samples: bpf: Refactor kprobe tracing programs with libbpf

For the problem of increasing fragmentation of the bpf loader programs,
instead of using bpf_loader.o, which is used in samples/bpf, this
commit refactors the existing kprobe tracing programs with libbbpf
bpf loader.

    - For kprobe events pointing to system calls, the SYSCALL() macro in
    trace_common.h was used.
    - Adding a kprobe event and attaching a bpf program to it was done
    through bpf_program_attach().
    - Instead of using the existing BPF MAP definition, MAP definition
    has been refactored with the new BTF-defined MAP format.

Signed-off-by: Daniel T. Lee <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

samples/bpf/Makefile

@@ -71,11 +71,11 @@ tracex4-objs := tracex4_user.o
 tracex5-objs := tracex5_user.o $(TRACE_HELPERS)
 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
+test_probe_write_user-objs := test_probe_write_user_user.o
+trace_output-objs := trace_output_user.o $(TRACE_HELPERS)
+lathist-objs := lathist_user.o
 offwaketime-objs := bpf_load.o offwaketime_user.o $(TRACE_HELPERS)
-spintest-objs := bpf_load.o spintest_user.o $(TRACE_HELPERS)
+spintest-objs := spintest_user.o $(TRACE_HELPERS)
 map_perf_test-objs := map_perf_test_user.o
 test_overhead-objs := bpf_load.o test_overhead_user.o
 test_cgrp2_array_pin-objs := test_cgrp2_array_pin.o
@@ -86,7 +86,7 @@ xdp1-objs := xdp1_user.o
 # reuse xdp1 source intentionally
 xdp2-objs := xdp1_user.o
 xdp_router_ipv4-objs := xdp_router_ipv4_user.o
-test_current_task_under_cgroup-objs := bpf_load.o $(CGROUP_HELPERS) \
+test_current_task_under_cgroup-objs := $(CGROUP_HELPERS) \
 				       test_current_task_under_cgroup_user.o
 trace_event-objs := trace_event_user.o $(TRACE_HELPERS)
 sampleip-objs := sampleip_user.o $(TRACE_HELPERS)

samples/bpf/lathist_kern.c

@@ -18,12 +18,12 @@
  * trace_preempt_[on|off] tracepoints hooks is not supported.
  */
 
-struct bpf_map_def SEC("maps") my_map = {
-	.type = BPF_MAP_TYPE_ARRAY,
-	.key_size = sizeof(int),
-	.value_size = sizeof(u64),
-	.max_entries = MAX_CPU,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, u64);
+	__uint(max_entries, MAX_CPU);
+} my_map SEC(".maps");
 
 SEC("kprobe/trace_preempt_off")
 int bpf_prog1(struct pt_regs *ctx)
@@ -61,12 +61,12 @@ static unsigned int log2l(unsigned long v)
 		return log2(v);
 }
 
-struct bpf_map_def SEC("maps") my_lat = {
-	.type = BPF_MAP_TYPE_ARRAY,
-	.key_size = sizeof(int),
-	.value_size = sizeof(long),
-	.max_entries = MAX_CPU * MAX_ENTRIES,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, long);
+	__uint(max_entries, MAX_CPU * MAX_ENTRIES);
+} my_lat SEC(".maps");
 
 SEC("kprobe/trace_preempt_on")
 int bpf_prog2(struct pt_regs *ctx)

samples/bpf/lathist_user.c

@@ -6,9 +6,8 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <signal.h>
-#include <linux/bpf.h>
+#include <bpf/libbpf.h>
 #include <bpf/bpf.h>
-#include "bpf_load.h"
 
 #define MAX_ENTRIES	20
 #define MAX_CPU		4
@@ -81,20 +80,51 @@ static void get_data(int fd)
 
 int main(int argc, char **argv)
 {
+	struct bpf_link *links[2];
+	struct bpf_program *prog;
+	struct bpf_object *obj;
 	char filename[256];
+	int map_fd, i = 0;
 
 	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;
+	}
 
-	if (load_bpf_file(filename)) {
-		printf("%s", bpf_log_buf);
-		return 1;
+	map_fd = bpf_object__find_map_fd_by_name(obj, "my_lat");
+	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[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++;
 	}
 
 	while (1) {
-		get_data(map_fd[1]);
+		get_data(map_fd);
 		print_hist();
 		sleep(5);
 	}
 
+cleanup:
+	for (i--; i >= 0; i--)
+		bpf_link__destroy(links[i]);
+
+	bpf_object__close(obj);
 	return 0;
 }

samples/bpf/spintest_kern.c

@@ -12,25 +12,25 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 
-struct bpf_map_def SEC("maps") my_map = {
-	.type = BPF_MAP_TYPE_HASH,
-	.key_size = sizeof(long),
-	.value_size = sizeof(long),
-	.max_entries = 1024,
-};
-struct bpf_map_def SEC("maps") my_map2 = {
-	.type = BPF_MAP_TYPE_PERCPU_HASH,
-	.key_size = sizeof(long),
-	.value_size = sizeof(long),
-	.max_entries = 1024,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, long);
+	__type(value, long);
+	__uint(max_entries, 1024);
+} my_map SEC(".maps");
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_HASH);
+	__uint(key_size, sizeof(long));
+	__uint(value_size, sizeof(long));
+	__uint(max_entries, 1024);
+} my_map2 SEC(".maps");
 
-struct bpf_map_def SEC("maps") stackmap = {
-	.type = BPF_MAP_TYPE_STACK_TRACE,
-	.key_size = sizeof(u32),
-	.value_size = PERF_MAX_STACK_DEPTH * sizeof(u64),
-	.max_entries = 10000,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_STACK_TRACE);
+	__uint(key_size, sizeof(u32));
+	__uint(value_size, PERF_MAX_STACK_DEPTH * sizeof(u64));
+	__uint(max_entries, 10000);
+} stackmap SEC(".maps");
 
 #define PROG(foo) \
 int foo(struct pt_regs *ctx) \

samples/bpf/spintest_user.c

@@ -1,40 +1,77 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <stdio.h>
 #include <unistd.h>
-#include <linux/bpf.h>
 #include <string.h>
 #include <assert.h>
 #include <sys/resource.h>
 #include <bpf/libbpf.h>
-#include "bpf_load.h"
+#include <bpf/bpf.h>
 #include "trace_helpers.h"
 
 int main(int ac, char **argv)
 {
 	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
+	char filename[256], symbol[256];
+	struct bpf_object *obj = NULL;
+	struct bpf_link *links[20];
 	long key, next_key, value;
-	char filename[256];
+	struct bpf_program *prog;
+	int map_fd, i, j = 0;
+	const char *title;
 	struct ksym *sym;
-	int i;
 
-	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
-	setrlimit(RLIMIT_MEMLOCK, &r);
+	if (setrlimit(RLIMIT_MEMLOCK, &r)) {
+		perror("setrlimit(RLIMIT_MEMLOCK)");
+		return 1;
+	}
 
 	if (load_kallsyms()) {
 		printf("failed to process /proc/kallsyms\n");
 		return 2;
 	}
 
-	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");
+		obj = NULL;
+		goto cleanup;
+	}
+
+	/* 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) {
+		title = bpf_program__title(prog, false);
+		if (sscanf(title, "kprobe/%s", symbol) != 1)
+			continue;
+
+		/* Attach prog only when symbol exists */
+		if (ksym_get_addr(symbol)) {
+			links[j] = bpf_program__attach(prog);
+			if (libbpf_get_error(links[j])) {
+				fprintf(stderr, "bpf_program__attach failed\n");
+				links[j] = NULL;
+				goto cleanup;
+			}
+			j++;
+		}
 	}
 
 	for (i = 0; i < 5; i++) {
 		key = 0;
 		printf("kprobing funcs:");
-		while (bpf_map_get_next_key(map_fd[0], &key, &next_key) == 0) {
-			bpf_map_lookup_elem(map_fd[0], &next_key, &value);
+		while (bpf_map_get_next_key(map_fd, &key, &next_key) == 0) {
+			bpf_map_lookup_elem(map_fd, &next_key, &value);
 			assert(next_key == value);
 			sym = ksym_search(value);
 			key = next_key;
@@ -48,10 +85,15 @@ int main(int ac, char **argv)
 		if (key)
 			printf("\n");
 		key = 0;
-		while (bpf_map_get_next_key(map_fd[0], &key, &next_key) == 0)
-			bpf_map_delete_elem(map_fd[0], &next_key);
+		while (bpf_map_get_next_key(map_fd, &key, &next_key) == 0)
+			bpf_map_delete_elem(map_fd, &next_key);
 		sleep(1);
 	}
 
+cleanup:
+	for (j--; j >= 0; j--)
+		bpf_link__destroy(links[j]);
+
+	bpf_object__close(obj);
 	return 0;
 }

samples/bpf/test_current_task_under_cgroup_kern.c

@@ -10,23 +10,24 @@
 #include <linux/version.h>
 #include <bpf/bpf_helpers.h>
 #include <uapi/linux/utsname.h>
+#include "trace_common.h"
 
-struct bpf_map_def SEC("maps") cgroup_map = {
-	.type			= BPF_MAP_TYPE_CGROUP_ARRAY,
-	.key_size		= sizeof(u32),
-	.value_size		= sizeof(u32),
-	.max_entries	= 1,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
+	__uint(key_size, sizeof(u32));
+	__uint(value_size, sizeof(u32));
+	__uint(max_entries, 1);
+} cgroup_map SEC(".maps");
 
-struct bpf_map_def SEC("maps") perf_map = {
-	.type			= BPF_MAP_TYPE_ARRAY,
-	.key_size		= sizeof(u32),
-	.value_size		= sizeof(u64),
-	.max_entries	= 1,
-};
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, u32);
+	__type(value, u64);
+	__uint(max_entries, 1);
+} perf_map SEC(".maps");
 
 /* Writes the last PID that called sync to a map at index 0 */
-SEC("kprobe/sys_sync")
+SEC("kprobe/" SYSCALL(sys_sync))
 int bpf_prog1(struct pt_regs *ctx)
 {
 	u64 pid = bpf_get_current_pid_tgid();

samples/bpf/test_current_task_under_cgroup_user.c

@@ -4,24 +4,54 @@
 
 #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>
 #include "cgroup_helpers.h"
 
 #define CGROUP_PATH		"/my-cgroup"
 
 int main(int argc, char **argv)
 {
 	pid_t remote_pid, local_pid = getpid();
-	int cg2, idx = 0, rc = 0;
+	struct bpf_link *link = NULL;
+	struct bpf_program *prog;
+	int cg2, idx = 0, rc = 1;
+	struct bpf_object *obj;
 	char filename[256];
+	int map_fd[2];
 
 	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
-	if (load_bpf_file(filename)) {
-		printf("%s", bpf_log_buf);
-		return 1;
+	obj = bpf_object__open_file(filename, NULL);
+	if (libbpf_get_error(obj)) {
+		fprintf(stderr, "ERROR: opening BPF object file failed\n");
+		return 0;
+	}
+
+	prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
+	if (!prog) {
+		printf("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;
+	}
+
+	map_fd[0] = bpf_object__find_map_fd_by_name(obj, "cgroup_map");
+	map_fd[1] = bpf_object__find_map_fd_by_name(obj, "perf_map");
+	if (map_fd[0] < 0 || map_fd[1] < 0) {
+		fprintf(stderr, "ERROR: finding a map in obj 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;
 	}
 
 	if (setup_cgroup_environment())
@@ -70,12 +100,14 @@ int main(int argc, char **argv)
 		goto err;
 	}
 
-	goto out;
-err:
-	rc = 1;
+	rc = 0;
 
-out:
+err:
 	close(cg2);
 	cleanup_cgroup_environment();
+
+cleanup:
+	bpf_link__destroy(link);
+	bpf_object__close(obj);
 	return rc;
 }