nob.c

#define NOB_IMPLEMENTATION
#define NOB_STRIP_PREFIX
#include "nob.h"

static const char *ARCH = "aarch64";
static const char *QEMU = "qemu-system-aarch64";
static const char *IMGK = "vmlinuz-lts";
static const char *USER_NAME = "mitre";
static const char *HOSTNAME = "mini";

static const char *KURL_FMT = "https://dl-cdn.alpinelinux.org/alpine/v3.20/releases/%s/netboot/vmlinuz-lts";

// Precomputed SHA-512 hash for password "mitre"
static const char *MITRE_HASH = "$6$nQmdwcmrIuU2vesW$SOH6oVx5GlCSGrl0LCmFPZIYPMHcw4rc9tTNnsuV1l641zxpU0p/cTbe.rH4ZJveoi8vSf7awzEzXTrI2pZGu0";

static bool write_text_file(const char *path, const char *txt)
{
    return write_entire_file(path, txt, strlen(txt));
}

static bool write_from_asset(const char *asset_path, const char *dst_path)
{
    Nob_String_Builder sb = {0};
    if (!read_entire_file(asset_path, &sb)) return false;
    bool ok = write_entire_file(dst_path, sb.items, sb.count);
    sb_free(sb);
    return ok;
}

int main(int argc, char **argv)
{
    NOB_GO_REBUILD_URSELF(argc, argv);

    const char *workdir = "mini-sinit";
    const char *cwd = get_current_dir_temp();

    log(NOB_INFO, "[*] Preparando carpetas...");
    mkdir_if_not_exists(workdir);
    const char *build_dir = temp_sprintf("%s/build", workdir);
    const char *out_dir   = temp_sprintf("%s/out", workdir);
    mkdir_if_not_exists(build_dir);
    mkdir_if_not_exists(out_dir);
    const char *rootfs = temp_sprintf("%s/rootfs", workdir);
    mkdir_if_not_exists(rootfs);
    const char *subdirs[] = {
        "bin", "sbin", "usr", "usr/bin", "usr/sbin", "etc", "proc", "sys", "dev", "run", "root", "home", "var", "tmp"
    };
    for (size_t i = 0; i < NOB_ARRAY_LEN(subdirs); ++i) {
        mkdir_if_not_exists(temp_sprintf("%s/%s", rootfs, subdirs[i]));
    }
    // chmod 1777 tmp
    {
        Cmd cmd = {0};
        cmd_append(&cmd, "chmod", "1777", temp_sprintf("%s/tmp", rootfs));
        if (!cmd_run(&cmd)) return 1;
    }

    const char *kernel_path = temp_sprintf("%s/%s", workdir, IMGK);
    if (!file_exists(kernel_path)) {
        log(NOB_INFO, "[*] Descargando kernel LTS Alpine (%s)...", ARCH);
        Cmd cmd = {0};
        const char *kurl = temp_sprintf(KURL_FMT, ARCH);
        cmd_append(&cmd, "curl", "-fsSL", kurl, "-o", kernel_path);
        if (!cmd_run(&cmd)) return 1;
    } else {
        log(NOB_INFO, "[*] Kernel LTS Alpine (%s) ya existe, saltando descarga...", ARCH);
    }

    const char *dockerfile_path = temp_sprintf("%s/build/Dockerfile", workdir);
    if (!copy_file("assets/Dockerfile", dockerfile_path)) {
        log(NOB_ERROR, "No se pudo escribir Dockerfile en %s", dockerfile_path);
        return 1;
    }

    size_t bin_count = 0;
    {
        Nob_File_Paths paths = {0};
        const char *bin_dir = temp_sprintf("%s/out/bin", workdir);
        if (read_entire_dir(bin_dir, &paths)) {
            bin_count = paths.count;
        }
        da_free(paths);
    }

    if (bin_count >= 150) {
        log(NOB_INFO, "[*] Binarios ya compilados encontrados (%zu archivos), saltando compilación...", bin_count);
    } else {
        log(NOB_INFO, "[*] Construyendo toolchain estática en Docker...");
        {
            Cmd cmd = {0};
            const char *abs_build = temp_sprintf("%s/%s", cwd, build_dir);
            cmd_append(&cmd, "env", "DOCKER_BUILDKIT=0", "docker", "build",
                       "-t", "mini-sinit-build",
                       "-f", dockerfile_path,
                       abs_build);
            if (!cmd_run(&cmd)) return 1;
        }
        log(NOB_INFO, "[*] Extrayendo binarios compilados...");
        {
            Cmd cmd = {0};
            const char *abs_out = temp_sprintf("%s/%s", cwd, out_dir);
            cmd_append(&cmd, "docker", "run", "--rm",
                       "-v", temp_sprintf("%s:/hostout", abs_out),
                       "mini-sinit-build", "sh", "-lc",
                       "cp -a /out/* /hostout/");
            if (!cmd_run(&cmd)) return 1;
        }
    }

    log(NOB_INFO, "[*] Poblado de rootfs con sbase/ubase/sinit/doas...");
    {
        (void) mkdir_if_not_exists(temp_sprintf("%s/rootfs/usr/bin", workdir));
        (void) mkdir_if_not_exists(temp_sprintf("%s/rootfs/usr/sbin", workdir));

        (void) copy_directory_recursively(temp_sprintf("%s/out/bin", workdir), temp_sprintf("%s/rootfs/bin", workdir));
        (void) copy_directory_recursively(temp_sprintf("%s/out/sbin", workdir), temp_sprintf("%s/rootfs/sbin", workdir));
    }

    if (!file_exists(temp_sprintf("%s/rootfs/bin/sh", workdir))) {
        log(NOB_ERROR, "ERROR: no se encontró /bin/sh (sbase).");
        return 1;
    }

    write_text_file(temp_sprintf("%s/rootfs/etc/fstab", workdir), "");
    if (!write_from_asset("assets/rc.init", temp_sprintf("%s/rootfs/etc/rc.init", workdir))) return 1;
    if (!write_from_asset("assets/rc.shutdown", temp_sprintf("%s/rootfs/etc/rc.shutdown", workdir))) return 1;
    // chmod +x
    {
        Cmd cmd = {0};
        cmd_append(&cmd, "chmod", "+x", temp_sprintf("%s/rootfs/etc/rc.init", workdir), temp_sprintf("%s/rootfs/etc/rc.shutdown", workdir));
        if (!cmd_run(&cmd)) return 1;
    }

    if (!write_from_asset("assets/doas.conf", temp_sprintf("%s/rootfs/etc/doas.conf", workdir))) return 1;

    {
        Nob_String_Builder sb = {0};
        if (!read_entire_file("assets/passwd.tmpl", &sb)) return 1;
        sb_append_null(&sb);
        const char *passwd_txt = temp_sprintf(sb.items, USER_NAME, USER_NAME, USER_NAME);
        sb_free(sb);
        write_text_file(temp_sprintf("%s/rootfs/etc/passwd", workdir), passwd_txt);
    }
    if (!write_from_asset("assets/group", temp_sprintf("%s/rootfs/etc/group", workdir))) return 1;
    {
        Nob_String_Builder sb = {0};
        if (!read_entire_file("assets/shadow.tmpl", &sb)) return 1;
        sb_append_null(&sb);
        const char *shadow_txt = temp_sprintf(sb.items, MITRE_HASH, USER_NAME, MITRE_HASH);
        sb_free(sb);
        write_text_file(temp_sprintf("%s/rootfs/etc/shadow", workdir), shadow_txt);
        Cmd cmd = {0};
        cmd_append(&cmd, "chmod", "600", temp_sprintf("%s/rootfs/etc/shadow", workdir));
        if (!cmd_run(&cmd)) return 1;
    }

    mkdir_if_not_exists(temp_sprintf("%s/rootfs/home/%s", workdir, USER_NAME));
    write_text_file(temp_sprintf("%s/rootfs/root/.profile", workdir), "export PATH=/bin:/sbin:/usr/bin:/usr/sbin\n");
    (void) copy_file(
        temp_sprintf("%s/rootfs/root/.profile", workdir),
        temp_sprintf("%s/rootfs/home/%s/.profile", workdir, USER_NAME)
    );

    write_text_file(temp_sprintf("%s/rootfs/etc/hostname", workdir), HOSTNAME);
    if (!write_from_asset("assets/motd", temp_sprintf("%s/rootfs/etc/motd", workdir))) return 1;

    {
        Cmd cmd = {0};
        cmd_append(&cmd, "ln", "-sf", "/sbin/sinit", temp_sprintf("%s/rootfs/sbin/init", workdir));
        if (!cmd_run(&cmd)) return 1;
    }

    log(NOB_INFO, "[*] Generando initramfs...");
    const char *initramfs_path = temp_sprintf("%s/initramfs.img", workdir);
    {
        Cmd cmd = {0};
        const char *pipeline = temp_sprintf("cd %s/rootfs && find . | cpio -H newc -o | gzip -9", workdir);
        cmd_append(&cmd, "sh", "-lc", pipeline);
        if (!cmd_run(&cmd, .stdout_path = initramfs_path)) return 1;
    }

    log(NOB_INFO, "[*] Booteando en QEMU (Ctrl+A X para salir si usa nographic)...");
    {
        Cmd cmd = {0};
        cmd_append(&cmd,
                   QEMU,
                   "-nodefaults", "-no-reboot", "-serial", "mon:stdio", "-nographic",
                   "-machine", "virt,accel=tcg",
                   "-cpu", "max",
                   "-smp", "2", "-m", "512M",
                   "-kernel", kernel_path,
                   "-initrd", initramfs_path,
                   "-append", "console=ttyAMA0,115200 earlyprintk rdinit=/etc/rc.init");
        if (!cmd_run(&cmd)) return 1;
    }

    return 0;
}