diff --git a/llvm/lib/Object/MachOObject.cpp b/llvm/lib/Object/MachOObject.cpp
index de87605..5c17dfc 100644
--- a/llvm/lib/Object/MachOObject.cpp
+++ b/llvm/lib/Object/MachOObject.cpp
@@ -10,13 +10,49 @@
 #include "llvm/Object/MachOObject.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/System/Host.h"
+#include "llvm/System/SwapByteOrder.h"
 
 using namespace llvm;
-using namespace object;
+using namespace llvm::object;
+
+template<typename T>
+static void SwapValue(T &Value) {
+  Value = sys::SwapByteOrder(Value);
+}
 
 MachOObject::MachOObject(MemoryBuffer *Buffer_, bool IsLittleEndian_,
                          bool Is64Bit_)
-  : Buffer(Buffer_), IsLittleEndian(IsLittleEndian_), Is64Bit(Is64Bit_) {
+  : Buffer(Buffer_), IsLittleEndian(IsLittleEndian_), Is64Bit(Is64Bit_),
+    IsSwappedEndian(IsLittleEndian != sys::isLittleEndianHost()),
+    LoadCommands(0), NumLoadedCommands(0) {
+  // Load the common header.
+  memcpy(&Header, Buffer->getBuffer().data(), sizeof(Header));
+  if (IsSwappedEndian) {
+    SwapValue(Header.Magic);
+    SwapValue(Header.CPUType);
+    SwapValue(Header.CPUSubtype);
+    SwapValue(Header.FileType);
+    SwapValue(Header.NumLoadCommands);
+    SwapValue(Header.SizeOfLoadCommands);
+    SwapValue(Header.Flags);
+  }
+
+  if (is64Bit()) {
+    memcpy(&Header64Ext, Buffer->getBuffer().data() + sizeof(Header),
+           sizeof(Header64Ext));
+    if (IsSwappedEndian) {
+      SwapValue(Header64Ext.Reserved);
+    }
+  }
+
+  // Create the load command array if sane.
+  if (getHeader().NumLoadCommands < (1 << 20))
+    LoadCommands = new LoadCommandInfo[getHeader().NumLoadCommands];
+}
+
+MachOObject::~MachOObject() {
+  delete LoadCommands;
 }
 
 MachOObject *MachOObject::LoadFromBuffer(MemoryBuffer *Buffer,
@@ -33,13 +69,54 @@
     IsLittleEndian = true;
     Is64Bit = true;
   } else {
-    *ErrorStr = "not a Mach object file";
+    if (ErrorStr) *ErrorStr = "not a Mach object file (invalid magic)";
+    return 0;
+  }
+
+  // Ensure that the at least the full header is present.
+  unsigned HeaderSize = Is64Bit ? macho::Header64Size : macho::Header32Size;
+  if (Buffer->getBufferSize() < HeaderSize) {
+    if (ErrorStr) *ErrorStr = "not a Mach object file (invalid header)";
     return 0;
   }
 
   OwningPtr<MachOObject> Object(new MachOObject(Buffer, IsLittleEndian,
                                                 Is64Bit));
 
+  // Check for bogus number of load commands.
+  if (Object->getHeader().NumLoadCommands >= (1 << 20)) {
+    if (ErrorStr) *ErrorStr = "not a Mach object file (unreasonable header)";
+    return 0;
+  }
+
   if (ErrorStr) *ErrorStr = "";
   return Object.take();
 }
+
+const MachOObject::LoadCommandInfo &
+MachOObject::getLoadCommandInfo(unsigned Index) const {
+  assert(Index < getHeader().NumLoadCommands && "Invalid index!");
+
+  // Load the command, if necessary.
+  if (Index >= NumLoadedCommands) {
+    uint64_t Offset;
+    if (Index == 0) {
+      Offset = getHeaderSize();
+    } else {
+      const LoadCommandInfo &Prev = getLoadCommandInfo(Index - 1);
+      Offset = Prev.Offset + Prev.Command.Size;
+    }
+
+    LoadCommandInfo &Info = LoadCommands[Index];
+    memcpy(&Info.Command, Buffer->getBuffer().data() + Offset,
+           sizeof(macho::LoadCommand));
+    if (IsSwappedEndian) {
+      SwapValue(Info.Command.Type);
+      SwapValue(Info.Command.Size);
+    }
+    Info.Offset = Offset;
+    NumLoadedCommands = Index + 1;
+  }
+
+  return LoadCommands[Index];
+}