1 files changed, 98 insertions, 0 deletions
diff --git a/llvm/lib/Object/Decompressor.cpp b/llvm/lib/Object/Decompressor.cpp
new file mode 100644
index 0000000000000..11efd857d1a16
--- /dev/null
+++ b/llvm/lib/Object/Decompressor.cpp
@@ -0,0 +1,98 @@
+//===-- 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);
+}