The Tor Browser: mozglue/linker/CustomElf.h@b8a032363ba2 (annotated)

mozglue/linker/CustomElf.h@b8a032363ba2 (annotated)

mozglue/linker/CustomElf.h

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* 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 CustomElf_h
 #define CustomElf_h
 #include "ElfLoader.h"
 #include "Logging.h"
 #include "Elfxx.h"
 /**
  * Library Handle class for ELF libraries we don't let the system linker
  * handle.
  */
 class CustomElf: public LibHandle, private ElfLoader::link_map
 {
   friend class ElfLoader;
   friend class SEGVHandler;
 public:
   /**
    * Returns a new CustomElf using the given file descriptor to map ELF
    * content. The file descriptor ownership is stolen, and it will be closed
    * in CustomElf's destructor if an instance is created, or by the Load
    * method otherwise. The path corresponds to the file descriptor, and flags
    * are the same kind of flags that would be given to dlopen(), though
    * currently, none are supported and the behaviour is more or less that of
    * RTLD_GLOBAL | RTLD_BIND_NOW.
    */
   static mozilla::TemporaryRef<LibHandle> Load(Mappable *mappable,
                                                const char *path, int flags);
   /**
    * Inherited from LibHandle
    */
   virtual ~CustomElf();
   virtual void *GetSymbolPtr(const char *symbol) const;
   virtual bool Contains(void *addr) const;
 #ifdef __ARM_EABI__
   virtual const void *FindExidx(int *pcount) const;
 #endif
 protected:
   virtual Mappable *GetMappable() const;
 public:
   /**
    * Shows some stats about the Mappable instance. The when argument is to be
    * used by the caller to give an identifier of the when the stats call is
    * made.
    */
   void stats(const char *when) const;
 private:
   /**
    * 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;
   /**
    * Returns the address corresponding to the given symbol name (with a
    * pre-computed hash).
    */
   void *GetSymbolPtr(const char *symbol, unsigned long hash) const;
   /**
    * Scan dependent libraries to find the address corresponding to the
    * given symbol name. This is used to find symbols that are undefined
    * in the Elf object.
    */
   void *GetSymbolPtrInDeps(const char *symbol) const;
   /**
    * Private constructor
    */
   CustomElf(Mappable *mappable, const char *path)
   : LibHandle(path)
   , mappable(mappable)
   , init(0)
   , fini(0)
   , initialized(false)
   , has_text_relocs(false)
   { }
   /**
    * Returns a pointer relative to the base address where the library is
    * loaded.
    */
   void *GetPtr(const Elf::Addr offset) const
   {
     return base + offset;
   }
   /**
    * Like the above, but returns a typed (const) pointer
    */
   template <typename T>
   const T *GetPtr(const Elf::Addr offset) const
   {
     return reinterpret_cast<const T *>(base + offset);
   }
   /**
    * Loads an Elf segment defined by the given PT_LOAD header.
    * Returns whether this succeeded or failed.
    */
   bool LoadSegment(const Elf::Phdr *pt_load) const;
   /**
    * 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);
   /**
    * Apply .rel.dyn/.rela.dyn relocations.
    * Returns whether this succeeded or failed.
    */
   bool Relocate();
   /**
    * Apply .rel.plt/.rela.plt relocations.
    * Returns whether this succeeded or failed.
    */
   bool RelocateJumps();
   /**
    * Call initialization functions (.init/.init_array)
    * Returns true;
    */
   bool CallInit();
   /**
    * Call destructor functions (.fini_array/.fini)
    * Returns whether this succeeded or failed.
    */
   void CallFini();
   /**
    * Call a function given a pointer to its location.
    */
   void CallFunction(void *ptr) const
   {
     /* C++ doesn't allow direct conversion between pointer-to-object
      * and pointer-to-function. */
     union {
       void *ptr;
       void (*func)(void);
     } f;
     f.ptr = ptr;
     DEBUG_LOG("%s: Calling function @%p", GetPath(), ptr);
     f.func();
   }
   /**
    * Call a function given a an address relative to the library base
    */
   void CallFunction(Elf::Addr addr) const
   {
     return CallFunction(GetPtr(addr));
   }
   /* Appropriated Mappable */
   mozilla::RefPtr<Mappable> mappable;
   /* Base address where the library is loaded */
   MappedPtr base;
   /* String table */
   Elf::Strtab strtab;
   /* Symbol table */
   UnsizedArray<Elf::Sym> symtab;
   /* Buckets and chains for the System V symbol hash table */
   Array<Elf::Word> buckets;
   UnsizedArray<Elf::Word> chains;
   /* List of dependent libraries */
   std::vector<mozilla::RefPtr<LibHandle> > dependencies;
   /* List of .rel.dyn/.rela.dyn relocations */
   Array<Elf::Reloc> relocations;
   /* List of .rel.plt/.rela.plt relocation */
   Array<Elf::Reloc> jumprels;
   /* Relative address of the initialization and destruction functions
    * (.init/.fini) */
   Elf::Addr init, fini;
   /* List of initialization and destruction functions
    * (.init_array/.fini_array) */
   Array<void *> init_array, fini_array;
   bool initialized;
   bool has_text_relocs;
 #ifdef __ARM_EABI__
   /* ARM.exidx information used by FindExidx */
   Array<uint32_t[2]> arm_exidx;
 #endif
 };
 #endif /* CustomElf_h */

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