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//===-- Decompressor.cpp --------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/Object/Decompressor.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Support/Compression.h"
#include "llvm/Support/DataExtractor.h"
#include "llvm/Support/Endian.h"
using namespace llvm;
using namespace llvm::support::endian;
using namespace object;
Expected<Decompressor> Decompressor::create(StringRef Name, StringRef Data,
bool IsLE, bool Is64Bit) {
if (!zlib::isAvailable())
return createError("zlib is not available");
Decompressor D(Data);
Error Err = isGnuStyle(Name) ? D.consumeCompressedGnuHeader()
: D.consumeCompressedZLibHeader(Is64Bit, IsLE);
if (Err)
return std::move(Err);
return D;
}
Decompressor::Decompressor(StringRef Data)
: SectionData(Data), DecompressedSize(0) {}
Error Decompressor::consumeCompressedGnuHeader() {
if (!SectionData.startswith("ZLIB"))
return createError("corrupted compressed section header");
SectionData = SectionData.substr(4);
// Consume uncompressed section size (big-endian 8 bytes).
if (SectionData.size() < 8)
return createError("corrupted uncompressed section size");
DecompressedSize = read64be(SectionData.data());
SectionData = SectionData.substr(8);
return Error::success();
}
Error Decompressor::consumeCompressedZLibHeader(bool Is64Bit,
bool IsLittleEndian) {
using namespace ELF;
uint64_t HdrSize = Is64Bit ? sizeof(Elf64_Chdr) : sizeof(Elf32_Chdr);
if (SectionData.size() < HdrSize)
return createError("corrupted compressed section header");
DataExtractor Extractor(SectionData, IsLittleEndian, 0);
uint64_t Offset = 0;
if (Extractor.getUnsigned(&Offset, Is64Bit ? sizeof(Elf64_Word)
: sizeof(Elf32_Word)) !=
ELFCOMPRESS_ZLIB)
return createError("unsupported compression type");
// Skip Elf64_Chdr::ch_reserved field.
if (Is64Bit)
Offset += sizeof(Elf64_Word);
DecompressedSize = Extractor.getUnsigned(
&Offset, Is64Bit ? sizeof(Elf64_Xword) : sizeof(Elf32_Word));
SectionData = SectionData.substr(HdrSize);
return Error::success();
}
bool Decompressor::isGnuStyle(StringRef Name) {
return Name.startswith(".zdebug");
}
bool Decompressor::isCompressed(const object::SectionRef &Section) {
if (Section.isCompressed())
return true;
Expected<StringRef> SecNameOrErr = Section.getName();
if (SecNameOrErr)
return isGnuStyle(*SecNameOrErr);
consumeError(SecNameOrErr.takeError());
return false;
}
bool Decompressor::isCompressedELFSection(uint64_t Flags, StringRef Name) {
return (Flags & ELF::SHF_COMPRESSED) || isGnuStyle(Name);
}
Error Decompressor::decompress(MutableArrayRef<char> Buffer) {
size_t Size = Buffer.size();
return zlib::uncompress(SectionData, Buffer.data(), Size);
}
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