Re: The Kernel for powermacs

[Dan Jacobowitz <youngdrow%geocities.com@localhost>]

>>>>>> "ws" == Wolfgang Solfrank <ws%kurt.tools.de@localhost> writes:
>
>ws> The PowerPC processor binding to IEEE1275 (i.e. OpenFirmware) is
>ws> quite explicit that the firmware is required to copy itself from
>ws> ROM to RAM and thus to change the trap vectors from 0xfff0#### to
>ws> 0x0000#### (these are the only two possible values for the trap
>ws> vector).
>
>ws>  Since the Apple firmware doesn't do that and presumably keeps
>ws> running from the ROM image, overwriting the trap vector for page
>ws> faults with the ones needed by e.g. NetBSD isn't possible.
>
>Can we get around this particular problem by copying a bunch of stub
>handlers to the low memory vectors that simply jump to the high memory
>vectors (for vectors that we don't want handled in the kernel), and
>set MSR_IP to 0 in the kernel?


While I don't claim to be particularly knowledgeable about processor
architecture on this level, after reading up on the ppc it looks possible;
in fact, I believe this is what linuxppc is doing.  I am not,
unfortunately, good enough to figure out quite where/how.  Any volunteers?

Dan.