Re: lemote-3a-itx-a1101 kernel and pmon

James Cowgill <[email protected]> Wed, 20 Jan 2016 14:39:58 +0000

Newsgroups	gmane.linux.debian.ports.mips
Message-ID	<[email protected]>

On Wed, 2016-01-20 at 13:23 +0100, David Kuehling wrote:
> > > > > > "James" == James Cowgill <[email protected]> writes:
> > On Sun, 2016-01-17 at 06:39 +0100, David Kuehling wrote:
> > > long time ago I was told that I need a newer PMON to boot recent
> > > linux kernels [5], but then read on debian-mips about problems after
> > > PMON upgrades [1].
> [..]
> 
> > So the old PMON in those machines (only itx-a1101) has a bug where it
> > loads the kernel at an address to close to the address the bootloader
> > is stored at. If the kernel being loaded has a large bss section (or
> > is large in memory for any reason), PMON will overwrite itself and
> > crash.
> 
> > The bug appeared after this kernel commit:
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c46173183657bbdbe0d54a981c28807581648422which
> > increased the size of the bss section to something like 20M on all
> > Loongson 3 kernels.
> 
> > Back then I tried using PMON 4.something but it wouldn't boot any
> > kernel I threw at it.
> 
> > In the end I patched the kernel to reduce the value of
> > MAX_PHYSMEM_BITS from 48 to 35 and it worked again - I think this
> > should be ok on all Loongson 3A machines.
> 
> > Hopefully if you try that, any recent kernel will work with the old
> > PMON.
> 
> Ok, just to make sure I understood correctly: you never managed to make
> the newer pmon 4 work with any kernels at all?  That would be somewhat
> surprising, given that people were repeatedly told to upgrade PMON on
> these Loongson3 boxes.

Yes you understood correctly, none of the small number of kernels I
tried would boot with PMON 4. Since I could never find the definitive
source and since the other solution was "good enough" at the time, I
never looked any further into it.

Maybe there was a new PMON version in the meantime? Like I said this
was all some time ago.

James

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