[U-Boot] [RFC] fit: include uncompression into fit_image_load

[Simon Glass]

Hi Simon,

On 17 October 2018 at 03:41, Simon Goldschmidt
<simon.k.r.goldschmidt at gmail.com> wrote:
> On Wed, Oct 17, 2018 at 8:54 AM Alexander Graf <agraf at suse.de> wrote:
>>
>>
>>
>> On 16.10.18 21:33, Simon Goldschmidt wrote:
>> > Currently, only the kernel can be compressed in a FIT image.
>> > By moving the uncompression logic to 'fit_image_load()', all types
>> > of images can be compressed.
>> >
>> > This works perfectly for me when using a gzip'ed FPGA image in
>> > a FIT image on a cyclone5 board (socrates). Also, a gzip'ed initrd
>> > being unzipped by U-Boot (not the kernel) worked.
>> >
>> > To clean this up, the uncompression function would have to be moved
>> > from bootm.c ('bootm_decomp_image()') to a more generic location,
>> > but I decided to keep it for now to make the patch easier to read.
>> > Because of this setup, the kernel is currently uncompressed twice.
>> > which doesn't work...
>> >
>> > There are, however, some more things to discuss:
>> > - The max. size passed to gunzip() (etc.) is not known before, so
>> >   we currently configure this to 8 MByte in U-Boot (via
>> >   CONFIG_SYS_BOOTM_LEN), which proved too small for my initrd...

We need the uncompressed size. If the legacy header doesn't have, stop
using it and use FIT?

Some compression formats include that in a header I think. But we
should record it in the U-Boot header.

>> > - CONFIG_SYS_BOOTM_LEN is set to 64 MByte default in SPL, so it's
>> >   a different default for SPL than for U-Boot !?!

Ick

>> > - CONFIG_SYS_BOOTM_LEN seemed to initially be used for kernel
>> >   uncompression but is now used as a copy-only limit, too (no unzip)

Yes.

>> > - Uncompression only works if a load address is given, what should
>> >   happen if the FIT image does not contain a load address?

Fail.

>> > - The whole memory management around FIT images is a bit messed up
>> >   in that memory allocation is a mix of where U-Boot relocates itself
>> >   (and which address ranges it used), the load addresses of the FIT
>> >   image and the load addresses of the FIT image contents (and sizes).
>> >   What's the point here to check CONFIG_SYS_BOOTM_LEN? Maybe it would
>> >   be better to keep a memory map of allowed and already used data to
>> >   check if we're overwriting things or to get the maximum size passed
>> >   to gunzip etc.?

See lmb

>>
>> So I can at least give input on the memory map part :).
>>
>> In efi_loader, we actually do maintain a full system memory map already,
>> including allocation functions that give you "safe" allocation
>> functionality (allocate somewhere in memory where you know nothing
>> overlaps).
>>
>> Maybe we should move this into a more generic system and reuse it for
>> big memory allocations that really don't need to be in the U-Boot
>> preallocated regions?
>
> Hmm, inspecting this further, it seems that there is such an allocator
> for bootm (using lmb_*() functions and struct lmb). Maybe this should be
> better integrated into the fit loading function. I don't know if the
> lmb functions
> correctly detect overlapping of regions allocated by known addresses though.
>
> Thanks for your thoughts!

Yes lmb is the right mechanism and I think it checks for overlap.

>
> Simon

Regards,
Simon