[Libre-soc-dev] microwatt booting linux-5.7 under verilator
mpe at ellerman.id.au
Tue Feb 1 11:53:14 GMT 2022
Nicholas Piggin <npiggin at gmail.com> writes:
> Excerpts from lkcl's message of January 31, 2022 2:19 pm:
>> On January 31, 2022 3:31:41 AM UTC, Nicholas Piggin <npiggin at gmail.com> wrote:
>>>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.
>>>> i also had to fix a couple of things in the linux kernel source
>>>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)
>>>> this led me to add support for CONFIG_KERNEL_UNCOMPRESSED
>>>> and cut that time entirely, hence why you can see this in the console
>>>> 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
>>> We should be able to upstream it pretty
>>>easily I think?
>> don't see why not.
> Okay then we should.
>> 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.
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