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/ADT/StringExtras.h"
11#include "llvm/BinaryFormat/ELF.h"
12#include "llvm/Object/ObjectFile.h"
13#include "llvm/Support/Compression.h"
14#include "llvm/Support/DataExtractor.h"
15#include "llvm/Support/Endian.h"
16
17using namespace llvm;
18using namespace llvm::support::endian;
19using namespace object;
20
21Expected<Decompressor> Decompressor::create(StringRef Name, StringRef Data,
22                                            bool IsLE, bool Is64Bit) {
23  Decompressor D(Data);
24  if (Error Err = D.consumeCompressedHeader(Is64Bit, IsLE))
25    return std::move(Err);
26  return D;
27}
28
29Decompressor::Decompressor(StringRef Data)
30    : SectionData(Data), DecompressedSize(0) {}
31
32Error Decompressor::consumeCompressedHeader(bool Is64Bit, bool IsLittleEndian) {
33  using namespace ELF;
34  uint64_t HdrSize = Is64Bit ? sizeof(Elf64_Chdr) : sizeof(Elf32_Chdr);
35  if (SectionData.size() < HdrSize)
36    return createError("corrupted compressed section header");
37
38  DataExtractor Extractor(SectionData, IsLittleEndian, 0);
39  uint64_t Offset = 0;
40  auto ChType = Extractor.getUnsigned(&Offset, Is64Bit ? sizeof(Elf64_Word)
41                                                       : sizeof(Elf32_Word));
42  switch (ChType) {
43  case ELFCOMPRESS_ZLIB:
44    CompressionType = DebugCompressionType::Zlib;
45    break;
46  case ELFCOMPRESS_ZSTD:
47    CompressionType = DebugCompressionType::Zstd;
48    break;
49  default:
50    return createError("unsupported compression type (" + Twine(ChType) + ")");
51  }
52  if (const char *Reason = llvm::compression::getReasonIfUnsupported(
53          compression::formatFor(CompressionType)))
54    return createError(Reason);
55
56  // Skip Elf64_Chdr::ch_reserved field.
57  if (Is64Bit)
58    Offset += sizeof(Elf64_Word);
59
60  DecompressedSize = Extractor.getUnsigned(
61      &Offset, Is64Bit ? sizeof(Elf64_Xword) : sizeof(Elf32_Word));
62  SectionData = SectionData.substr(HdrSize);
63  return Error::success();
64}
65
66Error Decompressor::decompress(MutableArrayRef<uint8_t> Output) {
67  return compression::decompress(CompressionType,
68                                 arrayRefFromStringRef(SectionData),
69                                 Output.data(), Output.size());
70}
71