AOutRelocationSectionReader.cc

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/*
    Copyright (c) 2002-2009 Tampere University.
 
    This file is part of TTA-Based Codesign Environment (TCE).
 
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/**
 * @file AOutRelocationSectionReader.cc
 *
 * Implementation of AOutRelocationSectionReader class.
 *
 * @author Jussi Nykänen 2003 (nykanen-no.spam-cs.tut.fi)
 * @author Mikael Lepistö 2003 (tmlepist-no.spam-cs.tut.fi)
 * @note reviewed 7 October 2003 by jn, ml, tr, ll
 *
 * @note rating: yellow
 */
 
#include "AOutRelocationSectionReader.hh"
#include "RelocElement.hh"
#include "ReferenceKey.hh"
#include "SafePointer.hh"
#include "AOutReader.hh"
#include "TPEFBaseType.hh"
#include "RelocSection.hh"
#include "CodeSection.hh"
#include "DataSection.hh"
#include "SectionReader.hh"
#include "AOutSymbolSectionReader.hh"
#include "AOutTextSectionReader.hh"
#include "ImmediateElement.hh"
#include "Swapper.hh"
 
namespace TPEF {
 
using std::string;
 
using ReferenceManager::SectionOffsetKey;
using ReferenceManager::SectionIndexKey;
using ReferenceManager::SafePointer;
 
AOutRelocationSectionReader AOutRelocationSectionReader::proto_;
const Byte AOutRelocationSectionReader::RELOCATION_TYPE_MASK = 0x1F;
 
/**
 * Constructor.
 *
 * Registers itself to AOutSectionReader.
 */
AOutRelocationSectionReader::AOutRelocationSectionReader() :
    AOutSectionReader() {
 
    SectionReader::registerSectionReader(this);
}
 
/**
 * Destructor.
 */
AOutRelocationSectionReader::~AOutRelocationSectionReader() {
}
 
/**
 * Returns the type of section that reader can read.
 *
 * @return The type of section that reader can read.
 */
Section::SectionType
AOutRelocationSectionReader::type() const {
    return Section::ST_RELOC;
}
 
/**
 * Reads relocation sections from a.out binary file.
 *
 * @param stream The stream to be read from.
 * @param section Section where to information is stored.
 * @exception UnreachableStream If reading of section fails.
 * @exception KeyAlreadyExists Key was in use when trying to register object.
 * @exception EndOfFile If end of file were reached while it shouldn't.
 * @exception OutOfRange Some of read values were out of range.
 * @exception WrongSubclass Some class couldn't do what it was asked for.
 * @exception UnexpectedValue If there was unexpected value when reading.
 */
void
AOutRelocationSectionReader::readData(
    BinaryStream& stream, Section* section) const {
    FileOffset offset = stream.readPosition();
 
    AOutReader* aOutReader = dynamic_cast<AOutReader*>(parent());
    assert(aOutReader != NULL);
 
    // find out whether this is for reading text relocation or data
    // relocation
    RelocSection* relocSection = dynamic_cast<RelocSection*>(section);
    assert(relocSection != NULL);
 
    const Section* refSection = relocSection->referencedSection();
    assert(refSection != NULL);
 
    SectionId refSectionID;
 
    Word length = 0;
    if (refSection->isCodeSection()) {
        refSectionID = AOutReader::ST_TEXT;
        length = aOutReader->header().sectionSizeTextReloc();
 
    } else if (refSection->type() == Section::ST_DATA) {
        refSectionID = AOutReader::ST_DATA;
        length = aOutReader->header().sectionSizeDataReloc();
 
    } else {
        string msg = "Relocating something else than text or data section";
        throw WrongSubclass(__FILE__, __LINE__, __func__, msg);
    }
 
    // all relocation information is read; to offset 'offset+length'
    for (; stream.readPosition() < offset + length;) {
 
        // create and read a new relocation element
        RelocElement* elem = new RelocElement();
        initializeRelocElement(stream, elem, refSectionID, aOutReader);
 
        relocSection->addElement(elem);
    }
}
 
/**
 * Initializes one RelocElement object with correct values.
 *
 * @param stream The stream to be read from.
 * @param elem Element to be initialized.
 * @param refSectionID Identification code of the section that holds
 *                     relocation source.
 * @param reader The base reader for a.out.
 * @exception UnexpectedValue If extern bit is not zero, or if relocation
 *            target is not text or data section.
 * @exception UnreachableStream If stream can't be read.
 * @exception OutOfRange Section offset of an address is invalid.
 */
void
AOutRelocationSectionReader::initializeRelocElement(
    BinaryStream& stream, RelocElement* elem, SectionId refSectionID,
    AOutReader* reader) const {
    Word r_address = stream.readWord();
 
    // if referenced section is text section fix r_address to point
    // starting element of instruction
    // (r_address pointed in the middle of move to immediate value before)
    if (refSectionID == AOutReader::ST_TEXT) {
        r_address -= AOutTextSectionReader::OFFSET_TO_IMMEDIATE_VALUE;
    }
 
    SectionOffsetKey sKey = SectionOffsetKey(refSectionID, r_address);
    elem->setLocation(CREATE_SAFEPOINTER(sKey));
 
    Word secondWord = stream.readWord();
 
    Word r_symbolnum = (secondWord >> BYTE_BITWIDTH);
 
    // addend is value that is stored in element in location pointed by
    // r_address
    AddressImage r_addend = stream.readWord();
 
    // It seems that extern flag and addend field is used to tell does
    // relocation have symbol or section index in symbolnum field.
    // If there is symbol it means that relocation is unresolved.
 
    // NOTE: above doesn't work if there is relocation to the 
    //       first instruction of program in this case secondWord seems to
    //       be always 1026... 
    if (r_addend == 0 &&  checkIfExtern(secondWord) && secondWord != 1026) {
        SectionIndexKey indexKey(AOutReader::ST_SYMBOL, r_symbolnum + 1);
        elem->setSymbol(CREATE_SAFEPOINTER(indexKey));
 
    } else {
        // if we are here r_symbolnum is a section id, not a symbol index
        SectionIndexKey undefSym(AOutReader::ST_SYMBOL,0);
        elem->setSymbol(CREATE_SAFEPOINTER(undefSym));
 
        Word r_offset = reader->sectionOffsetOfAddress(r_addend);
 
        SectionOffsetKey offKey =
            SectionOffsetKey(r_symbolnum, r_offset);
            
        elem->setDestination(CREATE_SAFEPOINTER(offKey));
    }
 
    // convert and set relocation type
    RelocType r_type =
        static_cast<RelocType>(secondWord & RELOCATION_TYPE_MASK);
 
    elem->setType(aOutToTPEFRelocType(r_type));
 
    elem->setSize(sizeof(Word)*BYTE_BITWIDTH);
}
 
/**
 * Finalizer method for AOut relocation sections.
 *
 * Fixes values of elements pointed by location(), MOVE linker does not
 * update values of elements referred from relocation. Also sets address
 * spaces for relocation elements.
 *
 * @param section Section to finalize.
 */
void
AOutRelocationSectionReader::finalize(Section* section) const {
 
    Section *refSection =
        dynamic_cast<RelocSection*>(section)->referencedSection();
 
    AOutReader *aOutReader = dynamic_cast<AOutReader*>(parent());
    assert(aOutReader != NULL);
 
    for (Word i = 0;
         i != section->elementCount();
         i++) {
 
        RelocElement *elem = dynamic_cast<RelocElement*>(section->element(i));
 
        // address space of section where element is or undef aSpace
        elem->setASpace(
            dynamic_cast<AOutReader*>
            (parent())->aSpaceOfElement(elem->destination()));
 
        // relocation is unresolved.
        if (elem->destination() == NULL) continue;
 
        AddressImage destAddress =
            aOutReader->addressOfElement(elem->destination());
 
        // fix value of immediate or chunk
        if (refSection->isCodeSection()) {
 
            // value of immediate element, is file offset to
            // that element, which to immediate refers
            ImmediateElement *imm =
                dynamic_cast<ImmediateElement*>(elem->location());
 
            // relocation must have Immediate or Chunk element as location
            assert(imm != NULL);
 
            // fix the address value
            imm->setWord(destAddress);
 
        } else if (refSection->type() == Section::ST_DATA) {
            Chunk* dataChunk = dynamic_cast<Chunk*>(elem->location());
            DataSection* dataSection = dynamic_cast<DataSection*>(refSection);
 
            // check that section is long enough
            if (dataChunk->offset() + sizeof(destAddress) >
                dataSection->length()) {
                bool requestedChunkWasOutOfRange = false;
                assert(requestedChunkWasOutOfRange);
            }
 
            // fix address of chunk
            Word mauIndex = dataSection->chunkToMAUIndex(dataChunk);
 
            dataSection->writeValue(
                mauIndex, 4, static_cast<unsigned long>(destAddress));
 
        } else {
            bool referencedSectionMustBeEitherCodeOrData = false;
            assert(referencedSectionMustBeEitherCodeOrData);
        }
    }
}
 
/**
 * Converts a.out relocation type into TPEF relocation.
 *
 * @param aOutRelocType Identification code of the relocation type to convert
 *                      to TPEF format.
 * @return TPEF relocation type.
 */
RelocElement::RelocType
AOutRelocationSectionReader::aOutToTPEFRelocType(
    RelocType aOutRelocType) const {
 
    // NOTE: check this conversion.
 
    switch (aOutRelocType) {
    case RELOC_8:
    case RELOC_16:
    case RELOC_32:
        return RelocElement::RT_SELF;
    case NO_RELOC:
        return RelocElement::RT_NOREL;
    default: {
        bool unknownAOutRelocationType = false;
        assert(unknownAOutRelocationType);
    }
    }
 
    // to prevent compile warnings
    return RelocElement::RT_NOREL;
}
 
}