Welcome to the landing page for Morello Open Source Software

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Morello is a research program led by Arm in association with partners and funded by the UKRI as part of the UK government Digital Security by Design (DSbD) programme . It defines a new prototype security architecture based on CHERI (Capability Hardware Enhanced RISC Instructions).

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A DSbD technology platform prototype (the Morello board) provides a SoC implementation of the architecture. This was created to enable software developers and researchers to explore real-world use cases and inform future development.


Please refer to the top level Documentation repository to get started.


Arm’s web pages provide curated resources for the Morello Program. Including Architecture specifications, platform model, technical reference manual, Morello forum and more.

Development Platforms

Morello Hardware Development Platform

The Morello hardware development platform is now available to organizations involved in defined research activities. Access to the platform is managed by the UK government’s Digital Security by Design (DSbD) Technology Access Programme.

Software support for the platform will evolve over time and specifics will be detailed via release-notes.rst in the Documentation code repository. Note that firmware pre-installed on boards should be updated to the latest versions immediately after first validation of boot.

Morello Platform Model

The Morello Platform Model is an open access FVP (Fixed Virtual Platform) implementation aligned with the development board. It is available to download from Arm’s Ecosystem FVP Developer page.

FVPs use Arm binary translation technology to create a register level functional model of system hardware (including processor, memory and peripherals) that can be run as an executable in a development environment. They implement a programmer’s view model suitable for software development, enabling execution of full software stacks on a widely available platform.

A walkthrough video of setting up the Android development environment on FVP is available on the resources pages

Morello software enablement

The diagram shows a high-level view of the software stacks targeting the Morello hardware and FVP platforms. Above the firmware, which environment is best suited for development is dictated by a range of factors relating to the specific aims of individual research projects. The CheriBSD port for Morello provides a mature environment for general research and userspace experimentation. However, the majority of commercial devices are based on Android and Linux, which is why Arm are also focused on exploring the application of the Morello prototype architecture to these environments.

These stacks and the supporting tooling are intended to provide a foundation for ecosystem research, enabling collaboration on existing work packages and new work on alternate RTOS/OS environments, tools and workloads. Functionality will evolve in stages throughout the lifetime of the Morello Program.

Integrated stack releases (manifests, build scripts, documentation) and component forks associated with this page are available via git.morello-project.org. Please start with the top level code repository Documentation.

Bare-metal Enablement

Bare-metal development is supported by exit from the firmware stack at two points:

  • Post SCP execution: System level IP is initialised, development is possible from Application processor reset. Supports true bare-metal scenarios.
  • Post TF-A execution: Lead Application processor is initialised and runtime services are available. Supports ports of new RTOS environments and more complex bare-metal workloads.

Please refer to standalone-baremetal-readme.rst in the Documentation repository.

Arm Development Studio Morello Edition provides a development environment for bare-metal configurations and includes a “hello world” example.

Android Enablement

An evolving Android environment has been available for Morello since the first release in October 2020.

This includes a minimal (nano) headless system Android (64-bit) profile suitable for use with the FVP. Full Android boot is supported on the Morello hardware platform.

Support for pure capability (purecap) applications (along with several example ports) is provided by a Morello Android Kernel and Bionic library variants built using the CHERI LLVM/Clang toolchain.

For more information on the status of the Android environment, please refer to android-readme.rst in the Documentation repository.

Further information on the timeline for ongoing work in the Morello Kernel and the use of libshim in C libraries is available below.

Linux Enablement (2022 onwards)

Support for a Morello Linux environment is still under development.

A prototype native (Arm on Arm) Linux development environment for the Morello board is expected Q3 2022. This will provide a (64-bit) Debian distribution with a modified kernel (implementing the transitional PCuABI) and a proof of concept minimal purecap userspace (based initially on musl libC) inside a chroot.

Examples of planned work packages, 2022/23 onwards:

  • Further evolution of musl libC support & purecap userspace application ports
  • Staged introduction of Morello Kernel PCuABI features
  • Introduction of a Morello GCC/GlibC based environment
  • Proof of concept work to demonstrate a Morello aware Distro framework

Further information on ongoing work in the Morello Kernel is available below.


A mature CheriBSD environment for Morello is implemented and hosted separately by the University of Cambridge Computer Laboratory. This provides a memory-safe kernel and userspace, as well as many example ports of application frameworks, demonstrating more complete integration of CHERI (and Morello) support into an OS design.

Component support & tooling


Platform ports of standard open source firmware components: SCP firmware, Trusted Firmware TF-A, UEFI EDK II are available for the Morello platform. These are standard 64-bit platform ports, with some additional low level hardware initialization to enable support of capabilities in higher level software.

Morello Linux kernel (under development)

Arm’s work on the Linux Kernel is focused on developing a new kernel-user ABI to support pure capability userspace software development. The aim is to replace all pointers at the kernel-user interface with capabilities, instead of 64-bit integers. This work is linked to development of associated C libraries (Bionic, Musl, GlibC) and developed against a PCuABI (pure capability kernel-user ABI) specification. Ultimately enabling Android and Linux environments capable of supporting a mix of pure capability and “COMPAT” standard 64-bit userspace components. (32-bit applications will not be supported)

Android releases will continue to rely on a lightly modified Kernel, supported by a temporary libshim translation layer in C libraries, until PCuABI support matures.

Throughout 2022/23 PCuABI support will be introduced in stages:

Stage1: Functional support

Provide native support for user-space applications built against the purecap ABI

  • A transitional PCuABI will support an initially limited set of syscalls, expanded over time.
  • Allows incremental reduction of functionality in the corresponding C library libshim (currently used to “bridge” syscalls to the standard Kernel ABI)

Stage2: Memory safety & security

Improve memory safety at the kernel-user boundary, leveraging the properties of capabilities

Morello LLVM toolchains & libraries

Morello is supported by LLVM-based open-source toolchains based on the CHERI Clang/LLVM toolchain from the University of Cambridge. Please note, these are experimental toolchains and as such features may be missing.

Bare-metal toolchain

A prebuilt x86-hosted Morello CHERI LLVM toolchain is available to support architecture exploration.

Includes a C/C++ compiler (clang), linker (lld), a standard C library (newlib), a standard C++ library (libc++, libc++abi) and various utilities (such as assembler & disassembler).

Linux and Android toolchains

Prebuilt x86-hosted and AArch64 hosted Morello CHERI LLVM toolchains are available.

These include a C/C++ compiler (clang), linker (lld), debugger (lldb), various utilities (such as assembler & disassembler) and run-time libraries.

The use of these toolchains is dependent upon C library support.

Linux and Android C libraries

To enable functional development & porting efforts in userspace ahead of full Kernel ABI support, some C libraries have been initially implemented using the concept of a libshim translation layer. This does not provide a secure implementation, but allows support for a full set of system calls ahead of a mature PCuABI and related Kernel and C library implementations. Functionality handled in libshim will reduce over time as the Kernel and C library implementations mature.

  • Bionic: Supports Android
  • musl libc: Lightweight C library intended to support initial “embedded” Linux environments

Morello GCC toolchain & libraries (under development)

Development of a GCC-based open-source toolchain and associated GlibC is ongoing.

An initial proof of concept release is expected in 2022, with expanded functionality (dynamic linking, C++, etc) emerging in stages after first release.

Graphics Enablement (under development)

Media support for Morello hardware (Mali-D35 display processor and Mali-G76 GPU) is based around Open Source Software.

The display processor relies on an existing upstream Kernel driver. GPU support is based on the Panfrost open-source driver framework for Mali Bifrost GPU architectures, enabling public ecosystem development

Initial UI support in development environments will be based on software rendering. Work is ongoing to validate a Morello platform port of a 64-bit Panfrost GPU driver in a Linux/Mesa graphics framework. This provides a foundation for graphics development and supports longer term investigation into the application of the security architecture to graphics stacks.

Support and Contributions

The Morello Gitlab and associated issues trackers are intended to enable Open Source Software development - supporting engineering contributions and targeted defects and patches relating to specific component projects. We welcome engineering collaboration.

Wider support queries and questions should be raised via Arm’s Morello forum

For questions specific to the CheriBSD environment visit https://www.cheribsd.org/