bpf: add initial bpf tracepoints

This work adds a number of tracepoints to paths that are either
considered slow-path or exception-like states, where monitoring or
inspecting them would be desirable.

For bpf(2) syscall, tracepoints have been placed for main commands
when they succeed. In XDP case, tracepoint is for exceptions, that
is, f.e. on abnormal BPF program exit such as unknown or XDP_ABORTED
return code, or when error occurs during XDP_TX action and the packet
could not be forwarded.

Both have been split into separate event headers, and can be further
extended. Worst case, if they unexpectedly should get into our way in
future, they can also removed [1]. Of course, these tracepoints (like
any other) can be analyzed by eBPF itself, etc. Example output:

  # ./perf record -a -e bpf:* sleep 10
  # ./perf script
  sock_example  6197 [005]   283.980322:      bpf:bpf_map_create: map type=ARRAY ufd=4 key=4 val=8 max=256 flags=0
  sock_example  6197 [005]   283.980721:       bpf:bpf_prog_load: prog=a5ea8fa30ea6849c type=SOCKET_FILTER ufd=5
  sock_example  6197 [005]   283.988423:   bpf:bpf_prog_get_type: prog=a5ea8fa30ea6849c type=SOCKET_FILTER
  sock_example  6197 [005]   283.988443: bpf:bpf_map_lookup_elem: map type=ARRAY ufd=4 key=[06 00 00 00] val=[00 00 00 00 00 00 00 00]
  [...]
  sock_example  6197 [005]   288.990868: bpf:bpf_map_lookup_elem: map type=ARRAY ufd=4 key=[01 00 00 00] val=[14 00 00 00 00 00 00 00]
       swapper     0 [005]   289.338243:    bpf:bpf_prog_put_rcu: prog=a5ea8fa30ea6849c type=SOCKET_FILTER

  [1] https://lwn.net/Articles/705270/

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 5 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index 67afd95ffb93..6ac43abf561b 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
@@ -42,6 +42,7 @@
  */
 
 #include <linux/bpf.h>
+#include <linux/bpf_trace.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
@@ -1459,7 +1460,7 @@ nfp_net_rx_drop(struct nfp_net_r_vector *r_vec, struct nfp_net_rx_ring *rx_ring,
 		dev_kfree_skb_any(skb);
 }
 
-static void
+static bool
 nfp_net_tx_xdp_buf(struct nfp_net *nn, struct nfp_net_rx_ring *rx_ring,
 		   struct nfp_net_tx_ring *tx_ring,
 		   struct nfp_net_rx_buf *rxbuf, unsigned int pkt_off,
@@ -1473,13 +1474,13 @@ nfp_net_tx_xdp_buf(struct nfp_net *nn, struct nfp_net_rx_ring *rx_ring,
 
 	if (unlikely(nfp_net_tx_full(tx_ring, 1))) {
 		nfp_net_rx_drop(rx_ring->r_vec, rx_ring, rxbuf, NULL);
-		return;
+		return false;
 	}
 
 	new_frag = nfp_net_napi_alloc_one(nn, DMA_BIDIRECTIONAL, &new_dma_addr);
 	if (unlikely(!new_frag)) {
 		nfp_net_rx_drop(rx_ring->r_vec, rx_ring, rxbuf, NULL);
-		return;
+		return false;
 	}
 	nfp_net_rx_give_one(rx_ring, new_frag, new_dma_addr);
 
@@ -1509,6 +1510,7 @@ nfp_net_tx_xdp_buf(struct nfp_net *nn, struct nfp_net_rx_ring *rx_ring,
 
 	tx_ring->wr_p++;
 	tx_ring->wr_ptr_add++;
+	return true;
 }
 
 static int nfp_net_run_xdp(struct bpf_prog *prog, void *data, unsigned int len)
@@ -1613,12 +1615,15 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget)
 			case XDP_PASS:
 				break;
 			case XDP_TX:
-				nfp_net_tx_xdp_buf(nn, rx_ring, tx_ring, rxbuf,
-						   pkt_off, pkt_len);
+				if (unlikely(!nfp_net_tx_xdp_buf(nn, rx_ring,
+								 tx_ring, rxbuf,
+								 pkt_off, pkt_len)))
+					trace_xdp_exception(nn->netdev, xdp_prog, act);
 				continue;
 			default:
 				bpf_warn_invalid_xdp_action(act);
 			case XDP_ABORTED:
+				trace_xdp_exception(nn->netdev, xdp_prog, act);
 			case XDP_DROP:
 				nfp_net_rx_give_one(rx_ring, rxbuf->frag,
 						    rxbuf->dma_addr);