1 // Copyright (c) 2008, Google Inc. 2 // All rights reserved. 3 // 4 // Redistribution and use in source and binary forms, with or without 5 // modification, are permitted provided that the following conditions are 6 // met: 7 // 8 // * Redistributions of source code must retain the above copyright 9 // notice, this list of conditions and the following disclaimer. 10 // * Redistributions in binary form must reproduce the above 11 // copyright notice, this list of conditions and the following disclaimer 12 // in the documentation and/or other materials provided with the 13 // distribution. 14 // * Neither the name of Google Inc. nor the names of its 15 // contributors may be used to endorse or promote products derived from 16 // this software without specific prior written permission. 17 // 18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 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_ 135
