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
create(StringRef Name,StringRef Data,bool IsLE,bool Is64Bit)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
Decompressor(StringRef Data)34 Decompressor::Decompressor(StringRef Data)
35 : SectionData(Data), DecompressedSize(0) {}
36
consumeCompressedGnuHeader()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
consumeCompressedZLibHeader(bool Is64Bit,bool IsLittleEndian)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
isGnuStyle(StringRef Name)76 bool Decompressor::isGnuStyle(StringRef Name) {
77 return Name.startswith(".zdebug");
78 }
79
isCompressed(const object::SectionRef & Section)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
isCompressedELFSection(uint64_t Flags,StringRef Name)87 bool Decompressor::isCompressedELFSection(uint64_t Flags, StringRef Name) {
88 return (Flags & ELF::SHF_COMPRESSED) || isGnuStyle(Name);
89 }
90
decompress(MutableArrayRef<char> Buffer)91 Error Decompressor::decompress(MutableArrayRef<char> Buffer) {
92 size_t Size = Buffer.size();
93 return zlib::uncompress(SectionData, Buffer.data(), Size);
94 }
95