Bender

Bender is a Multiboot chainloader intended to be loaded from Grub or a similar multiboot-capable boot loader. It tries to find PCI serial controllers and updates the BIOS Data Area to make them discoverable by legacy software.

Additionally, bender will move modules to a higher location in physical memory to avoid clashes when ELFs are unpacked.

Building with Nix (Recommended)

Get Nix and type:

% nix-build

You can find bender in result/.

If you have a Flakes-enabled Nix, try out nix build to build bender and nix flake check to run its tests.

Building without Nix

Be sure to have CMake and a C toolchain installed. Afterwards, you can build the source code via:

% mkdir -p build
% cd build
% cmake ..
% make

You will find bender in standalone/ in your build directory.

Usage

Check the documentation of your Multiboot-capable boot loader to see how Bender is booted. Bender will discover serial ports and then boot the next boot module as Multiboot2 or Multiboot1 kernel depending on what it supports.

Parameters

Bender supports the following command-line parameters:

• promisc: Be more forgiving which PCI serial controller to accept. Specifically, this makes Bender claim any PCI device with "Simple Communication Controller" PCI class and not only those claiming to be a legacy serial controller. This is typically needed for some multiport PCI serial adapters.
• accept_legacy: Don't claim a PCI serial controller, if the BIOS already indicates that there is a legacy serial controller available.
• phys_max=256M (literally only that specific string): Prevent bender from relocating modules past 256M in the physical address space.