samples: bpf: Convert xdp_monitor to XDP samples helper

Use the libbpf skeleton facility and other utilities provided by XDP
samples helper.

A lot of the code in xdp_monitor and xdp_redirect_cpu has been moved to
the xdp_sample_user.o helper, so we remove the duplicate functions here
that are no longer needed.

Thanks to BPF skeleton, we no longer depend on order of tracepoints to
uninstall them on startup. Instead, the sample mask is used to install
the needed tracepoints.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210821002010.845777-15-memxor@gmail.com

samples/bpf/Makefile

@@ -43,7 +43,6 @@ tprogs-y += xdp_redirect
 tprogs-y += xdp_redirect_map
 tprogs-y += xdp_redirect_map_multi
 tprogs-y += xdp_redirect_cpu
-tprogs-y += xdp_monitor
 tprogs-y += xdp_rxq_info
 tprogs-y += syscall_tp
 tprogs-y += cpustat
@@ -57,11 +56,14 @@ tprogs-y += xdp_sample_pkts
 tprogs-y += ibumad
 tprogs-y += hbm
 
+tprogs-y += xdp_monitor
+
 # Libbpf dependencies
 LIBBPF = $(TOOLS_PATH)/lib/bpf/libbpf.a
 
 CGROUP_HELPERS := ../../tools/testing/selftests/bpf/cgroup_helpers.o
 TRACE_HELPERS := ../../tools/testing/selftests/bpf/trace_helpers.o
+XDP_SAMPLE := xdp_sample_user.o
 
 fds_example-objs := fds_example.o
 sockex1-objs := sockex1_user.o
@@ -102,7 +104,6 @@ xdp_redirect-objs := xdp_redirect_user.o
 xdp_redirect_map-objs := xdp_redirect_map_user.o
 xdp_redirect_map_multi-objs := xdp_redirect_map_multi_user.o
 xdp_redirect_cpu-objs := xdp_redirect_cpu_user.o
-xdp_monitor-objs := xdp_monitor_user.o
 xdp_rxq_info-objs := xdp_rxq_info_user.o
 syscall_tp-objs := syscall_tp_user.o
 cpustat-objs := cpustat_user.o
@@ -116,6 +117,8 @@ xdp_sample_pkts-objs := xdp_sample_pkts_user.o
 ibumad-objs := ibumad_user.o
 hbm-objs := hbm.o $(CGROUP_HELPERS)
 
+xdp_monitor-objs := xdp_monitor_user.o $(XDP_SAMPLE)
+
 # Tell kbuild to always build the programs
 always-y := $(tprogs-y)
 always-y += sockex1_kern.o
@@ -310,6 +313,8 @@ verify_target_bpf: verify_cmds
 $(BPF_SAMPLES_PATH)/*.c: verify_target_bpf $(LIBBPF)
 $(src)/*.c: verify_target_bpf $(LIBBPF)
 
+$(obj)/xdp_monitor_user.o: $(obj)/xdp_monitor.skel.h
+
 $(obj)/tracex5_kern.o: $(obj)/syscall_nrs.h
 $(obj)/hbm_out_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
 $(obj)/hbm.o: $(src)/hbm.h

samples/bpf/Makefile.target

@@ -73,3 +73,14 @@ quiet_cmd_tprog-cobjs	= CC  $@
       cmd_tprog-cobjs	= $(CC) $(tprogc_flags) -c -o $@ $<
 $(tprog-cobjs): $(obj)/%.o: $(src)/%.c FORCE
 	$(call if_changed_dep,tprog-cobjs)
+
+# Override includes for xdp_sample_user.o because $(srctree)/usr/include in
+# TPROGS_CFLAGS causes conflicts
+XDP_SAMPLE_CFLAGS += -Wall -O2 -lm \
+		     -I./tools/include \
+		     -I./tools/include/uapi \
+		     -I./tools/lib \
+		     -I./tools/testing/selftests/bpf
+$(obj)/xdp_sample_user.o: $(src)/xdp_sample_user.c \
+	$(src)/xdp_sample_user.h $(src)/xdp_sample_shared.h
+	$(CC) $(XDP_SAMPLE_CFLAGS) -c -o $@ $<