On Fri, Dec 6, 2019 at 5:05 AM Eelco Chaudron <echaudro@xxxxxxxxxx> wrote:
>
> Thanks the hint that it should be the jitted arguments solved it… And
> you quick example worked, just in case some one else is playing with it,
> here is my working example:
>
> // SPDX-License-Identifier: GPL-2.0
> #include <linux/bpf.h>
> #include "bpf_helpers.h"
> #include "bpf_trace_helpers.h"
>
> #define bpf_debug(fmt, ...) \
> { \
> char __fmt[] = fmt; \
> bpf_trace_printk(__fmt, sizeof(__fmt), \
> ##__VA_ARGS__); \
> }
>
> struct net_device {
> /* Structure does not need to contain all entries,
> * as "preserve_access_index" will use BTF to fix this... */
> int ifindex;
> } __attribute__((preserve_access_index));
>
> struct xdp_rxq_info {
> /* Structure does not need to contain all entries,
> * as "preserve_access_index" will use BTF to fix this... */
> struct net_device *dev;
> __u32 queue_index;
> } __attribute__((preserve_access_index));
>
> struct xdp_buff {
> void *data;
> void *data_end;
> void *data_meta;
> void *data_hard_start;
> unsigned long handle;
> struct xdp_rxq_info *rxq;
> } __attribute__((preserve_access_index));
>
>
> BPF_TRACE_1("fentry/xdp_prog_simple", trace_on_entry,
> struct xdp_buff *, xdp)
> {
> bpf_debug("fentry: [ifindex = %u, queue = %u]\n",
> xdp->rxq->dev->ifindex, xdp->rxq->queue_index);
> return 0;
> }
>
>
> BPF_TRACE_2("fexit/xdp_prog_simple", trace_on_exit,
> struct xdp_buff*, xdp, int, ret)
> {
> bpf_debug("fexit: [ifindex = %u, queue = %u, ret = %d]\n",
> xdp->rxq->dev->ifindex, xdp->rxq->queue_index, ret);
This is great. Could you submit it as selftests/bpf ?
It will help others trying to do the same.
May be instead of bpf_debug() use global variables so the test will be
self checking ?
Long term we should teach verifier to understand 'struct xdp_md*'
in addition to 'struct xdp_buff *'. That will help ease of use.
