1//===- FDRRecordProducer.cpp - XRay FDR Mode Record Producer --------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8#include "llvm/XRay/FDRRecordProducer.h"
9#include "llvm/Support/DataExtractor.h"
10
11#include <cstdint>
12
13namespace llvm {
14namespace xray {
15
16namespace {
17
18// Keep this in sync with the values written in the XRay FDR mode runtime in
19// compiler-rt.
20enum MetadataRecordKinds : uint8_t {
21  NewBufferKind,
22  EndOfBufferKind,
23  NewCPUIdKind,
24  TSCWrapKind,
25  WalltimeMarkerKind,
26  CustomEventMarkerKind,
27  CallArgumentKind,
28  BufferExtentsKind,
29  TypedEventMarkerKind,
30  PidKind,
31  // This is an end marker, used to identify the upper bound for this enum.
32  EnumEndMarker,
33};
34
35Expected<std::unique_ptr<Record>>
36metadataRecordType(const XRayFileHeader &Header, uint8_t T) {
37
38  if (T >= static_cast<uint8_t>(MetadataRecordKinds::EnumEndMarker))
39    return createStringError(std::make_error_code(std::errc::invalid_argument),
40                             "Invalid metadata record type: %d", T);
41  switch (T) {
42  case MetadataRecordKinds::NewBufferKind:
43    return std::make_unique<NewBufferRecord>();
44  case MetadataRecordKinds::EndOfBufferKind:
45    if (Header.Version >= 2)
46      return createStringError(
47          std::make_error_code(std::errc::executable_format_error),
48          "End of buffer records are no longer supported starting version "
49          "2 of the log.");
50    return std::make_unique<EndBufferRecord>();
51  case MetadataRecordKinds::NewCPUIdKind:
52    return std::make_unique<NewCPUIDRecord>();
53  case MetadataRecordKinds::TSCWrapKind:
54    return std::make_unique<TSCWrapRecord>();
55  case MetadataRecordKinds::WalltimeMarkerKind:
56    return std::make_unique<WallclockRecord>();
57  case MetadataRecordKinds::CustomEventMarkerKind:
58    if (Header.Version >= 5)
59      return std::make_unique<CustomEventRecordV5>();
60    return std::make_unique<CustomEventRecord>();
61  case MetadataRecordKinds::CallArgumentKind:
62    return std::make_unique<CallArgRecord>();
63  case MetadataRecordKinds::BufferExtentsKind:
64    return std::make_unique<BufferExtents>();
65  case MetadataRecordKinds::TypedEventMarkerKind:
66    return std::make_unique<TypedEventRecord>();
67  case MetadataRecordKinds::PidKind:
68    return std::make_unique<PIDRecord>();
69  case MetadataRecordKinds::EnumEndMarker:
70    llvm_unreachable("Invalid MetadataRecordKind");
71  }
72  llvm_unreachable("Unhandled MetadataRecordKinds enum value");
73}
74
75constexpr bool isMetadataIntroducer(uint8_t FirstByte) {
76  return FirstByte & 0x01u;
77}
78
79} // namespace
80
81Expected<std::unique_ptr<Record>>
82FileBasedRecordProducer::findNextBufferExtent() {
83  // We seek one byte at a time until we find a suitable buffer extents metadata
84  // record introducer.
85  std::unique_ptr<Record> R;
86  while (!R) {
87    auto PreReadOffset = OffsetPtr;
88    uint8_t FirstByte = E.getU8(&OffsetPtr);
89    if (OffsetPtr == PreReadOffset)
90      return createStringError(
91          std::make_error_code(std::errc::executable_format_error),
92          "Failed reading one byte from offset %" PRId64 ".", OffsetPtr);
93
94    if (isMetadataIntroducer(FirstByte)) {
95      auto LoadedType = FirstByte >> 1;
96      if (LoadedType == MetadataRecordKinds::BufferExtentsKind) {
97        auto MetadataRecordOrErr = metadataRecordType(Header, LoadedType);
98        if (!MetadataRecordOrErr)
99          return MetadataRecordOrErr.takeError();
100
101        R = std::move(MetadataRecordOrErr.get());
102        RecordInitializer RI(E, OffsetPtr);
103        if (auto Err = R->apply(RI))
104          return std::move(Err);
105        return std::move(R);
106      }
107    }
108  }
109  llvm_unreachable("Must always terminate with either an error or a record.");
110}
111
112Expected<std::unique_ptr<Record>> FileBasedRecordProducer::produce() {
113  // First, we set up our result record.
114  std::unique_ptr<Record> R;
115
116  // Before we do any further reading, we should check whether we're at the end
117  // of the current buffer we're been consuming. In FDR logs version >= 3, we
118  // rely on the buffer extents record to determine how many bytes we should be
119  // considering as valid records.
120  if (Header.Version >= 3 && CurrentBufferBytes == 0) {
121    // Find the next buffer extents record.
122    auto BufferExtentsOrError = findNextBufferExtent();
123    if (!BufferExtentsOrError)
124      return joinErrors(
125          BufferExtentsOrError.takeError(),
126          createStringError(
127              std::make_error_code(std::errc::executable_format_error),
128              "Failed to find the next BufferExtents record."));
129
130    R = std::move(BufferExtentsOrError.get());
131    assert(R != nullptr);
132    assert(isa<BufferExtents>(R.get()));
133    auto BE = cast<BufferExtents>(R.get());
134    CurrentBufferBytes = BE->size();
135    return std::move(R);
136  }
137
138  //
139  // At the top level, we read one byte to determine the type of the record to
140  // create. This byte will comprise of the following bits:
141  //
142  //   - offset 0: A '1' indicates a metadata record, a '0' indicates a function
143  //     record.
144  //   - offsets 1-7: For metadata records, this will indicate the kind of
145  //     metadata record should be loaded.
146  //
147  // We read first byte, then create the appropriate type of record to consume
148  // the rest of the bytes.
149  auto PreReadOffset = OffsetPtr;
150  uint8_t FirstByte = E.getU8(&OffsetPtr);
151  if (OffsetPtr == PreReadOffset)
152    return createStringError(
153        std::make_error_code(std::errc::executable_format_error),
154        "Failed reading one byte from offset %" PRId64 ".", OffsetPtr);
155
156  // For metadata records, handle especially here.
157  if (isMetadataIntroducer(FirstByte)) {
158    auto LoadedType = FirstByte >> 1;
159    auto MetadataRecordOrErr = metadataRecordType(Header, LoadedType);
160    if (!MetadataRecordOrErr)
161      return joinErrors(
162          MetadataRecordOrErr.takeError(),
163          createStringError(
164              std::make_error_code(std::errc::executable_format_error),
165              "Encountered an unsupported metadata record (%d) "
166              "at offset %" PRId64 ".",
167              LoadedType, PreReadOffset));
168    R = std::move(MetadataRecordOrErr.get());
169  } else {
170    R = std::make_unique<FunctionRecord>();
171  }
172  RecordInitializer RI(E, OffsetPtr);
173
174  if (auto Err = R->apply(RI))
175    return std::move(Err);
176
177  // If we encountered a BufferExtents record, we should record the remaining
178  // bytes for the current buffer, to determine when we should start ignoring
179  // potentially malformed data and looking for buffer extents records.
180  if (auto BE = dyn_cast<BufferExtents>(R.get())) {
181    CurrentBufferBytes = BE->size();
182  } else if (Header.Version >= 3) {
183    if (OffsetPtr - PreReadOffset > CurrentBufferBytes)
184      return createStringError(
185          std::make_error_code(std::errc::executable_format_error),
186          "Buffer over-read at offset %" PRId64 " (over-read by %" PRId64
187          " bytes); Record Type = %s.",
188          OffsetPtr, (OffsetPtr - PreReadOffset) - CurrentBufferBytes,
189          Record::kindToString(R->getRecordType()).data());
190
191    CurrentBufferBytes -= OffsetPtr - PreReadOffset;
192  }
193  assert(R != nullptr);
194  return std::move(R);
195}
196
197} // namespace xray
198} // namespace llvm
199