Hi,
On 09/11/08 19:56, Johannes Berg wrote:
Yes, I think you're right, it appears that the 802.11 header isn't
aligned on a 2-byte boundary, which is extremely strange. Can you, with
your patch applied, do something like
printk(KERN_DEBUG "%p\n", skb->data);
before this code in zd_mac.c:
memcpy(skb_put(skb, length), buffer, length);
ieee80211_rx_irqsafe(hw, skb, &stats);
I have done this... but I think that there is too much output to place
here. What I can tell you with confidence is that every value is 4-byte
aligned.
However, I modify filter_ack() in zd_mac.c so that the code looks like this:
for (skb = q->next; skb != (struct sk_buff *)q; skb = skb->next) {
struct ieee80211_hdr *tx_hdr;
tx_hdr = (struct ieee80211_hdr *)skb->data;
printk(KERN_DEBUG "%s:%u: skb %p skb->data %p tx_hdr->addr2 %p
rx_hdr->addr1 %p\n", __FILE__, __LINE__, skb, skb->data, tx_hdr->addr2,
rx_hdr->addr1);
//if (likely(!memcmp(tx_hdr->addr2, rx_hdr->addr1,
ETH_ALEN)))
if (likely(!compare_ether_addr(tx_hdr->addr2,
rx_hdr->addr1)))
{
(note, I re-instated the compare_ether_addr() so that I could be sure
that the unaligned access corresponded with whatever values I was seeing
in the print).
Here is the output of the first print from this location that I see in
syslog:
Nov 10 00:47:17 trad kernel: [ 8239.534950]
drivers/net/wireless/zd1211rw/zd_mac.c:639: skb fffff8003d0d8fc0
skb->data fffff8003d874cdb tx_hdr->addr2 fffff8003d874ce5 rx_hdr->addr1
fffff8003f3e0009
Nov 10 00:47:17 trad kernel: [ 8239.534986] Kernel unaligned access at
TPC[100f5bd0] zd_mac_rx+0x1b0/0x398 [zd1211rw]
Nov 10 00:47:17 trad kernel: [ 8239.637697] Kernel unaligned access at
TPC[100f5bd4] zd_mac_rx+0x1b4/0x398 [zd1211rw]
Nov 10 00:47:17 trad kernel: [ 8239.740208] Kernel unaligned access at
TPC[100f5bd8] zd_mac_rx+0x1b8/0x398 [zd1211rw]
Nov 10 00:47:17 trad kernel: [ 8239.842417] Kernel unaligned access at
TPC[100f5bdc] zd_mac_rx+0x1bc/0x398 [zd1211rw]
Nov 10 00:47:17 trad kernel: [ 8239.944583] Kernel unaligned access at
TPC[100f5be0] zd_mac_rx+0x1c0/0x398 [zd1211rw]
So you can see that skb->data is not even 2-byte aligned. And my debug
leads me to believe that the problem is this line in zd_mac_tx_to_dev():
skb_pull(skb, sizeof(struct zd_ctrlset));
A before and after of this line gives me this output:
Nov 10 00:47:17 trad kernel: [ 8239.534065]
drivers/net/wireless/zd1211rw/zd_mac.c:376: skb fffff8003d0d8fc0
skb->data fffff8003d874cd0
Nov 10 00:47:17 trad kernel: [ 8239.534092]
drivers/net/wireless/zd1211rw/zd_mac.c:390: skb fffff8003d0d8fc0
skb->data fffff8003d874cdb
Perhaps there needs to be some padding there?
Also, I've just had a look at the git version of zd_mac.c, and I notice
it is all change there again. I would feel uncomfortable having studied
the 2.6.26 code to have to start again. Is it expected that I use the
latest available via git?
Thanks in advance,
Shaddy
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