[PATCH 8/15] zImage: Cleanup and improve zImage entry point

[Mark A. Greer]

On Mon, Mar 05, 2007 at 02:24:52PM +1100, David Gibson wrote:

<snip>

> 1) It can define a _zimage_start, in which case the platform code gets
>    control from the very beginning of execution.  In this case the
>    platform code is responsible for relocating the zImage if necessary,
>    clearing the BSS, performing any platform specific initialization, and
>    finally calling start() to load and enter the kernel.
> 
> 2) It can define platform_init().  In this case the generic crt0.S
>    handles initial entry, and calls platform_init() before calling
>    start().  The signature of platform_init() is changed, however, to
>    take up to 5 parameters (in r3..r7) as they come from the platform's
>    initial loader, instead of a fixed set of parameters based on OF's
>    usage.

<snip>

> In addition the wrapper script is rearranged to ensure that the
> platform .o is always linked first.  This means that platforms where
> the zImage entry point is at a fixed address or offset, rather than
> being encoded in the binary header can be supported using option (1).

But now you don't have a fixed address for _zimage_start when you use
option 2).  I don't know what address _zimage_start is at so I can't
start it.  This is an issue for fw's that don't understand ELF and simply
download a bucket of bits.  You have to tell the fw where to jump to
(e.g., go 0x410010).

Mark