Using it

We need to initialise the logger before we use it.

#![no_main]
#![no_std]

mod asm;
mod exceptions;
mod logger;
mod pl011;

use crate::pl011::Uart;
use core::panic::PanicInfo;
use core::ptr::NonNull;
use log::{LevelFilter, error, info};
use safe_mmio::UniqueMmioPointer;
use smccc::Hvc;
use smccc::psci::system_off;

/// Base address of the primary PL011 UART.
const PL011_BASE_ADDRESS: NonNull<pl011::Registers> =
    NonNull::new(0x900_0000 as _).unwrap();

// SAFETY: There is no other global function of this name.
#[unsafe(no_mangle)]
extern "C" fn main(x0: u64, x1: u64, x2: u64, x3: u64) {
    // SAFETY: `PL011_BASE_ADDRESS` is the base address of a PL011 device, and
    // nothing else accesses that address range.
    let uart = unsafe { Uart::new(UniqueMmioPointer::new(PL011_BASE_ADDRESS)) };
    logger::init(uart, LevelFilter::Trace).unwrap();

    info!("main({x0:#x}, {x1:#x}, {x2:#x}, {x3:#x})");

    assert_eq!(x1, 42);

    system_off::<Hvc>().unwrap();
}

#[panic_handler]
fn panic(info: &PanicInfo) -> ! {
    error!("{info}");
    system_off::<Hvc>().unwrap();
    loop {}
}