65c816: fix more asm paths

diff --git a/Kernel/lowlevel-65c816.s b/Kernel/lowlevel-65c816.s
index 1366596..1f0df83 100644 (file)
--- a/Kernel/lowlevel-65c816.s
+++ b/Kernel/lowlevel-65c816.s
@@ -84,7 +84,7 @@ syscall       =       $fe
 
 ;
 ;      Helper - given the udata bank in A set the DP value correctly. May
-;      be worth optimizing one day.
+;      be worth optimizing one day. Must not corrupt X or Y
 ;
 setdp:
        php
@@ -96,7 +96,10 @@ setdp:
        pha
        asl     a                       ; twice page
        adc     #STACK_BANKOFF          ; we now point at the stack
-       adc     #$0100                  ; now the DP
+       inc     a                       ; plus 0x100
+       xba                             ; Swap to get xx00 format we need
+       and     #$FF00
+       tcd
        pla
 
        plp
@@ -106,19 +109,24 @@ setdp:
        .i8
 ;
 ;      This is called from a stub we put into each user process bank that
-;      does a jsl to the kernel entry point then an rts
+;      does a jsl to the kernel entry point then an rts. Must be called
+;      in a8i8 state (or at least that's how you'll get the CPU back)
 ;
 syscall_entry:
-       php                             ; save cpu mode of caller on ustack
        sei                             ; interrupts off
        cld                             ; get into sane mode - no decimal, known state
+
        sep     #$30
        .a8
        .i8
-       stx     U_DATA__U_CALLNO
+
+       txa
+       sta     f:KERNEL_FAR+U_DATA__U_CALLNO
        cpy     #0
        beq     noargs
 
+       ; FIXME check if Y too large
+
        lda     sp
        sta     ptr1
        ldx     sp+1
@@ -143,7 +151,7 @@ copy_args:
        dey
        dey
        lda     (ptr1),y                ; copy the arguments over
-       sta     KERNEL_FAR+U_DATA__U_ARGN,x
+       sta     f:KERNEL_FAR+U_DATA__U_ARGN,x
         inx
        inx
        cpy     #0
@@ -162,6 +170,8 @@ noargs:
        .a16
        .i16
 
+       ldx     sp                      ; save the C stack before we swich DP
+
        lda     #KERNEL_DP
        tcd
 
@@ -169,9 +179,9 @@ noargs:
        .a16
        .i16
 
-       ldx     sp                      ; save the C stack
-       phx                             ; on the main stack
-       ; FIXME: how to check stack space in brk when this is not visible ?
+       phx                             ; push user sp onto stack so we can
+                                       ; see it (only brk() needs it, nor
+                                       ; is it needed for save/restore)
        tsx
        stx     U_DATA__U_SYSCALL_SP
        ldx     #kstack_top-1
@@ -179,7 +189,8 @@ noargs:
        ldx     #kstackc_top-1          ; set our C stack
        stx     sp                      ; 
 
-       sep     #$10
+       sep     #$30
+       .a8
        .i8
 
        lda     #1
@@ -194,15 +205,24 @@ noargs:
 
        ldx     U_DATA__U_SYSCALL_SP
        txs                             ; Back to the old stack
-                                       ; We can't restore sp yet as we are
-                                       ; in the wrong bank
+
        sep     #$10
        .i8
 
        lda     U_DATA__U_CURSIG
        bne     signal_out
-       sep     #$20
-       .a8
+
+       pla                             ; pull the saved sp off the ustack
+       pla                             ; discard it (it's still fine in
+                                       ; bank)
+
+       ; We may now be in decimal !
+       ldy     U_DATA__U_RETVAL
+       ldx     U_DATA__U_RETVAL+1
+       ; also sets z for us
+       lda     U_DATA__U_ERROR
+       pha                             ; save A
+
        lda     U_DATA__U_PAGE
        ;
        ;       We use this trick several times. U_PAGE holds the bank
@@ -213,20 +233,7 @@ noargs:
        plb                             ; User mapping for data bits
        jsr     setdp                   ; Set DP from A, corrupts A
 
-       rep     #$20
-       .a16
-       pla                             ; pull the saved sp off the ustack
-       sta     sp                      ; and store it 16bit
-
-       sep     #$20
-       .a8
-       .i8
-       ; We may now be in decimal !
-       ldy     U_DATA__U_RETVAL
-       ldx     U_DATA__U_RETVAL+1
-       ; also sets z for us
-       lda     U_DATA__U_ERROR
-       plp
+       pla                             ; Sets Z based on error
        rtl
 
        ;
@@ -253,6 +260,10 @@ noargs:
 signal_out:
        stz     U_DATA__U_CURSIG
        
+       ;
+       ;       Fixme stack correct U_DATA in x y a
+       ;
+
        rep     #$10
        .i16
        ply                             ; user stack pointer to go to sp
@@ -334,13 +345,12 @@ _doexec:
        sep     #$20
        .a8
 
-       ; Fix up the syscall vector
-
-       ldy     #syscall_vector
-       sty     syscall         ;       stores into user DP
-       ; And the C stack pointer
+       ; Set the C stack pointer
        ldy     U_DATA__U_ISP
        sty     sp              ;       sp is in DP so we write user version
+       ; Fix up the syscall vector in ZP
+       ldy     #syscall_vector
+       sty     syscall         ;       stores into user DP
 
        ;
        ;       From here we are entirely referencing user data but kernel
@@ -352,6 +362,8 @@ _doexec:
        pha                     ;       switch to userdata bank
        plb
 
+       sty     a:syscall       ;       and in bank:00FE
+
        pha                     ;       stack bank for rtl
 
        dex                     ;       Points to end of last instruction
@@ -480,6 +492,9 @@ join_interrupt_path:
        pla
        rti
 
+       .a8
+       .i16
+
 ret_to_user:
        ; TODO .. pre-emption
 
@@ -496,15 +511,17 @@ ret_to_user:
        ;       save the bank as a task switch or swap might move the
        ;       process
        ;
-       lda     U_DATA__U_PAGE
        sep     #$30
 
        .a8
        .i8
 
+       lda     U_DATA__U_PAGE
+
        pha
        plb     ; Now data is the user bank
-       jsr     setdp
+
+       jsr     setdp   ; as is DP
 
        rep     #$30
        .a16