bc240baba5
Confirmed on an image with GRUB2 payload and without seabios as secondary payload. Signed-off-by: Ivan Kuzneczov <ivan.kuzneczov@hardenedvault.net> Change-Id: I093a9b9e8cabe6b21ec9d755a1592438209a86c6 Reviewed-on: https://review.coreboot.org/c/coreboot/+/90658 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
66 lines
2.6 KiB
Markdown
66 lines
2.6 KiB
Markdown
# Payloads
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coreboot doesn't try to mandate how the boot process should look, it merely
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does hardware init and then passes on control to another piece of software
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that we carry along in firmware storage, the _payload_.
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There is various software in that space that is either explicitly written as
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payload or can be made to work as one.
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## SeaBIOS
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[SeaBIOS](https://www.seabios.org) is an open source implementation of
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the PCBIOS API that exists since the original IBM PC and was extended
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since. While originally written for emulators such as QEMU, it can be built
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as a coreboot payload. It supports executing Option ROMs in a more complete
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fashion than coreboot. It also supports Multiboot.
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When chainloaded from GRUB2, the following menuentry could be used:
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menuentry "SeaBIOS" --unrestricted {
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root=(cbfsdisk)
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multiboot /img/seabios
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module /vgaroms/seavgabios.bin
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}
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GRUB2 loading seabios from drive via command prompt is also possible:
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multiboot (usb0,msdos1)/seabios/bios.bin.elf
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module (usb0,msdos1)/seabios/vgabios.bin name=vgaroms/seavgabios.bin
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boot
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## edk2
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[edk2](https://github.com/tianocore/tianocore.github.io/wiki/Getting-Started-with-EDK-II) is an open-source modern, feature-rich,
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cross-platform firmware development environment for the UEFI and UEFI
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Platform Initialization (PI) specifications.
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## GRUB2
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GRUB2 was originally written as a bootloader and that's its most popular
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purpose, but it can also be compiled as a coreboot payload.
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## Linux
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There are several projects using Linux as a payload (which was the
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configuration that gave coreboot its original name, LinuxBIOS). That kernel is
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often rather small and serves to load a current kernel from somewhere, e.g.
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disk or network, and run that through the kexec mechanism.
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Two aspects emphasized by proponents of Linux-as-a-payload are the
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availability of well-tested, battle-hardened drivers (as compared to
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firmware project drivers that often reinvent the wheel) and the ability to
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define boot policy with familiar tools, no matter if those are shell scripts
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or compiled userland programs written in C, Go or other programming languages.
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## Heads
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[Heads] is a distribution that bundles coreboot, Linux, busybox and custom
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tools to provide reproducible ROMs. [Heads] aims to provide a secure and
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flexible boot environment for laptops and servers.
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It supports features like measured boot, kexec, GPG, OTP, TLS, firmware
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updates, but only works on a limited amount of mainboards.
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For more details have a look at [heads-wiki].
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[Heads]: https://github.com/osresearch/heads
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[heads-wiki]: http://osresearch.net/
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