tricks.s: fork and copy routine for the 6502

Or at least a first guess thereat

diff --git a/Kernel/platform-tgl6502/tricks.s b/Kernel/platform-tgl6502/tricks.s
index e46813e..1043d03 100644 (file)
--- a/Kernel/platform-tgl6502/tricks.s
+++ b/Kernel/platform-tgl6502/tricks.s
@@ -9,6 +9,8 @@
        .import _chksigs
        .import _trap_monitor
 
+       .import map_kernel
+
        .import _newproc
        .import _getproc
        .import _runticks
@@ -167,12 +169,13 @@ _dofork:
         ; now we're in a safe state for _switchin to return in the parent
        ; process.
 
-       ; --------- we switch stack copies in this call -----------
-;      jsr fork_copy                   ; copy 0x000 to udata.u_top and the
-                                       ; uarea and return on the childs
-                                       ; common
+       ;
+       ;       Assumes ptr1 still holds the new process ptr
+       ;
 
+       jsr fork_copy
 
+       ; --------- we switch stack copies here -----------
        lda U_DATA__U_PAGE
        sta $FF8A                       ; switch to child and child stack
                                        ; and zero page etc
@@ -208,46 +211,58 @@ _dofork:
        ; if it had done a switchout().
         rts
 
-fork_copy:
-;      ldd U_DATA__U_TOP
-;      addd #0x0fff            ; + 0x1000 (-1 for the rounding to follow)
-;      lsra            
-;      lsra
-;      lsra
-;      lsra
-;      lsra                    ; bits 2/1 for 8K pages
-;      anda #6                 ; lose bit 0
-;      adda #2                 ; and round up to the next bank (but in 8K terms)
 ;
-;      ldx fork_proc_ptr
-;      ldy P_TAB__P_PAGE_OFFSET,x
-;      ; y now points to the child page pointers
-;      ldx U_DATA__U_PAGE
-;      ; and x to the parent
-;fork_next:
-;      ld a,(hl)
-;      out (0x11), a           ; 0x4000 map the child
-;      ld c, a
-;      inc hl
-;      ld a, (de)
-;      out (0x12), a           ; 0x8000 maps the parent
-;      inc de
-;      exx
-;      ld hl, #0x8000          ; copy the bank
-;      ld de, #0x4000
-;      ld bc, #0x4000          ; we copy the whole bank, we could optimise
-;                              ; further
-;      ldir
-;      exx
-;      call map_kernel         ; put the maps back so we can look in p_tab
-; FIXME: can't map_kernel here - we've been playing with the maps, fix
-; directly
-;      suba #1
-;      bne fork_next
-
-;      ld a, c
-;      out (0x13), a           ; our last bank repeats up to common
-       ; --- we are now on the stack copy, parent stack is locked away ---
-;      rts                     ; this stack is copied so safe to return on
-
+;      On entry ptr1 points to the process table of the child, and
+;      the U_DATA is still not fully modified so holds the parents bank
+;      number.
+;
+fork_copy:
+       ldx U_DATA__U_PAGE
+       ldy #P_TAB__P_PAGE_OFFSET
+       lda (ptr1),y            ; child->p_page
+       tay
+       lda #0                  ; each bank is 56K
+copy_loop:
+       stx $FF8C               ; 0x4000
+       sty $FF8D               ; 0x6000
+       pha                     ; Oh for a 65C02 8)
+       tya
+       pha
+       txa
+       pha
+       jsr bank2bank           ; copies 8K
+       pla
+       tax
+       pla
+       tay
+       pla
+       inx
+       iny
+       clc
+       adc #1
+       cmp #8
+       bne copy_loop
+       jmp map_kernel          ; put the kernel mapping back as it should be
        
+bank2bank:                     ;       copy 4K between the blocks mapped
+                               ;       at 0x4000 and 0x6000
+       lda #$40
+       sta ptr3+1
+       lda #$60
+       sta ptr4+1
+       lda #0
+       sta ptr3
+       sta ptr4
+       tay
+       ldx #$20                ;       32 x 256 bytes = 8K
+copy1:
+       lda (ptr3),y
+       sta (ptr4),y
+       iny
+       bne copy1
+       inc ptr3+1
+       inc ptr4+1
+       dex
+       bne copy1
+       rts
+