zxdiv: update the bank switching code to save the kernel bank

Otherwise we end up returning to the right address but with the wrong kernel
page mapped.

diff --git a/Kernel/platform-zxdiv/tricks.s b/Kernel/platform-zxdiv/tricks.s
index 5bae347..3e11c9f 100644 (file)
--- a/Kernel/platform-zxdiv/tricks.s
+++ b/Kernel/platform-zxdiv/tricks.s
@@ -22,6 +22,7 @@
        .globl _ptab
        .globl _swapper
        .globl _int_disabled
+       .globl switch_bank
 
         ; imported debug symbols
         .globl outstring, outde, outhl, outbc, outnewline, outchar, outcharhex
@@ -45,6 +46,10 @@ _platform_switchout:
         push hl ; return code
         push ix
         push iy
+
+       ld a,(current_map)
+       push af
+
         ld (U_DATA__U_SP), sp ; this is where the SP is restored in _switchin
 
        ;
@@ -98,8 +103,10 @@ _switchin:
         push bc ; restore stack
        push hl ; far padding
 
+       push de
         ld hl, #P_TAB__P_PAGE_OFFSET
        add hl, de      ; process ptr
+       pop de
        ;
        ;       Get ourselves a valid private stack ASAP. We are going to
        ;       copy udata around and our main stacks are in udata
@@ -134,6 +141,12 @@ _switchin:
        di
        ld a, (hl)      ; We should now have a page assigned
 not_swapped:
+       ld hl,(U_DATA__U_PTAB)
+       or a
+       sbc hl,de
+; Turn this on once debugged
+;      jr z, skip_copyback
+
        ; We are in DI so we can poke these directly but must not invoke
        ; any code outside of common
        or #0x18        ; ROM
@@ -153,7 +166,6 @@ not_swapped:
        ld bc, #U_DATA__TOTALSIZE
        ldir
        exx
-
        ;
        ;        Remap the kernel proper
        ;
@@ -232,10 +244,14 @@ nofliplow:
        ; We can now use the stack again
        ;
 
+       pop af
         pop iy
         pop ix
         pop hl ; return code
 
+       ; Make sure we have the right kernel bank to return to
+       call switch_bank
+
         ; enable interrupts, if the ISR isn't already running
         ld a, (U_DATA__U_ININTERRUPT)
        ld (_int_disabled),a
@@ -302,6 +318,9 @@ _dofork:
         push ix
         push iy
 
+       ld a,(current_map)
+       push af
+
         ; save kernel stack pointer -- when it comes back in the parent we'll be in
         ; _switchin which will immediately return (appearing to be _dofork()
        ; returning) and with HL (ie return code) containing the child PID.
@@ -369,8 +388,9 @@ _dofork:
         ; _switchin will be expecting from our copy of the stack.
 
         pop bc
-        pop bc
-        pop bc
+        pop iy
+        pop ix
+       pop bc
 
         ; Make a new process table entry, etc.
         ld  hl, (fork_proc_ptr)