update comments

os/src/batch.rs

@@ -1,3 +1,5 @@
+//! batch subsystem
+
 use crate::sync::UPSafeCell;
 use crate::trap::TrapContext;
 use core::arch::asm;
@@ -111,14 +113,17 @@ lazy_static! {
     };
 }
 
+/// init batch subsystem
 pub fn init() {
     print_app_info();
 }
 
+/// print apps info
 pub fn print_app_info() {
     APP_MANAGER.exclusive_access().print_app_info();
 }
 
+/// run next app
 pub fn run_next_app() -> ! {
     let mut app_manager = APP_MANAGER.exclusive_access();
     let current_app = app_manager.get_current_app();

os/src/main.rs

@@ -24,17 +24,16 @@ use core::arch::global_asm;
 
 #[macro_use]
 mod console;
-mod batch;
+pub mod batch;
 mod lang_items;
 mod sbi;
 mod sync;
-mod syscall;
-mod trap;
+pub mod syscall;
+pub mod trap;
 
 global_asm!(include_str!("entry.asm"));
 global_asm!(include_str!("link_app.S"));
 
-
 /// clear BSS segment
 fn clear_bss() {
     extern "C" {

os/src/trap/context.rs

@@ -1,25 +1,30 @@
 use riscv::register::sstatus::{self, Sstatus, SPP};
-
+/// Trap Context
 #[repr(C)]
 pub struct TrapContext {
+    /// general regs[0..31]
     pub x: [usize; 32],
+    /// CSR sstatus      
     pub sstatus: Sstatus,
+    /// CSR sepc
     pub sepc: usize,
 }
 
 impl TrapContext {
+    /// set stack pointer to x_2 reg (sp)
     pub fn set_sp(&mut self, sp: usize) {
         self.x[2] = sp;
     }
+    /// init app context
     pub fn app_init_context(entry: usize, sp: usize) -> Self {
-        let mut sstatus = sstatus::read();
-        sstatus.set_spp(SPP::User);
+        let mut sstatus = sstatus::read(); // CSR sstatus
+        sstatus.set_spp(SPP::User); //previous privilege mode: user mode
         let mut cx = Self {
             x: [0; 32],
             sstatus,
-            sepc: entry,
+            sepc: entry, // entry point of app
         };
-        cx.set_sp(sp);
-        cx
+        cx.set_sp(sp); // app's user stack pointer
+        cx // return initial Trap Context of app
     }
 }