[Qemu-devel] Using load_elf

[Brian Vandenberg]

  I'm attempting to familiarize myself with the APIs used to add
support for boards in qemu, and I have a few questions.

* How does using load_elf differ from load_image_targphys?

  As an example, many of the boards I've looked at have a hard-coded
entrypoint.  In mpc8455, it looks as though it doesn't have a
hard-coded entrypoint but rather it gets the entrypoint directly from
the kernel module.  However, I'm guessing in an actual mpc 8455 board,
it would expect the image to be in ROM, which would be mapped at a
particular address, and it would expect the entrypoint to be some
fixed offset from the beginning of that ROM segment.

  So, in terms of how qemu will use the image (and any other related
info), how do load_elf and load_image_targphys differ?

* mpc8455 uses a device tree for describing a device-tree hierarchy to
qemu.  Where should I look to find useful documentation describing
these .dtb files (where they come from, what is used to create them,
etc)?

* On a related note: I'm working on getting VxWorks to boot in qemu
for a few different boards.  VxWorks doesn't use libfdt (or anything
similar) to describe the hardware; the BSP does that job.  My
assumption so far is that FDT is being used by qemu, but it's used to
ease development in qemu; libfdt isn't being used to provide any
information directly to the guest OS.  Is this a correct assumption?

-Brian