/* * Copyright 2017 The Abseil Authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * https://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ // Allow dynamic symbol lookup for in-memory Elf images. #ifndef ABSL_DEBUGGING_INTERNAL_ELF_MEM_IMAGE_H_ #define ABSL_DEBUGGING_INTERNAL_ELF_MEM_IMAGE_H_ // Including this will define the __GLIBC__ macro if glibc is being // used. #include #include "absl/base/config.h" // Maybe one day we can rewrite this file not to require the elf // symbol extensions in glibc, but for right now we need them. #ifdef ABSL_HAVE_ELF_MEM_IMAGE #error ABSL_HAVE_ELF_MEM_IMAGE cannot be directly set #endif #if defined(__ELF__) && !defined(__OpenBSD__) && !defined(__QNX__) && \ !defined(__native_client__) && !defined(__asmjs__) && !defined(__wasm__) #define ABSL_HAVE_ELF_MEM_IMAGE 1 #endif #ifdef ABSL_HAVE_ELF_MEM_IMAGE #include // for ElfW #if defined(__FreeBSD__) && !defined(ElfW) #define ElfW(x) __ElfN(x) #endif namespace absl { ABSL_NAMESPACE_BEGIN namespace debugging_internal { // An in-memory ELF image (may not exist on disk). class ElfMemImage { private: // Sentinel: there could never be an elf image at &kInvalidBaseSentinel. static const int kInvalidBaseSentinel; public: // Sentinel: there could never be an elf image at this address. static constexpr const void *const kInvalidBase = static_cast(&kInvalidBaseSentinel); // Information about a single vdso symbol. // All pointers are into .dynsym, .dynstr, or .text of the VDSO. // Do not free() them or modify through them. struct SymbolInfo { const char *name; // E.g. "__vdso_getcpu" const char *version; // E.g. "LINUX_2.6", could be "" // for unversioned symbol. const void *address; // Relocated symbol address. const ElfW(Sym) *symbol; // Symbol in the dynamic symbol table. }; // Supports iteration over all dynamic symbols. class SymbolIterator { public: friend class ElfMemImage; const SymbolInfo *operator->() const; const SymbolInfo &operator*() const; SymbolIterator& operator++(); bool operator!=(const SymbolIterator &rhs) const; bool operator==(const SymbolIterator &rhs) const; private: SymbolIterator(const void *const image, int index); void Update(int incr); SymbolInfo info_; int index_; const void *const image_; }; explicit ElfMemImage(const void *base); void Init(const void *base); bool IsPresent() const { return ehdr_ != nullptr; } const ElfW(Phdr)* GetPhdr(int index) const; const ElfW(Sym)* GetDynsym(int index) const; const ElfW(Versym)* GetVersym(int index) const; const ElfW(Verdef)* GetVerdef(int index) const; const ElfW(Verdaux)* GetVerdefAux(const ElfW(Verdef) *verdef) const; const char* GetDynstr(ElfW(Word) offset) const; const void* GetSymAddr(const ElfW(Sym) *sym) const; const char* GetVerstr(ElfW(Word) offset) const; int GetNumSymbols() const; SymbolIterator begin() const; SymbolIterator end() const; // Look up versioned dynamic symbol in the image. // Returns false if image is not present, or doesn't contain given // symbol/version/type combination. // If info_out is non-null, additional details are filled in. bool LookupSymbol(const char *name, const char *version, int symbol_type, SymbolInfo *info_out) const; // Find info about symbol (if any) which overlaps given address. // Returns true if symbol was found; false if image isn't present // or doesn't have a symbol overlapping given address. // If info_out is non-null, additional details are filled in. bool LookupSymbolByAddress(const void *address, SymbolInfo *info_out) const; private: const ElfW(Ehdr) *ehdr_; const ElfW(Sym) *dynsym_; const ElfW(Versym) *versym_; const ElfW(Verdef) *verdef_; const ElfW(Word) *hash_; const char *dynstr_; size_t strsize_; size_t verdefnum_; ElfW(Addr) link_base_; // Link-time base (p_vaddr of first PT_LOAD). }; } // namespace debugging_internal ABSL_NAMESPACE_END } // namespace absl #endif // ABSL_HAVE_ELF_MEM_IMAGE #endif // ABSL_DEBUGGING_INTERNAL_ELF_MEM_IMAGE_H_