1 //===-- Decompressor.cpp --------------------------------------------------===// 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 9 #include "llvm/Object/Decompressor.h" 10 #include "llvm/BinaryFormat/ELF.h" 11 #include "llvm/Object/ELFObjectFile.h" 12 #include "llvm/Support/Compression.h" 13 #include "llvm/Support/DataExtractor.h" 14 #include "llvm/Support/Endian.h" 15 16 using namespace llvm; 17 using namespace llvm::support::endian; 18 using namespace object; 19 20 Expected<Decompressor> Decompressor::create(StringRef Name, StringRef Data, 21 bool IsLE, bool Is64Bit) { 22 if (!zlib::isAvailable()) 23 return createError("zlib is not available"); 24 25 Decompressor D(Data); 26 Error Err = isGnuStyle(Name) ? D.consumeCompressedGnuHeader() 27 : D.consumeCompressedZLibHeader(Is64Bit, IsLE); 28 if (Err) 29 return std::move(Err); 30 return D; 31 } 32 33 Decompressor::Decompressor(StringRef Data) 34 : SectionData(Data), DecompressedSize(0) {} 35 36 Error Decompressor::consumeCompressedGnuHeader() { 37 if (!SectionData.startswith("ZLIB")) 38 return createError("corrupted compressed section header"); 39 40 SectionData = SectionData.substr(4); 41 42 // Consume uncompressed section size (big-endian 8 bytes). 43 if (SectionData.size() < 8) 44 return createError("corrupted uncompressed section size"); 45 DecompressedSize = read64be(SectionData.data()); 46 SectionData = SectionData.substr(8); 47 48 return Error::success(); 49 } 50 51 Error Decompressor::consumeCompressedZLibHeader(bool Is64Bit, 52 bool IsLittleEndian) { 53 using namespace ELF; 54 uint64_t HdrSize = Is64Bit ? sizeof(Elf64_Chdr) : sizeof(Elf32_Chdr); 55 if (SectionData.size() < HdrSize) 56 return createError("corrupted compressed section header"); 57 58 DataExtractor Extractor(SectionData, IsLittleEndian, 0); 59 uint64_t Offset = 0; 60 if (Extractor.getUnsigned(&Offset, Is64Bit ? sizeof(Elf64_Word) 61 : sizeof(Elf32_Word)) != 62 ELFCOMPRESS_ZLIB) 63 return createError("unsupported compression type"); 64 65 // Skip Elf64_Chdr::ch_reserved field. 66 if (Is64Bit) 67 Offset += sizeof(Elf64_Word); 68 69 DecompressedSize = Extractor.getUnsigned( 70 &Offset, Is64Bit ? sizeof(Elf64_Xword) : sizeof(Elf32_Word)); 71 SectionData = SectionData.substr(HdrSize); 72 return Error::success(); 73 } 74 75 bool Decompressor::isGnuStyle(StringRef Name) { 76 return Name.startswith(".zdebug"); 77 } 78 79 bool Decompressor::isCompressed(const object::SectionRef &Section) { 80 if (Section.isCompressed()) 81 return true; 82 83 Expected<StringRef> SecNameOrErr = Section.getName(); 84 if (SecNameOrErr) 85 return isGnuStyle(*SecNameOrErr); 86 87 consumeError(SecNameOrErr.takeError()); 88 return false; 89 } 90 91 bool Decompressor::isCompressedELFSection(uint64_t Flags, StringRef Name) { 92 return (Flags & ELF::SHF_COMPRESSED) || isGnuStyle(Name); 93 } 94 95 Error Decompressor::decompress(MutableArrayRef<char> Buffer) { 96 size_t Size = Buffer.size(); 97 return zlib::uncompress(SectionData, Buffer.data(), Size); 98 } 99