On Sun, 14 Jul 2019 at 17:00, Ulrich Teichert <
lists%ulrich-teichert.de@localhost> wrote:
> Yes, right.... What I wanted to say was: I haven't seen a bootloader in the
> NetBSD tree which can circumvent the firmware boot limit of ~2MB per file
> loaded (at least on 43p boxes).
>
> The experiments in the existing bootloader to access the SCSI controler
> after load to bypass that limit were more or less causing the whole trip
> into NetBSD-prep for me, as it turns out ;-)
Would you mind if I recap my understanding - its possible I'm missing something...
(Please treat all of this as enthusiastic cheerleading from the sides - you're the one poking at the kit, so feel free to tell me to calm down :)
Taking a quick dig into sys/arch/prep/stand. boot/conf.c seems to indicate the NetBSD/prep bootloader only supports booting from scsi, and specifically from the copy of boot/siop.c which is driving the 53c810 chipset directly
If Kernels <2M can be booted from the NetBSD bootload prompt (is this the case?) then that implies one of
- The NetBSD bootloader code has issues reading files >2MB
- Its loading into an area of memory which is only contiguous only up to 2M
- Something else is happening which I missed :)
I wonder what would happen if you took a copy of a working kernel and then appended some null data to the end - first keeping under 2M to see if it works, and then past 2M to see if that then fails. Possibly combinaed with adding some printf()s to boot/sd.c::sdstrategy to print out the details of each read request...
David
> Do you know if yaboot would be able to act as a secondary bootloader
> to load a kernel > 2MB directly from a NetBSD partition? Or should I
> try grub2? Fumbling with the SCSI controler in the bootloader without
> hardware documentation will be a waste of time, as I've already found
> out. I wasn't able to understand what interrupt/PCI/whatever setup was
> missing to get this working.
>
> CU,
> Uli
> --
> Dipl. Inf. Ulrich Teichert|e-mail:
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