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selftests/bpf: Add test for libbpf's custom log_buf behavior

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Add a selftest that validates that per-program and per-object log_buf
overrides work as expected. Also test same logic for low-level
bpf_prog_load() and bpf_btf_load() APIs.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211209193840.1248570-11-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko 2021-12-09 11:38:38 -08:00
parent dc94121b5c
commit 57e889269a
2 changed files with 300 additions and 0 deletions
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276
tools/testing/selftests/bpf/prog_tests/log_buf.c Normal file
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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Facebook */
#include <test_progs.h>
#include <bpf/btf.h>
#include "test_log_buf.skel.h"
static size_t libbpf_log_pos;
static char libbpf_log_buf[1024 * 1024];
static bool libbpf_log_error;
static int libbpf_print_cb(enum libbpf_print_level level, const char *fmt, va_list args)
{
int emitted_cnt;
size_t left_cnt;
left_cnt = sizeof(libbpf_log_buf) - libbpf_log_pos;
emitted_cnt = vsnprintf(libbpf_log_buf + libbpf_log_pos, left_cnt, fmt, args);
if (emitted_cnt < 0 || emitted_cnt + 1 > left_cnt) {
libbpf_log_error = true;
return 0;
}
libbpf_log_pos += emitted_cnt;
return 0;
}
static void obj_load_log_buf(void)
{
libbpf_print_fn_t old_print_cb = libbpf_set_print(libbpf_print_cb);
LIBBPF_OPTS(bpf_object_open_opts, opts);
const size_t log_buf_sz = 1024 * 1024;
struct test_log_buf* skel;
char *obj_log_buf, *good_log_buf, *bad_log_buf;
int err;
obj_log_buf = malloc(3 * log_buf_sz);
if (!ASSERT_OK_PTR(obj_log_buf, "obj_log_buf"))
return;
good_log_buf = obj_log_buf + log_buf_sz;
bad_log_buf = obj_log_buf + 2 * log_buf_sz;
obj_log_buf[0] = good_log_buf[0] = bad_log_buf[0] = '\0';
opts.kernel_log_buf = obj_log_buf;
opts.kernel_log_size = log_buf_sz;
opts.kernel_log_level = 4; /* for BTF this will turn into 1 */
/* In the first round every prog has its own log_buf, so libbpf logs
* don't have program failure logs
*/
skel = test_log_buf__open_opts(&opts);
if (!ASSERT_OK_PTR(skel, "skel_open"))
goto cleanup;
/* set very verbose level for good_prog so we always get detailed logs */
bpf_program__set_log_buf(skel->progs.good_prog, good_log_buf, log_buf_sz);
bpf_program__set_log_level(skel->progs.good_prog, 2);
bpf_program__set_log_buf(skel->progs.bad_prog, bad_log_buf, log_buf_sz);
/* log_level 0 with custom log_buf means that verbose logs are not
* requested if program load is successful, but libbpf should retry
* with log_level 1 on error and put program's verbose load log into
* custom log_buf
*/
bpf_program__set_log_level(skel->progs.bad_prog, 0);
err = test_log_buf__load(skel);
if (!ASSERT_ERR(err, "unexpected_load_success"))
goto cleanup;
ASSERT_FALSE(libbpf_log_error, "libbpf_log_error");
/* there should be no prog loading log because we specified per-prog log buf */
ASSERT_NULL(strstr(libbpf_log_buf, "-- BEGIN PROG LOAD LOG --"), "unexp_libbpf_log");
ASSERT_OK_PTR(strstr(libbpf_log_buf, "prog 'bad_prog': BPF program load failed"),
"libbpf_log_not_empty");
ASSERT_OK_PTR(strstr(obj_log_buf, "DATASEC license"), "obj_log_not_empty");
ASSERT_OK_PTR(strstr(good_log_buf, "0: R1=ctx(id=0,off=0,imm=0) R10=fp0"),
"good_log_verbose");
ASSERT_OK_PTR(strstr(bad_log_buf, "invalid access to map value, value_size=16 off=16000 size=4"),
"bad_log_not_empty");
if (env.verbosity > VERBOSE_NONE) {
printf("LIBBPF LOG: \n=================\n%s=================\n", libbpf_log_buf);
printf("OBJ LOG: \n=================\n%s=================\n", obj_log_buf);
printf("GOOD_PROG LOG:\n=================\n%s=================\n", good_log_buf);
printf("BAD_PROG LOG:\n=================\n%s=================\n", bad_log_buf);
}
/* reset everything */
test_log_buf__destroy(skel);
obj_log_buf[0] = good_log_buf[0] = bad_log_buf[0] = '\0';
libbpf_log_buf[0] = '\0';
libbpf_log_pos = 0;
libbpf_log_error = false;
/* In the second round we let bad_prog's failure be logged through print callback */
opts.kernel_log_buf = NULL; /* let everything through into print callback */
opts.kernel_log_size = 0;
opts.kernel_log_level = 1;
skel = test_log_buf__open_opts(&opts);
if (!ASSERT_OK_PTR(skel, "skel_open"))
goto cleanup;
/* set normal verbose level for good_prog to check log_level is taken into account */
bpf_program__set_log_buf(skel->progs.good_prog, good_log_buf, log_buf_sz);
bpf_program__set_log_level(skel->progs.good_prog, 1);
err = test_log_buf__load(skel);
if (!ASSERT_ERR(err, "unexpected_load_success"))
goto cleanup;
ASSERT_FALSE(libbpf_log_error, "libbpf_log_error");
/* this time prog loading error should be logged through print callback */
ASSERT_OK_PTR(strstr(libbpf_log_buf, "libbpf: prog 'bad_prog': -- BEGIN PROG LOAD LOG --"),
"libbpf_log_correct");
ASSERT_STREQ(obj_log_buf, "", "obj_log__empty");
ASSERT_STREQ(good_log_buf, "processed 4 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0\n",
"good_log_ok");
ASSERT_STREQ(bad_log_buf, "", "bad_log_empty");
if (env.verbosity > VERBOSE_NONE) {
printf("LIBBPF LOG: \n=================\n%s=================\n", libbpf_log_buf);
printf("OBJ LOG: \n=================\n%s=================\n", obj_log_buf);
printf("GOOD_PROG LOG:\n=================\n%s=================\n", good_log_buf);
printf("BAD_PROG LOG:\n=================\n%s=================\n", bad_log_buf);
}
cleanup:
free(obj_log_buf);
test_log_buf__destroy(skel);
libbpf_set_print(old_print_cb);
}
static void bpf_prog_load_log_buf(void)
{
const struct bpf_insn good_prog_insns[] = {
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
};
const size_t good_prog_insn_cnt = sizeof(good_prog_insns) / sizeof(struct bpf_insn);
const struct bpf_insn bad_prog_insns[] = {
BPF_EXIT_INSN(),
};
size_t bad_prog_insn_cnt = sizeof(bad_prog_insns) / sizeof(struct bpf_insn);
LIBBPF_OPTS(bpf_prog_load_opts, opts);
const size_t log_buf_sz = 1024 * 1024;
char *log_buf;
int fd = -1;
log_buf = malloc(log_buf_sz);
if (!ASSERT_OK_PTR(log_buf, "log_buf_alloc"))
return;
opts.log_buf = log_buf;
opts.log_size = log_buf_sz;
/* with log_level == 0 log_buf shoud stay empty for good prog */
log_buf[0] = '\0';
opts.log_level = 0;
fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, "good_prog", "GPL",
good_prog_insns, good_prog_insn_cnt, &opts);
ASSERT_STREQ(log_buf, "", "good_log_0");
ASSERT_GE(fd, 0, "good_fd1");
if (fd >= 0)
close(fd);
fd = -1;
/* log_level == 2 should always fill log_buf, even for good prog */
log_buf[0] = '\0';
opts.log_level = 2;
fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, "good_prog", "GPL",
good_prog_insns, good_prog_insn_cnt, &opts);
ASSERT_OK_PTR(strstr(log_buf, "0: R1=ctx(id=0,off=0,imm=0) R10=fp0"), "good_log_2");
ASSERT_GE(fd, 0, "good_fd2");
if (fd >= 0)
close(fd);
fd = -1;
/* log_level == 0 should fill log_buf for bad prog */
log_buf[0] = '\0';
opts.log_level = 0;
fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, "bad_prog", "GPL",
bad_prog_insns, bad_prog_insn_cnt, &opts);
ASSERT_OK_PTR(strstr(log_buf, "R0 !read_ok"), "bad_log_0");
ASSERT_LT(fd, 0, "bad_fd");
if (fd >= 0)
close(fd);
fd = -1;
free(log_buf);
}
static void bpf_btf_load_log_buf(void)
{
LIBBPF_OPTS(bpf_btf_load_opts, opts);
const size_t log_buf_sz = 1024 * 1024;
const void *raw_btf_data;
__u32 raw_btf_size;
struct btf *btf;
char *log_buf;
int fd = -1;
btf = btf__new_empty();
if (!ASSERT_OK_PTR(btf, "empty_btf"))
return;
ASSERT_GT(btf__add_int(btf, "int", 4, 0), 0, "int_type");
raw_btf_data = btf__raw_data(btf, &raw_btf_size);
if (!ASSERT_OK_PTR(raw_btf_data, "raw_btf_data_good"))
goto cleanup;
log_buf = malloc(log_buf_sz);
if (!ASSERT_OK_PTR(log_buf, "log_buf_alloc"))
goto cleanup;
opts.log_buf = log_buf;
opts.log_size = log_buf_sz;
/* with log_level == 0 log_buf shoud stay empty for good BTF */
log_buf[0] = '\0';
opts.log_level = 0;
fd = bpf_btf_load(raw_btf_data, raw_btf_size, &opts);
ASSERT_STREQ(log_buf, "", "good_log_0");
ASSERT_GE(fd, 0, "good_fd1");
if (fd >= 0)
close(fd);
fd = -1;
/* log_level == 2 should always fill log_buf, even for good BTF */
log_buf[0] = '\0';
opts.log_level = 2;
fd = bpf_btf_load(raw_btf_data, raw_btf_size, &opts);
printf("LOG_BUF: %s\n", log_buf);
ASSERT_OK_PTR(strstr(log_buf, "magic: 0xeb9f"), "good_log_2");
ASSERT_GE(fd, 0, "good_fd2");
if (fd >= 0)
close(fd);
fd = -1;
/* make BTF bad, add pointer pointing to non-existing type */
ASSERT_GT(btf__add_ptr(btf, 100), 0, "bad_ptr_type");
raw_btf_data = btf__raw_data(btf, &raw_btf_size);
if (!ASSERT_OK_PTR(raw_btf_data, "raw_btf_data_bad"))
goto cleanup;
/* log_level == 0 should fill log_buf for bad BTF */
log_buf[0] = '\0';
opts.log_level = 0;
fd = bpf_btf_load(raw_btf_data, raw_btf_size, &opts);
printf("LOG_BUF: %s\n", log_buf);
ASSERT_OK_PTR(strstr(log_buf, "[2] PTR (anon) type_id=100 Invalid type_id"), "bad_log_0");
ASSERT_LT(fd, 0, "bad_fd");
if (fd >= 0)
close(fd);
fd = -1;
cleanup:
free(log_buf);
btf__free(btf);
}
void test_log_buf(void)
{
if (test__start_subtest("obj_load_log_buf"))
obj_load_log_buf();
if (test__start_subtest("bpf_prog_load_log_buf"))
bpf_prog_load_log_buf();
if (test__start_subtest("bpf_btf_load_log_buf"))
bpf_btf_load_log_buf();
}

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tools/testing/selftests/bpf/progs/test_log_buf.c Normal file
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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Facebook */
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
int a[4];
const volatile int off = 4000;
SEC("raw_tp/sys_enter")
int good_prog(const void *ctx)
{
a[0] = (int)(long)ctx;
return a[1];
}
SEC("raw_tp/sys_enter")
int bad_prog(const void *ctx)
{
/* out of bounds access */
return a[off];
}
char _license[] SEC("license") = "GPL";