Chapter1: Update panic_handler.

os/src/main.rs

@@ -2,17 +2,28 @@
 #![no_main]
 #![feature(global_asm)]
 #![feature(llvm_asm)]
+#![feature(panic_info_message)]
 
-mod lang_items;
-mod sbi;
 #[macro_use]
 mod console;
+mod lang_items;
+mod sbi;
+
 
 global_asm!(include_str!("entry.asm"));
 
+fn clear_bss() {
+    extern "C" {
+        fn sbss();
+        fn ebss();
+    }
+    (sbss as usize..ebss as usize).for_each(|a| {
+        unsafe { (a as *mut u8).write_volatile(0) }
+    });
+}
+
 #[no_mangle]
 pub fn rust_main() -> ! {
-    println!("Hello, world!");
     extern "C" {
         fn stext();
         fn etext();
@@ -25,10 +36,12 @@ pub fn rust_main() -> ! {
         fn boot_stack();
         fn boot_stack_top();
     };
+    clear_bss();
+    println!("Hello, world!");
     println!(".text [{:#x}, {:#x})", stext as usize, etext as usize);
     println!(".rodata [{:#x}, {:#x})", srodata as usize, erodata as usize);
     println!(".data [{:#x}, {:#x})", sdata as usize, edata as usize);
     println!("boot_stack [{:#x}, {:#x})", boot_stack as usize, boot_stack_top as usize);
     println!(".bss [{:#x}, {:#x})", sbss as usize, ebss as usize);
-    loop {}
+    panic!("Shutdown machine!");
 }