1 // -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- 2 // Copyright (c) 2008, Google Inc. 3 // All rights reserved. 4 // 5 // Redistribution and use in source and binary forms, with or without 6 // modification, are permitted provided that the following conditions are 7 // met: 8 // 9 // * Redistributions of source code must retain the above copyright 10 // notice, this list of conditions and the following disclaimer. 11 // * Redistributions in binary form must reproduce the above 12 // copyright notice, this list of conditions and the following disclaimer 13 // in the documentation and/or other materials provided with the 14 // distribution. 15 // * Neither the name of Google Inc. nor the names of its 16 // contributors may be used to endorse or promote products derived from 17 // this software without specific prior written permission. 18 // 19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31 // --- 32 // Author: Paul Pluzhnikov 33 // 34 // Allow dynamic symbol lookup for in-memory Elf images. 35 36 #ifndef BASE_ELF_MEM_IMAGE_H_ 37 #define BASE_ELF_MEM_IMAGE_H_ 38 39 #include <config.h> 40 #ifdef HAVE_FEATURES_H 41 #include <features.h> // for __GLIBC__ 42 #endif 43 44 // Maybe one day we can rewrite this file not to require the elf 45 // symbol extensions in glibc, but for right now we need them. 46 #if defined(__ELF__) && defined(__GLIBC__) && !defined(__native_client__) 47 48 #define HAVE_ELF_MEM_IMAGE 1 49 50 #include <stdlib.h> 51 #include <link.h> // for ElfW 52 53 namespace base { 54 55 // An in-memory ELF image (may not exist on disk). 56 class ElfMemImage { 57 public: 58 // Sentinel: there could never be an elf image at this address. 59 static const void *const kInvalidBase; 60 61 // Information about a single vdso symbol. 62 // All pointers are into .dynsym, .dynstr, or .text of the VDSO. 63 // Do not free() them or modify through them. 64 struct SymbolInfo { 65 const char *name; // E.g. "__vdso_getcpu" 66 const char *version; // E.g. "LINUX_2.6", could be "" 67 // for unversioned symbol. 68 const void *address; // Relocated symbol address. 69 const ElfW(Sym) *symbol; // Symbol in the dynamic symbol table. 70 }; 71 72 // Supports iteration over all dynamic symbols. 73 class SymbolIterator { 74 public: 75 friend class ElfMemImage; 76 const SymbolInfo *operator->() const; 77 const SymbolInfo &operator*() const; 78 SymbolIterator& operator++(); 79 bool operator!=(const SymbolIterator &rhs) const; 80 bool operator==(const SymbolIterator &rhs) const; 81 private: 82 SymbolIterator(const void *const image, int index); 83 void Update(int incr); 84 SymbolInfo info_; 85 int index_; 86 const void *const image_; 87 }; 88 89 90 explicit ElfMemImage(const void *base); 91 void Init(const void *base); IsPresent()92 bool IsPresent() const { return ehdr_ != NULL; } 93 const ElfW(Phdr)* GetPhdr(int index) const; 94 const ElfW(Sym)* GetDynsym(int index) const; 95 const ElfW(Versym)* GetVersym(int index) const; 96 const ElfW(Verdef)* GetVerdef(int index) const; 97 const ElfW(Verdaux)* GetVerdefAux(const ElfW(Verdef) *verdef) const; 98 const char* GetDynstr(ElfW(Word) offset) const; 99 const void* GetSymAddr(const ElfW(Sym) *sym) const; 100 const char* GetVerstr(ElfW(Word) offset) const; 101 int GetNumSymbols() const; 102 103 SymbolIterator begin() const; 104 SymbolIterator end() const; 105 106 // Look up versioned dynamic symbol in the image. 107 // Returns false if image is not present, or doesn't contain given 108 // symbol/version/type combination. 109 // If info_out != NULL, additional details are filled in. 110 bool LookupSymbol(const char *name, const char *version, 111 int symbol_type, SymbolInfo *info_out) const; 112 113 // Find info about symbol (if any) which overlaps given address. 114 // Returns true if symbol was found; false if image isn't present 115 // or doesn't have a symbol overlapping given address. 116 // If info_out != NULL, additional details are filled in. 117 bool LookupSymbolByAddress(const void *address, SymbolInfo *info_out) const; 118 119 private: 120 const ElfW(Ehdr) *ehdr_; 121 const ElfW(Sym) *dynsym_; 122 const ElfW(Versym) *versym_; 123 const ElfW(Verdef) *verdef_; 124 const ElfW(Word) *hash_; 125 const char *dynstr_; 126 size_t strsize_; 127 size_t verdefnum_; 128 ElfW(Addr) link_base_; // Link-time base (p_vaddr of first PT_LOAD). 129 }; 130 131 } // namespace base 132 133 #endif // __ELF__ and __GLIBC__ and !__native_client__ 134 135 #endif // BASE_ELF_MEM_IMAGE_H_ 136