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1 //===-- Decompressor.cpp --------------------------------------------------===//
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2 //
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3 // The LLVM Compiler Infrastructure
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4 //
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5 // This file is distributed under the University of Illinois Open Source
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6 // License. See LICENSE.TXT for details.
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7 //
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8 //===----------------------------------------------------------------------===//
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9
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10 #include "llvm/Object/Decompressor.h"
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11 #include "llvm/BinaryFormat/ELF.h"
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12 #include "llvm/Object/ELFObjectFile.h"
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13 #include "llvm/Support/Compression.h"
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14 #include "llvm/Support/DataExtractor.h"
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15 #include "llvm/Support/Endian.h"
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16
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17 using namespace llvm;
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18 using namespace llvm::support::endian;
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19 using namespace object;
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20
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21 Expected<Decompressor> Decompressor::create(StringRef Name, StringRef Data,
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22 bool IsLE, bool Is64Bit) {
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23 if (!zlib::isAvailable())
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24 return createError("zlib is not available");
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25
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26 Decompressor D(Data);
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27 Error Err = isGnuStyle(Name) ? D.consumeCompressedGnuHeader()
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28 : D.consumeCompressedZLibHeader(Is64Bit, IsLE);
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29 if (Err)
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30 return std::move(Err);
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31 return D;
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32 }
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33
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34 Decompressor::Decompressor(StringRef Data)
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35 : SectionData(Data), DecompressedSize(0) {}
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36
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37 Error Decompressor::consumeCompressedGnuHeader() {
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38 if (!SectionData.startswith("ZLIB"))
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39 return createError("corrupted compressed section header");
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40
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41 SectionData = SectionData.substr(4);
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42
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43 // Consume uncompressed section size (big-endian 8 bytes).
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44 if (SectionData.size() < 8)
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45 return createError("corrupted uncompressed section size");
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46 DecompressedSize = read64be(SectionData.data());
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47 SectionData = SectionData.substr(8);
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48
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49 return Error::success();
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50 }
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51
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52 Error Decompressor::consumeCompressedZLibHeader(bool Is64Bit,
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53 bool IsLittleEndian) {
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54 using namespace ELF;
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55 uint64_t HdrSize = Is64Bit ? sizeof(Elf64_Chdr) : sizeof(Elf32_Chdr);
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56 if (SectionData.size() < HdrSize)
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57 return createError("corrupted compressed section header");
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58
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59 DataExtractor Extractor(SectionData, IsLittleEndian, 0);
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60 uint32_t Offset = 0;
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61 if (Extractor.getUnsigned(&Offset, Is64Bit ? sizeof(Elf64_Word)
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62 : sizeof(Elf32_Word)) !=
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63 ELFCOMPRESS_ZLIB)
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64 return createError("unsupported compression type");
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65
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66 // Skip Elf64_Chdr::ch_reserved field.
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67 if (Is64Bit)
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68 Offset += sizeof(Elf64_Word);
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69
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70 DecompressedSize = Extractor.getUnsigned(
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71 &Offset, Is64Bit ? sizeof(Elf64_Xword) : sizeof(Elf32_Word));
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72 SectionData = SectionData.substr(HdrSize);
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73 return Error::success();
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74 }
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75
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76 bool Decompressor::isGnuStyle(StringRef Name) {
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77 return Name.startswith(".zdebug");
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78 }
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79
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80 bool Decompressor::isCompressed(const object::SectionRef &Section) {
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81 StringRef Name;
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82 if (Section.getName(Name))
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83 return false;
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84 return Section.isCompressed() || isGnuStyle(Name);
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85 }
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86
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87 bool Decompressor::isCompressedELFSection(uint64_t Flags, StringRef Name) {
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88 return (Flags & ELF::SHF_COMPRESSED) || isGnuStyle(Name);
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89 }
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90
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91 Error Decompressor::decompress(MutableArrayRef<char> Buffer) {
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92 size_t Size = Buffer.size();
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93 return zlib::uncompress(SectionData, Buffer.data(), Size);
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94 }
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