Adding tracing02-xdp-monitor example

In this lesson we will show how to attach to and monitor all
xdp related raw tracepoints and some related info to user space
stat application.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>

Author: olsajiri

tracing02-xdp-monitor/Makefile

@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+
+# Departing from the implicit _user.c scheme
+XDP_TARGETS  := trace_prog_kern
+USER_TARGETS := trace_load_and_stats
+
+LIBBPF_DIR = ../libbpf/src/
+COMMON_DIR = ../common/
+
+include $(COMMON_DIR)/common.mk
+

tracing02-xdp-monitor/README.org

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+# -*- fill-column: 76; -*-
+#+TITLE: Tutorial: Tracing02 - monitor xdp raw tracepoints
+#+OPTIONS: ^:nil
+
+In this lesson we will show how to attach to and monitor all
+xdp related raw tracepoints and some related info to user space
+stat application.
+
+* Table of Contents                                                     :TOC:
+- [[#raw-tracepoint][RAW tracepoints]]
+  - [[#todo][TODO]]
+- [[#assignments][Assignments]]
+  - [[#assignment-1][Assignment 1: Monitor all xdp tracepoints]]
+
+* RAW tracepoints
+
+The RAW tracepoint is eBPF alternative to standard tracepoint,
+which allows attaching eBPF program to tracepoint without the
+perf layer being involved/executed.
+
+The bpf library expects the raw tracepoint eBPF program to be stored
+in a section with following name:
+
+#+begin_example sh
+raw_tracepoint/tracepoint/sys/tracepoint
+#+end_example
+
+where 'sys' is the tracepoint subsystem and 'tracepoint' is
+the tracepoint name, which can be done with following construct:
+
+#+begin_example sh
+SEC("raw_tracepoint/xdp/xdp_exception")
+int trace_xdp_exception(struct xdp_exception_ctx *ctx)
+#+end_example
+
+The libbpf library exports interface to load and attach raw tracepoint
+programs, following call will load every program in the cfg->filename
+object as raw tracepoint programs:
+
+#+begin_example sh
+err = bpf_prog_load(cfg->filename, BPF_PROG_TYPE_RAW_TRACEPOINT, &obj, &bpf_fd));
+#+end_example
+
+You can then iterate through all the programs and attach
+every program to the raw tracepoint:
+
+#+begin_example sh
+bpf_object__for_each_program(prog, obj) {
+	...
+	bpf_fd = bpf_program__fd(prog);
+	...
+	err = bpf_raw_tracepoint_open(tp, bpf_fd);
+	...
+}
+#+end_example
+
+for more details please check load_bpf_and_trace_attach function
+in trace_load_and_stats.c object.
+
+* Assignments
+
+** Assignment 1: Monitor all xdp tracepoints
+
+#+begin_example sh
+$ sudo ./trace_load_and_stats
+XDP-event       CPU:to  pps          drop-pps     extra-info
+XDP_REDIRECT    total   0            0            Success
+XDP_REDIRECT    total   0            0            Error
+Exception       0       0            11           XDP_UNKNOWN
+Exception       1       0            2            XDP_UNKNOWN
+Exception       2       0            36           XDP_UNKNOWN
+Exception       3       0            29           XDP_UNKNOWN
+Exception       4       0            3            XDP_UNKNOWN
+Exception       5       0            8            XDP_UNKNOWN
+Exception       total   0            91           XDP_UNKNOWN
+cpumap-kthread  total   0            0            0          
+devmap-xmit     total   0            0            0.00        
+#+end_example