rCore-Tutorial-v3

rCore-Tutorial version 3.5. See the Documentation in Chinese.

Official QQ group number: 735045051

news

• 2021.11.20: Now we are updating our labs. Please checkout chX-dev Branches for our current new labs. (Notice: please see the [Dependency] section in the end of this doc)

Overview

This project aims to show how to write an Unix-like OS running on RISC-V platforms from scratch in Rust for beginners without any background knowledge about computer architectures, assembly languages or operating systems.

Features

• Platform supported: qemu-system-riscv64 simulator or dev boards based on Kendryte K210 SoC such as Maix Dock
• OS
  • concurrency of multiple processes each of which contains mutiple native threads
  • preemptive scheduling(Round-Robin algorithm)
  • dynamic memory management in kernel
  • virtual memory
  • a simple file system with a block cache
  • an interactive shell in the userspace
• only 4K+ LoC
• A detailed documentation in Chinese in spite of the lack of comments in the code(English version is not available at present)

Prerequisites

Install Rust

See official guide.

Install some tools:

$ rustup target add riscv64gc-unknown-none-elf
$ cargo install cargo-binutils --vers =0.3.3
$ rustup component add llvm-tools-preview
$ rustup component add rust-src

Install Qemu

Here we manually compile and install Qemu 5.0.0. For example, on Ubuntu 18.04:

# install dependency packages
$ sudo apt install autoconf automake autotools-dev curl libmpc-dev libmpfr-dev libgmp-dev \
              gawk build-essential bison flex texinfo gperf libtool patchutils bc \
              zlib1g-dev libexpat-dev pkg-config  libglib2.0-dev libpixman-1-dev git tmux python3 python3-pip
# download Qemu source code
$ wget https://download.qemu.org/qemu-5.0.0.tar.xz
# extract to qemu-5.0.0/
$ tar xvJf qemu-5.0.0.tar.xz
$ cd qemu-5.0.0
# build
$ ./configure --target-list=riscv64-softmmu,riscv64-linux-user
$ make -j$(nproc)

Then, add following contents to ~/.bashrc(please adjust these paths according to your environment):

export PATH=$PATH:/home/shinbokuow/Downloads/built/qemu-5.0.0
export PATH=$PATH:/home/shinbokuow/Downloads/built/qemu-5.0.0/riscv64-softmmu
export PATH=$PATH:/home/shinbokuow/Downloads/built/qemu-5.0.0/riscv64-linux-user

Finally, update the current shell:

$ source ~/.bashrc

Now we can check the version of Qemu:

$ qemu-system-riscv64 --version
QEMU emulator version 5.0.0
Copyright (c) 2003-2020 Fabrice Bellard and the QEMU Project developers

Install RISC-V GNU Embedded Toolchain(including GDB)

Download the compressed file according to your platform From Sifive website(Ctrl+F 'toolchain').

Extract it and append the location of the 'bin' directory under its root directory to $PATH.

For example, we can check the version of GDB:

$ riscv64-unknown-elf-gdb --version
GNU gdb (SiFive GDB-Metal 10.1.0-2020.12.7) 10.1
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Install serial tools(Optional, if you want to run on K210)

$ pip3 install pyserial
$ sudo apt install python3-serial

Run our project

Qemu

$ git clone https://github.com/rcore-os/rCore-Tutorial-v3.git
$ cd rCore-Tutorial-v3/os
$ make run

After outputing some debug messages, the kernel lists all the applications available and enter the user shell:

/**** APPS ****
mpsc_sem
usertests
pipetest
forktest2
cat
initproc
race_adder_loop
threads_arg
race_adder_mutex_spin
race_adder_mutex_blocking
forktree
user_shell
huge_write
race_adder
race_adder_atomic
threads
stack_overflow
filetest_simple
forktest_simple
cmdline_args
run_pipe_test
forktest
matrix
exit
fantastic_text
sleep_simple
yield
hello_world
pipe_large_test
sleep
phil_din_mutex
**************/
Rust user shell
>> 

You can run any application except for initproc and user_shell itself. To run an application, just input its filename and hit enter. usertests can run a bunch of applications, thus it is recommended.

Type Ctrl+a then x to exit Qemu.

K210

Before chapter 6, you do not need a SD card:

$ git clone https://github.com/rcore-os/rCore-Tutorial-v3.git
$ cd rCore-Tutorial-v3/os
$ make run BOARD=k210

From chapter 6, before running the kernel, we should insert a SD card into PC and manually write the filesystem image to it:

$ cd rCore-Tutorial-v3/os
$ make sdcard

By default it will overwrite the device /dev/sdb which is the SD card, but you can provide another location. For example, make sdcard SDCARD=/dev/sdc.

After that, remove the SD card from PC and insert it to the slot of K210. Connect the K210 to PC and then:

$ git clone https://github.com/rcore-os/rCore-Tutorial-v3.git
$ cd rCore-Tutorial-v3/os
$ make run BOARD=k210

Type Ctrl+] to disconnect from K210.

Working in progress

Our first release 3.5.0 (chapter 1-7) has been published.

There will be 9 chapters in our next release 3.6.0, where 2 new chapters will be added:

• chapter 8: synchronization on a uniprocessor
• chapter 9: I/O devices

Current version is 3.6.0-alpha.1 and we are still working on it.

Here are the updates since 3.5.0:

Completed

• automatically clean up and rebuild before running our project on a different platform
• fix power series application in early chapters, now you can find modulus in the output
• use UPSafeCell instead of RefCell or spin::Mutex in order to access static data structures and adjust its API so that it cannot be borrowed twice at a time(mention & .exclusive_access().task[0] in run_first_task)
• move TaskContext into TaskControlBlock instead of restoring it in place on kernel stack(since ch3), eliminating annoying task_cx_ptr2
• replace llvm_asm! with asm!
• expand the fs image size generated by rcore-fs-fuse to 128MiB
• add a new test named huge_write which evaluates the fs performance(qemu~500KiB/s k210~50KiB/s)
• flush all block cache to disk after a fs transaction which involves write operation
• replace spin::Mutex with UPSafeCell before SMP chapter
• add codes for a new chapter about synchronization & mutual exclusion(uniprocessor only)
• bug fix: we should call find_pte rather than find_pte_create in PageTable::unmap
• clarify: "check validity of level-3 pte in find_pte instead of checking it outside this function" should not be a bug
• code of chapter 8: synchronization on a uniprocessor
• switch the code of chapter 6 and chapter 7
• support signal mechanism in chapter 7/8(only works for apps with a single thread)

Todo(High priority)

• review documentation, current progress: 5/9
• support user-level sync primitives in chapter 8
• code of chapter 9: device drivers based on interrupts, including UART and block devices
• use old fs image optionally, do not always rebuild the image
• add new system calls: getdents64/fstat
• shell functionality improvement(to be continued...)
• give every non-zero process exit code an unique and clear error type
• effective error handling of mm module

Todo(Low priority)

• rewrite practice doc and remove some inproper questions
• provide smooth debug experience at a Rust source code level
• format the code using official tools
• support other platforms

Crates

We will add them later.