add os[1-8]-ref for os refereces, add guide, add README

os3-ref/src/config.rs

@@ -0,0 +1,10 @@
+//! Constants used in rCore
+
+pub const USER_STACK_SIZE: usize = 4096;
+pub const KERNEL_STACK_SIZE: usize = 4096 * 2;
+pub const KERNEL_HEAP_SIZE: usize = 0x20000;
+pub const MAX_APP_NUM: usize = 16;
+pub const APP_BASE_ADDRESS: usize = 0x80400000;
+pub const APP_SIZE_LIMIT: usize = 0x20000;
+pub const CLOCK_FREQ: usize = 12500000;
+pub const MAX_SYSCALL_NUM: usize = 500;

os3-ref/src/console.rs

@@ -0,0 +1,35 @@
+//! SBI console driver, for text output
+
+use crate::sbi::console_putchar;
+use core::fmt::{self, Write};
+
+struct Stdout;
+
+impl Write for Stdout {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        for c in s.chars() {
+            console_putchar(c as usize);
+        }
+        Ok(())
+    }
+}
+
+pub fn print(args: fmt::Arguments) {
+    Stdout.write_fmt(args).unwrap();
+}
+
+#[macro_export]
+/// print string macro
+macro_rules! print {
+    ($fmt: literal $(, $($arg: tt)+)?) => {
+        $crate::console::print(format_args!($fmt $(, $($arg)+)?));
+    }
+}
+
+#[macro_export]
+/// println string macro
+macro_rules! println {
+    ($fmt: literal $(, $($arg: tt)+)?) => {
+        $crate::console::print(format_args!(concat!($fmt, "\n") $(, $($arg)+)?));
+    }
+}

os3-ref/src/entry.asm

@@ -0,0 +1,12 @@
+    .section .text.entry
+    .globl _start
+_start:
+    la sp, boot_stack_top
+    call rust_main
+
+    .section .bss.stack
+    .globl boot_stack
+boot_stack:
+    .space 4096 * 16
+    .globl boot_stack_top
+boot_stack_top:

os3-ref/src/heap_alloc.rs

@@ -0,0 +1,26 @@
+//! The global allocator
+
+use crate::config::KERNEL_HEAP_SIZE;
+use buddy_system_allocator::LockedHeap;
+
+#[global_allocator]
+/// heap allocator instance
+static HEAP_ALLOCATOR: LockedHeap = LockedHeap::empty();
+
+/// heap space ([u8; KERNEL_HEAP_SIZE])
+static mut HEAP_SPACE: [u8; KERNEL_HEAP_SIZE] = [0; KERNEL_HEAP_SIZE];
+
+/// initiate heap allocator
+pub fn init_heap() {
+    unsafe {
+        HEAP_ALLOCATOR
+            .lock()
+            .init(HEAP_SPACE.as_ptr() as usize, KERNEL_HEAP_SIZE);
+    }
+}
+
+#[alloc_error_handler]
+/// panic when heap allocation error occurs
+pub fn handle_alloc_error(layout: core::alloc::Layout) -> ! {
+    panic!("Heap allocation error, layout = {:?}", layout);
+}

os3-ref/src/lang_items.rs

@@ -0,0 +1,20 @@
+//! The panic handler
+
+use crate::sbi::shutdown;
+use core::panic::PanicInfo;
+
+#[panic_handler]
+/// panic handler
+fn panic(info: &PanicInfo) -> ! {
+    if let Some(location) = info.location() {
+        println!(
+            "Panicked at {}:{} {}",
+            location.file(),
+            location.line(),
+            info.message().unwrap()
+        );
+    } else {
+        println!("[kernel] Panicked: {}", info.message().unwrap());
+    }
+    shutdown()
+}

os3-ref/src/linker.ld

@@ -0,0 +1,48 @@
+OUTPUT_ARCH(riscv)
+ENTRY(_start)
+BASE_ADDRESS = 0x80200000;
+
+SECTIONS
+{
+    . = BASE_ADDRESS;
+    skernel = .;
+
+    stext = .;
+    .text : {
+        *(.text.entry)
+        *(.text .text.*)
+    }
+
+    . = ALIGN(4K);
+    etext = .;
+    srodata = .;
+    .rodata : {
+        *(.rodata .rodata.*)
+        *(.srodata .srodata.*)
+    }
+
+    . = ALIGN(4K);
+    erodata = .;
+    sdata = .;
+    .data : {
+        *(.data .data.*)
+        *(.sdata .sdata.*)
+    }
+
+    . = ALIGN(4K);
+    edata = .;
+    .bss : {
+        *(.bss.stack)
+        sbss = .;
+        *(.bss .bss.*)
+        *(.sbss .sbss.*)
+    }
+
+    . = ALIGN(4K);
+    ebss = .;
+    ekernel = .;
+
+    /DISCARD/ : {
+        *(.eh_frame)
+    }
+}

os3-ref/src/loader.rs

@@ -0,0 +1,101 @@
+//! Loading user applications into memory
+//!
+//! For chapter 3, user applications are simply part of the data included in the
+//! kernel binary, so we only need to copy them to the space allocated for each
+//! app to load them. We also allocate fixed spaces for each task's
+//! [`KernelStack`] and [`UserStack`].
+
+use crate::config::*;
+use crate::trap::TrapContext;
+
+#[repr(align(4096))]
+#[derive(Copy, Clone)]
+/// kernel stack structure
+struct KernelStack {
+    data: [u8; KERNEL_STACK_SIZE],
+}
+
+#[repr(align(4096))]
+#[derive(Copy, Clone)]
+/// user stack structure
+struct UserStack {
+    data: [u8; USER_STACK_SIZE],
+}
+
+/// kernel stack instance
+static KERNEL_STACK: [KernelStack; MAX_APP_NUM] = [KernelStack {
+    data: [0; KERNEL_STACK_SIZE],
+}; MAX_APP_NUM];
+
+/// user stack instance
+static USER_STACK: [UserStack; MAX_APP_NUM] = [UserStack {
+    data: [0; USER_STACK_SIZE],
+}; MAX_APP_NUM];
+
+impl KernelStack {
+    fn get_sp(&self) -> usize {
+        self.data.as_ptr() as usize + KERNEL_STACK_SIZE
+    }
+    pub fn push_context(&self, trap_cx: TrapContext) -> usize {
+        let trap_cx_ptr = (self.get_sp() - core::mem::size_of::<TrapContext>()) as *mut TrapContext;
+        unsafe {
+            *trap_cx_ptr = trap_cx;
+        }
+        trap_cx_ptr as usize
+    }
+}
+
+impl UserStack {
+    fn get_sp(&self) -> usize {
+        self.data.as_ptr() as usize + USER_STACK_SIZE
+    }
+}
+
+/// Get base address of app i.
+fn get_base_i(app_id: usize) -> usize {
+    APP_BASE_ADDRESS + app_id * APP_SIZE_LIMIT
+}
+
+/// Get the total number of applications.
+pub fn get_num_app() -> usize {
+    extern "C" {
+        fn _num_app();
+    }
+    unsafe { (_num_app as usize as *const usize).read_volatile() }
+}
+
+/// Load nth user app at
+/// [APP_BASE_ADDRESS + n * APP_SIZE_LIMIT, APP_BASE_ADDRESS + (n+1) * APP_SIZE_LIMIT).
+pub fn load_apps() {
+    extern "C" {
+        fn _num_app();
+    }
+    let num_app_ptr = _num_app as usize as *const usize;
+    let num_app = get_num_app();
+    let app_start = unsafe { core::slice::from_raw_parts(num_app_ptr.add(1), num_app + 1) };
+    // clear i-cache first
+    unsafe {
+        core::arch::asm!("fence.i");
+    }
+    // load apps
+    for i in 0..num_app {
+        let base_i = get_base_i(i);
+        // clear region
+        (base_i..base_i + APP_SIZE_LIMIT)
+            .for_each(|addr| unsafe { (addr as *mut u8).write_volatile(0) });
+        // load app from data section to memory
+        let src = unsafe {
+            core::slice::from_raw_parts(app_start[i] as *const u8, app_start[i + 1] - app_start[i])
+        };
+        let dst = unsafe { core::slice::from_raw_parts_mut(base_i as *mut u8, src.len()) };
+        dst.copy_from_slice(src);
+    }
+}
+
+/// get app info with entry and sp and save `TrapContext` in kernel stack
+pub fn init_app_cx(app_id: usize) -> usize {
+    KERNEL_STACK[app_id].push_context(TrapContext::app_init_context(
+        get_base_i(app_id),
+        USER_STACK[app_id].get_sp(),
+    ))
+}

os3-ref/src/logging.rs

@@ -0,0 +1,45 @@
+//! Global logger
+
+use log::{self, Level, LevelFilter, Log, Metadata, Record};
+
+/// a simple logger
+struct SimpleLogger;
+
+impl Log for SimpleLogger {
+    fn enabled(&self, _metadata: &Metadata) -> bool {
+        true
+    }
+    fn log(&self, record: &Record) {
+        if !self.enabled(record.metadata()) {
+            return;
+        }
+        let color = match record.level() {
+            Level::Error => 31, // Red
+            Level::Warn => 93,  // BrightYellow
+            Level::Info => 34,  // Blue
+            Level::Debug => 32, // Green
+            Level::Trace => 90, // BrightBlack
+        };
+        println!(
+            "\u{1B}[{}m[{:>5}] {}\u{1B}[0m",
+            color,
+            record.level(),
+            record.args(),
+        );
+    }
+    fn flush(&self) {}
+}
+
+/// initiate logger
+pub fn init() {
+    static LOGGER: SimpleLogger = SimpleLogger;
+    log::set_logger(&LOGGER).unwrap();
+    log::set_max_level(match option_env!("LOG") {
+        Some("ERROR") => LevelFilter::Error,
+        Some("WARN") => LevelFilter::Warn,
+        Some("INFO") => LevelFilter::Info,
+        Some("DEBUG") => LevelFilter::Debug,
+        Some("TRACE") => LevelFilter::Trace,
+        _ => LevelFilter::Off,
+    });
+}

os3-ref/src/main.rs

@@ -0,0 +1,70 @@
+//! The main module and entrypoint
+//!
+//! Various facilities of the kernels are implemented as submodules. The most
+//! important ones are:
+//!
+//! - [`trap`]: Handles all cases of switching from userspace to the kernel
+//! - [`task`]: Task management
+//! - [`syscall`]: System call handling and implementation
+//!
+//! The operating system also starts in this module. Kernel code starts
+//! executing from `entry.asm`, after which [`rust_main()`] is called to
+//! initialize various pieces of functionality. (See its source code for
+//! details.)
+//!
+//! We then call [`task::run_first_task()`] and for the first time go to
+//! userspace.
+
+#![no_std]
+#![no_main]
+#![feature(panic_info_message)]
+#![feature(alloc_error_handler)]
+
+#[macro_use]
+extern crate log;
+
+extern crate alloc;
+
+#[macro_use]
+mod console;
+mod config;
+mod heap_alloc;
+mod lang_items;
+mod loader;
+mod logging;
+mod sbi;
+mod sync;
+pub mod syscall;
+pub mod task;
+mod timer;
+pub mod trap;
+
+core::arch::global_asm!(include_str!("entry.asm"));
+core::arch::global_asm!(include_str!("link_app.S"));
+
+/// clear BSS segment
+fn clear_bss() {
+    extern "C" {
+        fn sbss();
+        fn ebss();
+    }
+    unsafe {
+        core::slice::from_raw_parts_mut(sbss as usize as *mut u8, ebss as usize - sbss as usize)
+            .fill(0);
+    }
+}
+
+#[no_mangle]
+/// the rust entry-point of os
+pub fn rust_main() -> ! {
+    clear_bss();
+    logging::init();
+    println!("[kernel] Hello, world!");
+    heap_alloc::init_heap();
+    trap::init();
+    loader::load_apps();
+    trap::enable_timer_interrupt();
+    timer::set_next_trigger();
+    task::run_first_task();
+    panic!("Unreachable in rust_main!");
+}

os3-ref/src/sbi.rs

@@ -0,0 +1,45 @@
+//! SBI call wrappers
+
+#![allow(unused)]
+
+const SBI_SET_TIMER: usize = 0;
+const SBI_CONSOLE_PUTCHAR: usize = 1;
+const SBI_CONSOLE_GETCHAR: usize = 2;
+const SBI_SHUTDOWN: usize = 8;
+
+#[inline(always)]
+/// general sbi call
+fn sbi_call(which: usize, arg0: usize, arg1: usize, arg2: usize) -> usize {
+    let mut ret;
+    unsafe {
+        core::arch::asm!(
+            "ecall",
+            inlateout("x10") arg0 => ret,
+            in("x11") arg1,
+            in("x12") arg2,
+            in("x17") which,
+        );
+    }
+    ret
+}
+
+/// use sbi call to set timer
+pub fn set_timer(timer: usize) {
+    sbi_call(SBI_SET_TIMER, timer, 0, 0);
+}
+
+/// use sbi call to putchar in console (qemu uart handler)
+pub fn console_putchar(c: usize) {
+    sbi_call(SBI_CONSOLE_PUTCHAR, c, 0, 0);
+}
+
+/// use sbi call to getchar from console (qemu uart handler)
+pub fn console_getchar() -> usize {
+    sbi_call(SBI_CONSOLE_GETCHAR, 0, 0, 0)
+}
+
+/// use sbi call to shutdown the kernel
+pub fn shutdown() -> ! {
+    sbi_call(SBI_SHUTDOWN, 0, 0, 0);
+    panic!("It should shutdown!");
+}

os3-ref/src/sync/mod.rs

@@ -0,0 +1,5 @@
+//! Synchronization and interior mutability primitives
+
+mod up;
+
+pub use up::UPSafeCell;

os3-ref/src/sync/up.rs

@@ -0,0 +1,31 @@
+//! Uniprocessor interior mutability primitives
+
+use core::cell::{RefCell, RefMut};
+
+/// Wrap a static data structure inside it so that we are
+/// able to access it without any `unsafe`.
+///
+/// We should only use it in uniprocessor.
+///
+/// In order to get mutable reference of inner data, call
+/// `exclusive_access`.
+pub struct UPSafeCell<T> {
+    /// inner data
+    inner: RefCell<T>,
+}
+
+unsafe impl<T> Sync for UPSafeCell<T> {}
+
+impl<T> UPSafeCell<T> {
+    /// User is responsible to guarantee that inner struct is only used in
+    /// uniprocessor.
+    pub unsafe fn new(value: T) -> Self {
+        Self {
+            inner: RefCell::new(value),
+        }
+    }
+    /// Panic if the data has been borrowed.
+    pub fn exclusive_access(&self) -> RefMut<'_, T> {
+        self.inner.borrow_mut()
+    }
+}

os3-ref/src/syscall/fs.rs

@@ -0,0 +1,18 @@
+//! File and filesystem-related syscalls
+
+const FD_STDOUT: usize = 1;
+
+// YOUR JOB: 修改 sys_write 使之通过测试
+pub fn sys_write(fd: usize, buf: *const u8, len: usize) -> isize {
+    match fd {
+        FD_STDOUT => {
+            let slice = unsafe { core::slice::from_raw_parts(buf, len) };
+            let str = core::str::from_utf8(slice).unwrap();
+            print!("{}", str);
+            len as isize
+        }
+        _ => {
+            panic!("Unsupported fd in sys_write!");
+        }
+    }
+}

os3-ref/src/syscall/mod.rs

@@ -0,0 +1,36 @@
+//! Implementation of syscalls
+//!
+//! The single entry point to all system calls, [`syscall()`], is called
+//! whenever userspace wishes to perform a system call using the `ecall`
+//! instruction. In this case, the processor raises an 'Environment call from
+//! U-mode' exception, which is handled as one of the cases in
+//! [`crate::trap::trap_handler`].
+//!
+//! For clarity, each single syscall is implemented as its own function, named
+//! `sys_` then the name of the syscall. You can find functions like this in
+//! submodules, and you should also implement syscalls this way.
+
+const SYSCALL_WRITE: usize = 64;
+const SYSCALL_EXIT: usize = 93;
+const SYSCALL_YIELD: usize = 124;
+const SYSCALL_GET_TIME: usize = 169;
+const SYSCALL_TASK_INFO: usize = 410;
+
+mod fs;
+mod process;
+
+use fs::*;
+use process::*;
+
+/// handle syscall exception with `syscall_id` and other arguments
+pub fn syscall(syscall_id: usize, args: [usize; 3]) -> isize {
+    // LAB1: You may need to update syscall info here.
+    match syscall_id {
+        SYSCALL_WRITE => sys_write(args[0], args[1] as *const u8, args[2]),
+        SYSCALL_EXIT => sys_exit(args[0] as i32),
+        SYSCALL_YIELD => sys_yield(),
+        SYSCALL_GET_TIME => sys_get_time(args[0] as *mut TimeVal, args[1]),
+        SYSCALL_TASK_INFO => sys_task_info(args[0] as *mut TaskInfo),
+        _ => panic!("Unsupported syscall_id: {}", syscall_id),
+    }
+}

os3-ref/src/syscall/process.rs

@@ -0,0 +1,48 @@
+//! Process management syscalls
+
+use crate::config::{MAX_APP_NUM, MAX_SYSCALL_NUM};
+use crate::task::{exit_current_and_run_next, suspend_current_and_run_next, TaskStatus};
+use crate::timer::get_time_us;
+
+#[repr(C)]
+#[derive(Debug)]
+pub struct TimeVal {
+    pub sec: usize,
+    pub usec: usize,
+}
+
+pub struct TaskInfo {
+    status: TaskStatus,
+    syscall_times: [u32; MAX_SYSCALL_NUM],
+    time: usize,
+}
+
+/// task exits and submit an exit code
+pub fn sys_exit(exit_code: i32) -> ! {
+    info!("[kernel] Application exited with code {}", exit_code);
+    exit_current_and_run_next();
+    panic!("Unreachable in sys_exit!");
+}
+
+/// current task gives up resources for other tasks
+pub fn sys_yield() -> isize {
+    suspend_current_and_run_next();
+    0
+}
+
+/// get time with second and microsecond
+pub fn sys_get_time(ts: *mut TimeVal, _tz: usize) -> isize {
+    let us = get_time_us();
+    unsafe {
+        *ts = TimeVal {
+            sec: us / 1_000_000,
+            usec: us % 1_000_000,
+        };
+    }
+    0
+}
+
+/// YOUR JOB: Finish sys_task_info to pass testcases
+pub fn sys_task_info(ti: *mut TaskInfo) -> isize {
+    -1
+}

os3-ref/src/task/context.rs

@@ -0,0 +1,30 @@
+//! Implementation of [`TaskContext`]
+
+#[derive(Copy, Clone)]
+#[repr(C)]
+/// task context structure containing some registers
+pub struct TaskContext {
+    ra: usize,
+    sp: usize,
+    s: [usize; 12],
+}
+
+impl TaskContext {
+    pub fn zero_init() -> Self {
+        Self {
+            ra: 0,
+            sp: 0,
+            s: [0; 12],
+        }
+    }
+    pub fn goto_restore(kstack_ptr: usize) -> Self {
+        extern "C" {
+            fn __restore();
+        }
+        Self {
+            ra: __restore as usize,
+            sp: kstack_ptr,
+            s: [0; 12],
+        }
+    }
+}

os3-ref/src/task/mod.rs

@@ -0,0 +1,176 @@
+//! Task management implementation
+//!
+//! Everything about task management, like starting and switching tasks is
+//! implemented here.
+//!
+//! A single global instance of [`TaskManager`] called `TASK_MANAGER` controls
+//! all the tasks in the operating system.
+//!
+//! Be careful when you see [`__switch`]. Control flow around this function
+//! might not be what you expect.
+
+mod context;
+mod switch;
+#[allow(clippy::module_inception)]
+mod task;
+
+use crate::config::{MAX_APP_NUM, MAX_SYSCALL_NUM};
+use crate::loader::{get_num_app, init_app_cx};
+use crate::sync::UPSafeCell;
+use lazy_static::*;
+pub use switch::__switch;
+pub use task::{TaskControlBlock, TaskStatus};
+
+pub use context::TaskContext;
+
+/// The task manager, where all the tasks are managed.
+///
+/// Functions implemented on `TaskManager` deals with all task state transitions
+/// and task context switching. For convenience, you can find wrappers around it
+/// in the module level.
+///
+/// Most of `TaskManager` are hidden behind the field `inner`, to defer
+/// borrowing checks to runtime. You can see examples on how to use `inner` in
+/// existing functions on `TaskManager`.
+pub struct TaskManager {
+    /// total number of tasks
+    num_app: usize,
+    /// use inner value to get mutable access
+    inner: UPSafeCell<TaskManagerInner>,
+}
+
+/// The task manager inner in 'UPSafeCell'
+struct TaskManagerInner {
+    /// task list
+    tasks: [TaskControlBlock; MAX_APP_NUM],
+    /// id of current `Running` task
+    current_task: usize,
+}
+
+lazy_static! {
+    /// a `TaskManager` instance through lazy_static!
+    pub static ref TASK_MANAGER: TaskManager = {
+        let num_app = get_num_app();
+        let mut tasks = [TaskControlBlock {
+            task_cx: TaskContext::zero_init(),
+            task_status: TaskStatus::UnInit,
+        }; MAX_APP_NUM];
+        for (i, t) in tasks.iter_mut().enumerate().take(num_app) {
+            t.task_cx = TaskContext::goto_restore(init_app_cx(i));
+            t.task_status = TaskStatus::Ready;
+        }
+        TaskManager {
+            num_app,
+            inner: unsafe {
+                UPSafeCell::new(TaskManagerInner {
+                    tasks,
+                    current_task: 0,
+                })
+            },
+        }
+    };
+}
+
+impl TaskManager {
+    /// Run the first task in task list.
+    ///
+    /// Generally, the first task in task list is an idle task (we call it zero process later).
+    /// But in ch3, we load apps statically, so the first task is a real app.
+    fn run_first_task(&self) -> ! {
+        let mut inner = self.inner.exclusive_access();
+        let task0 = &mut inner.tasks[0];
+        task0.task_status = TaskStatus::Running;
+        let next_task_cx_ptr = &task0.task_cx as *const TaskContext;
+        drop(inner);
+        let mut _unused = TaskContext::zero_init();
+        // before this, we should drop local variables that must be dropped manually
+        unsafe {
+            __switch(&mut _unused as *mut TaskContext, next_task_cx_ptr);
+        }
+        panic!("unreachable in run_first_task!");
+    }
+
+    /// Change the status of current `Running` task into `Ready`.
+    fn mark_current_suspended(&self) {
+        let mut inner = self.inner.exclusive_access();
+        let current = inner.current_task;
+        inner.tasks[current].task_status = TaskStatus::Ready;
+    }
+
+    /// Change the status of current `Running` task into `Exited`.
+    fn mark_current_exited(&self) {
+        let mut inner = self.inner.exclusive_access();
+        let current = inner.current_task;
+        inner.tasks[current].task_status = TaskStatus::Exited;
+    }
+
+    /// Find next task to run and return task id.
+    ///
+    /// In this case, we only return the first `Ready` task in task list.
+    fn find_next_task(&self) -> Option<usize> {
+        let inner = self.inner.exclusive_access();
+        let current = inner.current_task;
+        (current + 1..current + self.num_app + 1)
+            .map(|id| id % self.num_app)
+            .find(|id| inner.tasks[*id].task_status == TaskStatus::Ready)
+    }
+
+    /// Switch current `Running` task to the task we have found,
+    /// or there is no `Ready` task and we can exit with all applications completed
+    fn run_next_task(&self) {
+        if let Some(next) = self.find_next_task() {
+            let mut inner = self.inner.exclusive_access();
+            let current = inner.current_task;
+            inner.tasks[next].task_status = TaskStatus::Running;
+            inner.current_task = next;
+            let current_task_cx_ptr = &mut inner.tasks[current].task_cx as *mut TaskContext;
+            let next_task_cx_ptr = &inner.tasks[next].task_cx as *const TaskContext;
+            drop(inner);
+            // before this, we should drop local variables that must be dropped manually
+            unsafe {
+                __switch(current_task_cx_ptr, next_task_cx_ptr);
+            }
+            // go back to user mode
+        } else {
+            panic!("All applications completed!");
+        }
+    }
+
+    // LAB1: Try to implement your function to update or get task info!
+}
+
+/// Run the first task in task list.
+pub fn run_first_task() {
+    TASK_MANAGER.run_first_task();
+}
+
+/// Switch current `Running` task to the task we have found,
+/// or there is no `Ready` task and we can exit with all applications completed
+fn run_next_task() {
+    TASK_MANAGER.run_next_task();
+}
+
+/// Change the status of current `Running` task into `Ready`.
+fn mark_current_suspended() {
+    TASK_MANAGER.mark_current_suspended();
+}
+
+/// Change the status of current `Running` task into `Exited`.
+fn mark_current_exited() {
+    TASK_MANAGER.mark_current_exited();
+}
+
+/// Suspend the current 'Running' task and run the next task in task list.
+pub fn suspend_current_and_run_next() {
+    mark_current_suspended();
+    run_next_task();
+}
+
+/// Exit the current 'Running' task and run the next task in task list.
+pub fn exit_current_and_run_next() {
+    mark_current_exited();
+    run_next_task();
+}
+
+// LAB1: Public functions implemented here provide interfaces.
+// You may use TASK_MANAGER member functions to handle requests.

os3-ref/src/task/switch.S

@@ -0,0 +1,34 @@
+.altmacro
+.macro SAVE_SN n
+    sd s\n, (\n+2)*8(a0)
+.endm
+.macro LOAD_SN n
+    ld s\n, (\n+2)*8(a1)
+.endm
+    .section .text
+    .globl __switch
+__switch:
+    # __switch(
+    #     current_task_cx_ptr: *mut TaskContext,
+    #     next_task_cx_ptr: *const TaskContext
+    # )
+    # save kernel stack of current task
+    sd sp, 8(a0)
+    # save ra & s0~s11 of current execution
+    sd ra, 0(a0)
+    .set n, 0
+    .rept 12
+        SAVE_SN %n
+        .set n, n + 1
+    .endr
+    # restore ra & s0~s11 of next execution
+    ld ra, 0(a1)
+    .set n, 0
+    .rept 12
+        LOAD_SN %n
+        .set n, n + 1
+    .endr
+    # restore kernel stack of next task
+    ld sp, 8(a1)
+    ret
+

os3-ref/src/task/switch.rs

@@ -0,0 +1,16 @@
+//! Rust wrapper around `__switch`.
+//!
+//! Switching to a different task's context happens here. The actual
+//! implementation must not be in Rust and (essentially) has to be in assembly
+//! language (Do you know why?), so this module really is just a wrapper around
+//! `switch.S`.
+
+core::arch::global_asm!(include_str!("switch.S"));
+
+use super::TaskContext;
+
+extern "C" {
+    /// Switch to the context of `next_task_cx_ptr`, saving the current context
+    /// in `current_task_cx_ptr`.
+    pub fn __switch(current_task_cx_ptr: *mut TaskContext, next_task_cx_ptr: *const TaskContext);
+}

os3-ref/src/task/task.rs

@@ -0,0 +1,20 @@
+//! Types related to task management
+
+use super::TaskContext;
+
+#[derive(Copy, Clone)]
+/// task control block structure
+pub struct TaskControlBlock {
+    pub task_status: TaskStatus,
+    pub task_cx: TaskContext,
+    // LAB1: Add whatever you need about the Task.
+}
+
+#[derive(Copy, Clone, PartialEq)]
+/// task status: UnInit, Ready, Running, Exited
+pub enum TaskStatus {
+    UnInit,
+    Ready,
+    Running,
+    Exited,
+}

os3-ref/src/timer.rs

@@ -0,0 +1,23 @@
+//! RISC-V timer-related functionality
+
+use crate::config::CLOCK_FREQ;
+use crate::sbi::set_timer;
+use riscv::register::time;
+
+const TICKS_PER_SEC: usize = 100;
+const MICRO_PER_SEC: usize = 1_000_000;
+
+/// read the `mtime` register
+pub fn get_time() -> usize {
+    time::read()
+}
+
+/// get current time in microseconds
+pub fn get_time_us() -> usize {
+    time::read() / (CLOCK_FREQ / MICRO_PER_SEC)
+}
+
+/// set the next timer interrupt
+pub fn set_next_trigger() {
+    set_timer(get_time() + CLOCK_FREQ / TICKS_PER_SEC);
+}

os3-ref/src/trap/context.rs

@@ -0,0 +1,28 @@
+//! Implementation of [`TrapContext`]
+
+use riscv::register::sstatus::{self, Sstatus, SPP};
+
+#[repr(C)]
+/// trap context structure containing sstatus, sepc and registers
+pub struct TrapContext {
+    pub x: [usize; 32],
+    pub sstatus: Sstatus,
+    pub sepc: usize,
+}
+
+impl TrapContext {
+    pub fn set_sp(&mut self, sp: usize) {
+        self.x[2] = sp;
+    }
+    pub fn app_init_context(entry: usize, sp: usize) -> Self {
+        let mut sstatus = sstatus::read();
+        sstatus.set_spp(SPP::User);
+        let mut cx = Self {
+            x: [0; 32],
+            sstatus,
+            sepc: entry,
+        };
+        cx.set_sp(sp);
+        cx
+    }
+}

os3-ref/src/trap/mod.rs

@@ -0,0 +1,78 @@
+//! Trap handling functionality
+//!
+//! For rCore, we have a single trap entry point, namely `__alltraps`. At
+//! initialization in [`init()`], we set the `stvec` CSR to point to it.
+//!
+//! All traps go through `__alltraps`, which is defined in `trap.S`. The
+//! assembly language code does just enough work restore the kernel space
+//! context, ensuring that Rust code safely runs, and transfers control to
+//! [`trap_handler()`].
+//!
+//! It then calls different functionality based on what exactly the exception
+//! was. For example, timer interrupts trigger task preemption, and syscalls go
+//! to [`syscall()`].
+
+mod context;
+
+use crate::syscall::syscall;
+use crate::task::{exit_current_and_run_next, suspend_current_and_run_next};
+use crate::timer::set_next_trigger;
+use riscv::register::{
+    mtvec::TrapMode,
+    scause::{self, Exception, Interrupt, Trap},
+    sie, stval, stvec,
+};
+
+core::arch::global_asm!(include_str!("trap.S"));
+
+/// initialize CSR `stvec` as the entry of `__alltraps`
+pub fn init() {
+    extern "C" {
+        fn __alltraps();
+    }
+    unsafe {
+        stvec::write(__alltraps as usize, TrapMode::Direct);
+    }
+}
+
+/// timer interrupt enabled
+pub fn enable_timer_interrupt() {
+    unsafe {
+        sie::set_stimer();
+    }
+}
+
+#[no_mangle]
+/// handle an interrupt, exception, or system call from user space
+pub fn trap_handler(cx: &mut TrapContext) -> &mut TrapContext {
+    let scause = scause::read(); // get trap cause
+    let stval = stval::read(); // get extra value
+    match scause.cause() {
+        Trap::Exception(Exception::UserEnvCall) => {
+            cx.sepc += 4;
+            cx.x[10] = syscall(cx.x[17], [cx.x[10], cx.x[11], cx.x[12]]) as usize;
+        }
+        Trap::Exception(Exception::StoreFault) | Trap::Exception(Exception::StorePageFault) => {
+            error!("[kernel] PageFault in application, bad addr = {:#x}, bad instruction = {:#x}, core dumped.", stval, cx.sepc);
+            exit_current_and_run_next();
+        }
+        Trap::Exception(Exception::IllegalInstruction) => {
+            error!("[kernel] IllegalInstruction in application, core dumped.");
+            exit_current_and_run_next();
+        }
+        Trap::Interrupt(Interrupt::SupervisorTimer) => {
+            set_next_trigger();
+            suspend_current_and_run_next();
+        }
+        _ => {
+            panic!(
+                "Unsupported trap {:?}, stval = {:#x}!",
+                scause.cause(),
+                stval
+            );
+        }
+    }
+    cx
+}
+
+pub use context::TrapContext;

os3-ref/src/trap/trap.S

@@ -0,0 +1,61 @@
+.altmacro
+.macro SAVE_GP n
+    sd x\n, \n*8(sp)
+.endm
+.macro LOAD_GP n
+    ld x\n, \n*8(sp)
+.endm
+    .section .text
+    .globl __alltraps
+    .globl __restore
+    .align 2
+__alltraps:
+    csrrw sp, sscratch, sp
+    # now sp->kernel stack, sscratch->user stack
+    # allocate a TrapContext on kernel stack
+    addi sp, sp, -34*8
+    # save general-purpose registers
+    sd x1, 1*8(sp)
+    # skip sp(x2), we will save it later
+    sd x3, 3*8(sp)
+    # skip tp(x4), application does not use it
+    # save x5~x31
+    .set n, 5
+    .rept 27
+        SAVE_GP %n
+        .set n, n+1
+    .endr
+    # we can use t0/t1/t2 freely, because they were saved on kernel stack
+    csrr t0, sstatus
+    csrr t1, sepc
+    sd t0, 32*8(sp)
+    sd t1, 33*8(sp)
+    # read user stack from sscratch and save it on the kernel stack
+    csrr t2, sscratch
+    sd t2, 2*8(sp)
+    # set input argument of trap_handler(cx: &mut TrapContext)
+    mv a0, sp
+    call trap_handler
+
+__restore:
+    # now sp->kernel stack(after allocated), sscratch->user stack
+    # restore sstatus/sepc
+    ld t0, 32*8(sp)
+    ld t1, 33*8(sp)
+    ld t2, 2*8(sp)
+    csrw sstatus, t0
+    csrw sepc, t1
+    csrw sscratch, t2
+    # restore general-purpuse registers except sp/tp
+    ld x1, 1*8(sp)
+    ld x3, 3*8(sp)
+    .set n, 5
+    .rept 27
+        LOAD_GP %n
+        .set n, n+1
+    .endr
+    # release TrapContext on kernel stack
+    addi sp, sp, 34*8
+    # now sp->kernel stack, sscratch->user stack
+    csrrw sp, sscratch, sp
+    sret