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Scapula

This repository contains tools for performing testing and verification of ARM CPUs against a machine parsable version of the ARMv8-A Architecture Reference Manual.

The project consists of three major components:

  1. Scapula: A python package that makes it easy to generate executable test cases using the information contained in the manuals

  2. Scapula OS: A minimal runtime enviornment for test cases generated by Scapula

  3. Scapula Loader: A bootloader that packages up and loads the other components onto an ARM CPU

Generated test cases run as a single thread, bare-metal application that spans all exception levels (EL0, EL1, EL2, EL3). This allows tests to verify behaviors of a CPU that cross typical software isolation boundaries:

void example_test(void)
{
    switch_to_el(2);
    printf("This test is executing as a hypervisor in EL2\n");

    switch_to_el(1);
    printf("Now the test is executing as an OS in EL1\n");

    aarch64_sctlr_el3_get();
    printf("The test is now in EL%u, ", aarch64_currentel_el_get()); 
    printf("because the above register access caused a synchronous exception\n");
}

Support for crossing execution states (aarch32 and aarch64) and security states (secure world, non-secure world) are currently in the works.

Dependencies

Scapula officially supports building on Ubuntu 19.04+ using the following dependencies:

sudo apt-get install cmake gcc-aarch64-linux-gnu arm-linux-gnueabihf-gcc python3 python3-pip
sudo pip3 install lxml colorama

CMake version > 3.12 is required.

Building

The easiest way to build:

git clone https://github.com/ainfosec/scapula.git
mkdir build && cd build
cmake ../scapula
make

The better way to build:

mkdir workspace && cd workspace
git clone https://github.com/ainfosec/scapula.git
mkdir cache             # <-- Dependencies will download here, shared across builds
touch config.cmake      # <-- Edit this file to define your build configurations
mkdir build && cd build
cmake ../scapula
make -j<# of cores on your computer>

Configuring

Scapula uses CMake to configure build options. There are numerous ways that you can specify build options to CMake:

  1. Display all available options and configure the project with a menu based assistant:
sudo apt-get install cmake-curses-gui
ccmake </path/to/a/configured/build/directory>
  1. Configure options using the command line:
cmake ../scapula -DSYSREG_XML_PATH=~/workspace/sysregs
  1. Configure options using a CMake config file. For example, create a file with the following contents and save it to ~/workspace/config.cmake:
set(SYSREG_XML_PATH ~/workspace/sysregs)

then configure the build using:

cmake ../scapula -DCONFIG=~/workspace/config.cmake

In general, it is best to use only one configuration mechanism per build. If you do not specify any build configurations, the project will use the default options defined in scapula/scripts/cmake/config/default.cmake.

Supported Platforms

Offical hardware support currently includes the NVIDIA Jetson TX1 and TX2 development kits, as well as an emulator derived from a Sail model.

However, porting to a new hardware platform could be as simple as modifying a few build configuraiton options (assuming memory is already initialized):

# The base address of a serial port to be used for printing results
set(SERIAL_BASE 0x3c000000)

# The type of serial port, options: [8250_uart, pl011_primecell]
set(SERIAL_DEVICE pl011_primecell)

# The address that Scapula Loader will be loaded to by a preveous stage bootloader
set(START_ADDRESS 0x80000000)

# The amount of memory Scapula OS will use as a heap
set(HEAP_SIZE 0x10000)

# The amount of memory Scapula OS will use as a stack
set(STACK_SIZE 0x10000)