third_party/tcmalloc/chromium/src/base/elf_mem_image.h

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  29
  30 // ---
  31 // Author: Paul Pluzhnikov
  32 //
  33 // Allow dynamic symbol lookup for in-memory Elf images.
  34
  35 #ifndef BASE_ELF_MEM_IMAGE_H_
  36 #define BASE_ELF_MEM_IMAGE_H_
  37
  38 #include <config.h>
  39 #ifdef HAVE_FEATURES_H
  40 #include <features.h>   // for __GLIBC__
  41 #endif
  42
  43 // Maybe one day we can rewrite this file not to require the elf
  44 // symbol extensions in glibc, but for right now we need them.
  45 #if defined(__ELF__) && defined(__GLIBC__) && !defined(__native_client__)
  46
  47 #define HAVE_ELF_MEM_IMAGE 1
  48
  49 #include <stdlib.h>
  50 #include <link.h>  // for ElfW
  51
  52 namespace base {
  53
  54 // An in-memory ELF image (may not exist on disk).
  55 class ElfMemImage {
  56  public:
  57   // Sentinel: there could never be an elf image at this address.
  58   static const void *const kInvalidBase;
  59
  60   // Information about a single vdso symbol.
  61   // All pointers are into .dynsym, .dynstr, or .text of the VDSO.
  62   // Do not free() them or modify through them.
  63   struct SymbolInfo {
  64     const char      *name;      // E.g. "__vdso_getcpu"
  65     const char      *version;   // E.g. "LINUX_2.6", could be ""
  66                                 // for unversioned symbol.
  67     const void      *address;   // Relocated symbol address.
  68     const ElfW(Sym) *symbol;    // Symbol in the dynamic symbol table.
  69   };
  70
  71   // Supports iteration over all dynamic symbols.
  72   class SymbolIterator {
  73    public:
  74     friend class ElfMemImage;
  75     const SymbolInfo *operator->() const;
  76     const SymbolInfo &operator*() const;
  77     SymbolIterator& operator++();
  78     bool operator!=(const SymbolIterator &rhs) const;
  79     bool operator==(const SymbolIterator &rhs) const;
  80    private:
  81     SymbolIterator(const void *const image, int index);
  82     void Update(int incr);
  83     SymbolInfo info_;
  84     int index_;
  85     const void *const image_;
  86   };
  87
  88
  89   explicit ElfMemImage(const void *base);
  90   void                 Init(const void *base);
  91   bool                 IsPresent() const { return ehdr_ != NULL; }
  92   const ElfW(Phdr)*    GetPhdr(int index) const;
  93   const ElfW(Sym)*     GetDynsym(int index) const;
  94   const ElfW(Versym)*  GetVersym(int index) const;
  95   const ElfW(Verdef)*  GetVerdef(int index) const;
  96   const ElfW(Verdaux)* GetVerdefAux(const ElfW(Verdef) *verdef) const;
  97   const char*          GetDynstr(ElfW(Word) offset) const;
  98   const void*          GetSymAddr(const ElfW(Sym) *sym) const;
  99   const char*          GetVerstr(ElfW(Word) offset) const;
 100   int                  GetNumSymbols() const;
 101
 102   SymbolIterator begin() const;
 103   SymbolIterator end() const;
 104
 105   // Look up versioned dynamic symbol in the image.
 106   // Returns false if image is not present, or doesn't contain given
 107   // symbol/version/type combination.
 108   // If info_out != NULL, additional details are filled in.
 109   bool LookupSymbol(const char *name, const char *version,
 110                     int symbol_type, SymbolInfo *info_out) const;
 111
 112   // Find info about symbol (if any) which overlaps given address.
 113   // Returns true if symbol was found; false if image isn't present
 114   // or doesn't have a symbol overlapping given address.
 115   // If info_out != NULL, additional details are filled in.
 116   bool LookupSymbolByAddress(const void *address, SymbolInfo *info_out) const;
 117
 118  private:
 119   const ElfW(Ehdr) *ehdr_;
 120   const ElfW(Sym) *dynsym_;
 121   const ElfW(Versym) *versym_;
 122   const ElfW(Verdef) *verdef_;
 123   const ElfW(Word) *hash_;
 124   const char *dynstr_;
 125   size_t strsize_;
 126   size_t verdefnum_;
 127   ElfW(Addr) link_base_;     // Link-time base (p_vaddr of first PT_LOAD).
 128 };
 129
 130 }  // namespace base
 131
 132 #endif  // __ELF__ and __GLIBC__ and !__native_client__
 133
 134 #endif  // BASE_ELF_MEM_IMAGE_H_