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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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