Re: [Xen-devel] [PATCH] xen/arm: build as zImage

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-11-23 at 15:45 +0000, Stefano Stabellini wrote:
> The zImage format is extremely simple: it only consists of a magic
> number and 2 addresses in a specific position (see
> http://www.simtec.co.uk/products/SWLINUX/files/booting_article.html#d0e309).
> 
> Some bootloaders expect a zImage; considering that it doesn't cost us
> much to build Xen compatible with the format, make it so.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> 
> 
> diff --git a/xen/arch/arm/head.S b/xen/arch/arm/head.S
> index 25c4cfe..de9cdb2 100644
> --- a/xen/arch/arm/head.S
> +++ b/xen/arch/arm/head.S
> @@ -22,6 +22,9 @@
>  #include <asm/processor-ca15.h>
>  #include <asm/asm_defns.h>
>  
> +#define ZIMAGE_MAGIC_NUMBER 0x016f2818
> +#define XEN_PHYS_ADDRESS    0x80000000

This is platform specific. AIUI you can put 0 in the field and the boot
loader is expected to do something sensible, although that might require
a new enough bootloader (FSVO new enough).

If that doesn't work then this constant is actually in
xen/arch/arm/Makefile too and for the same reason:
        # XXX: VE model loads by VMA so instead of
        # making a proper ELF we link with LMA == VMA and adjust crudely
        $(OBJCOPY) --change-addresses +0x80000000 $< $@
        $(STRIP) $@

How about making this CONFIG_PHYSICAL_LOCAL_ADDR and plumbing through
like we do with CONFIG_DTB_FILE?

> +
>  #define PT_PT  0xe7f /* nG=1, AF=1, SH=10, AP=01, NS=1, ATTR=111, T=1, P=1 */
>  #define PT_MEM 0xe7d /* nG=1, AF=1, SH=10, AP=01, NS=1, ATTR=111, T=0, P=1 */
>  #define PT_DEV 0xe71 /* nG=1, AF=1, SH=10, AP=01, NS=1, ATTR=100, T=0, P=1 */
> @@ -52,6 +55,18 @@
>        * or the initial pagetable code below will need adjustment. */
>       .global start
>  start:
> +
> +     .rept   7
> +     mov     r0, r0
> +     .endr
> +     mov     r0, r0
> +     b       1f
> +
> +     .word   ZIMAGE_MAGIC_NUMBER                             @ Magic numbers 
> to help the loader
> +     .word   (_start + XEN_PHYS_ADDRESS)             @ absolute load/run 
> zImage address

Wacky spaces?

> +     .word   (_end + XEN_PHYS_ADDRESS)               @ zImage end address
> +
> +1:
>       cpsid aif                    /* Disable all interrupts */
>  
>       /* Save the bootloader arguments in less-clobberable registers */



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