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| 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_ |
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