Commit 63841bc0 authored by Daniel T. Lee's avatar Daniel T. Lee Committed by Daniel Borkmann
Browse files

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: default avatarDaniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200516040608.1377876-3-danieltimlee@gmail.com
parent 0efdcefb

samples/bpf/Makefile

+6 −6
Original line number Diff line number Diff line
@@ -64,13 +64,13 @@ fds_example-objs := fds_example.o 
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

0 → 100644
+13 −0
Original line number Diff line number Diff line 
// 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

+30 −7
Original line number Diff line number Diff line 
// 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;

	}



	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;

	}



	if (load_bpf_file(filename)) {

		printf("%s", bpf_log_buf);

		return 1;

	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");
@@ -23,5 +43,8 @@ int main(int ac, char **argv) 


	read_trace_pipe();



cleanup:

	bpf_link__destroy(link);

	bpf_object__close(obj);

	return 0;

}

samples/bpf/tracex2_kern.c

+2 −1
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#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,
@@ -77,7 +78,7 @@ struct bpf_map_def SEC("maps") my_hist_map = { 
	.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

+42 −9
Original line number Diff line number Diff line
@@ -3,17 +3,19 @@ 
#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 i;
@@ -115,18 +117,39 @@ static void int_exit(int sig) 
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);

	signal(SIGTERM, int_exit);
@@ -138,9 +161,14 @@ int main(int ac, char **argv) 
	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++) {
@@ -156,5 +184,10 @@ int main(int ac, char **argv) 
	}

	print_hist(map_fd[1]);



cleanup:

	for (j--; j >= 0; j--)

		bpf_link__destroy(links[j]);



	bpf_object__close(obj);

	return 0;

}

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