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diff --git a/mozglue/linker/BaseElf.h b/mozglue/linker/BaseElf.h
new file mode 100644
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+++ b/mozglue/linker/BaseElf.h
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef BaseElf_h
+#define BaseElf_h
+
+#include "ElfLoader.h"
+#include "Elfxx.h"
+
+
+/**
+ * Base class for ELF libraries. This class includes things that will be
+ * common between SystemElfs and CustomElfs.
+ */
+class BaseElf: public LibHandle
+{
+public:
+  /**
+   * Hash function for symbol lookup, as defined in ELF standard for System V.
+   */
+  static unsigned long Hash(const char *symbol);
+
+  /**
+   * Returns the address corresponding to the given symbol name (with a
+   * pre-computed hash).
+   */
+  void *GetSymbolPtr(const char *symbol, unsigned long hash) const;
+
+  /**
+   * Returns a pointer to the Elf Symbol in the Dynamic Symbol table
+   * corresponding to the given symbol name (with a pre-computed hash).
+   */
+  const Elf::Sym *GetSymbol(const char *symbol, unsigned long hash) const;
+
+  BaseElf(const char *path, Mappable *mappable = nullptr)
+  : LibHandle(path)
+  , mappable(mappable)
+  {
+  }
+
+protected:
+   /**
+    * Inherited from LibHandle. Those are temporary and are not supposed to
+    * be used.
+    */
+   virtual void *GetSymbolPtr(const char *symbol) const;
+   virtual bool Contains(void *addr) const;
+   virtual void *GetBase() const { return GetPtr(0); }
+
+#ifdef __ARM_EABI__
+  virtual const void *FindExidx(int *pcount) const;
+#endif
+
+  virtual Mappable *GetMappable() const { return NULL; };
+
+public:
+/* private: */
+  /**
+   * Returns a pointer relative to the base address where the library is
+   * loaded.
+   */
+  void *GetPtr(const Elf::Addr offset) const
+  {
+    if (reinterpret_cast<void *>(offset) > base)
+      return reinterpret_cast<void *>(offset);
+    return base + offset;
+  }
+
+  /**
+   * Like the above, but returns a typed (const) pointer
+   */
+  template <typename T>
+  const T *GetPtr(const Elf::Addr offset) const
+  {
+    if (reinterpret_cast<void *>(offset) > base)
+      return reinterpret_cast<const T *>(offset);
+    return reinterpret_cast<const T *>(base + offset);
+  }
+
+  /* Appropriated Mappable */
+  /* /!\ we rely on this being nullptr for BaseElf instances, but not
+   * CustomElf instances. */
+  RefPtr<Mappable> mappable;
+
+  /* Base address where the library is loaded */
+  MappedPtr base;
+
+  /* Buckets and chains for the System V symbol hash table */
+  Array<Elf::Word> buckets;
+  UnsizedArray<Elf::Word> chains;
+
+/* protected: */
+  /* String table */
+  Elf::Strtab strtab;
+
+  /* Symbol table */
+  UnsizedArray<Elf::Sym> symtab;
+
+#ifdef __ARM_EABI__
+  /* ARM.exidx information used by FindExidx */
+  Array<uint32_t[2]> arm_exidx;
+#endif
+};
+
+
+/**
+ * Class for ELF libraries that already loaded in memory.
+ */
+class LoadedElf: public BaseElf
+{
+public:
+  /**
+   * Returns a LoadedElf corresponding to the already loaded ELF
+   * at the given base address.
+   */
+  static already_AddRefed<LibHandle> Create(const char *path,
+                                                 void *base_addr);
+
+private:
+  LoadedElf(const char *path)
+  : BaseElf(path) { }
+
+  ~LoadedElf()
+  {
+    /* Avoid base's destructor unmapping something that doesn't actually
+     * belong to it. */
+    base.release();
+    ElfLoader::Singleton.Forget(this);
+  }
+
+  /**
+   * Initializes the library according to information found in the given
+   * PT_DYNAMIC header.
+   * Returns whether this succeeded or failed.
+   */
+  bool InitDyn(const Elf::Phdr *pt_dyn);
+};
+
+
+#endif /* BaseElf_h */