Commit bc1a8597 authored by Daniel T. Lee's avatar Daniel T. Lee Committed by Daniel Borkmann
Browse files

samples, bpf: Refactor tail call user progs with libbpf 



BPF tail call uses the BPF_MAP_TYPE_PROG_ARRAY type map for calling
into other BPF programs and this PROG_ARRAY should be filled prior to
use. Currently, samples with the PROG_ARRAY type MAP fill this program
array with bpf_load. For bpf_load to fill this map, kernel BPF program
must specify the section with specific format of <prog_type>/<array_idx>
(e.g. SEC("socket/0"))

But by using libbpf instead of bpf_load, user program can specify which
programs should be added to PROG_ARRAY. The advantage of this approach
is that you can selectively add only the programs you want, rather than
adding all of them to PROG_ARRAY, and it's much more intuitive than the
traditional approach.

This commit refactors user programs with the PROG_ARRAY type MAP with
libbpf instead of using bpf_load.

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/20200516040608.1377876-4-danieltimlee@gmail.com
parent 63841bc0

samples/bpf/Makefile

+2 −2
Original line number Diff line number Diff line
@@ -63,12 +63,12 @@ TRACE_HELPERS := ../../tools/testing/selftests/bpf/trace_helpers.o 
fds_example-objs := fds_example.o

sockex1-objs := sockex1_user.o

sockex2-objs := sockex2_user.o

sockex3-objs := bpf_load.o sockex3_user.o

sockex3-objs := sockex3_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)

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

samples/bpf/sockex3_user.c

+43 −21
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <stdio.h>

#include <assert.h>

#include <linux/bpf.h>

#include <bpf/bpf.h>

#include "bpf_load.h"

#include <bpf/libbpf.h>

#include "sock_example.h"

#include <unistd.h>

#include <arpa/inet.h>

#include <sys/resource.h>



#define PARSE_IP 3

#define PARSE_IP_PROG_FD (prog_fd[0])

#define PROG_ARRAY_FD (map_fd[0])



struct flow_key_record {

	__be32 src;

	__be32 dst;
@@ -30,31 +25,55 @@ struct pair { 


int main(int argc, char **argv)

{

	int i, sock, key, fd, main_prog_fd, jmp_table_fd, hash_map_fd;

	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};

	struct bpf_program *prog;

	struct bpf_object *obj;

	char filename[256];

	const char *title;

	FILE *f;

	int i, sock, err, id, key = PARSE_IP;

	struct bpf_prog_info info = {};

	uint32_t info_len = sizeof(info);



	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);

	setrlimit(RLIMIT_MEMLOCK, &r);



	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;

	}



	/* load BPF program */

	if (bpf_object__load(obj)) {

		fprintf(stderr, "ERROR: loading BPF object file failed\n");

		goto cleanup;

	}



	jmp_table_fd = bpf_object__find_map_fd_by_name(obj, "jmp_table");

	hash_map_fd = bpf_object__find_map_fd_by_name(obj, "hash_map");

	if (jmp_table_fd < 0 || hash_map_fd < 0) {

		fprintf(stderr, "ERROR: finding a map in obj file failed\n");

		goto cleanup;

	}



	/* Test fd array lookup which returns the id of the bpf_prog */

	err = bpf_obj_get_info_by_fd(PARSE_IP_PROG_FD, &info, &info_len);

	assert(!err);

	err = bpf_map_lookup_elem(PROG_ARRAY_FD, &key, &id);

	assert(!err);

	assert(id == info.id);

	bpf_object__for_each_program(prog, obj) {

		fd = bpf_program__fd(prog);



		title = bpf_program__title(prog, false);

		if (sscanf(title, "socket/%d", &key) != 1) {

			fprintf(stderr, "ERROR: finding prog failed\n");

			goto cleanup;

		}



		if (key == 0)

			main_prog_fd = fd;

		else

			bpf_map_update_elem(jmp_table_fd, &key, &fd, BPF_ANY);

	}



	sock = open_raw_sock("lo");



	assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd[4],

	/* attach BPF program to socket */

	assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &main_prog_fd,

			  sizeof(__u32)) == 0);



	if (argc > 1)
@@ -69,8 +88,8 @@ int main(int argc, char **argv) 


		sleep(1);

		printf("IP     src.port -> dst.port               bytes      packets\n");

		while (bpf_map_get_next_key(map_fd[2], &key, &next_key) == 0) {

			bpf_map_lookup_elem(map_fd[2], &next_key, &value);

		while (bpf_map_get_next_key(hash_map_fd, &key, &next_key) == 0) {

			bpf_map_lookup_elem(hash_map_fd, &next_key, &value);

			printf("%s.%05d -> %s.%05d %12lld %12lld\n",

			       inet_ntoa((struct in_addr){htonl(next_key.src)}),

			       next_key.port16[0],
@@ -80,5 +99,8 @@ int main(int argc, char **argv) 
			key = next_key;

		}

	}



cleanup:

	bpf_object__close(obj);

	return 0;

}

samples/bpf/tracex5_user.c

+58 −8
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <stdio.h>

#include <linux/bpf.h>

#include <stdlib.h>

#include <unistd.h>

#include <linux/filter.h>

#include <linux/seccomp.h>

#include <sys/prctl.h>

#include <bpf/bpf.h>

#include "bpf_load.h"

#include <bpf/libbpf.h>

#include <sys/resource.h>

#include "trace_helpers.h"



#ifdef __mips__

#define	MAX_ENTRIES  6000 /* MIPS n64 syscalls start at 5000 */

#else

#define	MAX_ENTRIES  1024

#endif



/* install fake seccomp program to enable seccomp code path inside the kernel,

 * so that our kprobe attached to seccomp_phase1() can be triggered

 */
@@ -28,16 +34,57 @@ static void install_accept_all_seccomp(void) 


int main(int ac, char **argv)

{

	FILE *f;

	char filename[256];

	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};

	struct bpf_link *link = NULL;

	struct bpf_program *prog;

	struct bpf_object *obj;

	int key, fd, progs_fd;

	char filename[256];

	const char *title;

	FILE *f;



	snprintf(filename, sizeof(filename), "%s_kern.o", argv[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;

	}



	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;

	}



	link = bpf_program__attach(prog);

	if (libbpf_get_error(link)) {

		fprintf(stderr, "ERROR: bpf_program__attach failed\n");

		link = NULL;

		goto cleanup;

	}



	progs_fd = bpf_object__find_map_fd_by_name(obj, "progs");

	if (progs_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);

		/* register only syscalls to PROG_ARRAY */

		if (sscanf(title, "kprobe/%d", &key) != 1)

			continue;



		fd = bpf_program__fd(prog);

		bpf_map_update_elem(progs_fd, &key, &fd, BPF_ANY);

	}



	install_accept_all_seccomp();
@@ -47,5 +94,8 @@ int main(int ac, char **argv) 


	read_trace_pipe();



cleanup:

	bpf_link__destroy(link);

	bpf_object__close(obj);

	return 0;

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE