Re: [Qemu-devel] [PATCH] loader: pad kernel size when loaded from

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Thu, Jul 29, 2010 at 06:48:24PM -0700, Hollis Blanchard wrote:
> The kernel's BSS size is lost by mkimage, which only considers file
> size. As a result, loading other blobs (e.g. device tree, initrd)
> immediately after the kernel location can result in them being zeroed by
> the kernel's BSS initialization code.
> 
> Signed-off-by: Hollis Blanchard <hollis@penguinppc.org>
> ---
>  hw/loader.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/loader.c b/hw/loader.c
> index 79a6f95..35bc25a 100644
> --- a/hw/loader.c
> +++ b/hw/loader.c
> @@ -507,6 +507,13 @@ int load_uimage(const char *filename, target_phys_addr_t *ep,
>  
>      ret = hdr->ih_size;
>  
> +	/* The kernel's BSS size is lost by mkimage, which only considers file
> +	 * size. We don't know how big it is, but we do know we can't place
> +	 * anything immediately after the kernel. The padding seems like it should
> +	 * be proportional to overall file size, but we also make sure it's at
> +	 * least 4-byte aligned. */
> +	ret += (hdr->ih_size / 16) & ~0x3;

Maybe it's only me, but it feels a bit akward to push down this kind of
knowledge down the abstraction layers. Does it work for you to have your
caller of load_uimage apply whatever resizing magic needed for your kernel
and arch?

Cheers