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1 //===- FileHeaderReader.cpp - XRay File Header Reader --------------------===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8 #include "llvm/XRay/FileHeaderReader.h"
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9
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10 namespace llvm {
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11 namespace xray {
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12
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13 // Populates the FileHeader reference by reading the first 32 bytes of the file.
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14 Expected<XRayFileHeader> readBinaryFormatHeader(DataExtractor &HeaderExtractor,
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15 uint64_t &OffsetPtr) {
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16 // FIXME: Maybe deduce whether the data is little or big-endian using some
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17 // magic bytes in the beginning of the file?
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18
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19 // First 32 bytes of the file will always be the header. We assume a certain
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20 // format here:
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21 //
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22 // (2) uint16 : version
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23 // (2) uint16 : type
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24 // (4) uint32 : bitfield
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25 // (8) uint64 : cycle frequency
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26 // (16) - : padding
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27 XRayFileHeader FileHeader;
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28 auto PreReadOffset = OffsetPtr;
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29 FileHeader.Version = HeaderExtractor.getU16(&OffsetPtr);
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30 if (OffsetPtr == PreReadOffset)
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31 return createStringError(
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32 std::make_error_code(std::errc::invalid_argument),
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33 "Failed reading version from file header at offset %" PRId64 ".",
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34 OffsetPtr);
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35
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36 PreReadOffset = OffsetPtr;
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37 FileHeader.Type = HeaderExtractor.getU16(&OffsetPtr);
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38 if (OffsetPtr == PreReadOffset)
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39 return createStringError(
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40 std::make_error_code(std::errc::invalid_argument),
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41 "Failed reading file type from file header at offset %" PRId64 ".",
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42 OffsetPtr);
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43
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44 PreReadOffset = OffsetPtr;
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45 uint32_t Bitfield = HeaderExtractor.getU32(&OffsetPtr);
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46 if (OffsetPtr == PreReadOffset)
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47 return createStringError(
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48 std::make_error_code(std::errc::invalid_argument),
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49 "Failed reading flag bits from file header at offset %" PRId64 ".",
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50 OffsetPtr);
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51
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52 FileHeader.ConstantTSC = Bitfield & 1uL;
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53 FileHeader.NonstopTSC = Bitfield & 1uL << 1;
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54 PreReadOffset = OffsetPtr;
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55 FileHeader.CycleFrequency = HeaderExtractor.getU64(&OffsetPtr);
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56 if (OffsetPtr == PreReadOffset)
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57 return createStringError(
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58 std::make_error_code(std::errc::invalid_argument),
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59 "Failed reading cycle frequency from file header at offset %" PRId64
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60 ".",
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61 OffsetPtr);
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62
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63 std::memcpy(&FileHeader.FreeFormData,
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64 HeaderExtractor.getData().bytes_begin() + OffsetPtr, 16);
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65
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66 // Manually advance the offset pointer 16 bytes, after getting a raw memcpy
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67 // from the underlying data.
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68 OffsetPtr += 16;
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69 return std::move(FileHeader);
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70 }
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71
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72 } // namespace xray
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73 } // namespace llvm
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