selftests/bpf: Add fixed vs rotating verifier log tests
Add selftests validating BPF_LOG_FIXED behavior, which used to be the only behavior, and now default rotating BPF verifier log, which returns just up to last N bytes of full verifier log, instead of returning -ENOSPC. To stress test correctness of in-kernel verifier log logic, we force it to truncate program's verifier log to all lengths from 1 all the way to its full size (about 450 bytes today). This was a useful stress test while developing the feature. For both fixed and rotating log modes we expect -ENOSPC if log contents doesn't fit in user-supplied log buffer. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Lorenz Bauer <lmb@isovalent.com> Link: https://lore.kernel.org/bpf/20230406234205.323208-7-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko
Daniel Borkmann
Родитель
d0d75c67c4
Коммит
b1a7a480a1
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@ -0,0 +1,179 @@
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// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
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#include <test_progs.h>
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#include <bpf/btf.h>
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#include "test_log_buf.skel.h"
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static bool check_prog_load(int prog_fd, bool expect_err, const char *tag)
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{
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if (expect_err) {
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if (!ASSERT_LT(prog_fd, 0, tag)) {
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close(prog_fd);
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return false;
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}
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} else /* !expect_err */ {
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if (!ASSERT_GT(prog_fd, 0, tag))
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return false;
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}
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return true;
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}
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static void verif_log_subtest(const char *name, bool expect_load_error, int log_level)
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{
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LIBBPF_OPTS(bpf_prog_load_opts, opts);
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struct {
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/* strategically placed before others to avoid accidental modification by kernel */
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char filler[1024];
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char buf[1024];
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/* strategically placed after buf[] to catch more accidental corruptions */
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char reference[1024];
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} logs;
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char *exp_log, prog_name[16], op_name[32];
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struct test_log_buf *skel;
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struct bpf_program *prog;
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const struct bpf_insn *insns;
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size_t insn_cnt, fixed_log_sz;
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int i, mode, err, prog_fd;
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skel = test_log_buf__open();
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if (!ASSERT_OK_PTR(skel, "skel_open"))
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return;
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bpf_object__for_each_program(prog, skel->obj) {
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if (strcmp(bpf_program__name(prog), name) == 0)
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bpf_program__set_autoload(prog, true);
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else
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bpf_program__set_autoload(prog, false);
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}
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err = test_log_buf__load(skel);
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if (!expect_load_error && !ASSERT_OK(err, "unexpected_load_failure"))
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goto cleanup;
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if (expect_load_error && !ASSERT_ERR(err, "unexpected_load_success"))
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goto cleanup;
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insns = bpf_program__insns(skel->progs.good_prog);
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insn_cnt = bpf_program__insn_cnt(skel->progs.good_prog);
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opts.log_buf = logs.reference;
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opts.log_size = sizeof(logs.reference);
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opts.log_level = log_level | 8 /* BPF_LOG_FIXED */;
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prog_fd = bpf_prog_load(BPF_PROG_TYPE_RAW_TRACEPOINT, "log_fixed",
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"GPL", insns, insn_cnt, &opts);
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if (!check_prog_load(prog_fd, expect_load_error, "fixed_buf_prog_load"))
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goto cleanup;
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close(prog_fd);
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fixed_log_sz = strlen(logs.reference) + 1;
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if (!ASSERT_GT(fixed_log_sz, 50, "fixed_log_sz"))
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goto cleanup;
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memset(logs.reference + fixed_log_sz, 0, sizeof(logs.reference) - fixed_log_sz);
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/* validate BPF_LOG_FIXED works as verifier log used to work, that is:
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* we get -ENOSPC and beginning of the full verifier log. This only
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* works for log_level 2 and log_level 1 + failed program. For log
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* level 2 we don't reset log at all. For log_level 1 + failed program
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* we don't get to verification stats output. With log level 1
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* for successful program final result will be just verifier stats.
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* But if provided too short log buf, kernel will NULL-out log->ubuf
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* and will stop emitting further log. This means we'll never see
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* predictable verifier stats.
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* Long story short, we do the following -ENOSPC test only for
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* predictable combinations.
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*/
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if (log_level >= 2 || expect_load_error) {
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opts.log_buf = logs.buf;
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opts.log_level = log_level | 8; /* fixed-length log */
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opts.log_size = 25;
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prog_fd = bpf_prog_load(BPF_PROG_TYPE_RAW_TRACEPOINT, "log_fixed50",
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"GPL", insns, insn_cnt, &opts);
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if (!ASSERT_EQ(prog_fd, -ENOSPC, "unexpected_log_fixed_prog_load_result")) {
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if (prog_fd >= 0)
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close(prog_fd);
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goto cleanup;
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}
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if (!ASSERT_EQ(strlen(logs.buf), 24, "log_fixed_25"))
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goto cleanup;
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if (!ASSERT_STRNEQ(logs.buf, logs.reference, 24, op_name))
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goto cleanup;
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}
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/* validate rolling verifier log logic: try all variations of log buf
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* length to force various truncation scenarios
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*/
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opts.log_buf = logs.buf;
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/* rotating mode, then fixed mode */
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for (mode = 1; mode >= 0; mode--) {
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/* prefill logs.buf with 'A's to detect any write beyond allowed length */
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memset(logs.filler, 'A', sizeof(logs.filler));
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logs.filler[sizeof(logs.filler) - 1] = '\0';
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memset(logs.buf, 'A', sizeof(logs.buf));
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logs.buf[sizeof(logs.buf) - 1] = '\0';
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for (i = 1; i < fixed_log_sz; i++) {
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opts.log_size = i;
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opts.log_level = log_level | (mode ? 0 : 8 /* BPF_LOG_FIXED */);
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snprintf(prog_name, sizeof(prog_name),
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"log_%s_%d", mode ? "roll" : "fixed", i);
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prog_fd = bpf_prog_load(BPF_PROG_TYPE_RAW_TRACEPOINT, prog_name,
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"GPL", insns, insn_cnt, &opts);
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snprintf(op_name, sizeof(op_name),
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"log_%s_prog_load_%d", mode ? "roll" : "fixed", i);
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if (!ASSERT_EQ(prog_fd, -ENOSPC, op_name)) {
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if (prog_fd >= 0)
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close(prog_fd);
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goto cleanup;
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}
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snprintf(op_name, sizeof(op_name),
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"log_%s_strlen_%d", mode ? "roll" : "fixed", i);
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ASSERT_EQ(strlen(logs.buf), i - 1, op_name);
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if (mode)
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exp_log = logs.reference + fixed_log_sz - i;
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else
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exp_log = logs.reference;
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snprintf(op_name, sizeof(op_name),
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"log_%s_contents_%d", mode ? "roll" : "fixed", i);
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if (!ASSERT_STRNEQ(logs.buf, exp_log, i - 1, op_name)) {
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printf("CMP:%d\nS1:'%s'\nS2:'%s'\n",
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strncmp(logs.buf, exp_log, i - 1),
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logs.buf, exp_log);
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goto cleanup;
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}
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/* check that unused portions of logs.buf is not overwritten */
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snprintf(op_name, sizeof(op_name),
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"log_%s_unused_%d", mode ? "roll" : "fixed", i);
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if (!ASSERT_STREQ(logs.buf + i, logs.filler + i, op_name)) {
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printf("CMP:%d\nS1:'%s'\nS2:'%s'\n",
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strcmp(logs.buf + i, logs.filler + i),
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logs.buf + i, logs.filler + i);
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goto cleanup;
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}
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}
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}
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cleanup:
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test_log_buf__destroy(skel);
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}
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void test_verifier_log(void)
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{
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if (test__start_subtest("good_prog-level1"))
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verif_log_subtest("good_prog", false, 1);
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if (test__start_subtest("good_prog-level2"))
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verif_log_subtest("good_prog", false, 2);
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if (test__start_subtest("bad_prog-level1"))
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verif_log_subtest("bad_prog", true, 1);
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if (test__start_subtest("bad_prog-level2"))
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verif_log_subtest("bad_prog", true, 2);
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}
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