samples, bpf: Refactor kprobe tracing user progs with libbpf

Currently, the kprobe BPF program attachment method for bpf_load is
quite old. The implementation of bpf_load "directly" controls and
manages(create, delete) the kprobe events of DEBUGFS. On the other hand,
using using the libbpf automatically manages the kprobe event.
(under bpf_link interface)

By calling bpf_program__attach(_kprobe) in libbpf, the corresponding
kprobe is created and the BPF program will be attached to this kprobe.
To remove this, by simply invoking bpf_link__destroy will clean up the
event.

This commit refactors kprobe tracing programs (tracex{1~7}_user.c) with
libbpf using bpf_link interface and bpf_program__attach.

tracex2_kern.c, which tracks system calls (sys_*), has been modified to
append prefix depending on architecture.

Signed-off-by: Daniel T. Lee <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Yonghong Song <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

samples/bpf/Makefile

···
 sockex1-objs := sockex1_user.o
 sockex2-objs := sockex2_user.o
 sockex3-objs := bpf_load.o sockex3_user.o
-tracex1-objs := bpf_load.o tracex1_user.o $(TRACE_HELPERS)
-tracex2-objs := bpf_load.o tracex2_user.o
-tracex3-objs := bpf_load.o tracex3_user.o
-tracex4-objs := bpf_load.o tracex4_user.o
+tracex1-objs := tracex1_user.o $(TRACE_HELPERS)
+tracex2-objs := tracex2_user.o
+tracex3-objs := tracex3_user.o
+tracex4-objs := tracex4_user.o
 tracex5-objs := bpf_load.o tracex5_user.o $(TRACE_HELPERS)
-tracex6-objs := bpf_load.o tracex6_user.o
-tracex7-objs := bpf_load.o tracex7_user.o
+tracex6-objs := tracex6_user.o
+tracex7-objs := tracex7_user.o
 test_probe_write_user-objs := bpf_load.o test_probe_write_user_user.o
 trace_output-objs := bpf_load.o trace_output_user.o $(TRACE_HELPERS)
 lathist-objs := bpf_load.o lathist_user.o

samples/bpf/trace_common.h

···
+// SPDX-License-Identifier: GPL-2.0
+#ifndef __TRACE_COMMON_H
+#define __TRACE_COMMON_H
+
+#ifdef __x86_64__
+#define SYSCALL(SYS) "__x64_" __stringify(SYS)
+#elif defined(__s390x__)
+#define SYSCALL(SYS) "__s390x_" __stringify(SYS)
+#else
+#define SYSCALL(SYS)  __stringify(SYS)
+#endif
+
+#endif

samples/bpf/tracex1_user.c

···
 // SPDX-License-Identifier: GPL-2.0
 #include <stdio.h>
-#include <linux/bpf.h>
 #include <unistd.h>
-#include <bpf/bpf.h>
-#include "bpf_load.h"
+#include <bpf/libbpf.h>
 #include "trace_helpers.h"
 
 int main(int ac, char **argv)
 {
-	FILE *f;
+	struct bpf_link *link = NULL;
+	struct bpf_program *prog;
+	struct bpf_object *obj;
 	char filename[256];
+	FILE *f;
 
 	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 0;
+	}
 
-	if (load_bpf_file(filename)) {
-		printf("%s", bpf_log_buf);
-		return 1;
+	prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
+	if (!prog) {
+		fprintf(stderr, "ERROR: finding a prog in obj file failed\n");
+		goto cleanup;
+	}
+
+	/* load BPF program */
+	if (bpf_object__load(obj)) {
+		fprintf(stderr, "ERROR: loading BPF object file failed\n");
+		goto cleanup;
+	}
+
+	link = bpf_program__attach(prog);
+	if (libbpf_get_error(link)) {
+		fprintf(stderr, "ERROR: bpf_program__attach failed\n");
+		link = NULL;
+		goto cleanup;
 	}
 
 	f = popen("taskset 1 ping -c5 localhost", "r");
···
 
 	read_trace_pipe();
 
+cleanup:
+	bpf_link__destroy(link);
+	bpf_object__close(obj);
 	return 0;
 }

samples/bpf/tracex2_kern.c

···
 #include <uapi/linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
+#include "trace_common.h"
 
 struct bpf_map_def SEC("maps") my_map = {
 	.type = BPF_MAP_TYPE_HASH,
···
 	.max_entries = 1024,
 };
 
-SEC("kprobe/sys_write")
+SEC("kprobe/" SYSCALL(sys_write))
 int bpf_prog3(struct pt_regs *ctx)
 {
 	long write_size = PT_REGS_PARM3(ctx);

samples/bpf/tracex2_user.c

···
 #include <unistd.h>
 #include <stdlib.h>
 #include <signal.h>
-#include <linux/bpf.h>
 #include <string.h>
 #include <sys/resource.h>
 
 #include <bpf/bpf.h>
-#include "bpf_load.h"
+#include <bpf/libbpf.h>
 #include "bpf_util.h"
 
 #define MAX_INDEX	64
 #define MAX_STARS	38
+
+/* my_map, my_hist_map */
+static int map_fd[2];
 
 static void stars(char *str, long val, long max, int width)
 {
···
 int main(int ac, char **argv)
 {
 	struct rlimit r = {1024*1024, RLIM_INFINITY};
-	char filename[256];
 	long key, next_key, value;
+	struct bpf_link *links[2];
+	struct bpf_program *prog;
+	struct bpf_object *obj;
+	char filename[256];
+	int i, j = 0;
 	FILE *f;
-	int i;
-
-	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
 
 	if (setrlimit(RLIMIT_MEMLOCK, &r)) {
 		perror("setrlimit(RLIMIT_MEMLOCK)");
 		return 1;
+	}
+
+	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 0;
+	}
+
+	/* 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, "my_map");
+	map_fd[1] = bpf_object__find_map_fd_by_name(obj, "my_hist_map");
+	if (map_fd[0] < 0 || map_fd[1] < 0) {
+		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
+		goto cleanup;
 	}
 
 	signal(SIGINT, int_exit);
···
 	f = popen("dd if=/dev/zero of=/dev/null count=5000000", "r");
 	(void) f;
 
-	if (load_bpf_file(filename)) {
-		printf("%s", bpf_log_buf);
-		return 1;
+	bpf_object__for_each_program(prog, obj) {
+		links[j] = bpf_program__attach(prog);
+		if (libbpf_get_error(links[j])) {
+			fprintf(stderr, "ERROR: bpf_program__attach failed\n");
+			links[j] = NULL;
+			goto cleanup;
+		}
+		j++;
 	}
 
 	for (i = 0; i < 5; i++) {
···
 	}
 	print_hist(map_fd[1]);
 
+cleanup:
+	for (j--; j >= 0; j--)
+		bpf_link__destroy(links[j]);
+
+	bpf_object__close(obj);
 	return 0;
 }

samples/bpf/tracex3_user.c

···
 #include <unistd.h>
 #include <stdbool.h>
 #include <string.h>
-#include <linux/bpf.h>
 #include <sys/resource.h>
 
 #include <bpf/bpf.h>
-#include "bpf_load.h"
+#include <bpf/libbpf.h>
 #include "bpf_util.h"
 
 #define SLOTS 100
···
 int main(int ac, char **argv)
 {
 	struct rlimit r = {1024*1024, RLIM_INFINITY};
+	struct bpf_link *links[2];
+	struct bpf_program *prog;
+	struct bpf_object *obj;
 	char filename[256];
-	int i;
-
-	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
-
-	if (setrlimit(RLIMIT_MEMLOCK, &r)) {
-		perror("setrlimit(RLIMIT_MEMLOCK)");
-		return 1;
-	}
-
-	if (load_bpf_file(filename)) {
-		printf("%s", bpf_log_buf);
-		return 1;
-	}
+	int map_fd, i, j = 0;
 
 	for (i = 1; i < ac; i++) {
 		if (strcmp(argv[i], "-a") == 0) {
···
 			       "  -t text only\n");
 			return 1;
 		}
+	}
+
+	if (setrlimit(RLIMIT_MEMLOCK, &r)) {
+		perror("setrlimit(RLIMIT_MEMLOCK)");
+		return 1;
+	}
+
+	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 0;
+	}
+
+	/* load BPF program */
+	if (bpf_object__load(obj)) {
+		fprintf(stderr, "ERROR: loading BPF object file failed\n");
+		goto cleanup;
+	}
+
+	map_fd = bpf_object__find_map_fd_by_name(obj, "lat_map");
+	if (map_fd < 0) {
+		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
+		goto cleanup;
+	}
+
+	bpf_object__for_each_program(prog, obj) {
+		links[j] = bpf_program__attach(prog);
+		if (libbpf_get_error(links[j])) {
+			fprintf(stderr, "ERROR: bpf_program__attach failed\n");
+			links[j] = NULL;
+			goto cleanup;
+		}
+		j++;
 	}
 
 	printf("  heatmap of IO latency\n");
···
 	for (i = 0; ; i++) {
 		if (i % 20 == 0)
 			print_banner();
-		print_hist(map_fd[1]);
+		print_hist(map_fd);
 		sleep(2);
 	}
 
+cleanup:
+	for (j--; j >= 0; j--)
+		bpf_link__destroy(links[j]);
+
+	bpf_object__close(obj);
 	return 0;
 }

samples/bpf/tracex4_user.c

···
 #include <stdbool.h>
 #include <string.h>
 #include <time.h>
-#include <linux/bpf.h>
 #include <sys/resource.h>
 
 #include <bpf/bpf.h>
-#include "bpf_load.h"
+#include <bpf/libbpf.h>
 
 struct pair {
 	long long val;
···
 	key = write(1, "\e[1;1H\e[2J", 12); /* clear screen */
 
 	key = -1;
-	while (bpf_map_get_next_key(map_fd[0], &key, &next_key) == 0) {
-		bpf_map_lookup_elem(map_fd[0], &next_key, &v);
+	while (bpf_map_get_next_key(fd, &key, &next_key) == 0) {
+		bpf_map_lookup_elem(fd, &next_key, &v);
 		key = next_key;
 		if (val - v.val < 1000000000ll)
 			/* object was allocated more then 1 sec ago */
···
 int main(int ac, char **argv)
 {
 	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
+	struct bpf_link *links[2];
+	struct bpf_program *prog;
+	struct bpf_object *obj;
 	char filename[256];
-	int i;
-
-	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+	int map_fd, i, j = 0;
 
 	if (setrlimit(RLIMIT_MEMLOCK, &r)) {
 		perror("setrlimit(RLIMIT_MEMLOCK, RLIM_INFINITY)");
 		return 1;
 	}
 
-	if (load_bpf_file(filename)) {
-		printf("%s", bpf_log_buf);
-		return 1;
+	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 0;
+	}
+
+	/* load BPF program */
+	if (bpf_object__load(obj)) {
+		fprintf(stderr, "ERROR: loading BPF object file failed\n");
+		goto cleanup;
+	}
+
+	map_fd = bpf_object__find_map_fd_by_name(obj, "my_map");
+	if (map_fd < 0) {
+		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
+		goto cleanup;
+	}
+
+	bpf_object__for_each_program(prog, obj) {
+		links[j] = bpf_program__attach(prog);
+		if (libbpf_get_error(links[j])) {
+			fprintf(stderr, "ERROR: bpf_program__attach failed\n");
+			links[j] = NULL;
+			goto cleanup;
+		}
+		j++;
 	}
 
 	for (i = 0; ; i++) {
-		print_old_objects(map_fd[1]);
+		print_old_objects(map_fd);
 		sleep(1);
 	}
 
+cleanup:
+	for (j--; j >= 0; j--)
+		bpf_link__destroy(links[j]);
+
+	bpf_object__close(obj);
 	return 0;
 }

samples/bpf/tracex6_user.c

···
 #include <assert.h>
 #include <fcntl.h>
 #include <linux/perf_event.h>
-#include <linux/bpf.h>
 #include <sched.h>
 #include <stdio.h>
 #include <stdlib.h>
···
 #include <sys/wait.h>
 #include <unistd.h>
 
-#include "bpf_load.h"
 #include <bpf/bpf.h>
+#include <bpf/libbpf.h>
 #include "perf-sys.h"
 
 #define SAMPLE_PERIOD  0x7fffffffffffffffULL
+
+/* counters, values, values2 */
+static int map_fd[3];
 
 static void check_on_cpu(int cpu, struct perf_event_attr *attr)
 {
···
 int main(int argc, char **argv)
 {
 	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
+	struct bpf_link *links[2];
+	struct bpf_program *prog;
+	struct bpf_object *obj;
 	char filename[256];
-
-	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+	int i = 0;
 
 	setrlimit(RLIMIT_MEMLOCK, &r);
-	if (load_bpf_file(filename)) {
-		printf("%s", bpf_log_buf);
-		return 1;
+
+	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 0;
+	}
+
+	/* 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, "counters");
+	map_fd[1] = bpf_object__find_map_fd_by_name(obj, "values");
+	map_fd[2] = bpf_object__find_map_fd_by_name(obj, "values2");
+	if (map_fd[0] < 0 || map_fd[1] < 0 || map_fd[2] < 0) {
+		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
+		goto cleanup;
+	}
+
+	bpf_object__for_each_program(prog, obj) {
+		links[i] = bpf_program__attach(prog);
+		if (libbpf_get_error(links[i])) {
+			fprintf(stderr, "ERROR: bpf_program__attach failed\n");
+			links[i] = NULL;
+			goto cleanup;
+		}
+		i++;
 	}
 
 	test_bpf_perf_event();
+
+cleanup:
+	for (i--; i >= 0; i--)
+		bpf_link__destroy(links[i]);
+
+	bpf_object__close(obj);
 	return 0;
 }

samples/bpf/tracex7_user.c

···
 #define _GNU_SOURCE
 
 #include <stdio.h>
-#include <linux/bpf.h>
 #include <unistd.h>
-#include <bpf/bpf.h>
-#include "bpf_load.h"
+#include <bpf/libbpf.h>
 
 int main(int argc, char **argv)
 {
-	FILE *f;
+	struct bpf_link *link = NULL;
+	struct bpf_program *prog;
+	struct bpf_object *obj;
 	char filename[256];
 	char command[256];
-	int ret;
+	int ret = 0;
+	FILE *f;
 
 	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 0;
+	}
 
-	if (load_bpf_file(filename)) {
-		printf("%s", bpf_log_buf);
-		return 1;
+	prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
+	if (!prog) {
+		fprintf(stderr, "ERROR: finding a prog in obj file failed\n");
+		goto cleanup;
+	}
+
+	/* load BPF program */
+	if (bpf_object__load(obj)) {
+		fprintf(stderr, "ERROR: loading BPF object file failed\n");
+		goto cleanup;
+	}
+
+	link = bpf_program__attach(prog);
+	if (libbpf_get_error(link)) {
+		fprintf(stderr, "ERROR: bpf_program__attach failed\n");
+		link = NULL;
+		goto cleanup;
 	}
 
 	snprintf(command, 256, "mount %s tmpmnt/", argv[1]);
 	f = popen(command, "r");
 	ret = pclose(f);
 
+cleanup:
+	bpf_link__destroy(link);
+	bpf_object__close(obj);
 	return ret ? 0 : 1;
 }