[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:

Hi David,

<snip>

> Index: working-2.6/arch/powerpc/boot/ops.h
> ===================================================================
> --- working-2.6.orig/arch/powerpc/boot/ops.h	2007-02-19 14:01:38.000000000 +1100
> +++ working-2.6/arch/powerpc/boot/ops.h	2007-02-19 14:01:43.000000000 +1100

<snip>

> @@ -100,4 +106,8 @@ static inline void exit(void)
>  	for(;;);
>  }
>  
> +#define BSS_STACK(size) \
> +	static char _bss_stack[size]; \
> +	void *_platform_stack_top = _bss_stack + sizeof(_bss_stack);
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> +
>  #endif /* _PPC_BOOT_OPS_H_ */

Statically initializing _platform_stack_top (or any variable) won't
work when you download/run the zImage at a location different than
where its linked at.  Yes, I know the image is "relocatable" but that
doesn't work for addresses put into variables/structs at link time
like this one.  That type of assignment has to be done at runtime.

What happens is the linker puts 0x0040_1234, say, into
_platform_stack_top but when you download the image to 0x0080_0000
it still has a value of 0x0040_1234 even though its running at
0x00800_0000+.

I think there's at least one more biting me in either yours
or Scott's patches that I'm looking for now.

Mark