kboot status report for 2023 Q2

website/content/en/status/report-2023-04-2023-06/kboot.adoc

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+=== LinuxBoot FreeBSD on aarch64
+
+Contact: Warner Losh <[email protected]>
+
+Links: +
+link:https://www.linuxboot.org/[LinuxBoot Project] URL: link:https://www.linuxboot.org/[]+
+link:https://docs.google.com/presentation/d/1N5Jp6XzYWv9Z9RhhETC-e6tFkqRHvp-ldRDW_9h2JCw/edit?usp=sharing[BSDCan 2023 kboot talk slides] URL: link:https://docs.google.com/presentation/d/1N5Jp6XzYWv9Z9RhhETC-e6tFkqRHvp-ldRDW_9h2JCw/edit?usp=sharing[]
+
+LinuxBoot is an effort to create a clean, robust, auditable and repeatable boot firmware.
+What originally started as a specific project at Google has grown to encompass any boot environment that uses Linux to launch the final operating system.
+Many platfors now support this environment, in some cases it is the only available boot environment.
+In addition, some embedded boxes have a LinuxBoot environment hard-coded that is quite hard to change, and being able to reboot into FreeBSD is desirable.
+
+The old Sony PlayStation 3 port used a boot loader called 'kboot' to accomplish booting the FreeBSD port from its Linux kernel (all predating the LinuxBoot project).
+That code has been greatly expanded, made generic with easily replaceable per-architecture plug ins.
+The normal FreeBSD [.filename]#/boot/loader# is built as a Linux binary that reads in the FreeBSD kernel, modules and tunables.
+It places them into memory as if it were running in a pre-boot environment and then loads that image into the Linux kernel with man:kexec_load[2] and does a special reboot to that kernel image.
+For UEFI enabled systems, it passes the UEFI memory table, and pointer to UEFI runtime services to the new kernel.
+
+It supports loading files from the host's filesystem, from any man:loader[8]-supported filesystem on the host's block devices (including pools that span multiple devices), from ram disk images and from files downloaded over the network.
+Any mix of these is available, so configuration overrides can be loaded from the host's filesystem, but the kernel can be loaded from dedicated storage (say NVME) or a ram disk image.
+It supports a host console running over stdin/stdout.
+It supports explicit locations such as `/dev/nvme0ns1:/boot/loader/gerbil.conf` for where to load filesystems from.
+It supports ZFS boot environments, including the boot-once feature.
+
+Additional details about kboot, what it supports and some general background can be found in Warner's BSDcan talk (slides linked above).
+
+FreeBSD/aarch64 now can boot from Linux in a LinuxBoot environment, with support and functionality comparable to man:loader.efi[8].
+Memory layout passed in for GICv3 workarounds.
+Need patch for aarch64 kernel for the GICv3 workaround.
+link:https://reviews.freebsd.org/D40902[]
+
+FreBSD/amd64 support is in progress and is maybe 80% done.
+The amd64 boot environment places more requirements on the boot loader to provide data for the kenrel than aarch64 due to amd64 being an older port.
+All sources for data in the BIOS enviornment had to be provided by the boot loader since the kernel had no access to them from long mode.
+While UEFI and ACPI provide ways for the kernel to get this data, much of the data must still be provided by the boot loader.
+The kernel panics during initialization since all these prerequisites have not been discovered and implemented.
+
+PowerPC builds, but nothing more of its state is known.
+Attempts to acquire a suitable Playstation 3 proved to be too time consuming for the author.
+
+Help needed:
+
+ 1. man:loader.kboot[8] needs to be written. It should document how to use loader.kboot, how to create images, and the different use cases that work today.
+ 1. Finish amd64 support.
+ 1. The current elf arch-specific metadata code is copied from efi. +
+Unifying the kboot and efi copies is needed. +
+While they are mostly the same, compile-time differences remain that complicate sharing. +
+In addtion, the build infrastructure makes sharing awkward.
+ 1. It would be nice to add riscv64 support
+ 1. PowerPC testing (it has been untested since the refactoring started).
+ 1. Help creating a script to repackage EDK-II image (say from QEMU) as a linux-boot image with a Linux kernel built on FreeBSD for CI testing.
+ 1. Help testing it from the coreboot LinuxBoot
+
+Sponsored by: Netflix, Inc