samples: bpf: Refactor ibumad program with libbpf

This commit refactors the existing ibumad program with libbpf bpf
loader. Attach/detach of Tracepoint bpf programs has been managed
with the generic bpf_program__attach() and bpf_link__destroy() from
the libbpf.

Also, instead of using the previous BPF MAP definition, this commit
refactors ibumad MAP definition with the new BTF-defined MAP format.

To verify that this bpf program works without an infiniband device,
try loading ib_umad kernel module and test the program as follows:

    # modprobe ib_umad
    # ./ibumad

Moreover, TRACE_HELPERS has been removed from the Makefile since it is
not used on this program.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201124090310.24374-5-danieltimlee@gmail.com

samples/bpf/Makefile

@@ -109,7 +109,7 @@ xsk_fwd-objs := xsk_fwd.o
 xdp_fwd-objs := xdp_fwd_user.o
 task_fd_query-objs := task_fd_query_user.o $(TRACE_HELPERS)
 xdp_sample_pkts-objs := xdp_sample_pkts_user.o $(TRACE_HELPERS)
-ibumad-objs := bpf_load.o ibumad_user.o $(TRACE_HELPERS)
+ibumad-objs := ibumad_user.o
 hbm-objs := hbm.o $(CGROUP_HELPERS)
 
 # Tell kbuild to always build the programs

samples/bpf/ibumad_kern.c

@@ -16,19 +16,19 @@
 #include <bpf/bpf_helpers.h>
 
 
-struct bpf_map_def SEC("maps") read_count = {
-	.type        = BPF_MAP_TYPE_ARRAY,
-	.key_size    = sizeof(u32), /* class; u32 required */
-	.value_size  = sizeof(u64), /* count of mads read */
-	.max_entries = 256, /* Room for all Classes */
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, u32); /* class; u32 required */
+	__type(value, u64); /* count of mads read */
+	__uint(max_entries, 256); /* Room for all Classes */
+} read_count SEC(".maps");
 
-struct bpf_map_def SEC("maps") write_count = {
-	.type        = BPF_MAP_TYPE_ARRAY,
-	.key_size    = sizeof(u32), /* class; u32 required */
-	.value_size  = sizeof(u64), /* count of mads written */
-	.max_entries = 256, /* Room for all Classes */
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, u32); /* class; u32 required */
+	__type(value, u64); /* count of mads written */
+	__uint(max_entries, 256); /* Room for all Classes */
+} write_count SEC(".maps");
 
 #undef DEBUG
 #ifndef DEBUG

samples/bpf/ibumad_user.c

@@ -23,10 +23,15 @@
 #include <getopt.h>
 #include <net/if.h>
 
-#include "bpf_load.h"
+#include <bpf/bpf.h>
 #include "bpf_util.h"
 #include <bpf/libbpf.h>
 
+static struct bpf_link *tp_links[3];
+static struct bpf_object *obj;
+static int map_fd[2];
+static int tp_cnt;
+
 static void dump_counts(int fd)
 {
 	__u32 key;
@@ -53,6 +58,11 @@ static void dump_all_counts(void)
 static void dump_exit(int sig)
 {
 	dump_all_counts();
+	/* Detach tracepoints */
+	while (tp_cnt)
+		bpf_link__destroy(tp_links[--tp_cnt]);
+
+	bpf_object__close(obj);
 	exit(0);
 }
 
@@ -73,19 +83,11 @@ static void usage(char *cmd)
 
 int main(int argc, char **argv)
 {
+	struct bpf_program *prog;
 	unsigned long delay = 5;
+	char filename[256];
 	int longindex = 0;
-	int opt;
-	char bpf_file[256];
-
-	/* Create the eBPF kernel code path name.
-	 * This follows the pattern of all of the other bpf samples
-	 */
-	snprintf(bpf_file, sizeof(bpf_file), "%s_kern.o", argv[0]);
-
-	/* Do one final dump when exiting */
-	signal(SIGINT, dump_exit);
-	signal(SIGTERM, dump_exit);
+	int opt, err = -1;
 
 	while ((opt = getopt_long(argc, argv, "hd:rSw",
 				  long_options, &longindex)) != -1) {
@@ -107,16 +109,51 @@ int main(int argc, char **argv)
 		}
 	}
 
-	if (load_bpf_file(bpf_file)) {
-		fprintf(stderr, "ERROR: failed to load eBPF from file : %s\n",
-			bpf_file);
-		return 1;
+	/* Do one final dump when exiting */
+	signal(SIGINT, dump_exit);
+	signal(SIGTERM, dump_exit);
+
+	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+	obj = bpf_object__open_file(filename, NULL);
+	if (libbpf_get_error(obj)) {
+		fprintf(stderr, "ERROR: opening BPF object file failed\n");
+		return err;
+	}
+
+	/* load BPF program */
+	if (bpf_object__load(obj)) {
+		fprintf(stderr, "ERROR: loading BPF object file failed\n");
+		goto cleanup;
+	}
+
+	map_fd[0] = bpf_object__find_map_fd_by_name(obj, "read_count");
+	map_fd[1] = bpf_object__find_map_fd_by_name(obj, "write_count");
+	if (map_fd[0] < 0 || map_fd[1] < 0) {
+		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
+		goto cleanup;
+	}
+
+	bpf_object__for_each_program(prog, obj) {
+		tp_links[tp_cnt] = bpf_program__attach(prog);
+		if (libbpf_get_error(tp_links[tp_cnt])) {
+			fprintf(stderr, "ERROR: bpf_program__attach failed\n");
+			tp_links[tp_cnt] = NULL;
+			goto cleanup;
+		}
+		tp_cnt++;
 	}
 
 	while (1) {
 		sleep(delay);
 		dump_all_counts();
 	}
+	err = 0;
 
-	return 0;
+cleanup:
+	/* Detach tracepoints */
+	while (tp_cnt)
+		bpf_link__destroy(tp_links[--tp_cnt]);
+
+	bpf_object__close(obj);
+	return err;
 }