|
| From: | B B |
| Subject: | RE: [lwip-users] lwip + sam7x = udef exception |
| Date: | Wed, 14 Feb 2007 12:23:51 +0000 |
From: address@hidden
To: address@hidden
Subject: RE: [lwip-users] lwip + sam7x = udef exception
Date: Wed, 14 Feb 2007 12:13:41 +0000
Hi again Kieran,
the value given for tcphdr is the address.
So it seems to be the address of the tcphdr variable
which is 2 byte aligned and not 4 byte, as required.
How can i enforce alignment of that variable?
regards,
Martin
> Subject: RE: [lwip-users] lwip + sam7x = udef exception
> From: address@hidden
> To: address@hidden
> Date: Wed, 14 Feb 2007 11:28:25 +0000
>
> On Wed, 2007-02-14 at 11:19 +0000, B B wrote:
>
> > offending instruction:
> > adds r4, r3, #0x0
> >
> > offending c statement:
> > tcphdr = (struct tcp_hdr *)((u8_t *)p->payload + IPH_HL(iphdr) * 4);
> >
> > Register data:
> > R3 = 0x0020135c
> > R4 = 0x0020b1fa
> > CPSR = 0x0000009b
> > SPSR_UND = 0x0000001f
> >
> > Packetdata:
> > tcphdr @0x0020b1fa
>
>
> Looks to me (not 100% sure what "adds" does or the argument format on
> your hardware) that it's the instruction that is trying to store the
> result of that C statement into tcphdr that is causing the problem. I
> think this because the value of R4 matches the address given for tcphdr.
> Please correct me if you disagree.
>
> The problem would seem to be that tcphdr has an address that is 2 byte
> aligned, not 4 byte aligned as you require. However, it's not clear
> from the above to me whether the value give for tcphdr is the address of
> the tcphdr variable, or the contents of the tcphdr variable (i.e. the
> address of what it points to).
>
> Can you clarify this?
>
> Kieran
>
>
>
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