Re: [PATCH v3 linux-trace 4/8] samples: bpf: simple tracing example in C

On Mon,  9 Feb 2015 19:45:57 -0800
Alexei Starovoitov [off-list ref] wrote:

+static void print_netif_receive_skb(void *data, int size)
+{
+	struct ftrace_raw_netif_receive_skb {
+		struct trace_entry t;
+		void *skb;
+		__u32 len;
+		__u32 name;
+	} *e = data;

Same here, there's no guarantee that this structure will always match.

cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/format 
name: netif_receive_skb
ID: 975
format:
	field:unsigned short common_type;	offset:0;	size:2;	signed:0;
	field:unsigned char common_flags;	offset:2;	size:1;	signed:0;
	field:unsigned char common_preempt_count;	offset:3;	size:1;	signed:0;
	field:int common_pid;	offset:4;	size:4;	signed:1;

	field:void * skbaddr;	offset:8;	size:8;	signed:0;
	field:unsigned int len;	offset:16;	size:4;	signed:0;
	field:__data_loc char[] name;	offset:20;	size:4;	signed:1;

print fmt: "dev=%s skbaddr=%p len=%u", __get_str(name), REC->skbaddr, REC->len

-- Steve