tricks,6502: fix bugs in fork/switchin

We can now fork and switch between both processes happily. Some problems seem
to be left with exiting but unclear if those are kernel or init

diff --git a/Kernel/platform-tgl6502/tricks.s b/Kernel/platform-tgl6502/tricks.s
index 9bd53b9..af84461 100644 (file)
--- a/Kernel/platform-tgl6502/tricks.s
+++ b/Kernel/platform-tgl6502/tricks.s
@@ -67,7 +67,8 @@ _switchout:
         ; we should never get here
         jsr _trap_monitor
 
-badswitchmsg: .asciiz "_switchin: FAIL\r\n"
+badswitchmsg: .byte "_switchin: FAIL"
+       .byte 13, 10, 0
 
 ;
 ;      On entry x,a holds the process to switch in
@@ -76,14 +77,25 @@ _switchin:
        sei
        sta     ptr1
        stx     ptr1+1
-;      jsr     outxa
+       ; Take a second saved set as we are going to swap stacks and ZP
+       ; with a CPU that hasn't got sufficient registers to keep it on
+       ; CPU
+       sta     switch_proc_ptr
+       stx     switch_proc_ptr+1
+       jsr     outxa
        ldy     #P_TAB__P_PAGE_OFFSET
        lda     (ptr1),y
 ;      pha
 ;      jsr     outcharhex
 ;      pla
        sta     $FF8A           ; switches zero page, stack memory area
-       ; ------- No stack -------
+       ; ------- New stack and ZP -------
+
+       ; Set ptr1 back up (the old ptr1 was on the other ZP)
+       lda     switch_proc_ptr
+       sta     ptr1
+       lda     switch_proc_ptr+1
+       sta     ptr1+1
 
         ; check u_data->u_ptab matches what we wanted
        lda     U_DATA__U_PTAB
@@ -119,17 +131,20 @@ swtchdone:
         rts
 
 switchinfail:
-       lda     ptr1
-       jsr     outcharhex
        lda     ptr1+1
        jsr     outcharhex
+       lda     ptr1
+       jsr     outcharhex
         lda    #<badswitchmsg
        ldx     #>badswitchmsg
         jsr outstring
        ; something went wrong and we didn't switch in what we asked for
         jmp _trap_monitor
 
-; FIXME: put this in ZP ?
+; Must not put this in ZP ?
+;
+; Move to commondata ??
+;
 fork_proc_ptr: .word 0 ; (C type is struct p_tab *) -- address of child process p_tab entry
 
 ;
@@ -180,7 +195,12 @@ _dofork:
        jsr fork_copy
 
        ; --------- we switch stack copies here -----------
-       lda U_DATA__U_PAGE
+        lda fork_proc_ptr
+       ldx fork_proc_ptr+1
+       sta ptr1
+       stx ptr1+1
+       ldy #P_TAB__P_PAGE_OFFSET
+       lda (ptr1),y
        sta $FF8A                       ; switch to child and child stack
                                        ; and zero page etc
        ; We are now in the kernel child context
@@ -269,3 +289,10 @@ copy1:
        bne copy1
        rts
 
+;
+;      The switch proc pointer cannot live anywhere in common as we switch
+;      common on process switch
+;
+       .data
+
+switch_proc_ptr: .word 0