On 04/20/2017 12:20 AM, Johannes Berg wrote:
On Wed, 2017-04-19 at 23:31 +0200, Johannes Berg wrote:
Hi Alexei, Daniel,
I'm looking at adding the __wifi_sk_buff I talked about, and I notice
that it uses CB space to store data_end. Unfortunately, in a lot of
cases, we don't have any CB space to spare in wifi.
I guess I can work around this, would this seem reasonable?
struct bpf_skb_data_end {
struct qdisc_skb_cb qdisc_cb;
- void *data_end;
+ /*
+ * The alignment here is for mac80211, since that doesn't use
+ * a pointer but a u64 value and needs to save/restore that
+ * across running its BPF programs.
+ */
+ void *data_end __aligned(sizeof(u64));
};
Yeah, should work as well for the 32 bit archs, on 64 bit we
have this effectively already:
struct bpf_skb_data_end {
struct qdisc_skb_cb qdisc_cb; /* 0 28 */
/* XXX 4 bytes hole, try to pack */
void * data_end; /* 32 8 */
/* size: 40, cachelines: 1, members: 2 */
/* sum members: 36, holes: 1, sum holes: 4 */
/* last cacheline: 40 bytes */
};
Can you elaborate on why this works for mac80211? It uses cb
only up to that point from where you invoke the prog?
