Add comments in ch6

os/src/main.rs

@@ -1,3 +1,25 @@
+//! 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
+//! - [`mm`]: Address map using SV39
+//! - [`sync`]: Wrap a static data structure inside it so that we are able to access it without any `unsafe`.
+//! - [`fs`]: Separate user from file system with some structures
+//! 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_tasks()`] and for the first time go to
+//! userspace.
+
+#![deny(missing_docs)]
+#![deny(warnings)]
+#![allow(unused_imports)]
 #![no_std]
 #![no_main]
 #![feature(panic_info_message)]
@@ -19,20 +41,20 @@ mod board;
 mod console;
 mod config;
 mod drivers;
-mod fs;
-mod lang_items;
-mod mm;
-mod sbi;
-mod sync;
-mod syscall;
-mod task;
-mod timer;
-mod trap;
+pub mod fs;
+pub mod lang_items;
+pub mod mm;
+pub mod sbi;
+pub mod sync;
+pub mod syscall;
+pub mod task;
+pub mod timer;
+pub mod trap;
 
 use core::arch::global_asm;
 
 global_asm!(include_str!("entry.asm"));
-
+/// clear BSS segment
 fn clear_bss() {
     extern "C" {
         fn sbss();
@@ -45,6 +67,7 @@ fn clear_bss() {
 }
 
 #[no_mangle]
+/// the rust entry-point of os
 pub fn rust_main() -> ! {
     clear_bss();
     println!("[kernel] Hello, world!");