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