dist/common/StELFFile.cpp

/*
 * File:  StELFFile.cpp
 *
 * Copyright (c) Freescale Semiconductor, Inc. All rights reserved.
 * See included license file for license details.
 */

#include "StELFFile.h"
#include <ios>
#include <stdexcept>
#include <stdio.h>
#include "EndianUtilities.h"

//! \exception StELFFileException is thrown if there is a problem with the file format.
//!
StELFFile::StELFFile(std::istream & inStream)
:         m_stream(inStream)
{
          readFileHeaders();
}

//! Disposes of the string table data.
StELFFile::~StELFFile()
{
          SectionDataMap::iterator it = m_sectionDataCache.begin();
          for (; it != m_sectionDataCache.end(); ++it)
          {
                    SectionDataInfo & info = it->second;
                    if (info.m_data != NULL)
                    {
                              delete [] info.m_data;
                    }
          }
}

//! \exception StELFFileException is thrown if the file is not an ELF file.
//!
void StELFFile::readFileHeaders()
{
          // move read head to beginning of stream
          m_stream.seekg(0, std::ios_base::beg);

          // read ELF header
          m_stream.read(reinterpret_cast<char *>(&m_header), sizeof(m_header));
          if (m_stream.bad())
          {
                    throw StELFFileException("could not read file header");
          }

          // convert endianness
          m_header.e_type = ENDIAN_LITTLE_TO_HOST_U16(m_header.e_type);
          m_header.e_machine = ENDIAN_LITTLE_TO_HOST_U16(m_header.e_machine);
          m_header.e_version = ENDIAN_LITTLE_TO_HOST_U32(m_header.e_version);
          m_header.e_entry = ENDIAN_LITTLE_TO_HOST_U32(m_header.e_entry);
          m_header.e_phoff = ENDIAN_LITTLE_TO_HOST_U32(m_header.e_phoff);
          m_header.e_shoff = ENDIAN_LITTLE_TO_HOST_U32(m_header.e_shoff);
          m_header.e_flags = ENDIAN_LITTLE_TO_HOST_U32(m_header.e_flags);
          m_header.e_ehsize = ENDIAN_LITTLE_TO_HOST_U16(m_header.e_ehsize);
          m_header.e_phentsize = ENDIAN_LITTLE_TO_HOST_U16(m_header.e_phentsize);
          m_header.e_phnum = ENDIAN_LITTLE_TO_HOST_U16(m_header.e_phnum);
          m_header.e_shentsize = ENDIAN_LITTLE_TO_HOST_U16(m_header.e_shentsize);
          m_header.e_shnum = ENDIAN_LITTLE_TO_HOST_U16(m_header.e_shnum);
          m_header.e_shstrndx = ENDIAN_LITTLE_TO_HOST_U16(m_header.e_shstrndx);

          // check magic number
          if (!(m_header.e_ident[EI_MAG0] == ELFMAG0 && m_header.e_ident[EI_MAG1] == ELFMAG1 && m_header.e_ident[EI_MAG2] == ELFMAG2 && m_header.e_ident[EI_MAG3] == ELFMAG3))
          {
                    throw StELFFileException("invalid magic number in ELF header");
          }

          try
          {
                    int i;

                    // read section headers
                    if (m_header.e_shoff != 0 && m_header.e_shnum > 0)
                    {
                              Elf32_Shdr sectionHeader;
                              for (i=0; i < m_header.e_shnum; ++i)
                              {
                                        m_stream.seekg(m_header.e_shoff + m_header.e_shentsize * i, std::ios::beg);
                                        m_stream.read(reinterpret_cast<char *>(&sectionHeader), sizeof(sectionHeader));
                                        if (m_stream.bad())
                                        {
                                                  throw StELFFileException("could not read section header");
                                        }

                                        // convert endianness
                                        sectionHeader.sh_name = ENDIAN_LITTLE_TO_HOST_U32(sectionHeader.sh_name);
                                        sectionHeader.sh_type = ENDIAN_LITTLE_TO_HOST_U32(sectionHeader.sh_type);
                                        sectionHeader.sh_flags = ENDIAN_LITTLE_TO_HOST_U32(sectionHeader.sh_flags);
                                        sectionHeader.sh_addr = ENDIAN_LITTLE_TO_HOST_U32(sectionHeader.sh_addr);
                                        sectionHeader.sh_offset = ENDIAN_LITTLE_TO_HOST_U32(sectionHeader.sh_offset);
                                        sectionHeader.sh_size = ENDIAN_LITTLE_TO_HOST_U32(sectionHeader.sh_size);
                                        sectionHeader.sh_link = ENDIAN_LITTLE_TO_HOST_U32(sectionHeader.sh_link);
                                        sectionHeader.sh_info = ENDIAN_LITTLE_TO_HOST_U32(sectionHeader.sh_info);
                                        sectionHeader.sh_addralign = ENDIAN_LITTLE_TO_HOST_U32(sectionHeader.sh_addralign);
                                        sectionHeader.sh_entsize = ENDIAN_LITTLE_TO_HOST_U32(sectionHeader.sh_entsize);

                                        m_sectionHeaders.push_back(sectionHeader);
                              }
                    }

                    // read program headers
                    if (m_header.e_phoff != 0 && m_header.e_phnum > 0)
                    {
                              Elf32_Phdr programHeader;
                              for (i=0; i < m_header.e_phnum; ++i)
                              {
                                        m_stream.seekg(m_header.e_phoff + m_header.e_phentsize * i, std::ios::beg);
                                        m_stream.read(reinterpret_cast<char *>(&programHeader), sizeof(programHeader));
                                        if (m_stream.bad())
                                        {
                                                  throw StELFFileException("could not read program header");
                                        }

                                        // convert endianness
                                        programHeader.p_type = ENDIAN_LITTLE_TO_HOST_U32(programHeader.p_type);
                                        programHeader.p_offset = ENDIAN_LITTLE_TO_HOST_U32(programHeader.p_type);
                                        programHeader.p_vaddr = ENDIAN_LITTLE_TO_HOST_U32(programHeader.p_vaddr);
                                        programHeader.p_paddr = ENDIAN_LITTLE_TO_HOST_U32(programHeader.p_paddr);
                                        programHeader.p_filesz = ENDIAN_LITTLE_TO_HOST_U32(programHeader.p_filesz);
                                        programHeader.p_memsz = ENDIAN_LITTLE_TO_HOST_U32(programHeader.p_memsz);
                                        programHeader.p_flags = ENDIAN_LITTLE_TO_HOST_U32(programHeader.p_flags);
                                        programHeader.p_align = ENDIAN_LITTLE_TO_HOST_U32(programHeader.p_align);

                                        m_programHeaders.push_back(programHeader);
                              }
                    }

                    // look up symbol table section index
                    {
                        std::string symtab_section_name(SYMTAB_SECTION_NAME);
                        m_symbolTableIndex = getIndexOfSectionWithName(symtab_section_name);
                    }
          }
          catch (...)
          {
                    throw StELFFileException("error reading file");
          }
}

const Elf32_Shdr & StELFFile::getSectionAtIndex(unsigned inIndex) const
{
          if (inIndex > m_sectionHeaders.size())
                    throw std::invalid_argument("inIndex");

          return m_sectionHeaders[inIndex];
}

//! If there is not a matching section, then #SHN_UNDEF is returned instead.
//!
unsigned StELFFile::getIndexOfSectionWithName(const std::string & inName)
{
          unsigned sectionIndex = 0;
          const_section_iterator it = getSectionBegin();
          for (; it != getSectionEnd(); ++it, ++sectionIndex)
          {
                    const Elf32_Shdr & header = *it;
                    if (header.sh_name != 0)
                    {
                              std::string sectionName = getSectionNameAtIndex(header.sh_name);
                              if (inName == sectionName)
                                        return sectionIndex;
                    }
          }

          // no matching section
          return SHN_UNDEF;
}

//! The pointer returned from this method must be freed with the delete array operator (i.e., delete []).
//! If either the section data offset (sh_offset) or the section size (sh_size) are 0, then NULL will
//! be returned instead.
//!
//! The data is read directly from the input stream passed into the constructor. The stream must
//! still be open, or an exception will be thrown.
//!
//! \exception StELFFileException is thrown if an error occurs while reading the file.
//! \exception std::bad_alloc is thrown if memory for the data cannot be allocated.
uint8_t * StELFFile::getSectionDataAtIndex(unsigned inIndex)
{
          return readSectionData(m_sectionHeaders[inIndex]);
}

//! The pointer returned from this method must be freed with the delete array operator (i.e., delete []).
//! If either the section data offset (sh_offset) or the section size (sh_size) are 0, then NULL will
//! be returned instead.
//!
//! The data is read directly from the input stream passed into the constructor. The stream must
//! still be open, or an exception will be thrown.
//!
//! \exception StELFFileException is thrown if an error occurs while reading the file.
//! \exception std::bad_alloc is thrown if memory for the data cannot be allocated.
uint8_t * StELFFile::getSectionData(const_section_iterator inSection)
{
          return readSectionData(*inSection);
}

//! \exception StELFFileException is thrown if an error occurs while reading the file.
//! \exception std::bad_alloc is thrown if memory for the data cannot be allocated.
uint8_t * StELFFile::readSectionData(const Elf32_Shdr & inHeader)
{
          // check for empty data
          if (inHeader.sh_offset == 0 || inHeader.sh_size == 0)
                    return NULL;

          uint8_t * sectionData = new uint8_t[inHeader.sh_size];

          try
          {
                    m_stream.seekg(inHeader.sh_offset, std::ios::beg);
                    m_stream.read(reinterpret_cast<char *>(sectionData), inHeader.sh_size);
                    if (m_stream.bad())
                              throw StELFFileException("could not read entire section");
          }
          catch (StELFFileException)
          {
                    throw;
          }
          catch (...)
          {
                    throw StELFFileException("error reading section data");
          }

          return sectionData;
}

const Elf32_Phdr & StELFFile::getSegmentAtIndex(unsigned inIndex) const
{
          if (inIndex > m_programHeaders.size())
                    throw std::invalid_argument("inIndex");

          return m_programHeaders[inIndex];
}

//! The pointer returned from this method must be freed with the delete array operator (i.e., delete []).
//! If either the segment offset (p_offset) or the segment file size (p_filesz) are 0, then NULL will
//! be returned instead.
//!
//! The data is read directly from the input stream passed into the constructor. The stream must
//! still be open, or an exception will be thrown.
//!
//! \exception StELFFileException is thrown if an error occurs while reading the file.
//! \exception std::bad_alloc is thrown if memory for the data cannot be allocated.
uint8_t * StELFFile::getSegmentDataAtIndex(unsigned inIndex)
{
          return readSegmentData(m_programHeaders[inIndex]);
}

//! The pointer returned from this method must be freed with the delete array operator (i.e., delete []).
//! If either the segment offset (p_offset) or the segment file size (p_filesz) are 0, then NULL will
//! be returned instead.
//!
//! The data is read directly from the input stream passed into the constructor. The stream must
//! still be open, or an exception will be thrown.
//!
//! \exception StELFFileException is thrown if an error occurs while reading the file.
//! \exception std::bad_alloc is thrown if memory for the data cannot be allocated.
uint8_t * StELFFile::getSegmentData(const_segment_iterator inSegment)
{
          return readSegmentData(*inSegment);
}

//! \exception StELFFileException is thrown if an error occurs while reading the file.
//! \exception std::bad_alloc is thrown if memory for the data cannot be allocated.
uint8_t * StELFFile::readSegmentData(const Elf32_Phdr & inHeader)
{
          // check for empty data
          if (inHeader.p_offset == 0 || inHeader.p_filesz== 0)
                    return NULL;

          uint8_t * segmentData = new uint8_t[inHeader.p_filesz];

          try
          {
                    m_stream.seekg(inHeader.p_offset, std::ios::beg);
                    m_stream.read(reinterpret_cast<char *>(segmentData), inHeader.p_filesz);
                    if (m_stream.bad())
                              throw StELFFileException("could not read entire segment");
          }
          catch (StELFFileException)
          {
                    throw;
          }
          catch (...)
          {
                    throw StELFFileException("error reading segment data");
          }

          return segmentData;
}

//! If the index is out of range, or if there is no string table in the file, then
//! an empty string will be returned instead. This will also happen when the index
//! is either 0 or the last byte in the table, since the table begins and ends with
//! zero bytes.
std::string StELFFile::getSectionNameAtIndex(unsigned inIndex)
{
          // make sure there's a section name string table
          if (m_header.e_shstrndx == SHN_UNDEF)
                    return std::string("");

          return getStringAtIndex(m_header.e_shstrndx, inIndex);
}

//! \exception std::invalid_argument is thrown if the section identified by \a
//!                 inStringTableSectionIndex is not actually a string table, or if \a
//!                 inStringIndex is out of range for the string table.
std::string StELFFile::getStringAtIndex(unsigned inStringTableSectionIndex, unsigned inStringIndex)
{
          // check section type
          const Elf32_Shdr & header = getSectionAtIndex(inStringTableSectionIndex);
          if (header.sh_type != SHT_STRTAB)
                    throw std::invalid_argument("inStringTableSectionIndex");

          if (inStringIndex >= header.sh_size)
                    throw std::invalid_argument("inStringTableSectionIndex");

          // check cache
          SectionDataInfo & info = getCachedSectionData(inStringTableSectionIndex);
          return std::string(&reinterpret_cast<char *>(info.m_data)[inStringIndex]);
}

StELFFile::SectionDataInfo & StELFFile::getCachedSectionData(unsigned inSectionIndex)
{
          // check cache
          SectionDataMap::iterator it = m_sectionDataCache.find(inSectionIndex);
          if (it != m_sectionDataCache.end())
                    return it->second;

          // not in cache, add it
          const Elf32_Shdr & header = getSectionAtIndex(inSectionIndex);
          uint8_t * data = getSectionDataAtIndex(inSectionIndex);

          SectionDataInfo info;
          info.m_data = data;
          info.m_size = header.sh_size;

          m_sectionDataCache[inSectionIndex] = info;
          return m_sectionDataCache[inSectionIndex];
}

//! The number of entries in the symbol table is the symbol table section size
//! divided by the size of each symbol entry (the #Elf32_Shdr::sh_entsize field of the
//! symbol table section header).
unsigned StELFFile::getSymbolCount()
{
          if (m_symbolTableIndex == SHN_UNDEF)
                    return 0;

          const Elf32_Shdr & header = getSectionAtIndex(m_symbolTableIndex);
          return header.sh_size / header.sh_entsize;
}

//! \exception std::invalid_argument is thrown if \a inIndex is out of range.]
//!
const Elf32_Sym & StELFFile::getSymbolAtIndex(unsigned inIndex)
{
          // get section data
          const Elf32_Shdr & header = getSectionAtIndex(m_symbolTableIndex);
          SectionDataInfo & info = getCachedSectionData(m_symbolTableIndex);

          // has the symbol table been byte swapped yet?
          if (!info.m_swapped)
          {
                    byteSwapSymbolTable(header, info);
          }

          unsigned symbolOffset = header.sh_entsize * inIndex;
          if (symbolOffset >= info.m_size)
          {
                    throw std::invalid_argument("inIndex");
          }

          Elf32_Sym * symbol = reinterpret_cast<Elf32_Sym *>(&info.m_data[symbolOffset]);
          return *symbol;
}

void StELFFile::byteSwapSymbolTable(const Elf32_Shdr & header, SectionDataInfo & info)
{
          unsigned symbolCount = getSymbolCount();
          unsigned i = 0;
          unsigned symbolOffset = 0;

          for (; i < symbolCount; ++i, symbolOffset += header.sh_entsize)
          {
                    Elf32_Sym * symbol = reinterpret_cast<Elf32_Sym *>(&info.m_data[symbolOffset]);
                    symbol->st_name = ENDIAN_LITTLE_TO_HOST_U32(symbol->st_name);
                    symbol->st_value = ENDIAN_LITTLE_TO_HOST_U32(symbol->st_value);
                    symbol->st_size = ENDIAN_LITTLE_TO_HOST_U32(symbol->st_size);
                    symbol->st_shndx = ENDIAN_LITTLE_TO_HOST_U16(symbol->st_shndx);
          }

          // remember that we've byte swapped the symbols
          info.m_swapped = true;
}

unsigned StELFFile::getSymbolNameStringTableIndex() const
{
          const Elf32_Shdr & header = getSectionAtIndex(m_symbolTableIndex);
          return header.sh_link;
}

std::string StELFFile::getSymbolName(const Elf32_Sym & inSymbol)
{
          unsigned symbolStringTableIndex = getSymbolNameStringTableIndex();
          return getStringAtIndex(symbolStringTableIndex, inSymbol.st_name);
}

//! Returns STN_UNDEF if it cannot find a symbol at the given \a symbolAddress.
unsigned StELFFile::getIndexOfSymbolAtAddress(uint32_t symbolAddress, bool strict)
{
          unsigned symbolCount = getSymbolCount();
          unsigned symbolIndex = 0;
          for (; symbolIndex < symbolCount; ++symbolIndex)
          {
                    const Elf32_Sym & symbol = getSymbolAtIndex(symbolIndex);

                    // the GHS toolchain puts in STT_FUNC symbols marking the beginning and ending of each
                    // file. if the entry point happens to be at the beginning of the file, the beginning-
                    // of-file symbol will have the same value and type. fortunately, the size of these
                    // symbols is 0 (or seems to be). we also ignore symbols that start with two dots just
                    // in case.
                    if (symbol.st_value == symbolAddress && (strict && ELF32_ST_TYPE(symbol.st_info) == STT_FUNC && symbol.st_size != 0))
                    {
                              std::string symbolName = getSymbolName(symbol);

                              // ignore symbols that start with two dots
                              if (symbolName[0] == '.' && symbolName[1] == '.')
                                        continue;

                              // found the symbol!
                              return symbolIndex;
                    }
          }

          return STN_UNDEF;
}

ARMSymbolType_t StELFFile::getTypeOfSymbolAtIndex(unsigned symbolIndex)
{
          ARMSymbolType_t symType = eARMSymbol;
          const Elf32_Sym & symbol = getSymbolAtIndex(symbolIndex);

          if (m_elfVariant == eGHSVariant)
          {
                    if (symbol.st_other & STO_THUMB)
                              symType = eThumbSymbol;
          }
          else
          {
                    unsigned mappingSymStart = 1;
                    unsigned mappingSymCount = getSymbolCount() - 1;  // don't include first undefined symbol
                    bool mapSymsFirst = (m_header.e_flags & EF_ARM_MAPSYMSFIRST) != 0;
                    if (mapSymsFirst)
                    {
                              // first symbol '$m' is number of mapping syms
                              const Elf32_Sym & mappingSymCountSym = getSymbolAtIndex(1);
                              if (getSymbolName(mappingSymCountSym) == MAPPING_SYMBOL_COUNT_TAGSYM)
                              {
                                        mappingSymCount = mappingSymCountSym.st_value;
                                        mappingSymStart = 2;
                              }

                    }

                    uint32_t lastMappingSymAddress = 0;
                    unsigned mappingSymIndex = mappingSymStart;
                    for (; mappingSymIndex < mappingSymCount + mappingSymStart; ++mappingSymIndex)
                    {
                              const Elf32_Sym & mappingSym = getSymbolAtIndex(mappingSymIndex);
                              std::string mappingSymName = getSymbolName(mappingSym);
                              ARMSymbolType_t nextSymType = eUnknownSymbol;

                              if (mappingSymName == ARM_SEQUENCE_MAPSYM)
                                        symType = eARMSymbol;
                              else if (mappingSymName == DATA_SEQUENCE_MAPSYM)
                                        symType = eDataSymbol;
                              else if (mappingSymName == THUMB_SEQUENCE_MAPSYM)
                                        symType = eThumbSymbol;

                              if (nextSymType != eUnknownSymbol)
                              {
                                        if (symbol.st_value >= lastMappingSymAddress && symbol.st_value < mappingSym.st_value)
                                                  break;

                                        symType = nextSymType;
                                        lastMappingSymAddress = mappingSym.st_value;
                              }
                    }
          }

          return symType;
}

void StELFFile::dumpSections()
{
          unsigned count = getSectionCount();
          unsigned i = 0;

          const char * sectionTypes[12] = { "NULL", "PROGBITS", "SYMTAB", "STRTAB", "RELA", "HASH", "DYNAMIC", "NOTE", "NOBITS", "REL", "SHLIB", "DYNSYM" };

          for (; i < count; ++i)
          {
                    const Elf32_Shdr & header = getSectionAtIndex(i);
                    std::string name = getSectionNameAtIndex(header.sh_name);

                    printf("%s: %s, 0x%08x, 0x%08x, 0x%08x, %d, %d, %d\n", name.c_str(), sectionTypes[header.sh_type], header.sh_addr, header.sh_offset, header.sh_size, header.sh_link, header.sh_info, header.sh_entsize);
          }
}

void StELFFile::dumpSymbolTable()
{
          const char * symbolTypes[5] = { "NOTYPE", "OBJECT", "FUNC", "SECTION", "FILE" };
          const char * symbolBinding[3] = { "LOCAL", "GLOBAL", "WEAK" };

          unsigned count = getSymbolCount();
          unsigned i = 0;

          for (; i < count; ++i)
          {
                    const Elf32_Sym & symbol = getSymbolAtIndex(i);
                    std::string name = getSymbolName(symbol);

                    printf("'%s': %s, %s, 0x%08x, 0x%08x, %d. 0x%08x\n", name.c_str(), symbolTypes[ELF32_ST_TYPE(symbol.st_info)], symbolBinding[ELF32_ST_BIND(symbol.st_info)], symbol.st_value, symbol.st_size, symbol.st_shndx, symbol.st_other);
          }
}