Re: [GIT PULL] x86 setup: correct booting on 486 (revised)

From: H. Peter Anvin
Date: Mon Nov 05 2007 - 20:32:19 EST


Jeremy Fitzhardinge wrote:

Another thing it would be nice to add is an elf-note-like notion so that
the kernel can export arbitrary key/value data to the bootloader (ie,
the converse of the bootloader->kernel value list). Xen currently does
this via ELF notes, but any semanically equivalent mechanism would do. It's probably simpler than trying to work out how to mush bzimage and
ELF together.


I suspect all we need is an offset-pointer field pointing into the kernel image. As far as the kernel build process is concerned, it becomes a section in the boot/compressed link script. That offset then needs to get exported to the setup.elf link stage and there adjusted to become a file offset.

The ELF note format is sane enough, although it looks like it's not self-terminating, so we'd either need an offset and a length field, or adopt the convention that namesz = descsz = type = 0 terminates the block (I prefer the latter, myself.) We also need the notes documented, obviously.

-hpa

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