tor-browser

The Tor Browser
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CustomElf.h (3858B)

      1 /* This Source Code Form is subject to the terms of the Mozilla Public
      2 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
      3 * You can obtain one at http://mozilla.org/MPL/2.0/. */
      4 
      5 #ifndef CustomElf_h
      6 #define CustomElf_h
      7 
      8 #include "ElfLoader.h"
      9 #include "BaseElf.h"
     10 #include "Logging.h"
     11 #include "Elfxx.h"
     12 
     13 /**
     14 * Library Handle class for ELF libraries we don't let the system linker
     15 * handle.
     16 */
     17 class CustomElf : public BaseElf, private ElfLoader::link_map {
     18  friend class ElfLoader;
     19  friend class SEGVHandler;
     20 
     21 public:
     22  /**
     23   * Returns a new CustomElf using the given file descriptor to map ELF
     24   * content. The file descriptor ownership is stolen, and it will be closed
     25   * in CustomElf's destructor if an instance is created, or by the Load
     26   * method otherwise. The path corresponds to the file descriptor, and flags
     27   * are the same kind of flags that would be given to dlopen(), though
     28   * currently, none are supported and the behaviour is more or less that of
     29   * RTLD_GLOBAL | RTLD_BIND_NOW.
     30   */
     31  static already_AddRefed<LibHandle> Load(Mappable* mappable, const char* path,
     32                                          int flags);
     33 
     34  /**
     35   * Inherited from LibHandle/BaseElf
     36   */
     37  virtual ~CustomElf();
     38 
     39 public:
     40  /**
     41   * Returns the instance, casted as BaseElf. (short of a better way to do
     42   * this without RTTI)
     43   */
     44  virtual BaseElf* AsBaseElf() { return this; }
     45 
     46 private:
     47  /**
     48   * Scan dependent libraries to find the address corresponding to the
     49   * given symbol name. This is used to find symbols that are undefined
     50   * in the Elf object.
     51   */
     52  void* GetSymbolPtrInDeps(const char* symbol) const;
     53 
     54  /**
     55   * Private constructor
     56   */
     57  CustomElf(Mappable* mappable, const char* path)
     58      : BaseElf(path, mappable),
     59        link_map(),
     60        init(0),
     61        fini(0),
     62        initialized(false),
     63        has_text_relocs(false) {}
     64 
     65  /**
     66   * Loads an Elf segment defined by the given PT_LOAD header.
     67   * Returns whether this succeeded or failed.
     68   */
     69  bool LoadSegment(const Elf::Phdr* pt_load) const;
     70 
     71  /**
     72   * Initializes the library according to information found in the given
     73   * PT_DYNAMIC header.
     74   * Returns whether this succeeded or failed.
     75   */
     76  bool InitDyn(const Elf::Phdr* pt_dyn);
     77 
     78  /**
     79   * Apply .rel.dyn/.rela.dyn relocations.
     80   * Returns whether this succeeded or failed.
     81   */
     82  bool Relocate();
     83 
     84  /**
     85   * Apply .rel.plt/.rela.plt relocations.
     86   * Returns whether this succeeded or failed.
     87   */
     88  bool RelocateJumps();
     89 
     90  /**
     91   * Call initialization functions (.init/.init_array)
     92   * Returns true;
     93   */
     94  bool CallInit();
     95 
     96  /**
     97   * Call destructor functions (.fini_array/.fini)
     98   * Returns whether this succeeded or failed.
     99   */
    100  void CallFini();
    101 
    102  /**
    103   * Call a function given a pointer to its location.
    104   */
    105  void CallFunction(void* ptr) const {
    106    /* C++ doesn't allow direct conversion between pointer-to-object
    107     * and pointer-to-function. */
    108    union {
    109      void* ptr;
    110      void (*func)(void);
    111    } f;
    112    f.ptr = ptr;
    113    DEBUG_LOG("%s: Calling function @%p", GetPath(), ptr);
    114    f.func();
    115  }
    116 
    117  /**
    118   * Call a function given a an address relative to the library base
    119   */
    120  void CallFunction(Elf::Addr addr) const { return CallFunction(GetPtr(addr)); }
    121 
    122  /* List of dependent libraries */
    123  std::vector<RefPtr<LibHandle> > dependencies;
    124 
    125  /* List of .rel.dyn/.rela.dyn relocations */
    126  Array<Elf::Reloc> relocations;
    127 
    128  /* List of .rel.plt/.rela.plt relocation */
    129  Array<Elf::Reloc> jumprels;
    130 
    131  /* Relative address of the initialization and destruction functions
    132   * (.init/.fini) */
    133  Elf::Addr init, fini;
    134 
    135  /* List of initialization and destruction functions
    136   * (.init_array/.fini_array) */
    137  Array<void*> init_array, fini_array;
    138 
    139  bool initialized;
    140 
    141  bool has_text_relocs;
    142 };
    143 
    144 #endif /* CustomElf_h */