zx128: swap in logic

With this in place we swap data out, we read it back in and then we crash.
Further debugging needed yet.

diff --git a/Kernel/platform-zx128/tricks.s b/Kernel/platform-zx128/tricks.s
index 9e09f03..e098669 100644 (file)
--- a/Kernel/platform-zx128/tricks.s
+++ b/Kernel/platform-zx128/tricks.s
@@ -21,6 +21,7 @@
         .globl interrupt_handler
        .globl current_map
        .globl _ptab
+       .globl _swapper
 
         ; imported debug symbols
         .globl outstring, outde, outhl, outbc, outnewline, outchar, outcharhex
@@ -114,17 +115,31 @@ _switchin:
         push bc ; restore stack
        push hl ; far padding
 
-
         ld hl, #P_TAB__P_PAGE_OFFSET
        add hl, de      ; process ptr
 
        ; We are in DI so we can poke these directly but must not invoke
        ; any code outside of common
 
+       ld sp, #_swapstack
+
         ld a, (hl)
+       or a
+       jr nz, not_swapped
+
+       ; Swap the process in (this may swap something else out first)
+
+       push hl
+       push de
+       push af
+       call _swapper
+       pop af
+       pop de
+       pop hl
+       ld a, (hl)
+not_swapped:
        or #0x18
 
-       ; Need to deal with swap here
 
        ; Pages please !
        ld bc, #0x7ffd