zx128: tricks.s updates

This still needs a lot of work doing but it's a starting point and we don't
crash waiting for input

diff --git a/Kernel/platform-zx128/tricks.s b/Kernel/platform-zx128/tricks.s
index d57ebdb..0141443 100644 (file)
--- a/Kernel/platform-zx128/tricks.s
+++ b/Kernel/platform-zx128/tricks.s
@@ -17,6 +17,7 @@
         .globl _runticks
         .globl unix_syscall_entry
         .globl interrupt_handler
+       .globl current_map
 
         ; imported debug symbols
         .globl outstring, outde, outhl, outbc, outnewline, outchar, outcharhex
@@ -58,11 +59,12 @@ _switchout:
        ld a, l
        ld bc, #0x7ffd
        out (c), a
+
        ld hl, #U_DATA
        ld de, #U_DATA_STASH
        ld bc, #U_DATA__TOTALSIZE
        ldir
-       xor a
+       ld a, (current_map)
        ld bc, #0x7ffd
        out (c), a
 
@@ -82,8 +84,15 @@ badswitchmsg: .ascii "_switchin: FAIL"
 swapped: .ascii "_switchin: SWAPPED"
             .db 13, 10, 0
 
+;
+;      FIXME: update this to use both pages and do the needed exchange
+;      on low pages.
+;
+;      FIXME: need to add swap to this yet 8(
+;
 _switchin:
         di
+       pop hl  ; far padding
         pop bc  ; return address
         pop de  ; new process pointer
 ;
@@ -91,19 +100,21 @@ _switchin:
 ;
         push de ; restore stack
         push bc ; restore stack
+       push hl ; far padding
 
-       xor a
-       ld bc, #0x7ffd
-       out (c), a
 
        push de
         ld hl, #P_TAB__P_PAGE_OFFSET
        add hl, de      ; process ptr
        pop de
 
+       ; We are in DI so we can poke these directly but must not use the
+       ; stack for this bit
+
         ld a, (hl)
        ; Pages please !
-       out (c), a      ; BC still contains 0x7ffd
+       ld bc, #0x7ffd
+       out (c), a
 
         ; bear in mind that the stack will be switched now, so we can't use it
        ; to carry values over this point
@@ -115,8 +126,9 @@ _switchin:
        ldir
        exx
 
-       xor a
-       out (c), a      ; and again 0x7ffd in BC
+       ld a, (current_map)
+       ld bc, #0x7ffd
+       out (c), a
         
         ; check u_data->u_ptab matches what we wanted
         ld hl, (U_DATA__U_PTAB) ; u_data->u_ptab
@@ -231,7 +243,7 @@ _dofork:
        ldir
 
        ld bc, #0x7ffd
-       xor a
+       ld a, (current_map)
        out (c), a
         ; now the copy operation is complete we can get rid of the stuff
         ; _switchin will be expecting from our copy of the stack.
@@ -269,6 +281,10 @@ _dofork:
 ;      Note: this needs reviewing. We now have a lot more program memory
 ;      we can use with a lazy copying model
 ;
+;
+;      FIXME: need to make this copy 0xC000-0xFFFF bank to bank
+;      and 0x8000 to the other bank
+;
 bankfork:
 ;      ld bc, #(0x4000 - 768)          ;       16K minus the uarea stash