82 lines
2.1 KiB
Rust
82 lines
2.1 KiB
Rust
// src/main.rs
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#![no_std]
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#![no_main]
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#![feature(naked_functions)]
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use core::panic::PanicInfo;
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mod heap;
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mod uart;
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#[naked]
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#[no_mangle]
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#[link_section = ".text.init"]
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unsafe extern "C" fn _enter() -> ! {
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use core::arch::asm;
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asm!(
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// before we use the `la` pseudo-instruction for the first time,
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// we need to set `gp` (google linker relaxation)
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".option push", // pushes the current option stack
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".option norelax", // disable relaxation so we can properly set `gp`
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// this instruction compiles to:
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// 1:
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// auipc gp, %pcrel_hi(_global_pointer)
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// addi gp, gp, %pcrel_lo(1b)
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// if relaxation were on, this would simply be `mv gp, gp` or `addi gp, gp, 0`
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"la gp, _global_pointer",
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".option pop", // pops the current option stack
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// set the stack pointer
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"la sp, _init_stack_top",
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// clear the BSS
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"la t0, _bss_start",
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"la t1, _bss_end",
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"bgeu t0, t1, 2f",
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"1:",
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"sb zero, 0(t0)",
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"addi t0, t0, 1",
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"bne t0, t1, 1b",
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"2:",
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// BSS is clear!
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// "tail-call" to {start} (call without saving a return address)
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"tail {start}",
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start = sym start, // {start} refers to the function [start] below
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options(noreturn) // we must handle "returning" from assembly
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);
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}
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extern "C" fn start() -> ! {
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// UNSAFE: Called exactly once, right here.
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unsafe { heap::init() };
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// Now we're free to use dynamic allocation!
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{
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extern crate alloc;
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use alloc::boxed::Box;
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let _my_heap_pointer = Box::new(10);
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// _my_heap_pointer lives on the heap!
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}
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println!("This should not print because the console is not initialised.");
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unsafe { uart::init_console(0x1000_0000) };
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println!("Hello, world!");
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loop {
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let c = uart::CONSOLE.lock().as_mut().and_then(uart::Device::get);
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if let Some(c) = c {
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print!("{}", c as char);
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}
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}
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}
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#[panic_handler]
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fn on_panic(info: &PanicInfo) -> ! {
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println!("{}", info);
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loop {}
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}
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// TODO unit testing
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