Retro68/Elf2Mac/Object.cc

/*
     Copyright 2017 Wolfgang Thaller.

     This file is part of Retro68.

     Retro68 is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation, either version 3 of the License, or
     (at your option) any later version.

     Retro68 is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with Retro68.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "Object.h"
#include "Symbol.h"
#include "Symtab.h"
#include "Section.h"
#include "SegmentMap.h"
#include "Reloc.h"

#include <err.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <sstream>
#include <string>

#include <boost/algorithm/string/predicate.hpp>

#include "ResourceFork.h"
#include "BinaryIO.h"
#include "ResourceFile.h"

using std::string;
using std::shared_ptr;
using std::make_shared;
using std::ofstream;
using std::unordered_map;
using std::vector;

Object::~Object()
{
}

Object::Object(string input)
{
    if(elf_version ( EV_CURRENT ) == EV_NONE)
        errx(EXIT_FAILURE , "ELF library initialization failed: %s", elf_errmsg( -1));

    int fd = open(input.c_str(), O_RDONLY, 0);
    elf = elf_begin(fd, ELF_C_READ, NULL);

    elf_getshdrstrndx(elf, &sectionHeaderStringTableIdx);

    GElf_Ehdr ehdr;
    gelf_getehdr(elf, &ehdr);

    int idx;

    idx = 1;
    for(Elf_Scn *scn = NULL; (scn = elf_nextscn(elf, scn)) != NULL; idx++)
    {
        GElf_Shdr shdr;
        gelf_getshdr(scn, &shdr);
        std::string name = elf_strptr(elf, sectionHeaderStringTableIdx, shdr.sh_name);
        if(shdr.sh_type == SHT_STRTAB)
        {
            if(name == ".strtab")
                mainStringTableIdx = idx;
        }
    }

    idx = 1;
    for(Elf_Scn *scn = NULL; (scn = elf_nextscn(elf, scn)) != NULL; idx++)
    {
        GElf_Shdr shdr;
        gelf_getshdr(scn, &shdr);
        std::string name = elf_strptr(elf, sectionHeaderStringTableIdx, shdr.sh_name);
        //std::cout << "section #" << idx << ": " << name << std::endl;
        //std::cout << "        =" << shdr.sh_addr << " + " << shdr.sh_size << std::endl;

        if(shdr.sh_type == SHT_SYMTAB
                    && !symtab)
        {
            symtab.reset(new Symtab(*this, scn));
        }
        if(shdr.sh_type == SHT_RELA)
        {
            if(boost::algorithm::starts_with(name,".rela."))
            {
                string progbitsName = name.substr(5);
                assert(sections.find(progbitsName) != sections.end());
                sections[progbitsName]->SetRela(scn);
            }
        }
        if(shdr.sh_type == SHT_PROGBITS && (shdr.sh_flags & SHF_ALLOC))
        {
            SectionKind kind = SectionKind::code;

            if(name == ".data")
                kind = SectionKind::data;
            if(name == ".strippedmacsbugnames")
                kind = SectionKind::undefined;

            auto section = make_shared<Section>(*this, name, idx, kind, scn);

            sections[name] = sectionsByElfIndex[idx] = section;
            if(kind == SectionKind::data)
                dataSection = section;
            else if(kind == SectionKind::code)
                codeSections.push_back(section);
        }
        if(shdr.sh_type == SHT_NOBITS)
        {
            bssSection = sections[name] = sectionsByElfIndex[idx] =
                    make_shared<Section>(*this, name, idx, SectionKind::bss, scn);
        }
    }

    std::sort(codeSections.begin(), codeSections.end(),
              [](shared_ptr<Section> a, shared_ptr<Section> b) { return a->name < b->name; });
}

void Object::FlatCode(std::ostream& out)
{
    for(auto sec : codeSections)
    {
        sec->FixRelocs(true);
        out << sec->GetData();
    }
        
    dataSection->FixRelocs(true);
    out << dataSection->GetData();

    std::vector<RuntimeReloc> relocs;
    for(auto sec : codeSections)
    {
        auto tmp = sec->GetRelocations(false);
        relocs.insert(relocs.end(), tmp.begin(), tmp.end());
    }
    {
        auto tmp = dataSection->GetRelocations(false);
        relocs.insert(relocs.end(), tmp.begin(), tmp.end());
    }
    out << SerializeRelocs(relocs);
}

void Object::FlatCode(string fn)
{
    ofstream out(fn);
    FlatCode(out);
}


std::string fromhex(std::string hex)
{
    std::string bin;
    int nibble;
    bool haveNibble = false;
    for(std::string::iterator p = hex.begin(); p != hex.end(); ++p)
    {
        if(std::isspace(*p))
            continue;
        assert(isdigit(*p) || (tolower(*p) >= 'a' && tolower(*p) <= 'f'));
        int digit;
        if(isdigit(*p))
            digit = *p - '0';
        else
            digit = tolower(*p) - 'a' + 0xA;

        if(haveNibble)
        {
            bin += (char) ((nibble << 4) | digit);
            haveNibble = false;
        }
        else
        {
            nibble = digit;
            haveNibble = true;
        }
    }
    return bin;
}



void Object::SingleSegmentApp(string output)
{
    ResourceFile file;
    Resources& rsrc = file.resources;

    rsrc.addResource(Resource(ResType("CODE"), 0,
        fromhex(
            "00000028 00000000 00000008 00000020"
            "0000 3F3C 0001 A9F0"
        )
    ));


    {
        std::ostringstream code1;
        word(code1, 0);
        word(code1, 1);
        FlatCode(code1);

        rsrc.addResource(Resource(ResType("CODE"), 1,
                                  code1.str()));
    }

    file.creator = ResType("????");
    file.type = ResType("APPL");

    file.write(output);
}



void Object::MultiSegmentApp(string output, SegmentMap& segmentMap)
{
    bool noisy = false;
    
    ResourceFile file;
    Resources& rsrc = file.resources;

    for(auto namedSec : sections)
    {
        namedSec.second->ScanRelocs();
    }

    int jtEntryCount = 0;
    unordered_map<int, vector<Symbol*>> jtEntries;
    for(Symbol& sym : symtab->symbols)
    {
        if(sym.valid)
        {
            if(sym.referencedExternally && sym.sectionKind == SectionKind::code)
            {
                sym.needsJT = true;
                sym.jtIndex = -1;
                sym.section->jtEntries.push_back(&sym);
                ++jtEntryCount;
            }
        }
    }

    uint32_t data_and_bss_size = dataSection->shdr.sh_size + bssSection->shdr.sh_size;

    {
        std::ostringstream code0;
        longword(code0, 0x20 + 8 * (jtEntryCount+2));
        longword(code0, data_and_bss_size);
        longword(code0, 8 * (jtEntryCount+2));
        longword(code0, 0x20);

        code0 << fromhex("0000 3F3C 0001 A9F0");    // jt entry for entrypoint
        code0 << fromhex("0000 FFFF 0000 0000");    // 32-bit entries start from here

        int jtIndex = 2;
        int id = 1;
        for(auto sec : codeSections)
        {
            sec->codeID = id;

            sec->firstJTEntryIndex = jtIndex;

            GElf_Shdr &shdr = sec->shdr;

            for(Symbol* jtEntry : sec->jtEntries)
            {
                word(code0, id);
                word(code0, 0xA9F0);
                uint32_t offset = jtEntry->st_value - shdr.sh_addr;
                if(id == 1)
                    offset += 4;
                else
                    offset += 40;
                longword(code0, offset);

                jtEntry->jtIndex = jtIndex++;

                //std::cout << "JT Entry " << jtEntry->jtIndex << ": " << jtEntry->name << std::endl;
            }

            id++;
        }

        if(noisy)
        {
            std::cout << "CODE 0: " << code0.str().size() << " bytes\n";
            std::cout << "above A5: " << 0x20 + 8 * (jtEntryCount+2) << " bytes\n";
            std::cout << "below A5: " << data_and_bss_size << " bytes\n";
            std::cout << ".data: " << dataSection->shdr.sh_size << " bytes at A5-"
                        << std::hex << data_and_bss_size << std::dec << "\n";
            std::cout << ".bss: " << bssSection->shdr.sh_size << " bytes at A5-"
                        << std::hex << bssSection->shdr.sh_size << std::dec << "\n";
        }
        rsrc.addResource(Resource(ResType("CODE"), 0, code0.str()));
    }

    for(auto sec : codeSections)
    {
        int id = sec->codeID;
        if(id == 1)
            sec->outputBase = 4;    // standard 'CODE' header
        else
            sec->outputBase = 40;    // far-model 'CODE' header

        string exceptionInfoMarker = "__EH_FRAME_BEGIN__";
        if(id != 1)
        {
            std::ostringstream ss;
            ss << std::setw(5) << std::setfill('0') << id;
            const std::string zero_padded_id = ss.str();
            exceptionInfoMarker += zero_padded_id;
        }
        int exceptionInfoSym = symtab->FindSym(exceptionInfoMarker);
        if(exceptionInfoSym != -1)
        {
            Symbol& s = symtab->GetSym(exceptionInfoSym);
            sec->exceptionInfoStart = s.st_value;

            int codeSize = sec->shdr.sh_size;
            int exceptionSize = sec->shdr.sh_addr + codeSize - sec->exceptionInfoStart;
            double percent = 100.0 * exceptionSize / codeSize;

            if(noisy)
                std::cout << "CODE " << id << " has " << exceptionSize << " bytes of exception info (" << percent << "%)\n";
        }
        else if(noisy)
            std::cout << "exception info marker not found: " << exceptionInfoMarker << std::endl;
    }
    dataSection->outputBase = -data_and_bss_size;
    bssSection->outputBase = -bssSection->shdr.sh_size;


    for(auto namedSec : sections)
    {
        namedSec.second->FixRelocs(false);
    }

    for(auto sec : codeSections)
    {
        int id = sec->codeID;
        std::ostringstream code;
        if(id == 1)
        {
            word(code, 0);
            word(code, 1);
        }
        else
        {
            word(code, 0xFFFF);
            word(code, 0);
            longword(code, 0);
            longword(code, 0);
            longword(code, 8 * sec->firstJTEntryIndex );
            longword(code, sec->jtEntries.size());
            longword(code, 0);    // reloc info for A5
            longword(code, 0);    // assumed address for A5
            longword(code, 0);    // reloc info for code
            longword(code, 0);    // assumed address for start of code resource
            longword(code, 0);
        }
        code << sec->GetData();

        if(noisy)
        {
            std::cout << "CODE " << id << ": " << code.str().size() << " bytes\n";

            if(code.str().size() == 80)
            {
                std::cout << "... empty. Skipping.\n";
                continue;
            }
        }

        string segmentName = segmentMap.GetSegmentName(id);

        rsrc.addResource(Resource(ResType("CODE"), id,
                                  code.str(),
                                  segmentName));


        rsrc.addResource(Resource(ResType("RELA"),id, SerializeRelocs(sec->GetRelocations(true))));
    }

    rsrc.addResource(Resource(ResType("DATA"),0, dataSection->GetData()));
    rsrc.addResource(Resource(ResType("RELA"),0, SerializeRelocs(dataSection->GetRelocations(true))));

    if(noisy)
        std::cout << "DATA 0: " << dataSection->shdr.sh_size << " bytes\n";

    file.creator = ResType("????");
    file.type = ResType("APPL");

    file.write(output);
}