Re: [OE-core] SFO17 Cross-Distro meeting notes

On 29 September 2017 at 21:26, Tom Rini <[email protected]> wrote:
> On Fri, Sep 29, 2017 at 02:06:21AM +0300, Riku Voipio wrote:
>
> [snip]
>> On arm64, Kernel doesn't self-decompress. The bootloaders are stringly
>> recommended to support decompressing kernel images. It's optional in
>> grub, make sure your grub does. At least iPXE and u-boot don't support
>> booting Image.gz on arm64, and should be fixed.
>
> Not strictly true.  We do expect that if you're loading in a
> compressed something that you uncompress it then boot it.  I assume part
> of the reason that Linux didn't go for self-decompression this time is
> the "my goodness, it's tricky to get here's where we are, here's what
> else is in the system, lets not stomp anything and get ourself to where
> we need to be" is in fact tricky.

Thanks for the clarification. The kernel
Documentation/arm64/booting.txt is vague in reasoning, but you are
right it's tricky. Kernel developers  assume the bootloader is better
equipped to know where in memory to decompress than a early kernel
decompress loop.

> That said, patches to check for ${VALID_COMPRESSION_HEADER}, uncompress
> a chunk, confirm valid Image header, and uncompress to where it needs to
> reside would be welcome.

While the unzip command hint is good, from cross-distro PoV I think
this kind of transparent decompression is needed to make the syslinux
bootmenu command "just work".

Riku