In 2006 the company of Open Firmware inventor Mitch Bradley, Firmworks, Inc, released their Open Firmware implementation (OFW) under a BSD license. This code shares some code with SUN's OpenBOOT implementation. The open source OFW supports x86, PowerPC, and ARM architectures. Other architectures, including SPARC and MIPS, may be added as time and interest dictate.
The x86 version is used on the OLPC "XO" computer. The x86 version can be configured for numerous other environments, including
- Direct QEMU ROM (replacing the "bios.bin" that is supplied with QEMU
- Coreboot payload
- Loadable on directly on top of a conventional PC BIOS (booted from floppy or hard disk like an OS). In this configuration it can run on an arbitrary PC, or on an emulator like QEMU, VirtualBox, or VMWare.
OFW can boot Linux directly from a disk file (FAT, ext2, ISO9660, or jffs2 filesystems) without the need for an intermediate bootloader like LILO or GRUB. The Linux image can be in either ELF format (as created by the first phase of the Linux kernel compilation process) or in the "bzImage" format that "wraps" the ELF image. When booting an ELF image, OFW can read the ELF symbol table so OFW's assembly language debugger can resolve kernel symbols.
OFW can also boot other ELF standalone images, providing to them rudimentary "libc" capability. That facility has been used for booting, for example, Minix, ReactOS, Plan9, Inferno and SqueakNOS. The OLPC system ROM includes several such "standalone client programs", including MicroEMACS, memtest86, and NANDblaster (a facility for fast OS updates over multicast wireless).
On the OLPC system, OFW emulates enough legacy BIOS "real mode INTs" to boot Windows XP. On another system, OFW supports booting Windows CE.
You can browse the source code online.
The repository is available through Subversion:
You can check it out as follows:
$ svn co svn://openfirmware.info/openfirmware/
if you want a specific revision:
$ svn co svn://openfirmware.info/openfirmware -r 35
If your company installed a firewall that blocks the svn port (3690) you can also check out using the webdav frontend:
$ svn co https://www.openfirmware.info/openfirmware-svn/ openfirmware
Building Different Versions
- Direct QEMU ROM: see Building OFW for QEMU
- Coreboot: see OFW as a Coreboot Payload
- OLPC: see Building OFW for OLPC
- BIOS-loaded: see Building OFW to Run Under BIOS
- ARM: see Building OFW for ARM
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