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// -*- 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 <cxxabi.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(iterator->value);
ext->name = SymbolString(iterator->name_offset, strings);
#if !defined(__ANDROID__) // Android NDK doesn't provide abi::__cxa_demangle.
int status = 0;
char* demangled =
abi::__cxa_demangle(ext->name.c_str(), NULL, NULL, &status);
if (demangled) {
if (status == 0)
ext->name = demangled;
free(demangled);
}
#endif
module->AddExtern(ext);
}
++iterator;
}
return true;
}
} // namespace google_breakpad
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