unbanked: Update comments

Will pointed out the comments in unbanked about Z180 were bogus, and indeed
were also out of date.

Also turns out we can't have the kernel at physical 0 and banks for user
copy and for udata on the Z180 as the N8VEM-4 and probably others have ROM
at physical 0

diff --git a/Kernel/unbanked.c b/Kernel/unbanked.c
index bffa61f..de3caf3 100644 (file)
--- a/Kernel/unbanked.c
+++ b/Kernel/unbanked.c
@@ -15,11 +15,25 @@
  *     support one linear block but the hole manager can manage multiple non linear
  *     chunks if need be.
  *
- *     We run with common 0 at physical 0x0 holding the vectors (why copy them!)
- *     The bank area then runs from 0x0100 -> PAGE_TOP. The common 1 area is 
- *     mapped to the uarea/common of this process. This costs us memory for the
- *     common code copies but saves us doing the uarea copying dance that
- *     UZI180 does
+ *     The proposed way to run Z180 is
+ *
+ *     User Space
+ *     0-xxxx          Mapped to physical blocks holding user binary, vectors
+ *                     and some small stubs to switch bank
+ *     xxxx-FFFF       Mapped to somewhere like ROM (stray write protection)
+ *
+ *     Kernel Space
+ *     0-EFFF          Kernel image including other end of stubs
+ *     F000            Udata of process (plus window space to make user
+ *                     copies easier)
+ *
+ *     (the upper being exchanged temporarily to access user memory, or we
+ *     could put the copiers above F000 and switch the 0-EFFF bank but that
+ *     makes irq handling uglier I suspect)
+ *
+ *     For 8086 we actually want two holes in some cases, one for cs: and one
+ *     for ds: but we don't have all the vector hassle as we have a vaguely
+ *     real notion of user/supervisor state.
  */
 
 #include <kernel.h>