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Commit d977ae59 authored by Daniel Borkmann's avatar Daniel Borkmann
Browse files

Merge branch 'bpf-libbpf-relo-fix-and-tests' 



Jesper Dangaard Brouer says:

====================
While playing with using libbpf for the Suricata project, we had
issues LLVM >= 4.0.1 generating ELF files that could not be loaded
with libbpf (tools/lib/bpf/).

During the troubleshooting phase, I wrote a test program and improved
the debugging output in libbpf.  I turned this into a selftests
program, and it also serves as a code example for libbpf in itself.

I discovered that there are at least three ELF load issues with
libbpf.  I left them as TODO comments in (tools/testing/selftests/bpf)
test_libbpf.sh. I've only fixed the load issue with eh_frames, and
other types of relo-section that does not have exec flags.  We can
work on the other issues later.
====================

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parents 69fe98ed e3d91b0c

tools/include/uapi/linux/bpf_common.h

+4 −3
Original line number Diff line number Diff line
@@ -15,9 +15,10 @@ 


/* ld/ldx fields */

#define BPF_SIZE(code)  ((code) & 0x18)

#define		BPF_W		0x00

#define		BPF_H		0x08

#define		BPF_B		0x10

#define		BPF_W		0x00 /* 32-bit */

#define		BPF_H		0x08 /* 16-bit */

#define		BPF_B		0x10 /*  8-bit */

/* eBPF		BPF_DW		0x18    64-bit */

#define BPF_MODE(code)  ((code) & 0xe0)

#define		BPF_IMM		0x00

#define		BPF_ABS		0x20

tools/lib/bpf/libbpf.c

+39 −12
Original line number Diff line number Diff line
@@ -319,8 +319,8 @@ bpf_program__init(void *data, size_t size, char *section_name, int idx, 


	prog->section_name = strdup(section_name);

	if (!prog->section_name) {

		pr_warning("failed to alloc name for prog under section %s\n",

			   section_name);

		pr_warning("failed to alloc name for prog under section(%d) %s\n",

			   idx, section_name);

		goto errout;

	}
@@ -742,6 +742,24 @@ bpf_object__init_maps(struct bpf_object *obj) 
	return 0;

}



static bool section_have_execinstr(struct bpf_object *obj, int idx)

{

	Elf_Scn *scn;

	GElf_Shdr sh;



	scn = elf_getscn(obj->efile.elf, idx);

	if (!scn)

		return false;



	if (gelf_getshdr(scn, &sh) != &sh)

		return false;



	if (sh.sh_flags & SHF_EXECINSTR)

		return true;



	return false;

}



static int bpf_object__elf_collect(struct bpf_object *obj)

{

	Elf *elf = obj->efile.elf;
@@ -763,29 +781,29 @@ static int bpf_object__elf_collect(struct bpf_object *obj) 


		idx++;

		if (gelf_getshdr(scn, &sh) != &sh) {

			pr_warning("failed to get section header from %s\n",

				   obj->path);

			pr_warning("failed to get section(%d) header from %s\n",

				   idx, obj->path);

			err = -LIBBPF_ERRNO__FORMAT;

			goto out;

		}



		name = elf_strptr(elf, ep->e_shstrndx, sh.sh_name);

		if (!name) {

			pr_warning("failed to get section name from %s\n",

				   obj->path);

			pr_warning("failed to get section(%d) name from %s\n",

				   idx, obj->path);

			err = -LIBBPF_ERRNO__FORMAT;

			goto out;

		}



		data = elf_getdata(scn, 0);

		if (!data) {

			pr_warning("failed to get section data from %s(%s)\n",

				   name, obj->path);

			pr_warning("failed to get section(%d) data from %s(%s)\n",

				   idx, name, obj->path);

			err = -LIBBPF_ERRNO__FORMAT;

			goto out;

		}

		pr_debug("section %s, size %ld, link %d, flags %lx, type=%d\n",

			 name, (unsigned long)data->d_size,

		pr_debug("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",

			 idx, name, (unsigned long)data->d_size,

			 (int)sh.sh_link, (unsigned long)sh.sh_flags,

			 (int)sh.sh_type);
@@ -825,6 +843,14 @@ static int bpf_object__elf_collect(struct bpf_object *obj) 
		} else if (sh.sh_type == SHT_REL) {

			void *reloc = obj->efile.reloc;

			int nr_reloc = obj->efile.nr_reloc + 1;

			int sec = sh.sh_info; /* points to other section */



			/* Only do relo for section with exec instructions */

			if (!section_have_execinstr(obj, sec)) {

				pr_debug("skip relo %s(%d) for section(%d)\n",

					 name, idx, sec);

				continue;

			}



			reloc = realloc(reloc,

					sizeof(*obj->efile.reloc) * nr_reloc);
@@ -840,6 +866,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj) 
				obj->efile.reloc[n].shdr = sh;

				obj->efile.reloc[n].data = data;

			}

		} else {

			pr_debug("skip section(%d) %s\n", idx, name);

		}

		if (err)

			goto out;
@@ -1119,8 +1147,7 @@ static int bpf_object__collect_reloc(struct bpf_object *obj) 


		prog = bpf_object__find_prog_by_idx(obj, idx);

		if (!prog) {

			pr_warning("relocation failed: no %d section\n",

				   idx);

			pr_warning("relocation failed: no section(%d)\n", idx);

			return -LIBBPF_ERRNO__RELOC;

		}

tools/testing/selftests/bpf/Makefile

+11 −1
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ endif 
CFLAGS += -Wall -O2 -I$(APIDIR) -I$(LIBDIR) -I$(GENDIR) $(GENFLAGS) -I../../../include

LDLIBS += -lcap -lelf -lrt -lpthread



# Order correspond to 'make run_tests' order

TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \

	test_align test_verifier_log test_dev_cgroup test_tcpbpf_user
@@ -22,15 +23,24 @@ TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test 
	test_l4lb_noinline.o test_xdp_noinline.o test_stacktrace_map.o \

	sample_map_ret0.o test_tcpbpf_kern.o



TEST_PROGS := test_kmod.sh test_xdp_redirect.sh test_xdp_meta.sh \

# Order correspond to 'make run_tests' order

TEST_PROGS := test_kmod.sh \

	test_libbpf.sh \

	test_xdp_redirect.sh \

	test_xdp_meta.sh \

	test_offload.py



# Compile but not part of 'make run_tests'

TEST_GEN_PROGS_EXTENDED = test_libbpf_open



include ../lib.mk



BPFOBJ := $(OUTPUT)/libbpf.a cgroup_helpers.c



$(TEST_GEN_PROGS): $(BPFOBJ)



$(TEST_GEN_PROGS_EXTENDED): $(OUTPUT)/libbpf.a



.PHONY: force



# force a rebuild of BPFOBJ when its dependencies are updated

tools/testing/selftests/bpf/test_libbpf.sh

0 → 100755
+49 −0
Original line number Diff line number Diff line 
#!/bin/sh

# SPDX-License-Identifier: GPL-2.0



export TESTNAME=test_libbpf



# Determine selftest success via shell exit code

exit_handler()

{

	if (( $? == 0 )); then

		echo "selftests: $TESTNAME [PASS]";

	else

		echo "$TESTNAME: failed at file $LAST_LOADED" 1>&2

		echo "selftests: $TESTNAME [FAILED]";

	fi

}



libbpf_open_file()

{

	LAST_LOADED=$1

	if [ -n "$VERBOSE" ]; then

	    ./test_libbpf_open $1

	else

	    ./test_libbpf_open --quiet $1

	fi

}



# Exit script immediately (well catched by trap handler) if any

# program/thing exits with a non-zero status.

set -e



# (Use 'trap -l' to list meaning of numbers)

trap exit_handler 0 2 3 6 9



libbpf_open_file test_l4lb.o



# TODO: fix libbpf to load noinline functions

# [warning] libbpf: incorrect bpf_call opcode

#libbpf_open_file test_l4lb_noinline.o



# TODO: fix test_xdp_meta.c to load with libbpf

# [warning] libbpf: test_xdp_meta.o doesn't provide kernel version

#libbpf_open_file test_xdp_meta.o



# TODO: fix libbpf to handle .eh_frame

# [warning] libbpf: relocation failed: no section(10)

#libbpf_open_file ../../../../samples/bpf/tracex3_kern.o



# Success

exit 0

tools/testing/selftests/bpf/test_libbpf_open.c

0 → 100644
+150 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0

 * Copyright (c) 2018 Jesper Dangaard Brouer, Red Hat Inc.

 */

static const char *__doc__ =

	"Libbpf test program for loading BPF ELF object files";



#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <stdarg.h>

#include <bpf/libbpf.h>

#include <getopt.h>



static const struct option long_options[] = {

	{"help",	no_argument,		NULL, 'h' },

	{"debug",	no_argument,		NULL, 'D' },

	{"quiet",	no_argument,		NULL, 'q' },

	{0, 0, NULL,  0 }

};



static void usage(char *argv[])

{

	int i;



	printf("\nDOCUMENTATION:\n%s\n\n", __doc__);

	printf(" Usage: %s (options-see-below) BPF_FILE\n", argv[0]);

	printf(" Listing options:\n");

	for (i = 0; long_options[i].name != 0; i++) {

		printf(" --%-12s", long_options[i].name);

		printf(" short-option: -%c",

		       long_options[i].val);

		printf("\n");

	}

	printf("\n");

}



#define DEFINE_PRINT_FN(name, enabled) \

static int libbpf_##name(const char *fmt, ...)  	\

{							\

        va_list args;					\

        int ret;					\

							\

        va_start(args, fmt);				\

	if (enabled) {					\

		fprintf(stderr, "[" #name "] ");	\

		ret = vfprintf(stderr, fmt, args);	\

	}						\

        va_end(args);					\

        return ret;					\

}

DEFINE_PRINT_FN(warning, 1)

DEFINE_PRINT_FN(info, 1)

DEFINE_PRINT_FN(debug, 1)



#define EXIT_FAIL_LIBBPF EXIT_FAILURE

#define EXIT_FAIL_OPTION 2



int test_walk_progs(struct bpf_object *obj, bool verbose)

{

	struct bpf_program *prog;

	int cnt = 0;



	bpf_object__for_each_program(prog, obj) {

		cnt++;

		if (verbose)

			printf("Prog (count:%d) section_name: %s\n", cnt,

			       bpf_program__title(prog, false));

	}

	return 0;

}



int test_walk_maps(struct bpf_object *obj, bool verbose)

{

	struct bpf_map *map;

	int cnt = 0;



	bpf_map__for_each(map, obj) {

		cnt++;

		if (verbose)

			printf("Map (count:%d) name: %s\n", cnt,

			       bpf_map__name(map));

	}

	return 0;

}



int test_open_file(char *filename, bool verbose)

{

	struct bpf_object *bpfobj = NULL;

	long err;



	if (verbose)

		printf("Open BPF ELF-file with libbpf: %s\n", filename);



	/* Load BPF ELF object file and check for errors */

	bpfobj = bpf_object__open(filename);

	err = libbpf_get_error(bpfobj);

	if (err) {

		char err_buf[128];

		libbpf_strerror(err, err_buf, sizeof(err_buf));

		if (verbose)

			printf("Unable to load eBPF objects in file '%s': %s\n",

			       filename, err_buf);

		return EXIT_FAIL_LIBBPF;

	}

	test_walk_progs(bpfobj, verbose);

	test_walk_maps(bpfobj, verbose);



	if (verbose)

		printf("Close BPF ELF-file with libbpf: %s\n",

		       bpf_object__name(bpfobj));

	bpf_object__close(bpfobj);



	return 0;

}



int main(int argc, char **argv)

{

	char filename[1024] = { 0 };

	bool verbose = 1;

	int longindex = 0;

	int opt;



	libbpf_set_print(libbpf_warning, libbpf_info, NULL);



	/* Parse commands line args */

	while ((opt = getopt_long(argc, argv, "hDq",

				  long_options, &longindex)) != -1) {

		switch (opt) {

		case 'D':

			libbpf_set_print(libbpf_warning, libbpf_info,

					 libbpf_debug);

			break;

		case 'q': /* Use in scripting mode */

			verbose = 0;

			break;

		case 'h':

		default:

			usage(argv);

			return EXIT_FAIL_OPTION;

		}

	}

	if (optind >= argc) {

		usage(argv);

		printf("ERROR: Expected BPF_FILE argument after options\n");

		return EXIT_FAIL_OPTION;

	}

	snprintf(filename, sizeof(filename), "%s", argv[optind]);



	return test_open_file(filename, verbose);

}