Difference between revisions of "Payloads"
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is a bootloader providing the UEFI interface. See http://www.tianocore.org/ for more information.
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Revision as of 15:38, 10 August 2010
coreboot in itself is "only" minimal code for initializing a mainboard with peripherals. After the initialization, it jumps to a payload.
SeaBIOS is an open-source implementation of the standard bootstrap callback layer implemented by an x86 bios. It enables booting from unmodified cdroms and hard drives.
SeaBIOS has been tested with Linux, NetBSD, FreeDOS, and Windows XP/Vista/7. Classic GRUB, lilo, and isolinux work well with SeaBIOS. Other x86 bootloaders and operating systems will likely also work.
Official GRUB 2
GRUB 2 is the official version 2 of GNU GRUB.
You can use the official GRUB 2 as a coreboot payload, in order to boot and operating system from a hard drive, for instance.
An old version of GRUB2 with coreboot and crypto support.
You can use GRUB2 as a coreboot payload, too, in order to boot and operating system from a hard drive, for instance.
FILO is a simple bootloader with filesystem support.
Etherboot is a network bootloader. It provides a direct replacement for proprietary PXE ROMs, with many extra features such as DNS, HTTP, iSCSI, etc.
Older versions of Etherboot included parts of FILO, and thus supported SATA and USB booting.
Mitch Bradley's Open Firmware, an IEEE1275-1994 Open Firmware implementation, can also be used as coreboot payload.
OpenBIOS — IEEE1275-1994 Open Firmware.
Coreboot can use a Linux kernel as payload directly. That is, the kernel is included in the ROM chip where coreboot resides.
This use-case is not well-tested yet, though.
jakllsch has worked on a partially-complete port of the x86 boot code to the role of native payload. However, with the advent of SeaBIOS, this is likely to become less of a priority. Consult Coreboot and NetBSD for further information.
We have successfully booted Windows XP, Windows Vista and Windows 7 (Beta).
OpenSolaris has multiboot compliant kernels, and so it is possible to boot it with GRUB2 (pending some bug fixes). Some Sun engineers even worked on it, see http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6475349 for information.
Currently, GRUB2 refuses to load the kernel due to a small bug in the multiboot header of the kernel, but the kernel still refuses to work if that is worked around. Maybe they reintroduced some BIOS calls again?
See also this blog entry.
Memtest86 / Memtest86+
Memtest86 is a program which checks your RAM modules.
It can be run from within GRUB, but also as a coreboot payload (i.e. included in your ROM chip).
Libpayload is a helper-library for payload-writers.
coreinfo is a coreboot payload which can display various system information.
Bayou is the working name for a coreboot payload that can choose, load and run other payloads from a LAR archive on the ROM.
GRUB invaders multi-boot compliant space invaders game.
It can either be started from within GRUB (as a "kernel"), or it can be used as a coreboot payload.
tint is a falling blocks game.
Possible future payloads
The following payloads might or might not work (with more or less changes required) with coreboot — their usage hasn't been tested or documented so far.
- CodeGen's SmartFirmware — IEEE1275-1994 Open Firmware
- GNUFI (UEFI)
- Plan 9 — A distributed operating system.
- RedBoot / eCos — Real-time OS for embedded systems; initial port to ELF completed but no longer available.
- GPXE — Needs some code changes
- OpenSolaris / BeleniX
- Windows CE
- NanoVM (small JVM)
- uip / lwip (small TCP/IP stacks)
The payload was originally intended to be a Linux kernel stored in flash. Flash ROM growth rate was anticipated optimistically however, today there are not many mainboards that actually have enough flash ROM room for a kernel. 512KB can be seen here-and-there and a few boards come with 1MB. Recent kernels really want that MB, and then you'll only have room for 300-400 KB of initial ramdisk, which could be too small too, depending on the application. During testing, a payload may also be downloaded via X-Modem from the serial debug console, saving flashing time.
So, other payloads are used; the two major ones are FILO and SeaBIOS. Also have a look at GRUB2 and Etherboot (soon to be deprecated in favor of GPXE). FILO loads a kernel from a filesystem on an IDE device and Etherboot loads a kernel from the network or from a filesystem on an IDE device.
If you're using FILO there is no Linux kernel until FILO loads it, and the kernel loaded by FILO (or Etherboot) can absolutely be the one you want to run in your system. Just set it up with the correct root and init commandline so that it can start init.