os_build/build.rs

use std::{
    env,
    fs,
    os::unix::ffi::OsStrExt,
    path::PathBuf,
    process::Command,
};

use gpt::{mbr::ProtectiveMBR, GptConfig};

const ROOT_DISK_SIZE_MB: usize = 256;

fn main() {
    println!("cargo:rerun-if-changed=sysroot");
    println!("cargo:rerun-if-changed=build.rs");
    println!("cargo:rerun-if-changed=initrd_file_list");
    println!("cargo:rerun-if-changed=bootloader-x86_64-uefi.efi");

    // set by cargo, build scripts should use this directory for output files
    let out_dir = std::env::var_os("OUT_DIR").unwrap();

    std::fs::write("out_dir_path", out_dir.as_os_str().as_bytes()).unwrap();

    let mut initrd_path = out_dir.clone();
    initrd_path.push("/initrd.tar");
    Command::new("bash")
        .arg("-c")
        .arg(format!(
            "cd sysroot; tar cvf {:?} $(cat ../initrd_file_list)",
            initrd_path
        ))
        .output()
        .unwrap();

    let kernel = PathBuf::from(env::var_os("CARGO_BIN_FILE_KERNEL_kernel").unwrap());

    let mut disk_path = out_dir.clone();
    disk_path.push("/root.img");

    Command::new("dd")
        .arg("if=/dev/zero")
        .arg(format!("of={}", disk_path.to_str().unwrap()))
        .arg("bs=1M")
        .arg(format!("count={}", ROOT_DISK_SIZE_MB))
        .output()
        .unwrap();

    let mut disk = GptConfig::new().writable(true).create(&disk_path).unwrap();

    ProtectiveMBR::new()
        .overwrite_lba0(disk.device_mut())
        .unwrap();

    let boot_part_id = disk
        .add_partition("boot", 32 * 1024 * 1024, gpt::partition_types::EFI, 0, None)
        .unwrap();
    let root_part_id = disk
        .add_partition(
            "root",
            disk.find_free_sectors()[1].1 * disk.logical_block_size().as_u64(),
            gpt::partition_types::LINUX_FS,
            0,
            None,
        )
        .unwrap();

    disk.write_inplace().unwrap();

    let boot_part = &disk.partitions()[&boot_part_id];
    let root_part = &disk.partitions()[&root_part_id];

    Command::new("dd")
        .arg(format!("if={}", disk_path.to_str().unwrap()))
        .arg("of=tmp_ext2.img")
        .arg(format!("bs={}", disk.logical_block_size().as_u64()))
        .arg(format!("skip={}", root_part.first_lba))
        .arg(format!("count={}", root_part.sectors_len().unwrap()))
        .output()
        .unwrap();

    Command::new("mkfs.ext2")
        .arg("-O")
        .arg("^resize_inode")
        .arg("-d")
        .arg("sysroot")
        .arg("tmp_ext2.img")
        .output()
        .unwrap();

    Command::new("dd")
        .arg("if=tmp_ext2.img")
        .arg(format!("of={}", disk_path.to_str().unwrap()))
        .arg(format!("bs={}", disk.logical_block_size().as_u64()))
        .arg(format!("seek={}", root_part.first_lba))
        .arg("conv=notrunc")
        .output()
        .unwrap();

    fs::remove_file("tmp_ext2.img").unwrap();

    Command::new("dd")
        .arg(format!("if={}", disk_path.to_str().unwrap()))
        .arg("of=tmp_esp.img")
        .arg(format!("bs={}", disk.logical_block_size().as_u64()))
        .arg(format!("skip={}", boot_part.first_lba))
        .arg(format!("count={}", boot_part.sectors_len().unwrap()))
        .output()
        .unwrap();

    Command::new("mkfs.fat")
        .arg("-g")
        .arg("64/32")
        .arg("-i")
        .arg("12345678")
        .arg("-n")
        .arg("kernel-bd3a")
        .arg("tmp_esp.img")
        .output()
        .unwrap();

    Command::new("mmd")
        .arg("-i")
        .arg("tmp_esp.img")
        .arg("efi")
        .output()
        .unwrap();
    Command::new("mmd")
        .arg("-i")
        .arg("tmp_esp.img")
        .arg("efi/boot")
        .output()
        .unwrap();
    Command::new("mcopy")
        .arg("-i")
        .arg("tmp_esp.img")
        .arg("bootloader-x86_64-uefi.efi")
        .arg("::efi/boot/bootx64.efi")
        .output()
        .unwrap();
    Command::new("mcopy")
        .arg("-i")
        .arg("tmp_esp.img")
        .arg(&kernel)
        .arg("::kernel-x86_64")
        .output()
        .unwrap();
    Command::new("mcopy")
        .arg("-i")
        .arg("tmp_esp.img")
        .arg(&initrd_path)
        .arg("::ramdisk")
        .output()
        .unwrap();

    Command::new("dd")
        .arg("if=tmp_esp.img")
        .arg(format!("of={}", disk_path.to_str().unwrap()))
        .arg(format!("bs={}", disk.logical_block_size().as_u64()))
        .arg(format!("seek={}", boot_part.first_lba))
        .arg("conv=notrunc")
        .output()
        .unwrap();

    fs::remove_file("tmp_esp.img").unwrap();

    println!("cargo:rustc-env=DISK_PATH={}", disk_path.to_string_lossy());
}