Nicholas Piggin [off-list ref] writes:

Excerpts from lkcl's message of January 31, 2022 2:19 pm:

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On January 31, 2022 3:31:41 AM UTC, Nicholas Piggin [off-list ref] wrote:

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Hi Luke,

Interesting to read about the project, thanks for the post.

no problem. it's been i think 18 years since i last did linux kernel work.

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i also had to fix a couple of things in the linux kernel source
https://git.kernel.org/pub/scm/linux/kernel/git/joel/microwatt.git

I think these have mostly (all?) been upstreamed now.

i believe so, although last i checked (6 months?) there was some of dts still to do. instructions online all tend to refer to joel or benh's tree(s)

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this led me to add support for CONFIG_KERNEL_UNCOMPRESSED
and cut that time entirely, hence why you can see this in the console

log:

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    0x5b0e10 bytes of uncompressed data copied

Interesting, it looks like your HAVE_KERNEL_UNCOMPRESSED support
patch is pretty trivial. 

yeah i was really surprised, it was all there

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We should be able to upstream it pretty
easily I think?

don't see why not.

Okay then we should.

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the next interesting thing which would save another hour when emulating HDL at this astoundingly-slow speed of sub-1000 instructions per second would be in-place execution: no memcpy, just jump.

i seem to recall this (inplace execution) being a standard option back in 2003 when i was doing xda-developers wince smartphone reverse-emgineering, although with it being 19 years ago i could be wrong

Not sure of the details on that. Is it memcpy()ing out of ROM or RAM to 
RAM? Is this in the arch boot code? (I don't know very well).

If you build with CONFIG_RELOCATABLE=y and CONFIG_RELOCATABLE_TEST=y the
kernel will run wherever you load it (must be 64K aligned), without
copying itself down to zero first. That will save you a few cycles.

cheers