chromium/third_party/perfetto/src/tracing/service/packet_stream_validator.cc

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "src/tracing/service/packet_stream_validator.h"

#include <stddef.h>

#include <cinttypes>

#include "perfetto/base/logging.h"
#include "perfetto/ext/base/utils.h"
#include "perfetto/protozero/proto_utils.h"

#include "protos/perfetto/trace/trace_packet.pbzero.h"

namespace perfetto {

namespace {

ProtoWireType;

const uint32_t kReservedFieldIds[] = …;

// This translation unit is quite subtle and perf-sensitive. Remember to check
// BM_PacketStreamValidator in perfetto_benchmarks when making changes.

// Checks that a packet, spread over several slices, is well-formed and doesn't
// contain reserved top-level fields.
// The checking logic is based on a state-machine that skips the fields' payload
// and operates as follows:
//              +-------------------------------+ <-------------------------+
// +----------> | Read field preamble (varint)  | <----------------------+  |
// |            +-------------------------------+                        |  |
// |              |              |            |                          |  |
// |       <Varint>        <Fixed 32/64>     <Length-delimited field>    |  |
// |          V                  |                      V                |  |
// |  +------------------+       |               +--------------+        |  |
// |  | Read field value |       |               | Read length  |        |  |
// |  | (another varint) |       |               |   (varint)   |        |  |
// |  +------------------+       |               +--------------+        |  |
// |           |                 V                      V                |  |
// +-----------+        +----------------+     +-----------------+       |  |
//                      | Skip 4/8 Bytes |     | Skip $len Bytes |-------+  |
//                      +----------------+     +-----------------+          |
//                               |                                          |
//                               +------------------------------------------+
class ProtoFieldParserFSM { … };

}  // namespace

// static
bool PacketStreamValidator::Validate(const Slices& slices) { … }

}  // namespace perfetto