[linux.git] / Documentation / powerpc / zImage_layout.txt

          Information about the Linux/PPC kernel images
=====================================================================

Please mail me (Cort Dougan, [email protected]) if you have questions,
comments or corrections.

This document is meant to answer several questions I've had about how
the PReP system boots and how Linux/PPC interacts with that mechanism.
It would be nice if we could have information on how other architectures
boot here as well.  If you have anything to contribute, please
let me know.


1. PReP boot file

  This is the file necessary to boot PReP systems from floppy or
  hard drive.  The firmware reads the PReP partition table entry
  and will load the image accordingly.

  To boot the zImage, copy it onto a floppy with dd if=zImage of=/dev/fd0h1440
  or onto a PReP hard drive partition with dd if=zImage of=/dev/sda4
  assuming you've created a PReP partition (type 0x41) with fdisk on
  /dev/sda4.

  The layout of the image format is:

  0x0     +------------+
          |            | PReP partition table entry
          |            |
  0x400   +------------+
          |            | Bootstrap program code + data
          |            |
          |            |
          +------------+
          |            | compressed kernel, elf header removed
          +------------+
          |            | initrd (if loaded)
          +------------+
          |            | Elf section table for bootstrap program
          +------------+


2. MBX boot file

  The MBX boards can load an elf image, and relocate it to the
  proper location in memory - it copies the image to the location it was
  linked at.
Commit	Line	Data
1da177e4 LT	1	Information about the Linux/PPC kernel images
	2	=====================================================================
	3
	4	Please mail me (Cort Dougan, [email protected]) if you have questions,
	5	comments or corrections.
	6
	7	This document is meant to answer several questions I've had about how
	8	the PReP system boots and how Linux/PPC interacts with that mechanism.
	9	It would be nice if we could have information on how other architectures
	10	boot here as well. If you have anything to contribute, please
	11	let me know.
	12
	13
	14	1. PReP boot file
	15
	16	This is the file necessary to boot PReP systems from floppy or
	17	hard drive. The firmware reads the PReP partition table entry
	18	and will load the image accordingly.
	19
	20	To boot the zImage, copy it onto a floppy with dd if=zImage of=/dev/fd0h1440
	21	or onto a PReP hard drive partition with dd if=zImage of=/dev/sda4
	22	assuming you've created a PReP partition (type 0x41) with fdisk on
	23	/dev/sda4.
	24
	25	The layout of the image format is:
	26
	27	0x0 +------------+
	28	\| \| PReP partition table entry
	29	\| \|
	30	0x400 +------------+
	31	\| \| Bootstrap program code + data
	32	\| \|
	33	\| \|
	34	+------------+
	35	\| \| compressed kernel, elf header removed
	36	+------------+
	37	\| \| initrd (if loaded)
	38	+------------+
	39	\| \| Elf section table for bootstrap program
	40	+------------+
	41
	42
	43	2. MBX boot file
	44
	45	The MBX boards can load an elf image, and relocate it to the
	46	proper location in memory - it copies the image to the location it was
	47	linked at.