Illegal instruction

Aklilu Noah
Thu May 11 16:19:00 GMT 2000

	I am compiling code to run on m68306 micro using 
gcc 2.95.2, binutils 2.9.1 and newlib 1.8.2.  However I am
encountering an illegal instruction when I call atexit from
my crt0.S as shown below 

	movel	IMM(__FINI_SECTION__),(sp)
	jsr	SYM(atexit)

I traced through the code using the monitor and it made the jump
to the atexit code but I dissambled the code and got the following
(atexit is entered at 304a0)

$000304A0 4E56 0000       link.w        A6,#0   ?  
$000304A4 2079 0003 12FE  movea.l       ($312FE).L,A0   ?  
$000304AA 2268 0146       movea.l       ($146,A0),A1    ?  
$000304AE 4A89            DC.W          ?  
$000304B0 6608            bne.b         $304BA  ?  
$000304B2 43E8 014A       lea.l         ($14A,A0),A1    ?  
$000304B6 2149 0146       move.l        A1,($146,A0)    ?  
$000304BA 701F            moveq.l       #$1F,D0 ?  
$000304BC B0A9 0004       cmp.l         ($4,A1),D0      ?  
$000304C0 6C26            bge.b         $304E8  ?  
$000304C2 4878 0088       pea.l         ($88).W ?  
$000304C6 4EB9 0003 0500  jsr           ($30500).L      ?  
$000304CC 2240            movea.l       D0,A1   ?  
$000304CE 4A89            DC.W          ?  
$000304D0 6604            bne.b         $304D6  ?  
$000304D2 70FF            moveq.l       #$FF,D0 ?  
$000304D4 6026            bra.b         $304FC  ?  
$000304D6 42A9 0004       clr.l         ($4,A1) ?  
$000304DA 2079 0003 12FE  movea.l       ($312FE).L,A0   ?  

The problem occurs at 304ae, where the illegal instruction
is. Note that there are additional illegal instructions 
at 304CE.  The problem seems to go away if I comment out 
that section of crt0 and things run ok. 

Not really actually malloc has a pointer (called from a test program to
make sure it works) that seems to be uninitialized, eventhough I
zero out the bss and shbss sections.  It causes an illegal memory access 
to occur which traps the monitor. It doesn't even get
to call sbrk (I have it output a character when it is entered)
before it dies.  But one problem at a time.

Noah Aklilu
"Integrity is something you do when no one is looking"

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