src/main.rs

@@ -14,12 +14,8 @@ mod uart;
 unsafe extern "C" fn _enter() -> ! {
     use core::arch::asm;
     asm!(
-        // load hartid into t0; if t0 =/= 0, then jump to busy loop
-        "csrr t0, mhartid",
-        "bnez t0, 3f",
-
         // before we use the `la` pseudo-instruction for the first time,
-        // we need to set `gp` (look up linker relaxation)
+        // we need to set `gp` (google linker relaxation)
         ".option push", // pushes the current option stack
         ".option norelax", // disable relaxation so we can properly set `gp`
         // this instruction compiles to:
@@ -42,14 +38,7 @@ unsafe extern "C" fn _enter() -> ! {
         "bne t0, t1, 1b",
     "2:",
         // BSS is clear!
-        "j 4f",
-    
-    // busy loop if hartid =/= 0
-    "3:",
-        "wfi", // wait for interrupt (or nop)
-        "j 3b",
-    
-    "4:",
+
         // "tail-call" to {start} (call without saving a return address)
         "tail {start}",
         start = sym start, // {start} refers to the function [start] below
@@ -73,10 +62,8 @@ extern "C" fn start() -> ! {
     unsafe { uart::init_console(0x1000_0000) };
     println!("Hello, world!");
 
-    // print current hartid
     println!("hartid: {}", riscv::register::mhartid::read());
 
-    // poll console for input and print characters back
     loop {
         let c = uart::CONSOLE.lock().as_mut().and_then(uart::Device::get);
         if let Some(c) = c {
@@ -87,7 +74,6 @@ extern "C" fn start() -> ! {
 
 #[panic_handler]
 fn on_panic(info: &PanicInfo) -> ! {
-    // print panic info and hang
     println!("{}", info);
 
     loop {}