lib/Object/Decompressor.cpp

   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 }