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Diffstat (limited to 'src/common/linux/elf_symbols_to_module.cc')
| -rw-r--r-- | src/common/linux/elf_symbols_to_module.cc | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/src/common/linux/elf_symbols_to_module.cc b/src/common/linux/elf_symbols_to_module.cc new file mode 100644 index 00000000..82d53dd1 --- /dev/null +++ b/src/common/linux/elf_symbols_to_module.cc @@ -0,0 +1,168 @@ +// -*- mode: c++ -*- + +// Copyright (c) 2011 Google Inc. All Rights Reserved. +// +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are +// met: +// +// * Redistributions of source code must retain the above copyright +// notice, this list of conditions and the following disclaimer. +// * Redistributions in binary form must reproduce the above +// copyright notice, this list of conditions and the following disclaimer +// in the documentation and/or other materials provided with the +// distribution. +// * Neither the name of Google Inc. nor the names of its +// contributors may be used to endorse or promote products derived from +// this software without specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +// Original author: Ted Mielczarek <ted.mielczarek@gmail.com> + +#include "common/linux/elf_symbols_to_module.h" + +#include <elf.h> +#include <string.h> + +#include "common/byte_cursor.h" +#include "common/module.h" + +namespace google_breakpad { + +class ELFSymbolIterator { +public: + // The contents of an ELF symbol, adjusted for the host's endianness, + // word size, and so on. Corresponds to the data in Elf32_Sym / Elf64_Sym. + struct Symbol { + // True if this iterator has reached the end of the symbol array. When + // this is set, the other members of this structure are not valid. + bool at_end; + + // The number of this symbol within the list. + size_t index; + + // The current symbol's name offset. This is the offset within the + // string table. + size_t name_offset; + + // The current symbol's value, size, info and shndx fields. + uint64_t value; + uint64_t size; + unsigned char info; + uint16_t shndx; + }; + + // Create an ELFSymbolIterator walking the symbols in BUFFER. Treat the + // symbols as big-endian if BIG_ENDIAN is true, as little-endian + // otherwise. Assume each symbol has a 'value' field whose size is + // VALUE_SIZE. + // + ELFSymbolIterator(const ByteBuffer *buffer, bool big_endian, + size_t value_size) + : value_size_(value_size), cursor_(buffer, big_endian) { + // Actually, weird sizes could be handled just fine, but they're + // probably mistakes --- expressed in bits, say. + assert(value_size == 4 || value_size == 8); + symbol_.index = 0; + Fetch(); + } + + // Move to the next symbol. This function's behavior is undefined if + // at_end() is true when it is called. + ELFSymbolIterator &operator++() { Fetch(); symbol_.index++; return *this; } + + // Dereferencing this iterator produces a reference to an Symbol structure + // that holds the current symbol's values. The symbol is owned by this + // SymbolIterator, and will be invalidated at the next call to operator++. + const Symbol &operator*() const { return symbol_; } + const Symbol *operator->() const { return &symbol_; } + +private: + // Read the symbol at cursor_, and set symbol_ appropriately. + void Fetch() { + // Elf32_Sym and Elf64_Sym have different layouts. + unsigned char other; + if (value_size_ == 4) { + // Elf32_Sym + cursor_ + .Read(4, false, &symbol_.name_offset) + .Read(4, false, &symbol_.value) + .Read(4, false, &symbol_.size) + .Read(1, false, &symbol_.info) + .Read(1, false, &other) + .Read(2, false, &symbol_.shndx); + } else { + // Elf64_Sym + cursor_ + .Read(4, false, &symbol_.name_offset) + .Read(1, false, &symbol_.info) + .Read(1, false, &other) + .Read(2, false, &symbol_.shndx) + .Read(8, false, &symbol_.value) + .Read(8, false, &symbol_.size); + } + symbol_.at_end = !cursor_; + } + + // The size of symbols' value field, in bytes. + size_t value_size_; + + // A byte cursor traversing buffer_. + ByteCursor cursor_; + + // Values for the symbol this iterator refers to. + Symbol symbol_; +}; + +const char *SymbolString(ptrdiff_t offset, ByteBuffer& strings) { + if (offset < 0 || (size_t) offset >= strings.Size()) { + // Return the null string. + offset = 0; + } + return reinterpret_cast<const char *>(strings.start + offset); +} + +bool ELFSymbolsToModule(const uint8_t *symtab_section, + size_t symtab_size, + const uint8_t *string_section, + size_t string_size, + const bool big_endian, + size_t value_size, + Module *module) { + ByteBuffer symbols(symtab_section, symtab_size); + // Ensure that the string section is null-terminated. + if (string_section[string_size - 1] != '\0') { + const void* null_terminator = memrchr(string_section, '\0', string_size); + string_size = reinterpret_cast<const uint8_t*>(null_terminator) + - string_section; + } + ByteBuffer strings(string_section, string_size); + + // The iterator walking the symbol table. + ELFSymbolIterator iterator(&symbols, big_endian, value_size); + + while(!iterator->at_end) { + if (ELF32_ST_TYPE(iterator->info) == STT_FUNC && + iterator->shndx != SHN_UNDEF) { + Module::Extern *ext = new Module::Extern; + ext->name = SymbolString(iterator->name_offset, strings); + ext->address = iterator->value; + module->AddExtern(ext); + } + ++iterator; + } + return true; +} + +} // namespace google_breakpad |