[stuff about compiling problems snipped]
> Another problem with newer kernel is that the building strategy Paul
> uses to build ECOFF kernel will not work anymore for 2.1.x kernels. The
> kernel uses a number of ELF features - too many for ld. It will die
> with funny messages.
Can it be that this affects the stack manipulation in do_sys(...)?
The DECstation kernel is now dying in the return from the first syscall
in kernel_thread(...). From what I have been able to find out so far
(with the help of two good old friends named printk and PRINT), the
regs->cp0_epc += 4;
in do_sys(...) is not visible after RESTORE_ALL in ret_from_syscall.
> Suggested alternative strategy: build an ELF kernel
> like all other systems do and convert it into ECOFF using the
> ELF -> ECOFF converter program from the Milo sources. That's will be
> a quite robust solution.
I have done some experiments with that, but I am sorry to tell that this
does not work :-(. It looks like the DECstation boot prom is very picky
about the layout of kernel images. Maybe it's time to put some effort in
a bootloader which is able to boot ELF kernels.