metadata partitions illustrated in the diagram above. Note that the sample disk image
+does not contain valid FWU metadata within the primary and backup metadata partitions. This
+condition is detected by the Update Agent which writes valid metadata that reflects the contents
+of the disk image file. Subsequent invocations of the app will use the valid metadata previously
+written to the disk image.
+
+The app can of course be used with flash image files created by a firmware build system.
+The command-line interface currently restricts updates to consist of just a single image,
+identified by an image type UUID. Extending the command-line interface to support multi-image
+update transactions is possible by for example adding the capability to process an FMP capsule
+file containing multiple images.
+
+Testing the Update Agent
+------------------------
+FWU components are tested in both native PC and embedded environments. PC based tests use the
+fwu_dut C++ class to simulate the role of the bootloader and to allow device reboot scenarios
+to be recreated. The simulated device-under-test maintains NV storage state through reboots
+to mimic real device behaviour. Test components that support PC based testing are summarized
+in the following table:
+
+.. list-table::
+ :header-rows: 1
+
+ * - Component
+ - Description
+ - Project Directory
+ * - *fwu_dut*
+ - Base class to represent a device-under-test (DUT). Presents an interface used by test
+ cases that allows for test-case reuse with different fwu_dut specializations.
+ - components/service/fwu/test/fwu_dut
+ * - *sim_fwu_dut*
+ - A specialization of the fwu_dut class that adds bootloader simulation and various
+ other test support capabilities.
+ - components/service/fwu/test/fwu_dut/sim
+ * - *proxy_fwu_dut*
+ - A specialization of the fwu_dut class that acts as a proxy for the fwu_dut that
+ actually hosts the Update Agent.
+ - components/service/fwu/test/fwu_dut/proxy
+ * - *fwu_client*
+ - Presents FWU methods (begin_staging, end_staging etc.) for use by test cases.
+ - components/service/fwu/test/fwu_client
+ * - *direct_fwu_client*
+ - An fwu_client that calls Update Agent interface functions directly.
+ - components/service/fwu/test/fwu_client/direct
+ * - *remote_fwu_client*
+ - An fwu_client that makes RPC call requests to invoke Update Agent operations. Call
+ parameters are serialized using the FWU access protocol.
+ - components/service/fwu/test/fwu_client/remote
+ * - *image_directory_checker*
+ - A test support class that fetches the serialized image directory and provides
+ methods for checking the fetched content.
+ - components/service/fwu/test/image_directory_checker
+ * - *metadata_checker*
+ - Provides methods to check that the fetched FWU metadata reflects the state expected
+ by test cases. Decouples test code from the underlying metadata format. Support
+ for V1 and V2 metadata is provided.
+ - components/service/fwu/test/metadata_checker
+ * - *metadata_fetcher*
+ - Provides an interface for fetching the metadata associated with the DUT. Depending
+ on the deployment, different strategies for fetching the metadata are needed.
+ - components/service/fwu/test/metadata_fetcher
+
+An extensive set of test suites uses the test framework components listed above to test
+various update scenarios. The following test suites live under::
+
+ components/service/fwu/test/ref_scenarios
+
+.. list-table::
+ :header-rows: 1
+
+ * - Test Suite
+ - Description
+ * - *image_directory_tests*
+ - Tests reading of the image directory via the Update Agent stream interface.
+ * - *invalid_behaviour_tests*
+ - Tests to check that invalid requests are rejected with the expected error codes.
+ * - *oversize_image_tests*
+ - Tests to check defenses against attempts to install images that are too big for
+ the available storage.
+ * - *power_failure_tests*
+ - Tests recreate power-failure scenarios at various points during an update transaction.
+ Tests check that a viable set of firmware is always available.
+ * - *rollback_tests*
+ - Tests recreate bootloader initiated and update client requested rollback scenarios.
+ * - *update_scenario_tests*
+ - Various normal update scenarios with a well-behaved client.
+
+The test suites list above are included in the following TS test deployments:
+
+ - **component-test** - runs tests in a native PC environment using a direct_fwu_client.
+ - **ts-service-test** - runs tests in a native PC environment using a remote_fwu_client.
+
+Reference Integration Test Environment
+--------------------------------------
+The following diagram provides an overview of the planned reference integration and test
+environment used for testing on FVP.
+
+.. image:: image/fwu-reference-integration.svg
+
+--------------
+
+*Copyright (c) 2023, Arm Limited and Contributors. All rights reserved.*
+
+SPDX-License-Identifier: BSD-3-Clause
diff --git a/docs/services/image/fwu-reference-integration.svg b/docs/services/image/fwu-reference-integration.svg
new file mode 100644
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+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Do not edit this file with editors other than diagrams.net -->
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\ No newline at end of file
diff --git a/docs/services/image/update-agent-components.svg b/docs/services/image/update-agent-components.svg
new file mode 100644
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\ No newline at end of file
diff --git a/docs/services/index.rst b/docs/services/index.rst
index b479f8b..dee2252 100644
--- a/docs/services/index.rst
+++ b/docs/services/index.rst
@@ -7,12 +7,13 @@
attest-service-description
crypto-service-description
+ fwu-service-description
secure-storage-service-description
block-storage-service-description
uefi-smm-services
--------------
-*Copyright (c) 2020-2022, Arm Limited and Contributors. All rights reserved.*
+*Copyright (c) 2020-2023, Arm Limited and Contributors. All rights reserved.*
SPDX-License-Identifier: BSD-3-Clause
diff --git a/docs/services/uml/FwStoreClassDiagram.puml b/docs/services/uml/FwStoreClassDiagram.puml
new file mode 100644
index 0000000..228c3db
--- /dev/null
+++ b/docs/services/uml/FwStoreClassDiagram.puml
@@ -0,0 +1,104 @@
+'-------------------------------------------------------------------------------
+' Copyright (c) 2023, Arm Limited and Contributors. All rights reserved.
+'
+' SPDX-License-Identifier: BSD-3-Clause
+'
+'-------------------------------------------------------------------------------
+
+@startuml
+
+ class fw_store
+class bank_tracker
+class metadata_manager
+class metadata_serializer
+class installer_index
+class volume_index
+class installer
+class volume
+
+class bank_tracker {
+ +accept()
+ +copy_accept()
+ +set_no_content()
+ +set_holds_content()
+ +set_holds_acceped_content()
+ +is_content()
+ +is_accepted()
+ +is_all_accepted()
+}
+
+class fw_store {
+ +synchronize()
+ +begin_install()
+ +cancel_install()
+ +finalize_install()
+ +select_installer()
+ +write_image()
+ +commit_image()
+ +notify_accepted()
+ +is_accepted()
+ +is_trial()
+ +commit_to_update()
+ +revert_to_previous()
+ +export()
+}
+
+class metadata_manager {
+ +check_and_repair()
+ +update()
+ +get_active_indices()
+ +preload_bank_tracker()
+}
+
+class metadata_serializer {
+ +serialize()
+ +size()
+ +max_size()
+ +deserialize_bank_info()
+ +deserialize_active_indices()
+}
+
+class installer_index {
+ +register()
+ +find()
+ +get()
+ +get_location_ids()
+}
+
+class installer {
+ +begin()
+ +finalize()
+ +abort()
+ +open()
+ +commit()
+ +write()
+ +enumerate()
+}
+
+class volume_index {
+ +add()
+ +find()
+}
+
+class volume {
+ +open()
+ +close()
+ +seek()
+ +size()
+ +read()
+ +write()
+ +erase()
+ +get_storage_ids()
+}
+
+fw_store -> metadata_manager
+fw_store -> bank_tracker
+fw_store -> installer_index
+fw_store -> volume_index
+metadata_manager -> metadata_serializer
+installer_index -> "*" installer
+volume_index -> "*" volume
+metadata_manager -> "2" volume
+installer ..> volume
+
+@enduml
diff --git a/docs/services/uml/UpdateAgentClassDiagram.puml b/docs/services/uml/UpdateAgentClassDiagram.puml
new file mode 100644
index 0000000..0dad627
--- /dev/null
+++ b/docs/services/uml/UpdateAgentClassDiagram.puml
@@ -0,0 +1,100 @@
+'-------------------------------------------------------------------------------
+' Copyright (c) 2023, Arm Limited and Contributors. All rights reserved.
+'
+' SPDX-License-Identifier: BSD-3-Clause
+'
+'-------------------------------------------------------------------------------
+
+@startuml
+
+class fw_directory
+class fw_inspector
+class img_dir_serializer
+class stream_manager
+class update_agent
+class fw_store
+class installer
+
+class update_agent {
+ +begin_staging()
+ +end_staging()
+ +cancel_staging()
+ +accept()
+ +select_previous()
+ +open()
+ +commit()
+ +read_stream()
+ +write_stream()
+}
+
+class fw_directory {
+ +set_boot_info()
+ +add_image_info()
+ +find_image_info()
+ +get_image_info()
+ +num_images()
+}
+
+class fw_inspector {
+ +inspect
+}
+
+class img_dir_serializer {
+ +serialize()
+ +get_len()
+}
+
+class stream_manager {
+ +open_buffer_stream()
+ +open_install_stream()
+ +close_stream()
+ +cancel_streams()
+ +is_open_streams()
+ +read()
+ +write()
+}
+
+class fw_store {
+ +synchronize()
+ +begin_install()
+ +cancel_install()
+ +finalize_install()
+ +select_installer()
+ +write_image()
+ +commit_image()
+ +notify_accepted()
+ +is_accepted()
+ +is_trial()
+ +commit_to_update()
+ +revert_to_previous()
+ +export()
+}
+
+class installer {
+ +begin()
+ +finalize()
+ +abort()
+ +open()
+ +commit()
+ +write()
+ +enumerate()
+}
+
+class installer_index {
+ +register()
+ +find()
+ +get()
+ +get_location_ids()
+}
+
+update_agent -> fw_store
+update_agent -> fw_directory
+update_agent -> fw_inspector
+update_agent -> stream_manager
+update_agent -> img_dir_serializer
+img_dir_serializer ..> fw_directory
+fw_inspector -> installer_index
+fw_inspector ..> installer
+stream_manager ..> installer
+
+@enduml
