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/ObjectFile.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 (!compression::zlib::isAvailable())
23     return createError("zlib is not available");
24 
25   Decompressor D(Data);
26   if (Error Err = D.consumeCompressedZLibHeader(Is64Bit, IsLE))
27     return std::move(Err);
28   return D;
29 }
30 
31 Decompressor::Decompressor(StringRef Data)
32     : SectionData(Data), DecompressedSize(0) {}
33 
34 Error Decompressor::consumeCompressedZLibHeader(bool Is64Bit,
35                                                 bool IsLittleEndian) {
36   using namespace ELF;
37   uint64_t HdrSize = Is64Bit ? sizeof(Elf64_Chdr) : sizeof(Elf32_Chdr);
38   if (SectionData.size() < HdrSize)
39     return createError("corrupted compressed section header");
40 
41   DataExtractor Extractor(SectionData, IsLittleEndian, 0);
42   uint64_t Offset = 0;
43   if (Extractor.getUnsigned(&Offset, Is64Bit ? sizeof(Elf64_Word)
44                                              : sizeof(Elf32_Word)) !=
45       ELFCOMPRESS_ZLIB)
46     return createError("unsupported compression type");
47 
48   // Skip Elf64_Chdr::ch_reserved field.
49   if (Is64Bit)
50     Offset += sizeof(Elf64_Word);
51 
52   DecompressedSize = Extractor.getUnsigned(
53       &Offset, Is64Bit ? sizeof(Elf64_Xword) : sizeof(Elf32_Word));
54   SectionData = SectionData.substr(HdrSize);
55   return Error::success();
56 }
57 
58 Error Decompressor::decompress(MutableArrayRef<uint8_t> Buffer) {
59   size_t Size = Buffer.size();
60   return compression::zlib::uncompress(arrayRefFromStringRef(SectionData),
61                                        Buffer.data(), Size);
62 }
63