elf_mem_image.h (4938B)
1 /* 2 * Copyright 2017 The Abseil Authors. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * https://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 // Allow dynamic symbol lookup for in-memory Elf images. 18 19 #ifndef ABSL_DEBUGGING_INTERNAL_ELF_MEM_IMAGE_H_ 20 #define ABSL_DEBUGGING_INTERNAL_ELF_MEM_IMAGE_H_ 21 22 // Including this will define the __GLIBC__ macro if glibc is being 23 // used. 24 #include <climits> 25 #include <cstdint> 26 27 #include "absl/base/config.h" 28 29 // Maybe one day we can rewrite this file not to require the elf 30 // symbol extensions in glibc, but for right now we need them. 31 #ifdef ABSL_HAVE_ELF_MEM_IMAGE 32 #error ABSL_HAVE_ELF_MEM_IMAGE cannot be directly set 33 #endif 34 35 #if defined(__ELF__) && !defined(__OpenBSD__) && !defined(__QNX__) && \ 36 !defined(__native_client__) && !defined(__asmjs__) && \ 37 !defined(__wasm__) && !defined(__HAIKU__) && !defined(__sun) && \ 38 !defined(__VXWORKS__) && !defined(__hexagon__) && !defined(__XTENSA__) 39 #define ABSL_HAVE_ELF_MEM_IMAGE 1 40 #endif 41 42 #ifdef ABSL_HAVE_ELF_MEM_IMAGE 43 44 #include <link.h> // for ElfW 45 46 #if defined(__FreeBSD__) && !defined(ElfW) 47 #define ElfW(x) __ElfN(x) 48 #endif 49 50 namespace absl { 51 ABSL_NAMESPACE_BEGIN 52 namespace debugging_internal { 53 54 // An in-memory ELF image (may not exist on disk). 55 class ElfMemImage { 56 private: 57 // Sentinel: there could never be an elf image at &kInvalidBaseSentinel. 58 static const int kInvalidBaseSentinel; 59 60 public: 61 // Sentinel: there could never be an elf image at this address. 62 static constexpr const void *const kInvalidBase = 63 static_cast<const void*>(&kInvalidBaseSentinel); 64 65 // Information about a single vdso symbol. 66 // All pointers are into .dynsym, .dynstr, or .text of the VDSO. 67 // Do not free() them or modify through them. 68 struct SymbolInfo { 69 const char *name; // E.g. "__vdso_getcpu" 70 const char *version; // E.g. "LINUX_2.6", could be "" 71 // for unversioned symbol. 72 const void *address; // Relocated symbol address. 73 const ElfW(Sym) *symbol; // Symbol in the dynamic symbol table. 74 }; 75 76 // Supports iteration over all dynamic symbols. 77 class SymbolIterator { 78 public: 79 friend class ElfMemImage; 80 const SymbolInfo *operator->() const; 81 const SymbolInfo &operator*() const; 82 SymbolIterator& operator++(); 83 bool operator!=(const SymbolIterator &rhs) const; 84 bool operator==(const SymbolIterator &rhs) const; 85 private: 86 SymbolIterator(const void *const image, uint32_t index); 87 void Update(uint32_t incr); 88 SymbolInfo info_; 89 uint32_t index_; 90 const void *const image_; 91 }; 92 93 94 explicit ElfMemImage(const void *base); 95 void Init(const void *base); 96 bool IsPresent() const { return ehdr_ != nullptr; } 97 const ElfW(Phdr)* GetPhdr(int index) const; 98 const ElfW(Sym) * GetDynsym(uint32_t index) const; 99 const ElfW(Versym)* GetVersym(uint32_t index) const; 100 const ElfW(Verdef)* GetVerdef(int index) const; 101 const ElfW(Verdaux)* GetVerdefAux(const ElfW(Verdef) *verdef) const; 102 const char* GetDynstr(ElfW(Word) offset) const; 103 const void* GetSymAddr(const ElfW(Sym) *sym) const; 104 const char* GetVerstr(ElfW(Word) offset) const; 105 uint32_t GetNumSymbols() const; 106 107 SymbolIterator begin() const; 108 SymbolIterator end() const; 109 110 // Look up versioned dynamic symbol in the image. 111 // Returns false if image is not present, or doesn't contain given 112 // symbol/version/type combination. 113 // If info_out is non-null, additional details are filled in. 114 bool LookupSymbol(const char *name, const char *version, 115 int symbol_type, SymbolInfo *info_out) const; 116 117 // Find info about symbol (if any) which overlaps given address. 118 // Returns true if symbol was found; false if image isn't present 119 // or doesn't have a symbol overlapping given address. 120 // If info_out is non-null, additional details are filled in. 121 bool LookupSymbolByAddress(const void *address, SymbolInfo *info_out) const; 122 123 private: 124 const ElfW(Ehdr) *ehdr_; 125 const ElfW(Sym) *dynsym_; 126 const ElfW(Versym) *versym_; 127 const ElfW(Verdef) *verdef_; 128 const char *dynstr_; 129 uint32_t num_syms_; 130 size_t strsize_; 131 size_t verdefnum_; 132 ElfW(Addr) link_base_; // Link-time base (p_vaddr of first PT_LOAD). 133 }; 134 135 } // namespace debugging_internal 136 ABSL_NAMESPACE_END 137 } // namespace absl 138 139 #endif // ABSL_HAVE_ELF_MEM_IMAGE 140 141 #endif // ABSL_DEBUGGING_INTERNAL_ELF_MEM_IMAGE_H_