linux/tools/testing/selftests/bpf/prog_tests/verifier_log.c

// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */

#include <test_progs.h>
#include <bpf/btf.h>

#include "test_log_buf.skel.h"


static bool check_prog_load(int prog_fd, bool expect_err, const char *tag)
{
	if (expect_err) {
		if (!ASSERT_LT(prog_fd, 0, tag)) {
			close(prog_fd);
			return false;
		}
	} else /* !expect_err */ {
		if (!ASSERT_GT(prog_fd, 0, tag))
			return false;
	}
	if (prog_fd >= 0)
		close(prog_fd);
	return true;
}

static struct {
	/* strategically placed before others to avoid accidental modification by kernel */
	char filler[16384];
	char buf[16384];
	/* strategically placed after buf[] to catch more accidental corruptions */
	char reference[16384];
} logs;
static const struct bpf_insn *insns;
static size_t insn_cnt;

static int load_prog(struct bpf_prog_load_opts *opts, bool expect_load_error)
{
	int prog_fd;

	prog_fd = bpf_prog_load(BPF_PROG_TYPE_RAW_TRACEPOINT, "log_prog",
				"GPL", insns, insn_cnt, opts);
	check_prog_load(prog_fd, expect_load_error, "prog_load");

	return prog_fd;
}

static void verif_log_subtest(const char *name, bool expect_load_error, int log_level)
{
	LIBBPF_OPTS(bpf_prog_load_opts, opts);
	char *exp_log, prog_name[24], op_name[32];
	struct test_log_buf *skel;
	struct bpf_program *prog;
	size_t fixed_log_sz;
	__u32 log_true_sz_fixed, log_true_sz_rolling;
	int i, mode, err, prog_fd, res;

	skel = test_log_buf__open();
	if (!ASSERT_OK_PTR(skel, "skel_open"))
		return;

	bpf_object__for_each_program(prog, skel->obj) {
		if (strcmp(bpf_program__name(prog), name) == 0)
			bpf_program__set_autoload(prog, true);
		else
			bpf_program__set_autoload(prog, false);
	}

	err = test_log_buf__load(skel);
	if (!expect_load_error && !ASSERT_OK(err, "unexpected_load_failure"))
		goto cleanup;
	if (expect_load_error && !ASSERT_ERR(err, "unexpected_load_success"))
		goto cleanup;

	insns = bpf_program__insns(skel->progs.good_prog);
	insn_cnt = bpf_program__insn_cnt(skel->progs.good_prog);

	opts.log_buf = logs.reference;
	opts.log_size = sizeof(logs.reference);
	opts.log_level = log_level | 8 /* BPF_LOG_FIXED */;
	load_prog(&opts, expect_load_error);

	fixed_log_sz = strlen(logs.reference) + 1;
	if (!ASSERT_GT(fixed_log_sz, 50, "fixed_log_sz"))
		goto cleanup;
	memset(logs.reference + fixed_log_sz, 0, sizeof(logs.reference) - fixed_log_sz);

	/* validate BPF_LOG_FIXED works as verifier log used to work, that is:
	 * we get -ENOSPC and beginning of the full verifier log. This only
	 * works for log_level 2 and log_level 1 + failed program. For log
	 * level 2 we don't reset log at all. For log_level 1 + failed program
	 * we don't get to verification stats output. With log level 1
	 * for successful program  final result will be just verifier stats.
	 * But if provided too short log buf, kernel will NULL-out log->ubuf
	 * and will stop emitting further log. This means we'll never see
	 * predictable verifier stats.
	 * Long story short, we do the following -ENOSPC test only for
	 * predictable combinations.
	 */
	if (log_level >= 2 || expect_load_error) {
		opts.log_buf = logs.buf;
		opts.log_level = log_level | 8; /* fixed-length log */
		opts.log_size = 25;

		prog_fd = bpf_prog_load(BPF_PROG_TYPE_RAW_TRACEPOINT, "log_fixed25",
					"GPL", insns, insn_cnt, &opts);
		if (!ASSERT_EQ(prog_fd, -ENOSPC, "unexpected_log_fixed_prog_load_result")) {
			if (prog_fd >= 0)
				close(prog_fd);
			goto cleanup;
		}
		if (!ASSERT_EQ(strlen(logs.buf), 24, "log_fixed_25"))
			goto cleanup;
		if (!ASSERT_STRNEQ(logs.buf, logs.reference, 24, "log_fixed_contents_25"))
			goto cleanup;
	}

	/* validate rolling verifier log logic: try all variations of log buf
	 * length to force various truncation scenarios
	 */
	opts.log_buf = logs.buf;

	/* rotating mode, then fixed mode */
	for (mode = 1; mode >= 0; mode--) {
		/* prefill logs.buf with 'A's to detect any write beyond allowed length */
		memset(logs.filler, 'A', sizeof(logs.filler));
		logs.filler[sizeof(logs.filler) - 1] = '\0';
		memset(logs.buf, 'A', sizeof(logs.buf));
		logs.buf[sizeof(logs.buf) - 1] = '\0';

		for (i = 1; i < fixed_log_sz; i++) {
			opts.log_size = i;
			opts.log_level = log_level | (mode ? 0 : 8 /* BPF_LOG_FIXED */);

			snprintf(prog_name, sizeof(prog_name),
				 "log_%s_%d", mode ? "roll" : "fixed", i);
			prog_fd = bpf_prog_load(BPF_PROG_TYPE_RAW_TRACEPOINT, prog_name,
						"GPL", insns, insn_cnt, &opts);

			snprintf(op_name, sizeof(op_name),
				 "log_%s_prog_load_%d", mode ? "roll" : "fixed", i);
			if (!ASSERT_EQ(prog_fd, -ENOSPC, op_name)) {
				if (prog_fd >= 0)
					close(prog_fd);
				goto cleanup;
			}

			snprintf(op_name, sizeof(op_name),
				 "log_%s_strlen_%d", mode ? "roll" : "fixed", i);
			ASSERT_EQ(strlen(logs.buf), i - 1, op_name);

			if (mode)
				exp_log = logs.reference + fixed_log_sz - i;
			else
				exp_log = logs.reference;

			snprintf(op_name, sizeof(op_name),
				 "log_%s_contents_%d", mode ? "roll" : "fixed", i);
			if (!ASSERT_STRNEQ(logs.buf, exp_log, i - 1, op_name)) {
				printf("CMP:%d\nS1:'%s'\nS2:'%s'\n",
					strncmp(logs.buf, exp_log, i - 1),
					logs.buf, exp_log);
				goto cleanup;
			}

			/* check that unused portions of logs.buf is not overwritten */
			snprintf(op_name, sizeof(op_name),
				 "log_%s_unused_%d", mode ? "roll" : "fixed", i);
			if (!ASSERT_STREQ(logs.buf + i, logs.filler + i, op_name)) {
				printf("CMP:%d\nS1:'%s'\nS2:'%s'\n",
					strcmp(logs.buf + i, logs.filler + i),
					logs.buf + i, logs.filler + i);
				goto cleanup;
			}
		}
	}

	/* (FIXED) get actual log size */
	opts.log_buf = logs.buf;
	opts.log_level = log_level | 8; /* BPF_LOG_FIXED */
	opts.log_size = sizeof(logs.buf);
	opts.log_true_size = 0;
	res = load_prog(&opts, expect_load_error);
	ASSERT_NEQ(res, -ENOSPC, "prog_load_res_fixed");

	log_true_sz_fixed = opts.log_true_size;
	ASSERT_GT(log_true_sz_fixed, 0, "log_true_sz_fixed");

	/* (FIXED, NULL) get actual log size */
	opts.log_buf = NULL;
	opts.log_level = log_level | 8; /* BPF_LOG_FIXED */
	opts.log_size = 0;
	opts.log_true_size = 0;
	res = load_prog(&opts, expect_load_error);
	ASSERT_NEQ(res, -ENOSPC, "prog_load_res_fixed_null");
	ASSERT_EQ(opts.log_true_size, log_true_sz_fixed, "log_sz_fixed_null_eq");

	/* (ROLLING) get actual log size */
	opts.log_buf = logs.buf;
	opts.log_level = log_level;
	opts.log_size = sizeof(logs.buf);
	opts.log_true_size = 0;
	res = load_prog(&opts, expect_load_error);
	ASSERT_NEQ(res, -ENOSPC, "prog_load_res_rolling");

	log_true_sz_rolling = opts.log_true_size;
	ASSERT_EQ(log_true_sz_rolling, log_true_sz_fixed, "log_true_sz_eq");

	/* (ROLLING, NULL) get actual log size */
	opts.log_buf = NULL;
	opts.log_level = log_level;
	opts.log_size = 0;
	opts.log_true_size = 0;
	res = load_prog(&opts, expect_load_error);
	ASSERT_NEQ(res, -ENOSPC, "prog_load_res_rolling_null");
	ASSERT_EQ(opts.log_true_size, log_true_sz_rolling, "log_true_sz_null_eq");

	/* (FIXED) expect -ENOSPC for one byte short log */
	opts.log_buf = logs.buf;
	opts.log_level = log_level | 8; /* BPF_LOG_FIXED */
	opts.log_size = log_true_sz_fixed - 1;
	opts.log_true_size = 0;
	res = load_prog(&opts, true /* should fail */);
	ASSERT_EQ(res, -ENOSPC, "prog_load_res_too_short_fixed");

	/* (FIXED) expect *not* -ENOSPC with exact log_true_size buffer */
	opts.log_buf = logs.buf;
	opts.log_level = log_level | 8; /* BPF_LOG_FIXED */
	opts.log_size = log_true_sz_fixed;
	opts.log_true_size = 0;
	res = load_prog(&opts, expect_load_error);
	ASSERT_NEQ(res, -ENOSPC, "prog_load_res_just_right_fixed");

	/* (ROLLING) expect -ENOSPC for one byte short log */
	opts.log_buf = logs.buf;
	opts.log_level = log_level;
	opts.log_size = log_true_sz_rolling - 1;
	res = load_prog(&opts, true /* should fail */);
	ASSERT_EQ(res, -ENOSPC, "prog_load_res_too_short_rolling");

	/* (ROLLING) expect *not* -ENOSPC with exact log_true_size buffer */
	opts.log_buf = logs.buf;
	opts.log_level = log_level;
	opts.log_size = log_true_sz_rolling;
	opts.log_true_size = 0;
	res = load_prog(&opts, expect_load_error);
	ASSERT_NEQ(res, -ENOSPC, "prog_load_res_just_right_rolling");

cleanup:
	test_log_buf__destroy(skel);
}

static const void *btf_data;
static u32 btf_data_sz;

static int load_btf(struct bpf_btf_load_opts *opts, bool expect_err)
{
	int fd;

	fd = bpf_btf_load(btf_data, btf_data_sz, opts);
	if (fd >= 0)
		close(fd);
	if (expect_err)
		ASSERT_LT(fd, 0, "btf_load_failure");
	else /* !expect_err */
		ASSERT_GT(fd, 0, "btf_load_success");
	return fd;
}

static void verif_btf_log_subtest(bool bad_btf)
{
	LIBBPF_OPTS(bpf_btf_load_opts, opts);
	struct btf *btf;
	struct btf_type *t;
	char *exp_log, op_name[32];
	size_t fixed_log_sz;
	__u32 log_true_sz_fixed, log_true_sz_rolling;
	int i, res;

	/* prepare simple BTF contents */
	btf = btf__new_empty();
	if (!ASSERT_OK_PTR(btf, "btf_new_empty"))
		return;
	res = btf__add_int(btf, "whatever", 4, 0);
	if (!ASSERT_GT(res, 0, "btf_add_int_id"))
		goto cleanup;
	if (bad_btf) {
		/* btf__add_int() doesn't allow bad value of size, so we'll just
		 * force-cast btf_type pointer and manually override size to invalid
		 * 3 if we need to simulate failure
		 */
		t = (void *)btf__type_by_id(btf, res);
		if (!ASSERT_OK_PTR(t, "int_btf_type"))
			goto cleanup;
		t->size = 3;
	}

	btf_data = btf__raw_data(btf, &btf_data_sz);
	if (!ASSERT_OK_PTR(btf_data, "btf_data"))
		goto cleanup;

	load_btf(&opts, bad_btf);

	opts.log_buf = logs.reference;
	opts.log_size = sizeof(logs.reference);
	opts.log_level = 1 | 8 /* BPF_LOG_FIXED */;
	load_btf(&opts, bad_btf);

	fixed_log_sz = strlen(logs.reference) + 1;
	if (!ASSERT_GT(fixed_log_sz, 50, "fixed_log_sz"))
		goto cleanup;
	memset(logs.reference + fixed_log_sz, 0, sizeof(logs.reference) - fixed_log_sz);

	/* validate BPF_LOG_FIXED truncation works as verifier log used to work */
	opts.log_buf = logs.buf;
	opts.log_level = 1 | 8; /* fixed-length log */
	opts.log_size = 25;
	res = load_btf(&opts, true);
	ASSERT_EQ(res, -ENOSPC, "half_log_fd");
	ASSERT_EQ(strlen(logs.buf), 24, "log_fixed_25");
	ASSERT_STRNEQ(logs.buf, logs.reference, 24, op_name);

	/* validate rolling verifier log logic: try all variations of log buf
	 * length to force various truncation scenarios
	 */
	opts.log_buf = logs.buf;
	opts.log_level = 1; /* rolling log */

	/* prefill logs.buf with 'A's to detect any write beyond allowed length */
	memset(logs.filler, 'A', sizeof(logs.filler));
	logs.filler[sizeof(logs.filler) - 1] = '\0';
	memset(logs.buf, 'A', sizeof(logs.buf));
	logs.buf[sizeof(logs.buf) - 1] = '\0';

	for (i = 1; i < fixed_log_sz; i++) {
		opts.log_size = i;

		snprintf(op_name, sizeof(op_name), "log_roll_btf_load_%d", i);
		res = load_btf(&opts, true);
		if (!ASSERT_EQ(res, -ENOSPC, op_name))
			goto cleanup;

		exp_log = logs.reference + fixed_log_sz - i;
		snprintf(op_name, sizeof(op_name), "log_roll_contents_%d", i);
		if (!ASSERT_STREQ(logs.buf, exp_log, op_name)) {
			printf("CMP:%d\nS1:'%s'\nS2:'%s'\n",
				strcmp(logs.buf, exp_log),
				logs.buf, exp_log);
			goto cleanup;
		}

		/* check that unused portions of logs.buf are not overwritten */
		snprintf(op_name, sizeof(op_name), "log_roll_unused_tail_%d", i);
		if (!ASSERT_STREQ(logs.buf + i, logs.filler + i, op_name)) {
			printf("CMP:%d\nS1:'%s'\nS2:'%s'\n",
				strcmp(logs.buf + i, logs.filler + i),
				logs.buf + i, logs.filler + i);
			goto cleanup;
		}
	}

	/* (FIXED) get actual log size */
	opts.log_buf = logs.buf;
	opts.log_level = 1 | 8; /* BPF_LOG_FIXED */
	opts.log_size = sizeof(logs.buf);
	opts.log_true_size = 0;
	res = load_btf(&opts, bad_btf);
	ASSERT_NEQ(res, -ENOSPC, "btf_load_res_fixed");

	log_true_sz_fixed = opts.log_true_size;
	ASSERT_GT(log_true_sz_fixed, 0, "log_true_sz_fixed");

	/* (FIXED, NULL) get actual log size */
	opts.log_buf = NULL;
	opts.log_level = 1 | 8; /* BPF_LOG_FIXED */
	opts.log_size = 0;
	opts.log_true_size = 0;
	res = load_btf(&opts, bad_btf);
	ASSERT_NEQ(res, -ENOSPC, "btf_load_res_fixed_null");
	ASSERT_EQ(opts.log_true_size, log_true_sz_fixed, "log_sz_fixed_null_eq");

	/* (ROLLING) get actual log size */
	opts.log_buf = logs.buf;
	opts.log_level = 1;
	opts.log_size = sizeof(logs.buf);
	opts.log_true_size = 0;
	res = load_btf(&opts, bad_btf);
	ASSERT_NEQ(res, -ENOSPC, "btf_load_res_rolling");

	log_true_sz_rolling = opts.log_true_size;
	ASSERT_EQ(log_true_sz_rolling, log_true_sz_fixed, "log_true_sz_eq");

	/* (ROLLING, NULL) get actual log size */
	opts.log_buf = NULL;
	opts.log_level = 1;
	opts.log_size = 0;
	opts.log_true_size = 0;
	res = load_btf(&opts, bad_btf);
	ASSERT_NEQ(res, -ENOSPC, "btf_load_res_rolling_null");
	ASSERT_EQ(opts.log_true_size, log_true_sz_rolling, "log_true_sz_null_eq");

	/* (FIXED) expect -ENOSPC for one byte short log */
	opts.log_buf = logs.buf;
	opts.log_level = 1 | 8; /* BPF_LOG_FIXED */
	opts.log_size = log_true_sz_fixed - 1;
	opts.log_true_size = 0;
	res = load_btf(&opts, true);
	ASSERT_EQ(res, -ENOSPC, "btf_load_res_too_short_fixed");

	/* (FIXED) expect *not* -ENOSPC with exact log_true_size buffer */
	opts.log_buf = logs.buf;
	opts.log_level = 1 | 8; /* BPF_LOG_FIXED */
	opts.log_size = log_true_sz_fixed;
	opts.log_true_size = 0;
	res = load_btf(&opts, bad_btf);
	ASSERT_NEQ(res, -ENOSPC, "btf_load_res_just_right_fixed");

	/* (ROLLING) expect -ENOSPC for one byte short log */
	opts.log_buf = logs.buf;
	opts.log_level = 1;
	opts.log_size = log_true_sz_rolling - 1;
	res = load_btf(&opts, true);
	ASSERT_EQ(res, -ENOSPC, "btf_load_res_too_short_rolling");

	/* (ROLLING) expect *not* -ENOSPC with exact log_true_size buffer */
	opts.log_buf = logs.buf;
	opts.log_level = 1;
	opts.log_size = log_true_sz_rolling;
	opts.log_true_size = 0;
	res = load_btf(&opts, bad_btf);
	ASSERT_NEQ(res, -ENOSPC, "btf_load_res_just_right_rolling");

cleanup:
	btf__free(btf);
}

void test_verifier_log(void)
{
	if (test__start_subtest("good_prog-level1"))
		verif_log_subtest("good_prog", false, 1);
	if (test__start_subtest("good_prog-level2"))
		verif_log_subtest("good_prog", false, 2);
	if (test__start_subtest("bad_prog-level1"))
		verif_log_subtest("bad_prog", true, 1);
	if (test__start_subtest("bad_prog-level2"))
		verif_log_subtest("bad_prog", true, 2);
	if (test__start_subtest("bad_btf"))
		verif_btf_log_subtest(true /* bad btf */);
	if (test__start_subtest("good_btf"))
		verif_btf_log_subtest(false /* !bad btf */);
}