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samples/bpf: xdp_monitor first 8 bytes are not accessible by bpf 

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 98b5c2c65c ("perf, bpf: allow bpf programs attach to tracepoints")

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jesper Dangaard Brouer 2017-10-06 10:41:41 +02:00 committed by David S. Miller
parent c6a157525b
commit f4ce0a0116
1 changed files with 9 additions and 13 deletions
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22
samples/bpf/xdp_monitor_kern.c
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@ -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,