[PATCH] QEMU: ARM: boot: Load kernel at an Image friendly address

[Peter Maydell]

On 25 March 2014 03:34, Joel Fernandes <joelf at ti.com> wrote:
> Loading kernel at offset 0x10000 works only for zImage, but not for Image,
> because the kernel expect the start of decompressed kernel (.head.text) to be
> at an address that's a distance that's 16MB aligned from  PAGE_OFFSET +
> TEXT_OFFSET (see vmlinux.lds.S). This check is enfornced in __fixup_pv_table in
> arch/arm/kernel/head.S TEXT_OFFSET is 0x00008000, so a 16MB alignment needs to
> have a "0x8000" in the lower 16 bits so that they cancel out. Currently the
> offset Qemu loads it at is 0x10000.
>
> With zImage, this need is met because zImage loads the uncompressed Image
> correctly, however when loading an Image and executing directly Qemu is
> required it to load it at the correct location. Doing so, doesn't break Qemu's
> zImage loading. With this patch, both zImage and Image work correctly.
>
> Signed-off-by: Joel Fernandes <joelf at ti.com>
> ---
>  hw/arm/boot.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/arm/boot.c b/hw/arm/boot.c
> index dc62918..566b5c2 100644
> --- a/hw/arm/boot.c
> +++ b/hw/arm/boot.c
> @@ -23,7 +23,7 @@
>   * They have different preferred image load offsets from system RAM base.
>   */
>  #define KERNEL_ARGS_ADDR 0x100
> -#define KERNEL_LOAD_ADDR 0x00010000
> +#define KERNEL_LOAD_ADDR 0x00008000
>  #define KERNEL64_LOAD_ADDR 0x00080000

The patch and rationale seem plausible, but I'm a bit
reluctant to apply this this close to 2.0 release, because
QEMU has loaded images at this address for 8 years without
anybody complaining, and I worry that we might accidentally
break some other use case somehow.

thanks
-- PMM