6502: add crt0nostdio

diff --git a/Library/libs/crt0nostdio_6502.s b/Library/libs/crt0nostdio_6502.s
new file mode 100644 (file)
index 0000000..b87634d
--- /dev/null
+++ b/Library/libs/crt0nostdio_6502.s
@@ -0,0 +1,124 @@
+;
+; Startup code for cc65 on FUZIX
+;
+; Based on code by Debrune Jérôme <jede@oric.org>
+; and Ullrich von Bassewitz <uz@cc65.org> 2014-08-22, Greg King
+;
+
+       .import         __CODE_SIZE__, __RODATA_SIZE__
+       .import         __DATA_SIZE__, __BSS_SIZE__
+       .import         _exit
+       .export         _environ
+       .export         initmainargs
+       .import         _main
+       .import         popax, pushax
+       .import         ___stdio_init_vars
+
+       .export __STARTUP__ : absolute = 1;
+
+        .include        "zeropage.inc"
+
+.segment "STARTUP"
+
+       jmp     start
+
+       .byte   'F'
+       .byte   'Z'
+       .byte   'X'
+       .byte   '1'
+       .byte   $20
+       .word   0
+       .word   __CODE_SIZE__ + __RODATA_SIZE__
+       .word   __DATA_SIZE__
+       .word   __BSS_SIZE__
+       .word   0
+       .word   0       ; padding
+       .word   __sighandler            ; IRQ path signal handling helper
+
+;
+;      First cut at sighandling stubs, horrible on 6502!
+;
+;      The user stack may be invalid. If we hit mid update then the low
+;      byte may be updated but the carry into the high byte not done.
+;
+;      I think therefore that providing we dec sp+1 we are always ok and
+;      will be somewhere between 0 and 255 bytes of valid
+;
+;
+__sighandler:
+       jsr     stash_zp        ; saves sp etc
+       dec     sp+1            ; ensure we are safe C stack wise
+       pla
+       sta     ptr1            ; ZP was swapped
+       pla
+       sta     ptr1+1          ; ptr1 is now the function
+       pla
+       ldx     #0
+       jsr     pushax          ; signal(int sig)
+       jsr     jptr1           ; no jsr (x) so fake it
+       jsr     stash_zp        ; recovers sp
+initmainargs:                  ; Hardcoded compiler dumbness
+       rts                     ; will return via the kernel stub
+                               ; to user space
+jptr1: jmp     (ptr1)
+;
+;
+;      On entry sp/sp+1 have been set up by the kernel (this has to be
+;      done in kernel as we might take a signal very early on). Above the
+;      sp are the argument vectors, environment etc. In other words we
+;      are basically a straight function call from the kernel stub.
+;
+;      Our image has been loaded into RAM, any spare memory has been zeroed
+;      for us and we are ready to roll.
+;
+start:
+; Push the command-line arguments; and, call main().
+;
+; Need to save the environment ptr. The rest of the stack should be
+; fine.
+;
+;
+       lda     sp
+       ldx     sp+1
+       clc
+       adc     #4
+       bcc     l1
+       inx
+l1:    sta     _environ
+       stx     _environ+1
+       jsr     popax           ; Pull argv off the stack leaving argc
+       ldy     #2              ; 2 bytes of args
+        jsr     _main
+
+; Call the module destructors. This is also the exit() entry.
+
+       jmp     _exit           ; exit cleanup, AX holds our return code
+                               ; for a fastcall return to nowhere.
+
+;
+;      The following is taken from the debugger example as referenced in
+;      the compiler documentation. We swap a stashed ZP in our commondata
+;      with an IRQ handler one. The commondata is per process and we depend
+;      upon this to make it all work
+;
+; Swap the C temporaries
+;
+stash_zp:
+        ldy     #zpsavespace-1
+Swap1:  ldx     CTemp,y
+        lda     <sp,y
+        sta     CTemp,y
+        txa
+        sta     sp,y
+        dey
+        bpl     Swap1
+        rts
+
+
+       .bss
+_environ:      .res    2
+oldsp:         .res    2
+CTemp:
+               .res    2               ; sp
+               .res    2               ; sreg
+               .res    (zpsavespace-4) ; Other stuff