The Embeddable Linux Kernel Subset

The first question people ask (other than is this for real) is why? Several reasons actually:

• An 8/16bit processor kernel is badly needed. There are really no other options except Minix (research & educational use only). A kernel that can run on this kind of hardware is useful for embedded systems projects and for third world deployment where 80x86 x>0 machines are not easily available.
• A Linux kernel small enough to run on such systems ought to be understandable by one person, and because it is a subset also useful learning material to then look at the full kernel.
• Various palmtops use an 801C86 or variant embedded processor set. Linux on the HP palmtops and potentially Psion 3 is a very interesting option.
• Hack Value. I for one would dearly love to end up with a backport to the PDP-11 that was V7 binary compatible.

The project state so far:

• Key goals have been chosen.
  • V7 and as much as possible POSIX compliance
  • Minix file system, as this performs best with small buffer cache
  • Ability to compile both with its own compiler and standard DOS compilers.
  • Capable of running programs from ROM.
  • 8086 combined I/D and split I/D (ie 64K or 64K code + 64K data) is a hard to avoid but acceptable limit.
  • Initial drivers will be BIOS drivers and real mode.
  • Use a vt52 style console (for size)
• We now have the 'bcc' GPL'd K&R compiler for minix running on Linux.
• A system call library builder has been written. This writes 8086 system call modules from a descriptor file, and in future will also write the kernel side tables and potentially the function stubs.
• The C library is near enough complete as is emulation and build environment for testing
• We have curses, ash and other tools built.
• The bootloader is working. It loads split I/D minix binaries+setup off a floppy disk happily.
• We have task switching/interrupts and a bios console behaving. The disk driver is now mostly done but has the floppy drive type hard coded.
• The consoles we have include both a bios console and a raw console that also supports virtual consoles.

We need volunteers to

• Scan archives and build small free applications to match the GNU ones used in the bigger Linux systems.
• Join in extracting modules from the main Linux kernel, and in rewriting the 'oversized/overfeatured' bits.

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