Em Wed, Jan 28, 2015 at 01:24:15PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Tue, Jan 27, 2015 at 08:06:09PM -0800, Alexei Starovoitov escreveu:
> > diff --git a/samples/bpf/tracex1_kern.c b/samples/bpf/tracex1_kern.c
> > new file mode 100644
> > index 000000000000..7849ceb4bce6
> > --- /dev/null
> > +++ b/samples/bpf/tracex1_kern.c
> > @@ -0,0 +1,28 @@
> > +#include <linux/skbuff.h>
> > +#include <linux/netdevice.h>
> > +#include <uapi/linux/bpf.h>
> > +#include <trace/bpf_trace.h>
> > +#include "bpf_helpers.h"
> > +
> > +SEC("events/net/netif_receive_skb")
> > +int bpf_prog1(struct bpf_context *ctx)
> > +{
> > + /*
> > + * attaches to /sys/kernel/debug/tracing/events/net/netif_receive_skb
> > + * prints events for loobpack device only
> > + */
> > + char devname[] = "lo";
> > + struct net_device *dev;
> > + struct sk_buff *skb = 0;
> > +
> > + skb = (struct sk_buff *) ctx->arg1;
> > + dev = bpf_fetch_ptr(&skb->dev);
> > + if (bpf_memcmp(dev->name, devname, 2) == 0)
>
> I'm only starting to look at all this, so bear with me... But why do we
> need to have it as "bpf_memcmp"? Can't we simply use it as "memcmp" and
> have it use the right function?
>
> Less typing, perhaps we would need to have a:
>
> #define memcmp bpf_memcmp(s1, s2, n) bpf_memcmp(s1, s2, n)
Argh, like this:
#define memcmp(s1, s2, n) bpf_memcmp(s1, s2, n)
> in bpf_helpers.h to have it work?
>
> - Arnaldo
>
> > + /* print event using default tracepoint format */
> > + return 1;
> > +
> > + /* drop event */
> > + return 0;
> > +}
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