[okl4-developer] <iguana_server> alignment fault at 0xdeadbefb from thread: 80000004

[Lukas HANEL]

Hi Geoffrey

I attached the disassembled code. In the clist create function, it seems 
as if the first malloc returned a bad pointer(r4, MR04: 0x00000101). 
Maybe this is indicating an error condition? So when the code tries to 
write in the array, it is not performing a word aligned access (e.g. 
0x101+12)

Lukas Hänel

----
struct clist *
server_clist_create(struct pd *pd)
{
80002800:       e92d4070        stmdb   sp!, {r4, r5, r6, lr}
80002804:       e1a05000        mov     r5, r0
iguana/server/src/clist.c:85
     struct clist *clist;

     clist = malloc(sizeof(*clist));
80002808:       e3a0001c        mov     r0, #28 ; 0x1c
8000280c:       eb001da0        bl      80009e94 <malloc>
iguana/server/src/clist.c:86
     if (clist != NULL) {
80002810:       e2504000        subs    r4, r0, #0      ; 0x0
iguana/server/src/clist.c:89
         clist->magic = CLIST_MAGIC;
         clist->owner = pd;
         clist->used = 0;
80002814:       e3a06000        mov     r6, #0  ; 0x0
iguana/server/src/clist.c:91
         clist->size = MIN_CLIST_SLOTS;
         clist->cap = malloc(clist->size * sizeof(cap_t));
80002818:       e3a00080        mov     r0, #128        ; 0x80
iguana/server/src/clist.c:86
8000281c:       0a000017        beq     80002880 <server_clist_create+0x80>
iguana/server/src/clist.c:87
80002820:       e59f3060        ldr     r3, [pc, #96]   ; 80002888 
<.text+0x2888>
80002824:       e5932000        ldr     r2, [r3]
iguana/server/src/clist.c:90
80002828:       e3a03010        mov     r3, #16 ; 0x10
8000282c:       e584300c        str     r3, [r4, #12]
iguana/server/src/clist.c:87
80002830:       e8840064        stmia   r4, {r2, r5, r6}
iguana/server/src/clist.c:91
80002834:       eb001d96        bl      80009e94 <malloc>

----
Geoffrey Lee wrote:
> On Wed, Jun 04, 2008 at 01:22:07PM +0200, Lukas HANEL wrote:
>> Hi,
>>
>> when compiling with debug_trace=1 I get the following error message. 
>> However, it seems as if the system is working fine even with this thing.
>> So I was trying this with the drivers example and with oklinux and in 
>> both ways the normal behaviour was not affected.
> 
> Hi Lukas
> 
> It looks like the system tried to cause an unaligned access by
> accessing memory at 0xdeaddefb.  This makes the hardware trap and
> causes an exception IPC to be sent.  The best way would be to disassmeble
> the relevant parts of OKL4 and find out what it is doing.
> 
> 	-gl
> 
>> Can you comment on source and impact of this? E.g. is this a problem?
>>
>> Thanks,
>> Lukas
>>
>> ----
>> <iguana_server> alignment fault at 0xdeadbefb from thread: 80000004
>> IP: 0x8040282c SP: 0x8001ff4c FLAGS: 0x20000010
>>    --  TAG: 0xffb00005
>>       MR01: 0x8040282c
>>       MR02: 0x8001ff4c
>>       MR03: 0x20000010
>>       MR04: 0x00000101
>>       MR05: 0xdeadbefb
>>
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>