diff mbox series

[net-next,1/3] samples/bpf: xdp_monitor first 8 bytes are not accessible by bpf

Message ID 150727930151.4460.3117254071267380300.stgit@firesoul
State Accepted, archived
Delegated to: David Miller
Headers show
Series Improve xdp_monitor samples/bpf | expand

Commit Message

Jesper Dangaard Brouer Oct. 6, 2017, 8:41 a.m. UTC 
The first 8 bytes of the tracepoint context struct are not accessible
by the bpf code.  This is a choice that dates back to the original
inclusion of this code.

See explaination in:
 commit 98b5c2c65c29 ("perf, bpf: allow bpf programs attach to tracepoints")

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 samples/bpf/xdp_monitor_kern.c |   22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

Comments

Alexei Starovoitov Oct. 6, 2017, 4:13 p.m. UTC | #1 
On Fri, Oct 06, 2017 at 10:41:41AM +0200, Jesper Dangaard Brouer wrote:
> The first 8 bytes of the tracepoint context struct are not accessible
> by the bpf code.  This is a choice that dates back to the original
> inclusion of this code.
> 
> See explaination in:
>  commit 98b5c2c65c29 ("perf, bpf: allow bpf programs attach to tracepoints")
> 
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

thank you for fixing it.
Acked-by: Alexei Starovoitov <ast@kernel.org>
diff mbox series

Patch

diff --git a/samples/bpf/xdp_monitor_kern.c b/samples/bpf/xdp_monitor_kern.c
index 74f3fd8ed729..cc7e19d2ad76 100644
--- a/samples/bpf/xdp_monitor_kern.c
+++ b/samples/bpf/xdp_monitor_kern.c
@@ -17,19 +17,15 @@  struct bpf_map_def SEC("maps") redirect_err_cnt = {
  * Code in:                kernel/include/trace/events/xdp.h
  */
 struct xdp_redirect_ctx {
-	unsigned short common_type;	//	offset:0;  size:2; signed:0;
-	unsigned char common_flags;	//	offset:2;  size:1; signed:0;
-	unsigned char common_preempt_count;//	offset:3;  size:1; signed:0;
-	int common_pid;			//	offset:4;  size:4; signed:1;
-
-	int prog_id;			//	offset:8;  size:4; signed:1;
-	u32 act;			//	offset:12  size:4; signed:0;
-	int ifindex;			//	offset:16  size:4; signed:1;
-	int err;			//	offset:20  size:4; signed:1;
-	int to_ifindex;			//	offset:24  size:4; signed:1;
-	u32 map_id;			//	offset:28  size:4; signed:0;
-	int map_index;			//	offset:32  size:4; signed:1;
-};					//	offset:36
+	u64 __pad;		// First 8 bytes are not accessible by bpf code
+	int prog_id;		//	offset:8;  size:4; signed:1;
+	u32 act;		//	offset:12  size:4; signed:0;
+	int ifindex;		//	offset:16  size:4; signed:1;
+	int err;		//	offset:20  size:4; signed:1;
+	int to_ifindex;		//	offset:24  size:4; signed:1;
+	u32 map_id;		//	offset:28  size:4; signed:0;
+	int map_index;		//	offset:32  size:4; signed:1;
+};				//	offset:36
 
 enum {
 	XDP_REDIRECT_SUCCESS = 0,