coco2cart: introduce swap enabled single process model

With the small core changes the 6809 banked ports can now swap while the
interrupts are enabled. This relies upon the fact the vectors are always
mapped so while not too hard on 6809 and 6502 the Z80 ports where the low
256 bytes are both IRQ vectors and part of the user map will probably need
a bit more work.

diff --git a/Kernel/platform-coco2cart/README b/Kernel/platform-coco2cart/README
index f6962ef..6c06095 100644 (file)
--- a/Kernel/platform-coco2cart/README
+++ b/Kernel/platform-coco2cart/README
@@ -15,7 +15,7 @@ Memory Map
 User View
 =========
 0000-00FF      Interrupt stack
-0100-01FF      Vectors (then wasted - could hide libc.o in there ?)
+0100-01FF      Vectors plus the swap stack
 0200-19FF      Display
 1A00-1BFF      udata/stack
 1C00-7FFF      Common, data and some kernel code
@@ -26,7 +26,7 @@ FF00-FFFF     I/O etc
 Kernel Mode View
 ================
 0000-00FF      Interrupt stack
-0100-01FF      Vectors
+0100-01FF      Vectors plus swap stack
 0200-19FF      Display
 1A00-1BFF      udata/stack
 1C00-7FFF      Common, data and some kernel code

diff --git a/Kernel/platform-coco2cart/tricks.s b/Kernel/platform-coco2cart/tricks.s
index e2e3475..8e62a8f 100644 (file)
--- a/Kernel/platform-coco2cart/tricks.s
+++ b/Kernel/platform-coco2cart/tricks.s
@@ -16,6 +16,7 @@
         .globl map_process_always
         .globl copybank
        .globl _nready
+       .globl _inswap
        .globl _platform_idle
 
        # exported
@@ -70,25 +71,31 @@ _switchin:
         orcc #0x10             ; irq off
 
        stx newpp
+       inc _inswap
        ; get process table
        lda P_TAB__P_PAGE_OFFSET+1,x            ; LSB of 16-bit page no
 
        cmpa #0
        bne not_swapped
+
+       lds #$0200              ;       $1xx is vectors and swap stack
+
        ldx U_DATA__U_PTAB
        ldx P_TAB__P_PAGE_OFFSET+1,x
        beq not_swapout         ;       it's dead don't swap it out
        ldx U_DATA__U_PTAB
+       andcc #0xef
        jsr _swapout            ;       swapout(pptr)
 not_swapout:
-       lds #$0100              ;       FIXME: need to use something else
-                               ;       when we enable IRQ during this !!
        ldx newpp
+       andcc #0xef
        jsr _swapper            ;       fetch our process
        ldx newpp
        lda #1
        sta P_TAB__P_PAGE_OFFSET+1,x    ; marked paged in
 not_swapped:
+       orcc #0x10
+       dec _inswap
        ; we have now new stacks so get new stack pointer before any jsr
        lds U_DATA__U_SP
 
@@ -162,7 +169,18 @@ _dofork:
        ; process.
 
        ldx U_DATA__U_PTAB
+       ;
+       ; FIXME: review what is needed for IRQ safety here before we turn
+       ; on IRQs during the swapout
+       ;
+       inc _inswap
+       lds #$0200              ;       Use the swap stack
+       andcc #0xef
        jsr _swapout
+       orcc #0x10
+       dec _inswap
+       lds U_DATA__U_SP
+
         ; now the copy operation is complete we can get rid of the stuff
         ; _switchin will be expecting from our copy of the stack.
        cmpx #0