This project was part of Operating Systems 1 and Operating Systems 2 class.
It was real fun to do and I learned a lot about risc-v and OS during the process.
First part of the project (OS1, 2022 second semester) was to create basic Kernel functionalities on top of xv6 kernel part of used just to initialize risc-v processor and jump to the main function of the kernel.
Project included ABI, C API and CPP API for system calls for working with memory, threads, semaphores and console(IO). For all that functionalities to be realized kernel must have many components: interrupt routines, scheduler, memory allocator, IO thread and many structures for representation control blocks etc.
Second part of the project (OS2, 2023 first semester) was to update the kernel I made for the OS1 class with new slab allocator for managing the memory, and to introduce virtualization so the Kernel and the userspace could be separated and user program cannot access the kernel space(which was not managed in the first part).
The tests were provided by class assistants and professors.
System is working with one processor so there is only one thread controlling the processor at the time. Kernel itself isn't preemptive, but userspace is. Kernel is minimalistic so it can run only single user function(userMain) which represents one program. This function is run upon initialization of the kernel and after all of the user threads are finished the kernel stops.
Installing required linux packages:
sudo apt install git build-essential qemu-system-misc gcc-riscv64-linux-gnu binutils-riscv64-linux-gnu gdb-multiarch g++-riscv64-linux-gnu
Getting the repository on the local machine:
git clone https://github.com/ikac22/Risc-V-Kernel.git
Building the code and running the kernel in virtual machine:
cd Risc-V-Kernel
make clean
make qemu
When the kernel finishes or you want to stop the virtual machine just tipe ctrl-a and then press x (ctrl-a x).
When kernel is started, first it will print out some initialization text. After that initialization, kernel will run the userMain function which can be found in the src/user/userMain.cpp file. This function is where userspace starts and where new threads could be created. If you want to create user program just change the userMain.