Commit d977ae59 authored by Daniel Borkmann's avatar Daniel Borkmann

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
......@@ -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
......
......@@ -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;
}
......
......@@ -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
......
#!/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
/* 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);
}
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment