x86 boot: 32-bit boot protocol

This patch set defines a 32-bit boot protocol for x86 platform, adds an extensible boot parameter passing mechanism, export the boot parameters via sysfs.

The patch set has been tested against kernel of git version v2.6.23-6623-g55b70a0 (with Rusty's git tree pulled) on x86_64 and i386.

This patch set is based on the proposal of Peter Anvin.

v7:

- Rebase on Rusty's git tree.
- Revise the 32-bit boot protocol document.

v6:

- The linked list of setup_data is copied to memory area right after the kernel _end during early kernel bootstrap to solve the issue that where the safe place is to place linked list of setup_data.

v5:

- Use bt_ioremap/bt_iounmap in copy_setup_data.

v4:

- Reserve setup_data and boot parameters for accessing during runtime.
- Export boot parameters via sysfs.

v3:

- Move hd0_info and hd1_info back to zero page for compatibility.

v2:

- Increase the boot protocol version number
- Check version number before parsing setup data.
- Revise zero page description according to the source code and move them to zero-page.txt.

Best Regards,
Huang Ying

This patchset should spend a cycle in -mm before being merged, though.

-hpa

Do you think it is possible that the 3rd patch of the patchset: document for 32 bit boot protocol can be merged into upstream firstly? It has been used by kexec/LinuxBIOS already and the EFI support patches depend on it too.

Best Regards,
Huang Ying

Well, the part of it that doesn't document the 2.08 boot protocol, at least, since it documents existing practice.

-hpa