1 //===- FileHeaderReader.cpp - XRay File Header Reader --------------------===//
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/FileHeaderReader.h"
9
10 namespace llvm {
11 namespace xray {
12
13 // Populates the FileHeader reference by reading the first 32 bytes of the file.
readBinaryFormatHeader(DataExtractor & HeaderExtractor,uint64_t & OffsetPtr)14 Expected<XRayFileHeader> readBinaryFormatHeader(DataExtractor &HeaderExtractor,
15 uint64_t &OffsetPtr) {
16 // FIXME: Maybe deduce whether the data is little or big-endian using some
17 // magic bytes in the beginning of the file?
18
19 // First 32 bytes of the file will always be the header. We assume a certain
20 // format here:
21 //
22 // (2) uint16 : version
23 // (2) uint16 : type
24 // (4) uint32 : bitfield
25 // (8) uint64 : cycle frequency
26 // (16) - : padding
27 XRayFileHeader FileHeader;
28 auto PreReadOffset = OffsetPtr;
29 FileHeader.Version = HeaderExtractor.getU16(&OffsetPtr);
30 if (OffsetPtr == PreReadOffset)
31 return createStringError(
32 std::make_error_code(std::errc::invalid_argument),
33 "Failed reading version from file header at offset %" PRId64 ".",
34 OffsetPtr);
35
36 PreReadOffset = OffsetPtr;
37 FileHeader.Type = HeaderExtractor.getU16(&OffsetPtr);
38 if (OffsetPtr == PreReadOffset)
39 return createStringError(
40 std::make_error_code(std::errc::invalid_argument),
41 "Failed reading file type from file header at offset %" PRId64 ".",
42 OffsetPtr);
43
44 PreReadOffset = OffsetPtr;
45 uint32_t Bitfield = HeaderExtractor.getU32(&OffsetPtr);
46 if (OffsetPtr == PreReadOffset)
47 return createStringError(
48 std::make_error_code(std::errc::invalid_argument),
49 "Failed reading flag bits from file header at offset %" PRId64 ".",
50 OffsetPtr);
51
52 FileHeader.ConstantTSC = Bitfield & 1uL;
53 FileHeader.NonstopTSC = Bitfield & 1uL << 1;
54 PreReadOffset = OffsetPtr;
55 FileHeader.CycleFrequency = HeaderExtractor.getU64(&OffsetPtr);
56 if (OffsetPtr == PreReadOffset)
57 return createStringError(
58 std::make_error_code(std::errc::invalid_argument),
59 "Failed reading cycle frequency from file header at offset %" PRId64
60 ".",
61 OffsetPtr);
62
63 std::memcpy(&FileHeader.FreeFormData,
64 HeaderExtractor.getData().bytes_begin() + OffsetPtr, 16);
65
66 // Manually advance the offset pointer 16 bytes, after getting a raw memcpy
67 // from the underlying data.
68 OffsetPtr += 16;
69 return std::move(FileHeader);
70 }
71
72 } // namespace xray
73 } // namespace llvm
74