These cpus only support a simple 16 bit offset from PC, so cannot use it
in start.S to compute a large offset. This is okay, because the code
that needs it is only for cpus with an MMU, which these dont have.
-Wire up the make plumbing for setting the kernel vm bits
-Implement stubbed out arch_mmu routines.
-Set up a high mapping in start.S that should be compatible with the mmu
code.
Port to the really neat 68010 based board at https://rosco-m68k.com/
Port Features:
-10Mhz 68010
-1MB ram
-Dual UART + timer implemented as a 68c681 chip
-timer running at 1Khz, UART A for console
-interrupt driven RX support
Some amount of extending of the 68k exceptinon code was needed to
support the autovectored irqs that the 68681 uart uses. Added build
system support for 68010.
It's non ideal, since there's no relaxation done in the linker so we
have to assume the branch target is > 16 bits away and do what the
compiler usually does and emit a full 32bit jsr.
Uses the QEMU virt machine for 68k defined in qemu 6.0+.
Basic support that boots, prints to the console, takes input from
console, and context switches.
TODO: interrupt support, timer support.
