multiboot2/multiboot2/src/lib.rs

#![no_std]
#![cfg_attr(feature = "unstable", feature(error_in_core))]
#![deny(missing_debug_implementations)]
// --- BEGIN STYLE CHECKS ---
// These checks are optional in CI for PRs, as discussed in
// https://github.com/rust-osdev/multiboot2/pull/92
#![deny(clippy::all)]
#![deny(rustdoc::all)]
#![allow(rustdoc::private_doc_tests)]
// --- END STYLE CHECKS ---

//! Library that helps you to parse the multiboot information structure (mbi) from
//! Multiboot2-compliant bootloaders, like GRUB. It supports all tags from the specification
//! including full support for the sections of ELF-64. This library is `no_std` and can be
//! used in a Multiboot2-kernel.
//!
//! The GNU Multiboot(2) specification aims to provide a standardised
//! method of sharing commonly used information about the host machine at
//! boot time and give the payload, i.e. a kernel, a well defined machine
//! state.
//!
//! ## Example
//!
//! ```rust
//! use multiboot2::load;
//! fn kmain(multiboot_info_ptr: u32) {
//!     let boot_info = unsafe { load(multiboot_info_ptr as usize).unwrap() };
//!     println!("{:?}", boot_info);
//! }
//! ```
//!
//! ## MSRV
//! The MSRV is 1.56.1 stable.

#[cfg(feature = "builder")]
extern crate alloc;

// this crate can use std in tests only
#[cfg_attr(test, macro_use)]
#[cfg(test)]
extern crate std;

use core::fmt;
use derive_more::Display;
// Must be public so that custom tags can be DSTs.
pub use ptr_meta::Pointee;

use crate::framebuffer::UnknownFramebufferType;
pub use boot_loader_name::BootLoaderNameTag;
#[cfg(feature = "builder")]
use builder::traits::StructAsBytes;
pub use command_line::CommandLineTag;
pub use efi::{EFIImageHandle32, EFIImageHandle64, EFISdt32, EFISdt64};
pub use elf_sections::{
    ElfSection, ElfSectionFlags, ElfSectionIter, ElfSectionType, ElfSectionsTag,
};
pub use framebuffer::{FramebufferColor, FramebufferField, FramebufferTag, FramebufferType};
pub use image_load_addr::ImageLoadPhysAddr;
pub use memory_map::{
    BasicMemoryInfoTag, EFIBootServicesNotExited, EFIMemoryAreaType, EFIMemoryDesc,
    EFIMemoryMapTag, MemoryArea, MemoryAreaIter, MemoryAreaType, MemoryMapTag,
};
pub use module::{ModuleIter, ModuleTag};
pub use rsdp::{RsdpV1Tag, RsdpV2Tag};
pub use smbios::SmbiosTag;
use tag_type::TagIter;
pub use tag_type::{EndTag, Tag, TagType, TagTypeId};
pub use vbe_info::{
    VBECapabilities, VBEControlInfo, VBEDirectColorAttributes, VBEField, VBEInfoTag,
    VBEMemoryModel, VBEModeAttributes, VBEModeInfo, VBEWindowAttributes,
};

#[macro_use]
extern crate bitflags;

mod boot_loader_name;
mod command_line;
mod efi;
mod elf_sections;
mod framebuffer;
mod image_load_addr;
mod memory_map;
mod module;
mod rsdp;
mod smbios;
mod tag_type;
mod vbe_info;

#[cfg(feature = "builder")]
pub mod builder;

/// Magic number that a multiboot2-compliant boot loader will store in `eax` register
/// right before handoff to the payload (the kernel). This value can be used to check,
/// that the kernel was indeed booted via multiboot2.
///
/// Caution: You might need some assembly code (e.g. GAS or NASM) first, which
/// moves `eax` to another register, like `edi`. Otherwise it probably happens,
/// that the Rust compiler output changes `eax` before you can access it.
pub const MULTIBOOT2_BOOTLOADER_MAGIC: u32 = 0x36d76289;

/// Load the multiboot boot information struct from an address.
///
/// This is the same as [`load_with_offset`] but the offset is omitted and set
/// to zero.
///
/// ## Example
///
/// ```rust
/// use multiboot2::load;
///
/// fn kmain(multiboot_info_ptr: u32) {
///     let boot_info = unsafe { load(multiboot_info_ptr as usize).unwrap() };
///     println!("{:?}", boot_info);
/// }
/// ```
///
/// ## Safety
/// * `address` must be valid for reading. Otherwise this function might
///   terminate the program. This can be the case in environments with standard
///   environment (segfault) but also in UEFI-applications, where the referenced
///   memory is not (identity) mapped (UEFI does only identity mapping).
/// * The memory at `address` must not be modified after calling `load` or the
///   program may observe unsynchronized mutation.
pub unsafe fn load(address: usize) -> Result<BootInformation, MbiLoadError> {
    load_with_offset(address, 0)
}

/// Load the multiboot boot information struct from an address at an offset.
///
/// ## Example
///
/// ```rust,no_run
/// use multiboot2::load_with_offset;
///
/// let ptr = 0xDEADBEEF as *const u32;
/// let boot_info = unsafe { load_with_offset(ptr as usize, 0xCAFEBABE).unwrap() };
/// println!("{:?}", boot_info);
/// ```
///
/// ## Safety
/// * `address` must be valid for reading. Otherwise this function might
///   terminate the program. This can be the case in environments with standard
///   environment (segfault) but also in UEFI-applications, where the referenced
///   memory is not (identity) mapped (UEFI does only identity mapping).
/// * The memory at `address` must not be modified after calling `load` or the
///   program may observe unsynchronized mutation.
pub unsafe fn load_with_offset(
    address: usize,
    offset: usize,
) -> Result<BootInformation, MbiLoadError> {
    let address = address + offset;
    let null_ptr = address == 0;
    let eight_byte_aligned = address & 0b111 == 0;
    if null_ptr || !eight_byte_aligned {
        return Err(MbiLoadError::IllegalAddress);
    }

    let multiboot = &*(address as *const BootInformationInner);
    // Check if total size is a multiple of 8.
    // See MbiLoadError::IllegalTotalSize for comments
    if multiboot.total_size & 0b111 != 0 {
        return Err(MbiLoadError::IllegalTotalSize(multiboot.total_size));
    }
    if !multiboot.has_valid_end_tag() {
        return Err(MbiLoadError::NoEndTag);
    }

    Ok(BootInformation {
        inner: multiboot,
        offset,
    })
}

/// Error type that describes errors while loading/parsing a multiboot2 information structure
/// from a given address.
#[derive(Debug, Display)]
pub enum MbiLoadError {
    /// The address is invalid. Make sure that the address is 8-byte aligned,
    /// according to the spec.
    #[display(fmt = "The address is invalid")]
    IllegalAddress,
    /// The total size of the multiboot2 information structure must be a multiple of 8.
    /// (Not in spec, but it is implicitly the case, because the begin of MBI
    /// and all tags are 8-byte aligned and the end tag is exactly 8 byte long).
    #[display(fmt = "The size of the MBI is unexpected")]
    IllegalTotalSize(u32),
    /// End tag missing. Each multiboot2 header requires to have an end tag.
    #[display(fmt = "There is no end tag")]
    NoEndTag,
}

#[cfg(feature = "unstable")]
impl core::error::Error for MbiLoadError {}

/// A Multiboot 2 Boot Information struct.
pub struct BootInformation {
    inner: *const BootInformationInner,
    offset: usize,
}

#[derive(Clone, Copy)]
#[repr(C)]
struct BootInformationInner {
    total_size: u32,
    _reserved: u32,
}

impl BootInformationInner {
    #[cfg(feature = "builder")]
    fn new(total_size: u32) -> Self {
        Self {
            total_size,
            _reserved: 0,
        }
    }
}

#[cfg(feature = "builder")]
impl StructAsBytes for BootInformationInner {
    fn byte_size(&self) -> usize {
        core::mem::size_of::<Self>()
    }
}

impl BootInformation {
    /// Get the start address of the boot info.
    pub fn start_address(&self) -> usize {
        self.inner as usize
    }

    /// Get the end address of the boot info.
    ///
    /// This is the same as doing:
    ///
    /// ```rust,no_run
    /// # let boot_info = unsafe { multiboot2::load(0xdeadbeef).unwrap() };
    /// let end_addr = boot_info.start_address() + boot_info.total_size();
    /// ```
    pub fn end_address(&self) -> usize {
        self.start_address() + self.total_size()
    }

    /// Get the total size of the boot info struct.
    pub fn total_size(&self) -> usize {
        self.get().total_size as usize
    }

    /// Search for the basic memory info tag.
    pub fn basic_memory_info_tag(&self) -> Option<&BasicMemoryInfoTag> {
        self.get_tag::<BasicMemoryInfoTag, _>(TagType::BasicMeminfo)
    }

    /// Search for the ELF Sections.
    ///
    /// # Examples
    ///
    /// ```rust,no_run
    /// # let boot_info = unsafe { multiboot2::load(0xdeadbeef).unwrap() };
    /// if let Some(sections) = boot_info.elf_sections() {
    ///     let mut total = 0;
    ///     for section in sections {
    ///         println!("Section: {:?}", section);
    ///         total += 1;
    ///     }
    /// }
    /// ```
    pub fn elf_sections(&self) -> Option<ElfSectionIter> {
        let tag = self.get_tag::<ElfSectionsTag, _>(TagType::ElfSections);
        tag.map(|t| {
            assert!((t.entry_size * t.shndx) <= t.size);
            t.sections(self.offset)
        })
    }

    /// Search for the Memory map tag.
    pub fn memory_map_tag(&self) -> Option<&MemoryMapTag> {
        self.get_tag::<MemoryMapTag, _>(TagType::Mmap)
    }

    /// Get an iterator of all module tags.
    pub fn module_tags(&self) -> ModuleIter {
        module::module_iter(self.tags())
    }

    /// Search for the BootLoader name tag.
    pub fn boot_loader_name_tag(&self) -> Option<&BootLoaderNameTag> {
        self.get_tag::<BootLoaderNameTag, _>(TagType::BootLoaderName)
    }

    /// Search for the Command line tag.
    pub fn command_line_tag(&self) -> Option<&CommandLineTag> {
        self.get_tag::<CommandLineTag, _>(TagType::Cmdline)
    }

    /// Search for the VBE framebuffer tag. The result is `Some(Err(e))`, if the
    /// framebuffer type is unknown, while the framebuffer tag is present.
    pub fn framebuffer_tag(&self) -> Option<Result<&FramebufferTag, UnknownFramebufferType>> {
        self.get_tag::<FramebufferTag, _>(TagType::Framebuffer)
            .map(|tag| match tag.buffer_type() {
                Ok(_) => Ok(tag),
                Err(e) => Err(e),
            })
    }

    /// Search for the EFI 32-bit SDT tag.
    pub fn efi_sdt_32_tag(&self) -> Option<&EFISdt32> {
        self.get_tag::<EFISdt32, _>(TagType::Efi32)
    }

    /// Search for the EFI 64-bit SDT tag.
    pub fn efi_sdt_64_tag(&self) -> Option<&EFISdt64> {
        self.get_tag::<EFISdt64, _>(TagType::Efi64)
    }

    /// Search for the (ACPI 1.0) RSDP tag.
    pub fn rsdp_v1_tag(&self) -> Option<&RsdpV1Tag> {
        self.get_tag::<RsdpV1Tag, _>(TagType::AcpiV1)
    }

    /// Search for the (ACPI 2.0 or later) RSDP tag.
    pub fn rsdp_v2_tag(&self) -> Option<&RsdpV2Tag> {
        self.get_tag::<RsdpV2Tag, _>(TagType::AcpiV2)
    }

    /// Search for the EFI Memory map tag, if the boot services were exited.
    /// Otherwise, if the [`TagType::EfiBs`] tag is present, this returns `None`
    /// as it is strictly recommended to get the memory map from the `uefi`
    /// services.
    pub fn efi_memory_map_tag(&self) -> Option<&EFIMemoryMapTag> {
        // If the EFIBootServicesNotExited is present, then we should not use
        // the memory map, as it could still be in use.
        match self.get_tag::<Tag, _>(TagType::EfiBs) {
            Some(_tag) => None,
            None => self.get_tag::<EFIMemoryMapTag, _>(TagType::EfiMmap),
        }
    }

    /// Search for the EFI 32-bit image handle pointer.
    pub fn efi_32_ih(&self) -> Option<&EFIImageHandle32> {
        self.get_tag::<EFIImageHandle32, _>(TagType::Efi32Ih)
    }

    /// Search for the EFI 64-bit image handle pointer.
    pub fn efi_64_ih(&self) -> Option<&EFIImageHandle64> {
        self.get_tag::<EFIImageHandle64, _>(TagType::Efi64Ih)
    }

    /// Search for the Image Load Base Physical Address.
    pub fn load_base_addr(&self) -> Option<&ImageLoadPhysAddr> {
        self.get_tag::<ImageLoadPhysAddr, _>(TagType::LoadBaseAddr)
    }

    /// Search for the VBE information tag.
    pub fn vbe_info_tag(&self) -> Option<&VBEInfoTag> {
        self.get_tag::<VBEInfoTag, _>(TagType::Vbe)
    }

    /// Search for the SMBIOS tag.
    pub fn smbios_tag(&self) -> Option<&SmbiosTag> {
        self.get_tag::<SmbiosTag, _>(TagType::Smbios)
    }

    fn get(&self) -> &BootInformationInner {
        unsafe { &*self.inner }
    }

    /// Public getter to find any Multiboot tag by its type, including
    /// specified and custom ones.
    ///
    /// The parameter can be of type `u32`, [`TagType`], or [`TagTypeId`].
    ///
    /// # Specified or Custom Tags
    /// The Multiboot2 specification specifies a list of tags, see [`TagType`].
    /// However, it doesn't forbid to use custom tags. Because of this, there
    /// exists the [`TagType`] abstraction. It is recommended to use this
    /// getter only for custom tags. For specified tags, use getters, such as
    /// [`Self::efi_64_ih`].
    ///
    /// ## Use Custom Tags
    /// The following example shows how you may use this interface to parse
    /// custom tags from the MBI. If they are dynamically sized (DST), a few more
    /// special handling is required. This is reflected by code-comments.
    ///
    /// ```no_run
    /// use std::str::Utf8Error;
    /// use multiboot2::{Tag, TagTrait, TagTypeId};
    ///
    /// #[repr(C, align(8))]
    /// #[derive(multiboot2::Pointee)] // Only needed for DSTs.
    /// struct CustomTag {
    ///     // new type from the lib: has repr(u32)
    ///     tag: TagTypeId,
    ///     size: u32,
    ///     // begin of inline string
    ///     name: [u8],
    /// }
    ///
    /// // This implementation is only necessary for tags that are DSTs.
    /// impl TagTrait for CustomTag {
    ///     fn dst_size(base_tag: &Tag) -> usize {
    ///         // The size of the sized portion of the custom tag.
    ///         let tag_base_size = 8; // id + size is 8 byte in size
    ///         assert!(base_tag.size >= 8);
    ///         base_tag.size as usize - tag_base_size
    ///     }
    /// }
    ///
    /// impl CustomTag {
    ///     fn name(&self) -> Result<&str, Utf8Error> {
    ///         Tag::get_dst_str_slice(&self.name)
    ///     }
    /// }
    ///
    /// let mbi = unsafe { multiboot2::load(0xdeadbeef).unwrap() };
    ///
    /// let tag = mbi
    ///     .get_tag::<CustomTag, _>(0x1337)
    ///     .unwrap();
    /// assert_eq!(tag.name(), Ok("name"));
    /// ```
    pub fn get_tag<TagT: TagTrait + ?Sized, TagType: Into<TagTypeId>>(
        &self,
        typ: TagType,
    ) -> Option<&TagT> {
        let typ = typ.into();
        self.tags()
            .find(|tag| tag.typ == typ)
            .map(|tag| tag.cast_tag::<TagT>())
    }

    fn tags(&self) -> TagIter {
        TagIter::new(unsafe { self.inner.offset(1) } as *const _)
    }
}

impl BootInformationInner {
    fn has_valid_end_tag(&self) -> bool {
        let end_tag_prototype = EndTag::default();

        let self_ptr = self as *const _;
        let end_tag_addr = self_ptr as usize + (self.total_size - end_tag_prototype.size) as usize;
        let end_tag = unsafe { &*(end_tag_addr as *const Tag) };

        end_tag.typ == end_tag_prototype.typ && end_tag.size == end_tag_prototype.size
    }
}

// SAFETY: BootInformation contains a const ptr to memory that is never mutated.
// Sending this pointer to other threads is sound.
unsafe impl Send for BootInformation {}

impl fmt::Debug for BootInformation {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        /// Limit how many Elf-Sections should be debug-formatted.
        /// Can be thousands of sections for a Rust binary => this is useless output.
        /// If the user really wants this, they should debug-format the field directly.
        const ELF_SECTIONS_LIMIT: usize = 17;

        let mut debug = f.debug_struct("Multiboot2 Boot Information");
        debug
            .field("start_address", &(self.start_address() as *const u64))
            .field("end_address", &(self.end_address() as *const u64))
            .field("total_size", &(self.total_size() as *const u64))
            .field(
                "boot_loader_name_tag",
                &self
                    .boot_loader_name_tag()
                    .and_then(|x| x.name().ok())
                    .unwrap_or("<unknown>"),
            )
            .field(
                "command_line",
                &self
                    .command_line_tag()
                    .and_then(|x| x.command_line().ok())
                    .unwrap_or(""),
            )
            .field("memory_areas", &self.memory_map_tag())
            // so far, I didn't found a nice way to connect the iterator with ".field()" because
            // the iterator isn't Debug
            .field("module_tags", &self.module_tags());
        // usually this is REALLY big (thousands of tags) => skip it here

        let elf_sections_tag_entries_count = self.elf_sections().map(|x| x.count()).unwrap_or(0);

        if elf_sections_tag_entries_count > ELF_SECTIONS_LIMIT {
            debug.field("elf_sections_tags (count)", &elf_sections_tag_entries_count);
        } else {
            debug.field(
                "elf_sections_tags",
                &self.elf_sections().unwrap_or_default(),
            );
        }

        debug
            .field("efi_32_ih", &self.efi_32_ih())
            .field("efi_64_ih", &self.efi_64_ih())
            .field("efi_sdt_32_tag", &self.efi_sdt_32_tag())
            .field("efi_sdt_64_tag", &self.efi_sdt_64_tag())
            .field("efi_memory_map_tag", &self.efi_memory_map_tag())
            .finish()
    }
}

pub(crate) struct Reader {
    pub(crate) ptr: *const u8,
    pub(crate) off: usize,
}

impl Reader {
    pub(crate) fn new<T>(ptr: *const T) -> Reader {
        Reader {
            ptr: ptr as *const u8,
            off: 0,
        }
    }

    pub(crate) fn read_u8(&mut self) -> u8 {
        self.off += 1;
        unsafe { *self.ptr.add(self.off - 1) }
    }

    pub(crate) fn read_u16(&mut self) -> u16 {
        self.read_u8() as u16 | (self.read_u8() as u16) << 8
    }

    pub(crate) fn read_u32(&mut self) -> u32 {
        self.read_u16() as u32 | (self.read_u16() as u32) << 16
    }

    pub(crate) fn read_u64(&mut self) -> u64 {
        self.read_u32() as u64 | (self.read_u32() as u64) << 32
    }

    pub(crate) fn skip(&mut self, n: usize) {
        self.off += n;
    }

    pub(crate) fn current_address(&self) -> usize {
        unsafe { self.ptr.add(self.off) as usize }
    }
}

/// A trait to abstract over all sized and unsized tags (DSTs). For sized tags,
/// this trait does not much. For DSTs, a `TagTrait::dst_size` implementation
/// must me provided, which returns the right size hint for the dynamically
/// sized portion of the struct.
///
/// The [`TagTrait::from_base_tag`] method has a default implementation for all
/// tags that are `Sized`.
///
/// # Trivia
/// This crate uses the [`Pointee`]-abstraction of the [`ptr_meta`] crate to
/// create fat pointers.
pub trait TagTrait: Pointee {
    /// Returns
    fn dst_size(base_tag: &Tag) -> Self::Metadata;

    /// Creates a reference to a (dynamically sized) tag type in a safe way.
    /// DST tags need to implement a proper [`Self::dst_size`] implementation.
    ///
    /// # Safety
    /// Callers must be sure that the "size" field of the provided [`Tag`] is
    /// sane and the underlying memory valid. The implementation of this trait
    /// **must have** a correct [`Self::dst_size`] implementation.
    unsafe fn from_base_tag<'a>(tag: &Tag) -> &'a Self {
        let ptr = tag as *const _ as *const ();
        let ptr = ptr_meta::from_raw_parts(ptr, Self::dst_size(tag));
        &*ptr
    }
}

// All sized tags automatically have a Pointee implementation where
// Pointee::Metadata is (). Hence, the TagTrait is implemented automatically for
// all tags that are sized.
impl<T: Pointee<Metadata = ()>> TagTrait for T {
    #[allow(clippy::unused_unit)]
    fn dst_size(_: &Tag) -> Self::Metadata {
        ()
    }
}

/* TODO doesn't work, missing support in Rust (so far):
 https://github.com/rust-lang/rust/issues/20400
    fn dst_size(base_tag: &Tag) -> usize {
        // The size of the sized portion of the module tag.
        let tag_base_size = 16;
        assert!(base_tag.size >= 8);
        base_tag.size as usize - tag_base_size
    }
}
*/

#[cfg(test)]
mod tests {
    use super::*;
    use core::str::Utf8Error;

    #[test]
    fn no_tags() {
        #[repr(C, align(8))]
        struct Bytes([u8; 16]);
        let bytes: Bytes = Bytes([
            16, 0, 0, 0, // total_size
            0, 0, 0, 0, // reserved
            0, 0, 0, 0, // end tag type
            8, 0, 0, 0, // end tag size
        ]);
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());
        assert!(bi.elf_sections().is_none());
        assert!(bi.memory_map_tag().is_none());
        assert!(bi.module_tags().next().is_none());
        assert!(bi.boot_loader_name_tag().is_none());
        assert!(bi.command_line_tag().is_none());
    }

    #[test]
    #[should_panic]
    fn invalid_total_size() {
        #[repr(C, align(8))]
        struct Bytes([u8; 15]);
        let bytes: Bytes = Bytes([
            15, 0, 0, 0, // total_size
            0, 0, 0, 0, // reserved
            0, 0, 0, 0, // end tag type
            8, 0, 0, // end tag size
        ]);
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());
        assert!(bi.elf_sections().is_none());
        assert!(bi.memory_map_tag().is_none());
        assert!(bi.module_tags().next().is_none());
        assert!(bi.boot_loader_name_tag().is_none());
        assert!(bi.command_line_tag().is_none());
    }

    #[test]
    #[should_panic]
    fn invalid_end_tag() {
        #[repr(C, align(8))]
        struct Bytes([u8; 16]);
        let bytes: Bytes = Bytes([
            16, 0, 0, 0, // total_size
            0, 0, 0, 0, // reserved
            0, 0, 0, 0, // end tag type
            9, 0, 0, 0, // end tag size
        ]);
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());
        assert!(bi.elf_sections().is_none());
        assert!(bi.memory_map_tag().is_none());
        assert!(bi.module_tags().next().is_none());
        assert!(bi.boot_loader_name_tag().is_none());
        assert!(bi.command_line_tag().is_none());
    }

    #[test]
    fn name_tag() {
        #[repr(C, align(8))]
        struct Bytes([u8; 32]);
        let bytes: Bytes = Bytes([
            32, 0, 0, 0, // total_size
            0, 0, 0, 0, // reserved
            2, 0, 0, 0, // boot loader name tag type
            13, 0, 0, 0, // boot loader name tag size
            110, 97, 109, 101, // boot loader name 'name'
            0, 0, 0, 0, // boot loader name null + padding
            0, 0, 0, 0, // end tag type
            8, 0, 0, 0, // end tag size
        ]);
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());
        assert!(bi.elf_sections().is_none());
        assert!(bi.memory_map_tag().is_none());
        assert!(bi.module_tags().next().is_none());
        assert_eq!(
            "name",
            bi.boot_loader_name_tag()
                .expect("tag must be present")
                .name()
                .expect("must be valid utf8")
        );
        assert!(bi.command_line_tag().is_none());
    }

    #[test]
    fn framebuffer_tag_rgb() {
        // direct RGB mode test:
        // taken from GRUB2 running in QEMU at
        // 1280x720 with 32bpp in BGRA format.
        #[repr(C, align(8))]
        struct Bytes([u8; 56]);
        let bytes: Bytes = Bytes([
            56, 0, 0, 0, // total size
            0, 0, 0, 0, // reserved
            8, 0, 0, 0, // framebuffer tag type
            40, 0, 0, 0, // framebuffer tag size
            0, 0, 0, 253, // framebuffer low dword of address
            0, 0, 0, 0, // framebuffer high dword of address
            0, 20, 0, 0, // framebuffer pitch
            0, 5, 0, 0, // framebuffer width
            208, 2, 0, 0, // framebuffer height
            32, 1, 0, 0, // framebuffer bpp, type, reserved word
            16, 8, 8, 8, // framebuffer red pos/size, green pos/size
            0, 8, 0, 0, // framebuffer blue pos/size, padding word
            0, 0, 0, 0, // end tag type
            8, 0, 0, 0, // end tag size
        ]);
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());
        use framebuffer::{FramebufferField, FramebufferType};
        assert!(bi.framebuffer_tag().is_some());
        let fbi = bi
            .framebuffer_tag()
            .expect("Framebuffer info should be available")
            .expect("Framebuffer info type should be valid");
        assert_eq!(fbi.address(), 4244635648);
        assert_eq!(fbi.pitch(), 5120);
        assert_eq!(fbi.width(), 1280);
        assert_eq!(fbi.height(), 720);
        assert_eq!(fbi.bpp(), 32);
        assert_eq!(
            fbi.buffer_type().unwrap(),
            FramebufferType::RGB {
                red: FramebufferField {
                    position: 16,
                    size: 8
                },
                green: FramebufferField {
                    position: 8,
                    size: 8
                },
                blue: FramebufferField {
                    position: 0,
                    size: 8
                }
            }
        );
    }

    #[test]
    fn framebuffer_tag_indexed() {
        // indexed mode test:
        // this is synthetic, as I can't get QEMU
        // to run in indexed color mode.
        #[repr(C, align(8))]
        struct Bytes([u8; 64]);
        let bytes: Bytes = Bytes([
            64, 0, 0, 0, // total size
            0, 0, 0, 0, // reserved
            8, 0, 0, 0, // framebuffer tag type
            48, 0, 0, 0, // framebuffer tag size
            0, 0, 0, 253, // framebuffer low dword of address
            0, 0, 0, 0, // framebuffer high dword of address
            0, 20, 0, 0, // framebuffer pitch
            0, 5, 0, 0, // framebuffer width
            208, 2, 0, 0, // framebuffer height
            32, 0, 0, 0, // framebuffer bpp, type, reserved word
            4, 0, 0, 0, // framebuffer palette length
            255, 0, 0, 0, // framebuffer palette
            255, 0, 0, 0, 255, 0, 0, 0, 0, 0, 0, 0, // end tag type
            8, 0, 0, 0, // end tag size
        ]);
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());
        use framebuffer::{FramebufferColor, FramebufferType};
        assert!(bi.framebuffer_tag().is_some());
        let fbi = bi
            .framebuffer_tag()
            .expect("Framebuffer info should be available")
            .expect("Framebuffer info type should be valid");
        assert_eq!(fbi.address(), 4244635648);
        assert_eq!(fbi.pitch(), 5120);
        assert_eq!(fbi.width(), 1280);
        assert_eq!(fbi.height(), 720);
        assert_eq!(fbi.bpp(), 32);
        match fbi.buffer_type().unwrap() {
            FramebufferType::Indexed { palette } => assert_eq!(
                palette,
                [
                    FramebufferColor {
                        red: 255,
                        green: 0,
                        blue: 0
                    },
                    FramebufferColor {
                        red: 0,
                        green: 255,
                        blue: 0
                    },
                    FramebufferColor {
                        red: 0,
                        green: 0,
                        blue: 255
                    },
                    FramebufferColor {
                        red: 0,
                        green: 0,
                        blue: 0
                    }
                ]
            ),
            _ => panic!("Expected indexed framebuffer type."),
        }
    }

    #[test]
    fn vbe_info_tag() {
        //Taken from GRUB2 running in QEMU.
        #[repr(C, align(8))]
        struct Bytes([u8; 800]);
        let bytes = Bytes([
            32, 3, 0, 0, // Total size.
            0, 0, 0, 0, // Reserved
            7, 0, 0, 0, // Tag type.
            16, 3, 0, 0, // Tag size.
            122, 65, 255, 255, // VBE mode, protected mode interface segment,
            0, 96, 79, 0, // protected mode interface offset, and length.
            86, 69, 83, 65, // "VESA" signature.
            0, 3, 220, 87, // VBE version, lower half of OEM string ptr,
            0, 192, 1, 0, // upper half of OEM string ptr, lower half of capabilities
            0, 0, 34, 128, // upper half of capabilities, lower half of vide mode ptr,
            0, 96, 0, 1, // upper half of video mode ptr, number of 64kb memory blocks
            0, 0, 240, 87, // OEM software revision, lower half of OEM vendor string ptr,
            0, 192, 3,
            88, // upper half of OEM vendor string ptr, lower half of OEM product string ptr,
            0, 192, 23,
            88, // upper half of OEM product string ptr, lower half of OEM revision string ptr,
            0, 192, 0, 1, // upper half of OEM revision string ptr.
            1, 1, 2, 1, // Reserved data....
            3, 1, 4, 1, 5, 1, 6, 1, 7, 1, 13, 1, 14, 1, 15, 1, 16, 1, 17, 1, 18, 1, 19, 1, 20, 1,
            21, 1, 22, 1, 23, 1, 24, 1, 25, 1, 26, 1, 27, 1, 28, 1, 29, 1, 30, 1, 31, 1, 64, 1, 65,
            1, 66, 1, 67, 1, 68, 1, 69, 1, 70, 1, 71, 1, 72, 1, 73, 1, 74, 1, 75, 1, 76, 1, 117, 1,
            118, 1, 119, 1, 120, 1, 121, 1, 122, 1, 123, 1, 124, 1, 125, 1, 126, 1, 127, 1, 128, 1,
            129, 1, 130, 1, 131, 1, 132, 1, 133, 1, 134, 1, 135, 1, 136, 1, 137, 1, 138, 1, 139, 1,
            140, 1, 141, 1, 142, 1, 143, 1, 144, 1, 145, 1, 146, 1, 0, 0, 1, 0, 2, 0, 3, 0, 4, 0,
            5, 0, 6, 0, 7, 0, 13, 0, 14, 0, 15, 0, 16, 0, 17, 0, 18, 0, 19, 0, 106, 0, 255, 255, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // Until Here
            187, 0, 7, 0, // Mode attributes, window A and B attributes
            64, 0, 64, 0, // Window granularity and size.
            0, 160, 0, 0, // Window A and B segments.
            186, 84, 0, 192, // Window relocation function pointer.
            0, 20, 0, 5, // Pitch, X resolution.
            32, 3, 8, 16, // Y resolution, X char size, Y char size.
            1, 32, 1, 6, // Number of planes, BPP, number of banks, memory model.
            0, 3, 1, 8, // Bank size, number of images, reserved, red mask size.
            16, 8, 8,
            8, // Red mask position, green mask size, green mask position, blue mask size,
            0, 8, 24,
            2, // blue mask position, reserved mask size, reserved mask position, color attributes.
            0, 0, 0, 253, // Frame buffer base address.
            0, 0, 0, 0, // Off screen memory offset.
            0, 0, 0, 20, // Off screen memory size, reserved data...
            0, 0, 8, 16, 8, 8, 8, 0, 8, 24, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
            0, 0, // Until here.
            0, 0, 0, 0, // End tag type.
            8, 0, 0, 0, // End tag size.
        ]);

        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());
        assert!(bi.vbe_info_tag().is_some());
        let vbe = bi.vbe_info_tag().unwrap();
        use vbe_info::*;

        assert_eq!({ vbe.mode }, 16762);
        assert_eq!({ vbe.interface_segment }, 65535);
        assert_eq!({ vbe.interface_offset }, 24576);
        assert_eq!({ vbe.interface_length }, 79);
        assert_eq!({ vbe.control_info.signature }, [86, 69, 83, 65]);
        assert_eq!({ vbe.control_info.version }, 768);
        assert_eq!({ vbe.control_info.oem_string_ptr }, 3221247964);
        assert_eq!(
            { vbe.control_info.capabilities },
            VBECapabilities::SWITCHABLE_DAC
        );
        assert_eq!({ vbe.control_info.mode_list_ptr }, 1610645538);
        assert_eq!({ vbe.control_info.total_memory }, 256);
        assert_eq!({ vbe.control_info.oem_software_revision }, 0);
        assert_eq!({ vbe.control_info.oem_vendor_name_ptr }, 3221247984);
        assert_eq!({ vbe.control_info.oem_product_name_ptr }, 3221248003);
        assert_eq!({ vbe.control_info.oem_product_revision_ptr }, 3221248023);
        assert!({ vbe.mode_info.mode_attributes }.contains(
            VBEModeAttributes::SUPPORTED
                | VBEModeAttributes::COLOR
                | VBEModeAttributes::GRAPHICS
                | VBEModeAttributes::NOT_VGA_COMPATIBLE
                | VBEModeAttributes::LINEAR_FRAMEBUFFER
        ));
        assert!(vbe.mode_info.window_a_attributes.contains(
            VBEWindowAttributes::RELOCATABLE
                | VBEWindowAttributes::READABLE
                | VBEWindowAttributes::WRITEABLE
        ));
        assert_eq!({ vbe.mode_info.window_granularity }, 64);
        assert_eq!({ vbe.mode_info.window_size }, 64);
        assert_eq!({ vbe.mode_info.window_a_segment }, 40960);
        assert_eq!({ vbe.mode_info.window_function_ptr }, 3221247162);
        assert_eq!({ vbe.mode_info.pitch }, 5120);
        assert_eq!({ vbe.mode_info.resolution }, (1280, 800));
        assert_eq!(vbe.mode_info.character_size, (8, 16));
        assert_eq!(vbe.mode_info.number_of_planes, 1);
        assert_eq!(vbe.mode_info.bpp, 32);
        assert_eq!(vbe.mode_info.number_of_banks, 1);
        assert_eq!(vbe.mode_info.memory_model, VBEMemoryModel::DirectColor);
        assert_eq!(vbe.mode_info.bank_size, 0);
        assert_eq!(vbe.mode_info.number_of_image_pages, 3);
        assert_eq!(
            vbe.mode_info.red_field,
            VBEField {
                position: 16,
                size: 8
            }
        );
        assert_eq!(
            vbe.mode_info.green_field,
            VBEField {
                position: 8,
                size: 8
            }
        );
        assert_eq!(
            vbe.mode_info.blue_field,
            VBEField {
                position: 0,
                size: 8
            }
        );
        assert_eq!(
            vbe.mode_info.reserved_field,
            VBEField {
                position: 24,
                size: 8
            }
        );
        assert_eq!(
            vbe.mode_info.direct_color_attributes,
            VBEDirectColorAttributes::RESERVED_USABLE
        );
        assert_eq!({ vbe.mode_info.framebuffer_base_ptr }, 4244635648);
        assert_eq!({ vbe.mode_info.offscreen_memory_offset }, 0);
        assert_eq!({ vbe.mode_info.offscreen_memory_size }, 0);
    }

    #[test]
    /// Compile time test for [`VBEInfoTag`].
    fn vbe_info_tag_size() {
        unsafe {
            // 16 for the start + 512 from `VBEControlInfo` + 256 from `VBEModeInfo`.
            core::mem::transmute::<[u8; 784], VBEInfoTag>([0u8; 784]);
        }
    }

    #[test]
    fn grub2() {
        #[repr(C, align(8))]
        struct Bytes([u8; 960]);
        let mut bytes: Bytes = Bytes([
            192, 3, 0, 0, // total_size
            0, 0, 0, 0, // reserved
            1, 0, 0, 0, // boot command tag type
            9, 0, 0, 0, // boot command tag size
            0, 0, 0, 0, // boot command null + padding
            0, 0, 0, 0, // boot command padding
            2, 0, 0, 0, // boot loader name tag type
            26, 0, 0, 0, // boot loader name tag size
            71, 82, 85, 66, // boot loader name
            32, 50, 46, 48, // boot loader name
            50, 126, 98, 101, // boot loader name
            116, 97, 51, 45, // boot loader name
            53, 0, 0, 0, // boot loader name null + padding
            0, 0, 0, 0, // boot loader name padding
            10, 0, 0, 0, // APM tag type
            28, 0, 0, 0, // APM tag size
            2, 1, 0, 240, // APM version, cseg
            207, 212, 0, 0, // APM offset
            0, 240, 0, 240, // APM cseg_16, dseg
            3, 0, 240, 255, // APM flags, cseg_len
            240, 255, 240, 255, // APM cseg_16_len, dseg_len
            0, 0, 0, 0, // APM padding
            6, 0, 0, 0, // memory map tag type
            160, 0, 0, 0, // memory map tag size
            24, 0, 0, 0, // memory map entry_size
            0, 0, 0, 0, // memory map entry_version
            0, 0, 0, 0, // memory map entry 0 base_addr
            0, 0, 0, 0, // memory map entry 0 base_addr
            0, 252, 9, 0, // memory map entry 0 length
            0, 0, 0, 0, // memory map entry 0 length
            1, 0, 0, 0, // memory map entry 0 type
            0, 0, 0, 0, // memory map entry 0 reserved
            0, 252, 9, 0, // memory map entry 1 base_addr
            0, 0, 0, 0, // memory map entry 1 base_addr
            0, 4, 0, 0, // memory map entry 1 length
            0, 0, 0, 0, // memory map entry 1 length
            2, 0, 0, 0, // memory map entry 1 type
            0, 0, 0, 0, // memory map entry 1 reserved
            0, 0, 15, 0, // memory map entry 2 base_addr
            0, 0, 0, 0, // memory map entry 2 base_addr
            0, 0, 1, 0, // memory map entry 2 length
            0, 0, 0, 0, // memory map entry 2 length
            2, 0, 0, 0, // memory map entry 2 type
            0, 0, 0, 0, // memory map entry 2 reserved
            0, 0, 16, 0, // memory map entry 3 base_addr
            0, 0, 0, 0, // memory map entry 3 base_addr
            0, 0, 238, 7, // memory map entry 3 length
            0, 0, 0, 0, // memory map entry 3 length
            1, 0, 0, 0, // memory map entry 3 type
            0, 0, 0, 0, // memory map entry 3 reserved
            0, 0, 254, 7, // memory map entry 4 base_addr
            0, 0, 0, 0, // memory map entry 4 base_addr
            0, 0, 2, 0, // memory map entry 4 length
            0, 0, 0, 0, // memory map entry 4 length
            2, 0, 0, 0, // memory map entry 4 type
            0, 0, 0, 0, // memory map entry 4 reserved
            0, 0, 252, 255, // memory map entry 5 base_addr
            0, 0, 0, 0, // memory map entry 5 base_addr
            0, 0, 4, 0, // memory map entry 5 length
            0, 0, 0, 0, // memory map entry 5 length
            2, 0, 0, 0, // memory map entry 5 type
            0, 0, 0, 0, // memory map entry 5 reserved
            9, 0, 0, 0, // elf symbols tag type
            84, 2, 0, 0, // elf symbols tag size
            9, 0, 0, 0, // elf symbols num
            64, 0, 0, 0, // elf symbols entsize
            8, 0, 0, 0, // elf symbols shndx
            0, 0, 0, 0, // elf symbols entry 0 name
            0, 0, 0, 0, // elf symbols entry 0 type
            0, 0, 0, 0, // elf symbols entry 0 flags
            0, 0, 0, 0, // elf symbols entry 0 flags
            0, 0, 0, 0, // elf symbols entry 0 addr
            0, 0, 0, 0, // elf symbols entry 0 addr
            0, 0, 0, 0, // elf symbols entry 0 offset
            0, 0, 0, 0, // elf symbols entry 0 offset
            0, 0, 0, 0, // elf symbols entry 0 size
            0, 0, 0, 0, // elf symbols entry 0 size
            0, 0, 0, 0, // elf symbols entry 0 link
            0, 0, 0, 0, // elf symbols entry 0 info
            0, 0, 0, 0, // elf symbols entry 0 addralign
            0, 0, 0, 0, // elf symbols entry 0 addralign
            0, 0, 0, 0, // elf symbols entry 0 entsize
            0, 0, 0, 0, // elf symbols entry 0 entsize
            27, 0, 0, 0, // elf symbols entry 1 name
            1, 0, 0, 0, // elf symbols entry 1 type
            2, 0, 0, 0, // elf symbols entry 1 flags
            0, 0, 0, 0, // elf symbols entry 1 flags
            0, 0, 16, 0, // elf symbols entry 1 addr
            0, 128, 255, 255, // elf symbols entry 1 addr
            0, 16, 0, 0, // elf symbols entry 1 offset
            0, 0, 0, 0, // elf symbols entry 1 offset
            0, 48, 0, 0, // elf symbols entry 1 size
            0, 0, 0, 0, // elf symbols entry 1 size
            0, 0, 0, 0, // elf symbols entry 1 link
            0, 0, 0, 0, // elf symbols entry 1 info
            16, 0, 0, 0, // elf symbols entry 1 addralign
            0, 0, 0, 0, // elf symbols entry 1 addralign
            0, 0, 0, 0, // elf symbols entry 1 entsize
            0, 0, 0, 0, // elf symbols entry 1 entsize
            35, 0, 0, 0, // elf symbols entry 2 name
            1, 0, 0, 0, // elf symbols entry 2 type
            6, 0, 0, 0, // elf symbols entry 2 flags
            0, 0, 0, 0, // elf symbols entry 2 flags
            0, 48, 16, 0, // elf symbols entry 2 addr
            0, 128, 255, 255, // elf symbols entry 2 addr
            0, 64, 0, 0, // elf symbols entry 2 offset
            0, 0, 0, 0, // elf symbols entry 2 offset
            0, 144, 0, 0, // elf symbols entry 2 size
            0, 0, 0, 0, // elf symbols entry 2 size
            0, 0, 0, 0, // elf symbols entry 2 link
            0, 0, 0, 0, // elf symbols entry 2 info
            16, 0, 0, 0, // elf symbols entry 2 addralign
            0, 0, 0, 0, // elf symbols entry 2 addralign
            0, 0, 0, 0, // elf symbols entry 2 entsize
            0, 0, 0, 0, // elf symbols entry 2 entsize
            41, 0, 0, 0, // elf symbols entry 3 name
            1, 0, 0, 0, // elf symbols entry 3 type
            3, 0, 0, 0, // elf symbols entry 3 flags
            0, 0, 0, 0, // elf symbols entry 3 flags
            0, 192, 16, 0, // elf symbols entry 3 addr
            0, 128, 255, 255, // elf symbols entry 3 addr
            0, 208, 0, 0, // elf symbols entry 3 offset
            0, 0, 0, 0, // elf symbols entry 3 offset
            0, 32, 0, 0, // elf symbols entry 3 size
            0, 0, 0, 0, // elf symbols entry 3 size
            0, 0, 0, 0, // elf symbols entry 3 link
            0, 0, 0, 0, // elf symbols entry 3 info
            8, 0, 0, 0, // elf symbols entry 3 addralign
            0, 0, 0, 0, // elf symbols entry 3 addralign
            0, 0, 0, 0, // elf symbols entry 3 entsize
            0, 0, 0, 0, // elf symbols entry 3 entsize
            47, 0, 0, 0, // elf symbols entry 4 name
            8, 0, 0, 0, // elf symbols entry 4 type
            3, 0, 0, 0, // elf symbols entry 4 flags
            0, 0, 0, 0, // elf symbols entry 4 flags
            0, 224, 16, 0, // elf symbols entry 4 addr
            0, 128, 255, 255, // elf symbols entry 4 addr
            0, 240, 0, 0, // elf symbols entry 4 offset
            0, 0, 0, 0, // elf symbols entry 4 offset
            0, 80, 0, 0, // elf symbols entry 4 size
            0, 0, 0, 0, // elf symbols entry 4 size
            0, 0, 0, 0, // elf symbols entry 4 link
            0, 0, 0, 0, // elf symbols entry 4 info
            0, 16, 0, 0, // elf symbols entry 4 addralign
            0, 0, 0, 0, // elf symbols entry 4 addralign
            0, 0, 0, 0, // elf symbols entry 4 entsize
            0, 0, 0, 0, // elf symbols entry 4 entsize
            52, 0, 0, 0, // elf symbols entry 5 name
            1, 0, 0, 0, // elf symbols entry 5 type
            3, 0, 0, 0, // elf symbols entry 5 flags
            0, 0, 0, 0, // elf symbols entry 5 flags
            0, 48, 17, 0, // elf symbols entry 5 addr
            0, 128, 255, 255, // elf symbols entry 5 addr
            0, 240, 0, 0, // elf symbols entry 5 offset
            0, 0, 0, 0, // elf symbols entry 5 offset
            0, 0, 0, 0, // elf symbols entry 5 size
            0, 0, 0, 0, // elf symbols entry 5 size
            0, 0, 0, 0, // elf symbols entry 5 link
            0, 0, 0, 0, // elf symbols entry 5 info
            1, 0, 0, 0, // elf symbols entry 5 addralign
            0, 0, 0, 0, // elf symbols entry 5 addralign
            0, 0, 0, 0, // elf symbols entry 5 entsize
            0, 0, 0, 0, // elf symbols entry 5 entsize
            1, 0, 0, 0, // elf symbols entry 6 name
            2, 0, 0, 0, // elf symbols entry 6 type
            0, 0, 0, 0, // elf symbols entry 6 flags
            0, 0, 0, 0, // elf symbols entry 6 flags
            0, 48, 17, 0, // elf symbols entry 6 addr
            0, 0, 0, 0, // elf symbols entry 6 addr
            0, 240, 0, 0, // elf symbols entry 6 offset
            0, 0, 0, 0, // elf symbols entry 6 offset
            224, 43, 0, 0, // elf symbols entry 6 size
            0, 0, 0, 0, // elf symbols entry 6 size
            7, 0, 0, 0, // elf symbols entry 6 link
            102, 1, 0, 0, // elf symbols entry 6 info
            8, 0, 0, 0, // elf symbols entry 6 addralign
            0, 0, 0, 0, // elf symbols entry 6 addralign
            24, 0, 0, 0, // elf symbols entry 6 entsize
            0, 0, 0, 0, // elf symbols entry 6 entsize
            9, 0, 0, 0, // elf symbols entry 7 name
            3, 0, 0, 0, // elf symbols entry 7 type
            0, 0, 0, 0, // elf symbols entry 7 flags
            0, 0, 0, 0, // elf symbols entry 7 flags
            224, 91, 17, 0, // elf symbols entry 7 addr
            0, 0, 0, 0, // elf symbols entry 7 addr
            224, 27, 1, 0, // elf symbols entry 7 offset
            0, 0, 0, 0, // elf symbols entry 7 offset
            145, 55, 0, 0, // elf symbols entry 7 size
            0, 0, 0, 0, // elf symbols entry 7 size
            0, 0, 0, 0, // elf symbols entry 7 link
            0, 0, 0, 0, // elf symbols entry 7 info
            1, 0, 0, 0, // elf symbols entry 7 addralign
            0, 0, 0, 0, // elf symbols entry 7 addralign
            0, 0, 0, 0, // elf symbols entry 7 entsize
            0, 0, 0, 0, // elf symbols entry 7 entsize
            17, 0, 0, 0, // elf symbols entry 8 name
            3, 0, 0, 0, // elf symbols entry 8 type
            0, 0, 0, 0, // elf symbols entry 8 flags
            0, 0, 0, 0, // elf symbols entry 8 flags
            113, 147, 17, 0, // elf symbols entry 8 addr
            0, 0, 0, 0, // elf symbols entry 8 addr
            113, 83, 1, 0, // elf symbols entry 8 offset
            0, 0, 0, 0, // elf symbols entry 8 offset
            65, 0, 0, 0, // elf symbols entry 8 size
            0, 0, 0, 0, // elf symbols entry 8 size
            0, 0, 0, 0, // elf symbols entry 8 link
            0, 0, 0, 0, // elf symbols entry 8 info
            1, 0, 0, 0, // elf symbols entry 8 addralign
            0, 0, 0, 0, // elf symbols entry 8 addralign
            0, 0, 0, 0, // elf symbols entry 8 entsize
            0, 0, 0, 0, // elf symbols entry 8 entsize
            0, 0, 0, 0, // elf symbols padding
            4, 0, 0, 0, // basic memory tag type
            16, 0, 0, 0, // basic memory tag size
            127, 2, 0, 0, // basic memory mem_lower
            128, 251, 1, 0, // basic memory mem_upper
            5, 0, 0, 0, // BIOS boot device tag type
            20, 0, 0, 0, // BIOS boot device tag size
            224, 0, 0, 0, // BIOS boot device biosdev
            255, 255, 255, 255, // BIOS boot device partition
            255, 255, 255, 255, // BIOS boot device subpartition
            0, 0, 0, 0, // BIOS boot device padding
            8, 0, 0, 0, // framebuffer info tag type
            32, 0, 0, 0, // framebuffer info tag size
            0, 128, 11, 0, // framebuffer info framebuffer_addr
            0, 0, 0, 0, // framebuffer info framebuffer_addr
            160, 0, 0, 0, // framebuffer info framebuffer_pitch
            80, 0, 0, 0, // framebuffer info framebuffer_width
            25, 0, 0, 0, // framebuffer info framebuffer_height
            16, 2, 0, 0, // framebuffer info framebuffer_[bpp,type], reserved, color_info
            14, 0, 0, 0, // ACPI old tag type
            28, 0, 0, 0, // ACPI old tag size
            82, 83, 68, 32, // ACPI old
            80, 84, 82, 32, // ACPI old
            89, 66, 79, 67, // ACPI old
            72, 83, 32, 0, // ACPI old
            220, 24, 254, 7, // ACPI old
            0, 0, 0, 0, // ACPI old padding
            0, 0, 0, 0, // end tag type
            8, 0, 0, 0, // end tag size
        ]);
        #[repr(C, align(8))]
        struct StringBytes([u8; 65]);
        let string_bytes: StringBytes = StringBytes([
            0, 46, 115, 121, 109, 116, 97, 98, 0, 46, 115, 116, 114, 116, 97, 98, 0, 46, 115, 104,
            115, 116, 114, 116, 97, 98, 0, 46, 114, 111, 100, 97, 116, 97, 0, 46, 116, 101, 120,
            116, 0, 46, 100, 97, 116, 97, 0, 46, 98, 115, 115, 0, 46, 100, 97, 116, 97, 46, 114,
            101, 108, 46, 114, 111, 0,
        ]);
        let string_addr = string_bytes.0.as_ptr() as u64;
        for i in 0..8 {
            bytes.0[796 + i] = (string_addr >> (i * 8)) as u8;
        }
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        test_grub2_boot_info(bi, addr, string_addr, &bytes.0, &string_bytes.0);
        let bi = unsafe { load_with_offset(addr, 0) };
        let bi = bi.unwrap();
        test_grub2_boot_info(bi, addr, string_addr, &bytes.0, &string_bytes.0);
        let offset = 8usize;
        for i in 0..8 {
            bytes.0[796 + i] = ((string_addr - offset as u64) >> (i * 8)) as u8;
        }
        let bi = unsafe { load_with_offset(addr - offset, offset) };
        let bi = bi.unwrap();
        test_grub2_boot_info(
            bi,
            addr,
            string_addr - offset as u64,
            &bytes.0,
            &string_bytes.0,
        );
    }

    fn test_grub2_boot_info(
        bi: BootInformation,
        addr: usize,
        string_addr: u64,
        bytes: &[u8],
        string_bytes: &[u8],
    ) {
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.len(), bi.end_address());
        assert_eq!(bytes.len(), bi.total_size());
        let mut es = bi.elf_sections().unwrap();
        let s1 = es.next().expect("Should have one more section");
        assert_eq!(".rodata", s1.name().expect("Should be valid utf-8"));
        assert_eq!(0xFFFF_8000_0010_0000, s1.start_address());
        assert_eq!(0xFFFF_8000_0010_3000, s1.end_address());
        assert_eq!(0x0000_0000_0000_3000, s1.size());
        assert_eq!(ElfSectionFlags::ALLOCATED, s1.flags());
        assert_eq!(ElfSectionType::ProgramSection, s1.section_type());
        let s2 = es.next().expect("Should have one more section");
        assert_eq!(".text", s2.name().expect("Should be valid utf-8"));
        assert_eq!(0xFFFF_8000_0010_3000, s2.start_address());
        assert_eq!(0xFFFF_8000_0010_C000, s2.end_address());
        assert_eq!(0x0000_0000_0000_9000, s2.size());
        assert_eq!(
            ElfSectionFlags::EXECUTABLE | ElfSectionFlags::ALLOCATED,
            s2.flags()
        );
        assert_eq!(ElfSectionType::ProgramSection, s2.section_type());
        let s3 = es.next().expect("Should have one more section");
        assert_eq!(".data", s3.name().expect("Should be valid utf-8"));
        assert_eq!(0xFFFF_8000_0010_C000, s3.start_address());
        assert_eq!(0xFFFF_8000_0010_E000, s3.end_address());
        assert_eq!(0x0000_0000_0000_2000, s3.size());
        assert_eq!(
            ElfSectionFlags::ALLOCATED | ElfSectionFlags::WRITABLE,
            s3.flags()
        );
        assert_eq!(ElfSectionType::ProgramSection, s3.section_type());
        let s4 = es.next().expect("Should have one more section");
        assert_eq!(".bss", s4.name().expect("Should be valid utf-8"));
        assert_eq!(0xFFFF_8000_0010_E000, s4.start_address());
        assert_eq!(0xFFFF_8000_0011_3000, s4.end_address());
        assert_eq!(0x0000_0000_0000_5000, s4.size());
        assert_eq!(
            ElfSectionFlags::ALLOCATED | ElfSectionFlags::WRITABLE,
            s4.flags()
        );
        assert_eq!(ElfSectionType::Uninitialized, s4.section_type());
        let s5 = es.next().expect("Should have one more section");
        assert_eq!(".data.rel.ro", s5.name().expect("Should be valid utf-8"));
        assert_eq!(0xFFFF_8000_0011_3000, s5.start_address());
        assert_eq!(0xFFFF_8000_0011_3000, s5.end_address());
        assert_eq!(0x0000_0000_0000_0000, s5.size());
        assert_eq!(
            ElfSectionFlags::ALLOCATED | ElfSectionFlags::WRITABLE,
            s5.flags()
        );
        assert_eq!(ElfSectionType::ProgramSection, s5.section_type());
        let s6 = es.next().expect("Should have one more section");
        assert_eq!(".symtab", s6.name().expect("Should be valid utf-8"));
        assert_eq!(0x0000_0000_0011_3000, s6.start_address());
        assert_eq!(0x0000_0000_0011_5BE0, s6.end_address());
        assert_eq!(0x0000_0000_0000_2BE0, s6.size());
        assert_eq!(ElfSectionFlags::empty(), s6.flags());
        assert_eq!(ElfSectionType::LinkerSymbolTable, s6.section_type());
        let s7 = es.next().expect("Should have one more section");
        assert_eq!(".strtab", s7.name().expect("Should be valid utf-8"));
        assert_eq!(0x0000_0000_0011_5BE0, s7.start_address());
        assert_eq!(0x0000_0000_0011_9371, s7.end_address());
        assert_eq!(0x0000_0000_0000_3791, s7.size());
        assert_eq!(ElfSectionFlags::empty(), s7.flags());
        assert_eq!(ElfSectionType::StringTable, s7.section_type());
        let s8 = es.next().expect("Should have one more section");
        assert_eq!(".shstrtab", s8.name().expect("Should be valid utf-8"));
        assert_eq!(string_addr, s8.start_address());
        assert_eq!(string_addr + string_bytes.len() as u64, s8.end_address());
        assert_eq!(string_bytes.len() as u64, s8.size());
        assert_eq!(ElfSectionFlags::empty(), s8.flags());
        assert_eq!(ElfSectionType::StringTable, s8.section_type());
        assert!(es.next().is_none());
        let mut mm = bi.memory_map_tag().unwrap().available_memory_areas();
        let mm1 = mm.next().unwrap();
        assert_eq!(0x00000000, mm1.start_address());
        assert_eq!(0x009_FC00, mm1.end_address());
        assert_eq!(0x009_FC00, mm1.size());
        assert_eq!(MemoryAreaType::Available, mm1.typ());
        let mm2 = mm.next().unwrap();
        assert_eq!(0x010_0000, mm2.start_address());
        assert_eq!(0x7FE_0000, mm2.end_address());
        assert_eq!(0x7EE_0000, mm2.size());
        assert_eq!(MemoryAreaType::Available, mm2.typ());
        assert!(mm.next().is_none());

        // Test the RSDP tag
        let rsdp_old = bi.rsdp_v1_tag().unwrap();
        assert_eq!("RSD PTR ", rsdp_old.signature().unwrap());
        assert!(rsdp_old.checksum_is_valid());
        assert_eq!("BOCHS ", rsdp_old.oem_id().unwrap());
        assert_eq!(0, rsdp_old.revision());
        assert_eq!(0x7FE18DC, rsdp_old.rsdt_address());

        assert!(bi.module_tags().next().is_none());
        assert_eq!(
            "GRUB 2.02~beta3-5",
            bi.boot_loader_name_tag()
                .expect("tag must be present")
                .name()
                .expect("must be valid utf-8")
        );
        assert_eq!(
            "",
            bi.command_line_tag()
                .expect("tag must present")
                .command_line()
                .expect("must be valid utf-8")
        );

        // Test the Framebuffer tag
        let fbi = bi
            .framebuffer_tag()
            .expect("Framebuffer info should be available")
            .expect("Framebuffer info type should be valid");
        assert_eq!(fbi.address(), 753664);
        assert_eq!(fbi.pitch(), 160);
        assert_eq!(fbi.width(), 80);
        assert_eq!(fbi.height(), 25);
        assert_eq!(fbi.bpp(), 16);
        assert_eq!(fbi.buffer_type(), Ok(FramebufferType::Text));
    }

    #[test]
    fn elf_sections() {
        #[repr(C, align(8))]
        struct Bytes([u8; 168]);
        let mut bytes: Bytes = Bytes([
            168, 0, 0, 0, // total_size
            0, 0, 0, 0, // reserved
            9, 0, 0, 0, // elf symbols tag type
            20, 2, 0, 0, // elf symbols tag size
            2, 0, 0, 0, // elf symbols num
            64, 0, 0, 0, // elf symbols entsize
            1, 0, 0, 0, // elf symbols shndx
            0, 0, 0, 0, // elf symbols entry 0 name
            0, 0, 0, 0, // elf symbols entry 0 type
            0, 0, 0, 0, // elf symbols entry 0 flags
            0, 0, 0, 0, // elf symbols entry 0 flags
            0, 0, 0, 0, // elf symbols entry 0 addr
            0, 0, 0, 0, // elf symbols entry 0 addr
            0, 0, 0, 0, // elf symbols entry 0 offset
            0, 0, 0, 0, // elf symbols entry 0 offset
            0, 0, 0, 0, // elf symbols entry 0 size
            0, 0, 0, 0, // elf symbols entry 0 size
            0, 0, 0, 0, // elf symbols entry 0 link
            0, 0, 0, 0, // elf symbols entry 0 info
            0, 0, 0, 0, // elf symbols entry 0 addralign
            0, 0, 0, 0, // elf symbols entry 0 addralign
            0, 0, 0, 0, // elf symbols entry 0 entsize
            0, 0, 0, 0, // elf symbols entry 0 entsize
            1, 0, 0, 0, // elf symbols entry 1 name
            3, 0, 0, 0, // elf symbols entry 1 type
            0, 0, 0, 0, // elf symbols entry 1 flags
            0, 0, 0, 0, // elf symbols entry 1 flags
            255, 255, 255, 255, // elf symbols entry 1 addr
            255, 255, 255, 255, // elf symbols entry 1 addr
            113, 83, 1, 0, // elf symbols entry 1 offset
            0, 0, 0, 0, // elf symbols entry 1 offset
            11, 0, 0, 0, // elf symbols entry 1 size
            0, 0, 0, 0, // elf symbols entry 1 size
            0, 0, 0, 0, // elf symbols entry 1 link
            0, 0, 0, 0, // elf symbols entry 1 info
            1, 0, 0, 0, // elf symbols entry 1 addralign
            0, 0, 0, 0, // elf symbols entry 1 addralign
            0, 0, 0, 0, // elf symbols entry 1 entsize
            0, 0, 0, 0, // elf symbols entry 1 entsize
            0, 0, 0, 0, // elf symbols padding
            0, 0, 0, 0, // end tag type
            8, 0, 0, 0, // end tag size
        ]);
        #[repr(C, align(8))]
        struct StringBytes([u8; 11]);
        let string_bytes: StringBytes =
            StringBytes([0, 46, 115, 104, 115, 116, 114, 116, 97, 98, 0]);
        let string_addr = string_bytes.0.as_ptr() as u64;
        for i in 0..8 {
            let offset = 108;
            assert_eq!(255, bytes.0[offset + i]);
            bytes.0[offset + i] = (string_addr >> (i * 8)) as u8;
        }
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());
        let mut es = bi.elf_sections().unwrap();
        let s1 = es.next().expect("Should have one more section");
        assert_eq!(".shstrtab", s1.name().expect("Should be valid utf-8"));
        assert_eq!(string_addr, s1.start_address());
        assert_eq!(string_addr + string_bytes.0.len() as u64, s1.end_address());
        assert_eq!(string_bytes.0.len() as u64, s1.size());
        assert_eq!(ElfSectionFlags::empty(), s1.flags());
        assert_eq!(ElfSectionType::StringTable, s1.section_type());
        assert!(es.next().is_none());
    }

    #[test]
    fn efi_memory_map() {
        use memory_map::EFIMemoryAreaType;
        #[repr(C, align(8))]
        struct Bytes([u8; 72]);
        // test that the EFI memory map is detected.
        let bytes: Bytes = Bytes([
            72, 0, 0, 0, // size
            0, 0, 0, 0, // reserved
            17, 0, 0, 0, // EFI memory map type
            56, 0, 0, 0, // EFI memory map size
            48, 0, 0, 0, // EFI descriptor size
            1, 0, 0, 0, // EFI descriptor version, don't think this matters.
            7, 0, 0, 0, // Type: EfiConventionalMemory
            0, 0, 0, 0, // Padding
            0, 0, 16, 0, // Physical Address: should be 0x100000
            0, 0, 0, 0, // Extension of physical address.
            0, 0, 16, 0, // Virtual Address: should be 0x100000
            0, 0, 0, 0, // Extension of virtual address.
            4, 0, 0, 0, // 4 KiB Pages: 16 KiB
            0, 0, 0, 0, // Extension of pages
            0, 0, 0, 0, // Attributes of this memory range.
            0, 0, 0, 0, // Extension of attributes
            0, 0, 0, 0, // end tag type.
            8, 0, 0, 0, // end tag size.
        ]);
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());
        let efi_memory_map = bi.efi_memory_map_tag().unwrap();
        let mut efi_mmap_iter = efi_memory_map.memory_areas();
        let desc = efi_mmap_iter.next().unwrap();
        assert_eq!(desc.physical_address(), 0x100000);
        assert_eq!(desc.size(), 16384);
        assert_eq!(desc.typ(), EFIMemoryAreaType::EfiConventionalMemory);
        // test that the EFI memory map is not detected if the boot services
        // are not exited.
        struct Bytes2([u8; 80]);
        let bytes2: Bytes2 = Bytes2([
            80, 0, 0, 0, // size
            0, 0, 0, 0, // reserved
            17, 0, 0, 0, // EFI memory map type
            56, 0, 0, 0, // EFI memory map size
            48, 0, 0, 0, // EFI descriptor size
            1, 0, 0, 0, // EFI descriptor version, don't think this matters.
            7, 0, 0, 0, // Type: EfiConventionalMemory
            0, 0, 0, 0, // Padding
            0, 0, 16, 0, // Physical Address: should be 0x100000
            0, 0, 0, 0, // Extension of physical address.
            0, 0, 16, 0, // Virtual Address: should be 0x100000
            0, 0, 0, 0, // Extension of virtual address.
            4, 0, 0, 0, // 4 KiB Pages: 16 KiB
            0, 0, 0, 0, // Extension of pages
            0, 0, 0, 0, // Attributes of this memory range.
            0, 0, 0, 0, // Extension of attributes
            18, 0, 0, 0, // Tag ExitBootServices not terminated.
            8, 0, 0, 0, // Tag ExitBootServices size.
            0, 0, 0, 0, // end tag type.
            8, 0, 0, 0, // end tag size.
        ]);
        let bi = unsafe { load(bytes2.0.as_ptr() as usize) };
        let bi = bi.unwrap();
        let efi_mmap = bi.efi_memory_map_tag();
        assert!(efi_mmap.is_none());
    }

    #[test]
    #[cfg(feature = "unstable")]
    /// This test succeeds if it compiles.
    fn mbi_load_error_implements_error() {
        fn consumer<E: core::error::Error>(_e: E) {}
        consumer(MbiLoadError::IllegalAddress)
    }

    /// Example for a custom tag.
    #[test]
    fn get_custom_tag_from_mbi() {
        const CUSTOM_TAG_ID: u32 = 0x1337;

        #[repr(C, align(8))]
        struct CustomTag {
            tag: TagTypeId,
            size: u32,
            foo: u32,
        }

        #[repr(C, align(8))]
        struct AlignedBytes([u8; 32]);
        // Raw bytes of a MBI that only contains the custom tag.
        let bytes: AlignedBytes = AlignedBytes([
            32,
            0,
            0,
            0, // end: total size
            0,
            0,
            0,
            0, // end: padding; end of multiboot2 boot information begin
            CUSTOM_TAG_ID.to_ne_bytes()[0],
            CUSTOM_TAG_ID.to_ne_bytes()[1],
            CUSTOM_TAG_ID.to_ne_bytes()[2],
            CUSTOM_TAG_ID.to_ne_bytes()[3], // end: my custom tag id
            12,
            0,
            0,
            0, // end: tag size
            42,
            0,
            0,
            0,
            0,
            0,
            0,
            0, // 8 byte padding
            0,
            0,
            0,
            0, // end: end tag type
            8,
            0,
            0,
            0, // end: end tag size
        ]);
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());

        let tag = bi.get_tag::<CustomTag, _>(CUSTOM_TAG_ID).unwrap();
        assert_eq!(tag.foo, 42);
    }

    /// Example for a custom DST tag.
    #[test]
    fn get_custom_dst_tag_from_mbi() {
        const CUSTOM_TAG_ID: u32 = 0x1337;

        #[repr(C, align(8))]
        #[derive(crate::Pointee)]
        struct CustomTag {
            tag: TagTypeId,
            size: u32,
            name: [u8],
        }

        impl CustomTag {
            fn name(&self) -> Result<&str, Utf8Error> {
                Tag::get_dst_str_slice(&self.name)
            }
        }

        impl TagTrait for CustomTag {
            fn dst_size(base_tag: &Tag) -> usize {
                // The size of the sized portion of the command line tag.
                let tag_base_size = 8;
                assert!(base_tag.size >= 8);
                base_tag.size as usize - tag_base_size
            }
        }

        #[repr(C, align(8))]
        struct AlignedBytes([u8; 32]);
        // Raw bytes of a MBI that only contains the custom tag.
        let bytes: AlignedBytes = AlignedBytes([
            32,
            0,
            0,
            0, // end: total size
            0,
            0,
            0,
            0, // end: padding; end of multiboot2 boot information begin
            CUSTOM_TAG_ID.to_ne_bytes()[0],
            CUSTOM_TAG_ID.to_ne_bytes()[1],
            CUSTOM_TAG_ID.to_ne_bytes()[2],
            CUSTOM_TAG_ID.to_ne_bytes()[3], // end: my custom tag id
            14,
            0,
            0,
            0, // end: tag size
            b'h',
            b'e',
            b'l',
            b'l',
            b'o',
            b'\0',
            0,
            0, // 2 byte padding
            0,
            0,
            0,
            0, // end: end tag type
            8,
            0,
            0,
            0, // end: end tag size
        ]);
        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();
        assert_eq!(addr, bi.start_address());
        assert_eq!(addr + bytes.0.len(), bi.end_address());
        assert_eq!(bytes.0.len(), bi.total_size());

        let tag = bi.get_tag::<CustomTag, _>(CUSTOM_TAG_ID).unwrap();
        assert_eq!(tag.name(), Ok("hello"));
    }

    /// Tests that `get_tag` can consume multiple types that implement `Into<TagTypeId>`
    #[test]
    fn get_tag_into_variants() {
        #[repr(C, align(8))]
        struct Bytes([u8; 32]);
        let bytes: Bytes = Bytes([
            32,
            0,
            0,
            0, // total_size
            0,
            0,
            0,
            0, // reserved
            TagType::Cmdline.val().to_ne_bytes()[0],
            TagType::Cmdline.val().to_ne_bytes()[1],
            TagType::Cmdline.val().to_ne_bytes()[2],
            TagType::Cmdline.val().to_ne_bytes()[3],
            13,
            0,
            0,
            0, // tag size
            110,
            97,
            109,
            101, // ASCII string 'name'
            0,
            0,
            0,
            0, // null byte + padding
            0,
            0,
            0,
            0, // end tag type
            8,
            0,
            0,
            0, // end tag size
        ]);

        let addr = bytes.0.as_ptr() as usize;
        let bi = unsafe { load(addr) };
        let bi = bi.unwrap();

        let _tag = bi.get_tag::<CommandLineTag, _>(TagType::Cmdline).unwrap();

        let _tag = bi.get_tag::<CommandLineTag, _>(1).unwrap();

        let _tag = bi.get_tag::<CommandLineTag, _>(TagTypeId::new(1)).unwrap();
    }
}