Hi Stefan,
On Wed, Jun 22, 2016 at 04:49:04PM +0200, Stefan Müller-Klieser wrote:
> According to the kernel documentation it is recommended to place the
> compressed image between 32MiB and 128MiB. We will conform to this if we
> have at least 64MiB of RAM. If this is not the case, we fall back to the
> old scheme but take the relocated image into account.
> This is required because of the ARM default kernel config changes
> regarding RODATA layout, which lead to an increased compression factor
> of the kernel image.
>
> Signed-off-by: Stefan Müller-Klieser <s.mueller-klieser@xxxxxxxxx>
> ---
> arch/arm/lib/bootm.c | 24 +++++++++++++++---------
> 1 file changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm/lib/bootm.c b/arch/arm/lib/bootm.c
> index 803aa94..d4fe9a4 100644
> --- a/arch/arm/lib/bootm.c
> +++ b/arch/arm/lib/bootm.c
> @@ -73,18 +73,24 @@ static int get_kernel_addresses(size_t image_size,
> {
> unsigned long mem_start, mem_size;
> int ret;
> - size_t image_decomp_size;
> - unsigned long spacing;
> + unsigned long decomp_space, spacing;
I renamed back decomp_space to image_decomp_size which leads to this
easier to read patch:
> diff --git a/arch/arm/lib/bootm.c b/arch/arm/lib/bootm.c
> index 803aa94..8630f2c 100644
> --- a/arch/arm/lib/bootm.c
> +++ b/arch/arm/lib/bootm.c
> @@ -81,10 +81,17 @@ static int get_kernel_addresses(size_t image_size,
> return ret;
>
> /*
> - * We don't know the exact decompressed size so just use a conservative
> - * default of 4 times the size of the compressed image.
> + * The kernel documentation "Documentation/arm/Booting" advises
> + * to place the compressed image outside of the lowest 32MiB to
> + * avoid relocation. We should do this if we have at least 64MiB
> + * of ram. If we have less space, we assume a maximum
> + * compression factor of 4 plus 1. The latter factor is the
> + * space for the relocated image.
Why space for the relocated image? Our mission is to place the image
where it doesn't have to be relocated.
> */
> - image_decomp_size = PAGE_ALIGN(image_size * 4);
> + if (mem_size >= SZ_64M)
> + image_decomp_size = SZ_32M;
> + else
> + image_decomp_size = PAGE_ALIGN(image_size * 5);
image_decomp_size = PAGE_ALIGN(image_size * 5);
if (mem_size >= SZ_64M)
image_decomp_size = max(image_decomp_size, SZ_32M);
>
> /*
> * By default put oftree/initrd close behind compressed kernel image to
> @@ -111,7 +118,7 @@ static int get_kernel_addresses(size_t image_size,
> spacing += image_decomp_size;
> }
>
> - *mem_free = PAGE_ALIGN(*load_address + image_size + spacing);
> + *mem_free = PAGE_ALIGN(*load_address + image_decomp_size + spacing);
Now why this change? We have two cases to consider. First, when the
*load_address is unspecified, we aim for this setup:
|- uncompressed image -||- compressed image -||- spacing -||- free for initrd/oftree -|
The code should be correct for this case without this hunk:
*load_address = mem_start + image_decomp_size
*mem_free = *load_address + image_size + spacing
Second case is when the load address is specified. In this case we
adjust the spacing by image_decomp_size, this also seems to be done
correctly in the current code.
So I think this hunk is wrong.
Instead we should consider adding the following at the end:
if (mem_size > SZ_256M)
*mem_free = max(*mem_free, mem_start + SZ_128M);
This would make sure to follow the recommendation to put the
initrd/device tree at 128MiB.
Sascha
--
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Industrial Linux Solutions | http://www.pengutronix.de/ |
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