// Copyright 2017 The Crashpad Authors. All rights reserved.
//
// 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
//
// http://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.
#ifndef CRASHPAD_SNAPSHOT_ELF_ELF_IMAGE_READER_H_
#define CRASHPAD_SNAPSHOT_ELF_ELF_IMAGE_READER_H_
#include <elf.h>
#include <stdint.h>
#include <sys/types.h>
#include <memory>
#include <string>
#include "base/macros.h"
#include "snapshot/elf/elf_dynamic_array_reader.h"
#include "snapshot/elf/elf_symbol_table_reader.h"
#include "util/misc/address_types.h"
#include "util/misc/initialization_state.h"
#include "util/misc/initialization_state_dcheck.h"
#include "util/process/process_memory_range.h"
namespace crashpad {
//! \brief A reader for ELF images mapped into another process.
//!
//! This class is capable of reading both 32-bit and 64-bit images.
class ElfImageReader {
private:
class ProgramHeaderTable;
public:
//! \brief This class enables reading note segments from an ELF image.
//!
//! Objects of this class should be created by calling
//! ElfImageReader::Notes() or ElfImageReader::NotesWithNameAndType().
class NoteReader {
public:
~NoteReader();
//! \brief The return value for NextNote().
enum class Result {
//! \brief An error occurred. The NoteReader is invalidated and message is
//! logged.
kError,
//! \brief A note was found.
kSuccess,
//! \brief No more notes were found.
kNoMoreNotes,
};
//! \brief A type large enough to hold a note type, potentially across
//! bitness.
using NoteType = decltype(Elf64_Nhdr::n_type);
//! \brief Searches for the next note in the image.
//!
//! \param[out] name The name of the note owner, if not `nullptr`.
//! \param[out] type A type for the note, if not `nullptr`.
//! \param[out] desc The note descriptor.
//! \return a #Result value. \a name, \a type, and \a desc are only valid if
//! this method returns Result::kSuccess.
Result NextNote(std::string* name, NoteType* type, std::string* desc);
// private
NoteReader(const ElfImageReader* elf_reader_,
const ProcessMemoryRange* range,
const ProgramHeaderTable* phdr_table,
ssize_t max_note_size,
const std::string& name_filter = std::string(),
NoteType type_filter = 0,
bool use_filter = false);
private:
// Reads the next note at the current segment address. Sets retry_ to true
// and returns kError if use_filter_ is true and the note's name and type do
// not match name_filter_ and type_filter_.
template <typename T>
Result ReadNote(std::string* name, NoteType* type, std::string* desc);
VMAddress current_address_;
VMAddress segment_end_address_;
const ElfImageReader* elf_reader_; // weak
const ProcessMemoryRange* range_; // weak
const ProgramHeaderTable* phdr_table_; // weak
std::unique_ptr<ProcessMemoryRange> segment_range_;
size_t phdr_index_;
ssize_t max_note_size_;
std::string name_filter_;
NoteType type_filter_;
bool use_filter_;
bool is_valid_;
bool retry_;
DISALLOW_COPY_AND_ASSIGN(NoteReader);
};
ElfImageReader();
~ElfImageReader();
//! \brief Initializes the reader.
//!
//! This method must be called once on an object and must be successfully
//! called before any other method in this class may be called.
//!
//! \param[in] memory A memory reader for the remote process.
//! \param[in] address The address in the remote process' address space where
//! the ELF image is loaded.
bool Initialize(const ProcessMemoryRange& memory, VMAddress address);
//! \brief Returns the base address of the image's memory range.
//!
//! This may differ from the address passed to Initialize() if the ELF header
//! is not loaded at the start of the first `PT_LOAD` segment.
VMAddress Address() const { return memory_.Base(); }
//! \brief Returns the size of the range containing all loaded segments for
//! this image.
//!
//! The size may include memory that is unmapped or mapped to other objects if
//! this image's `PT_LOAD` segments are not contiguous.
VMSize Size() const { return memory_.Size(); }
//! \brief Returns the file type for the image.
//!
//! Possible values include `ET_EXEC` or `ET_DYN` from `<elf.h>`.
uint16_t FileType() const;
//! \brief Returns the load bias for the image.
//!
//! The load bias is the actual load address minus the preferred load address.
VMOffset GetLoadBias() const { return load_bias_; }
//! \brief Reads information from the dynamic symbol table about the symbol
//! identified by \a name.
//!
//! \param[in] name The name of the symbol to search for.
//! \param[out] address The address of the symbol in the target process'
//! address space, if found.
//! \param[out] size The size of the symbol, if found.
//! \return `true` if the symbol was found.
bool GetDynamicSymbol(const std::string& name,
VMAddress* address,
VMSize* size);
//! \brief Reads a `NUL`-terminated C string from this image's dynamic string
//! table.
//!
//! \param[in] offset the byte offset in the string table to start reading.
//! \param[out] string the string read.
//! \return `true` on success. Otherwise `false` with a message logged.
bool ReadDynamicStringTableAtOffset(VMSize offset, std::string* string);
//! \brief Determine the debug address.
//!
//! The debug address is a pointer to an `r_debug` struct defined in
//! `<link.h>`.
//!
//! \param[out] debug the debug address, if found.
//! \return `true` if the debug address was found.
bool GetDebugAddress(VMAddress* debug);
//! \brief Return a NoteReader for this image, which scans all PT_NOTE
//! segments in the image.
//!
//! The returned NoteReader is only valid for the lifetime of the
//! ElfImageReader that created it.
//!
//! \param[in] max_note_size The maximum note size to read. Notes whose
//! combined name, descriptor, and padding size are greater than
//! \a max_note_size will be silently skipped. A \a max_note_size of -1
//! indicates infinite maximum note size.
//! \return A NoteReader object capable of reading notes in this image.
std::unique_ptr<NoteReader> Notes(ssize_t max_note_size);
//! \brief Return a NoteReader for this image, which scans all PT_NOTE
//! segments in the image, filtering by name and type.
//!
//! The returned NoteReader is only valid for the lifetime of the
//! ElfImageReader that created it.
//!
//! \param[in] name The note name to match.
//! \param[in] type The note type to match.
//! \param[in] max_note_size The maximum note size to read. Notes whose
//! combined name, descriptor, and padding size are greater than
//! \a max_note_size will be silently skipped. A \a max_note_size of -1
//! indicates infinite maximum note size.
//! \return A NoteReader object capable of reading notes in this image.
std::unique_ptr<NoteReader> NotesWithNameAndType(const std::string& name,
NoteReader::NoteType type,
ssize_t max_note_size);
//! \brief Return a ProcessMemoryRange restricted to the range of this image.
//!
//! The caller does not take ownership of the returned object.
const ProcessMemoryRange* Memory() const;
private:
template <typename PhdrType>
class ProgramHeaderTableSpecific;
bool InitializeProgramHeaders();
bool InitializeDynamicArray();
bool InitializeDynamicSymbolTable();
bool GetAddressFromDynamicArray(uint64_t tag, VMAddress* address);
union {
Elf32_Ehdr header_32_;
Elf64_Ehdr header_64_;
};
VMAddress ehdr_address_;
VMOffset load_bias_;
ProcessMemoryRange memory_;
std::unique_ptr<ProgramHeaderTable> program_headers_;
std::unique_ptr<ElfDynamicArrayReader> dynamic_array_;
std::unique_ptr<ElfSymbolTableReader> symbol_table_;
InitializationStateDcheck initialized_;
InitializationState dynamic_array_initialized_;
InitializationState symbol_table_initialized_;
DISALLOW_COPY_AND_ASSIGN(ElfImageReader);
};
} // namespace crashpad
#endif // CRASHPAD_SNAPSHOT_ELF_ELF_IMAGE_READER_H_