multiboot2-header

Rust library with type definitions and parsing functions for Multiboot2 headers. This library is no_std and can be used in bootloaders.

What this library is good for:

• writing a small binary which writes you a valid Multiboot2 header into a file (such as header.bin)
• understanding Multiboot2 headers better
• analyze Multiboot2 headers at runtime

What this library is not optimal for:

• compiling a Multiboot2 header statically into an object file using only Rust code

Features and no_std Compatibility

This library is always no_std. However, the default builder-feature requires the alloc-crate to be available. You need the builder only if you want to construct new headers at run time. For parsing, this is not relevant, and you can deactivate the default feature.

# without `builder`-feature (and without `alloc`-crate)
multiboot2-header = { version = "<latest>", default-features = false }
# else (requires `alloc`-crate)
multiboot2-header = "<latest>"

Example 1: Builder + Parse

use multiboot2_header::builder::{InformationRequestHeaderTagBuilder, Multiboot2HeaderBuilder};
use multiboot2_header::{HeaderTagFlag, HeaderTagISA, MbiTagType, RelocatableHeaderTag, RelocatableHeaderTagPreference, Multiboot2Header};

/// Small example that creates a Multiboot2 header and parses it afterwards.
fn main() {
    // We create a Multiboot2 header during runtime here. A practical example is that your
    // program gets the header from a file and parses it afterwards.
    let mb2_hdr_bytes = Multiboot2HeaderBuilder::new(HeaderTagISA::I386)
        .relocatable_tag(RelocatableHeaderTag::new(
            HeaderTagFlag::Required,
            0x1337,
            0xdeadbeef,
            4096,
            RelocatableHeaderTagPreference::None,
        ))
        .information_request_tag(
            InformationRequestHeaderTagBuilder::new(HeaderTagFlag::Required)
                .add_irs(&[MbiTagType::Cmdline, MbiTagType::BootLoaderName]),
        )
        .build();

    // Cast bytes in vector to Multiboot2 information structure
    let mb2_hdr = unsafe { Multiboot2Header::from_addr(mb2_hdr_bytes.as_ptr().cast()) };
    println!("{:#?}", mb2_hdr);
}

Example 2: Multiboot2 header as static data in Rust file

You can use the builder, construct a Multiboot2 header, write it to a file and include it like this:

#[used]
#[no_mangle]
#[link_section = ".text.multiboot2_header"]
static MULTIBOOT2_HDR: &[u8; 64] = include_bytes!("mb2_hdr_dump.bin");

You may need a special linker script to place this in a LOAD segment with a file offset with less than 32768 bytes. See specification.

MSRV

The MSRV is 1.68.0 stable.

License & Contribution

See main README file.