armv4vm

armv4vm is minimalist but usable implementation of an ARMv4 processor. Although this implementation is based on booklet 4 of the ARM7TDMI-S instructions set, no particular feature to this processor has been developed. So this implementation is probably common to a wide range of ARM cpu.

Because used in a larger project and not necessary, coprocessor operations and thumb mode were not implemented.

Please send your feedback, bug reports or feature requests.

Requirements

Qt5 is optional but recommended to run unit tests.
A GCC cross toolchain. A crosstool-ng config file is provide and allow to build a suitable toolchain. Some instructions are also given to manually build your toolchain.

Usage

Exchange informations between your host and guest through a dedicated memory space and however it suits you. (uart, queue, etc.) So, set your ld script (armv4vm.ld) and more especially the address for exchanges.

...
uart      : ORIGIN = 0x05000000, LENGTH = 0x00100000 /* 1 mio */
...
uart_base    = ORIGIN(uart);

And use VirtualMachine classe as follow :

#define MEMSIZE 256
#define UARTPOS 0x05000000

    vmProperties.m_memsize = 1024 * 1024 * MEMSIZE;
    vmProperties.m_bin     = "/path/to/your/binfile";
    uint8_t *mem           = nullptr;
    uint8_t *uart          = nullptr;
    bool     running       = true;

    
    // Instanciate and init your vm.
    VirtualMachine vm(&vmProperties);
    mem = vm.init();
    
    // Set Uart localisation
    uart = mem + UARTPOS;

    // Load vm
    if(vm.load()) {

        while (running) {

            // Run infinite loop and get out when a swi occurs.
            switch (vm.run()) {

            case VirtualMachine::Resume:
                break;

            case VirtualMachine::Stop:
                running = false;
                break;

            case VirtualMachine::Suspend:
                std::cout << (char)*uart;
                break;

            default:
                break;
            }
        }
    }

Nota bene

There is no memory protection. Illegal memory access by the guest program will probably cause a host program fault.

Contributions

Debugging the guest program through gdb or a homemade debugger would be great ! Any help about this or any other subject will be appreciated !

Todo

Obviously a lot of things but maybe the first improvement would be to write computational tests and get a reference benchmark results. This would condition future developments.

Writing benchmark
Implement software interrupt to get a better control on vm (finish, standy-by, resume, etc.)
Implement a memory protection.
Implementing the thumb mode would be a good thing to reduce memory usage.
Register and Getting statistics.
Positioning the Qt signals started, finished, suspended, crashed, etc. to easily embedded into a Qt application.
Setting gcov, gprof and valgrind configs.
...

Reference

ARM Instruction Set ARM7TDMI-S Data Sheet

License

This project is free software and released under the GNU General Public License.

thierry-auto/armv4vm