// Copyright 2015 Philipp Oppermann. See the README.md
// file at the top-level directory of this distribution.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

#![feature(lang_items)]
#![feature(const_fn, unique)]
#![feature(step_by)]
#![no_std]

extern crate rlibc;
extern crate spin;
extern crate multiboot2;
#[macro_use]
extern crate bitflags;
extern crate x86;

#[macro_use]
mod vga_buffer;
mod memory;

#[no_mangle]
pub extern "C" fn rust_main(multiboot_information_address: usize) {
    // ATTENTION: we have a very small stack and no guard page
    vga_buffer::clear_screen();
    println!("Hello World{}", "!");

    let boot_info = unsafe { multiboot2::load(multiboot_information_address) };
    let memory_map_tag = boot_info.memory_map_tag().expect("Memory map tag required");
    let elf_sections_tag = boot_info.elf_sections_tag().expect("Elf sections tag required");

    let kernel_start = elf_sections_tag.sections().map(|s| s.addr).min().unwrap();
    let kernel_end = elf_sections_tag.sections().map(|s| s.addr + s.size).max().unwrap();

    let multiboot_start = multiboot_information_address;
    let multiboot_end = multiboot_start + (boot_info.total_size as usize);

    println!("kernel start: 0x{:x}, kernel end: 0x{:x}",
             kernel_start,
             kernel_end);
    println!("multiboot start: 0x{:x}, multiboot end: 0x{:x}",
             multiboot_start,
             multiboot_end);

    let mut frame_allocator = memory::AreaFrameAllocator::new(kernel_start as usize,
                                                              kernel_end as usize,
                                                              multiboot_start,
                                                              multiboot_end,
                                                              memory_map_tag.memory_areas());

    enable_nxe_bit();
    enable_write_protect_bit();

    memory::remap_the_kernel(&mut frame_allocator, boot_info);
    println!("It did not crash!");

    loop {}
}

fn enable_nxe_bit() {
    use x86::msr::{IA32_EFER, rdmsr, wrmsr};

    let nxe_bit = 1 << 11;
    unsafe {
        let efer = rdmsr(IA32_EFER);
        wrmsr(IA32_EFER, efer | nxe_bit);
    }
}

fn enable_write_protect_bit() {
    use x86::controlregs::{cr0, cr0_write};

    let wp_bit = 1 << 16;
    unsafe { cr0_write(cr0() | wp_bit) };
}

#[cfg(not(test))]
#[lang = "eh_personality"]
extern "C" fn eh_personality() {}

#[cfg(not(test))]
#[lang = "panic_fmt"]
extern "C" fn panic_fmt(fmt: core::fmt::Arguments, file: &str, line: u32) -> ! {
    println!("\n\nPANIC in {} at line {}:", file, line);
    println!("    {}", fmt);
    loop {}
}