OS 简单教程三
打印
继续打印，幸好 SBI 实现了打印，省去了自己实现驱动，调用系统调用就行了。 实现系统调用，在 scall_sbi/mod.rs 中
#[inline(always)]
fn scall(which: usize, arg0: usize, arg1: usize, arg2: usize) -> usize {
let mut ret;
unsafe {
asm!("ecall",
in( "x10") arg0,
in("x11") arg1,
in ("x12") arg2,
in("x17") which,
lateout("x10") ret,
options(nostack)
);
}
ret
}
const SBI_CONSOLE_PUTCHAR: usize = 1;
const SBI_SHUTDOWN: usize = 8;
pub fn shutdown() -> ! {
scall(SBI_SHUTDOWN, 0, 0, 0);
panic!("It should shutdown!");
}
pub fn put_char(c: usize) {
scall(SBI_CONSOLE_PUTCHAR, c, 0, 0);
}建立 console.rs 调用刚才的系统调用，内容是
use core::fmt::{self, Write};
use crate::scall_sbi::put_char;
struct STDOUT;
impl Write for STDOUT {
fn write_str(&mut self, s: &str) -> core::fmt::Result {
for c in s.chars() {
put_char(c as usize);
}
Ok(())
}
}
pub fn print(args: fmt::Arguments){
STDOUT.write_fmt(args).unwrap();
}
#[macro_export]
macro_rules! print {
($fmt: literal $(, $($arg: tt)+)?) => {
$crate::console::print(format_args!($fmt $(, $($arg)+)?));
}
}
#[macro_export]
macro_rules! println {
($fmt: literal $(, $($arg: tt)+)?) => {
$crate::console::print(format_args!(concat!($fmt, "\n") $(, $($arg)+)?));
}
}说明一下
- 利用 宏 + core::fmt::Write 来解析参数 main.rs 里就可以调用宏输出了，这时 main.rs 的内容
#![feature(llvm_asm)]
#![feature(global_asm)]
#![no_std]
#![no_main]
use scall_sbi::shutdown;
mod lang;
mod scall_sbi;
#[macro_use]
mod console;
global_asm!(include_str!("stack.asm"));
#[no_mangle]
extern "C" fn rust_main() ->! {
println!("hello OS");
shutdown();
}编译一下，make build，编译过了，运行一下 make run 也成功了，输出
[rustsbi] RustSBI version 0.2.0-alpha.3
.______ __ __ _______.___________. _______..______ __
| _ \ | | | | / | | / || _ \ | |
| |_) | | | | | | (----`---| |----`| (----`| |_) || |
| / | | | | \ \ | | \ \ | _ < | |
| |\ \----.| `--' |.----) | | | .----) | | |_) || |
| _| `._____| \______/ |_______/ |__| |_______/ |______/ |__|
[rustsbi] Platform: K210 (Version 0.2.0)
[rustsbi] misa: RV64ACDFIMSU
[rustsbi] mideleg: 0x22
[rustsbi] medeleg: 0x1ab
[rustsbi] Kernel entry: 0x80020000
hello OS
[rustsbi] reset triggered! todo: shutdown all harts on k210; program halt. Type: 0, reason: 0至此我们成功准备了运行环境并在 k210 上输出，接下来我们开始虚拟化 CPU 和内存，这更有趣！
后续
- 全局位初始化变量清零
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) }
});
}