1 //===-- Decompressor.cpp --------------------------------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "llvm/Object/Decompressor.h" 11 #include "llvm/BinaryFormat/ELF.h" 12 #include "llvm/Object/ELFObjectFile.h" 13 #include "llvm/Support/Compression.h" 14 #include "llvm/Support/DataExtractor.h" 15 #include "llvm/Support/Endian.h" 16 17 using namespace llvm; 18 using namespace llvm::support::endian; 19 using namespace object; 20 21 Expected<Decompressor> Decompressor::create(StringRef Name, StringRef Data, 22 bool IsLE, bool Is64Bit) { 23 if (!zlib::isAvailable()) 24 return createError("zlib is not available"); 25 26 Decompressor D(Data); 27 Error Err = isGnuStyle(Name) ? D.consumeCompressedGnuHeader() 28 : D.consumeCompressedZLibHeader(Is64Bit, IsLE); 29 if (Err) 30 return std::move(Err); 31 return D; 32 } 33 34 Decompressor::Decompressor(StringRef Data) 35 : SectionData(Data), DecompressedSize(0) {} 36 37 Error Decompressor::consumeCompressedGnuHeader() { 38 if (!SectionData.startswith("ZLIB")) 39 return createError("corrupted compressed section header"); 40 41 SectionData = SectionData.substr(4); 42 43 // Consume uncompressed section size (big-endian 8 bytes). 44 if (SectionData.size() < 8) 45 return createError("corrupted uncompressed section size"); 46 DecompressedSize = read64be(SectionData.data()); 47 SectionData = SectionData.substr(8); 48 49 return Error::success(); 50 } 51 52 Error Decompressor::consumeCompressedZLibHeader(bool Is64Bit, 53 bool IsLittleEndian) { 54 using namespace ELF; 55 uint64_t HdrSize = Is64Bit ? sizeof(Elf64_Chdr) : sizeof(Elf32_Chdr); 56 if (SectionData.size() < HdrSize) 57 return createError("corrupted compressed section header"); 58 59 DataExtractor Extractor(SectionData, IsLittleEndian, 0); 60 uint32_t Offset = 0; 61 if (Extractor.getUnsigned(&Offset, Is64Bit ? sizeof(Elf64_Word) 62 : sizeof(Elf32_Word)) != 63 ELFCOMPRESS_ZLIB) 64 return createError("unsupported compression type"); 65 66 // Skip Elf64_Chdr::ch_reserved field. 67 if (Is64Bit) 68 Offset += sizeof(Elf64_Word); 69 70 DecompressedSize = Extractor.getUnsigned( 71 &Offset, Is64Bit ? sizeof(Elf64_Xword) : sizeof(Elf32_Word)); 72 SectionData = SectionData.substr(HdrSize); 73 return Error::success(); 74 } 75 76 bool Decompressor::isGnuStyle(StringRef Name) { 77 return Name.startswith(".zdebug"); 78 } 79 80 bool Decompressor::isCompressed(const object::SectionRef &Section) { 81 StringRef Name; 82 if (Section.getName(Name)) 83 return false; 84 return Section.isCompressed() || isGnuStyle(Name); 85 } 86 87 bool Decompressor::isCompressedELFSection(uint64_t Flags, StringRef Name) { 88 return (Flags & ELF::SHF_COMPRESSED) || isGnuStyle(Name); 89 } 90 91 Error Decompressor::decompress(MutableArrayRef<char> Buffer) { 92 size_t Size = Buffer.size(); 93 return zlib::uncompress(SectionData, Buffer.data(), Size); 94 } 95