elna/backend/target.cpp

#include "elna/backend/target.hpp"
#include "elna/backend/riscv.hpp"
#include <cstring>

namespace elna::riscv
{
    elfio_section_writer::iterator::reference elfio_section_writer::iterator::operator*() const noexcept
    {
        return payload;
    }

    elfio_section_writer::iterator::pointer elfio_section_writer::iterator::operator->() const noexcept
    {
        return &payload;
    }

    elfio_section_writer::iterator& elfio_section_writer::iterator::operator++()
    {
        this->payload.data += *this->sizes;
        this->payload.label = *(++this->labels);
        this->payload.size = *(++this->sizes);

        return *this;
    }

    elfio_section_writer::iterator& elfio_section_writer::iterator::operator++(int)
    {
        auto tmp = *this;
        ++(*this);
        return *this;
    }

    bool elfio_section_writer::iterator::operator==(const iterator& that) const
    {
        return this->labels == that.labels;
    }

    bool elfio_section_writer::iterator::operator!=(const iterator& that) const
    {
        return !(*this == that);
    }

    elfio_section_writer::elfio_section_writer(ELFIO::section *section)
        : m_section(section)
    {
    }

    void elfio_section_writer::operator()(const std::string& label, const std::byte *data, std::size_t size)
    {
        labels.push_back(label);
        sizes.push_back(size);
        m_section->append_data(reinterpret_cast<const char *>(data), size);
    }

    std::pair<std::string_view, bool> elfio_section_writer::operator()(const std::byte *data, std::size_t size)
    {
        auto found = std::find_if(begin(), end(),
                [data, size](elfio_section_writer::entry entry) {
                    return size == entry.size && std::memcmp(entry.data, data, size) == 0;
                });
        if (found == end())
        {
            (*this)(".CL" + std::to_string(labels.size()), data, size);
            return std::pair<std::string_view, bool>(labels.back(), true);
        }
        return std::pair<std::string_view, bool>(found->label, false);
    }

    elfio_section_writer::iterator elfio_section_writer::begin() const
    {
        return elfio_section_writer::iterator(labels.cbegin(), sizes.cbegin(),
                reinterpret_cast<const std::byte *>(m_section->get_data()));
    }

    elfio_section_writer::iterator elfio_section_writer::end() const
    {
        return elfio_section_writer::iterator(labels.cend(), sizes.cend());
    }

    ELFIO::section *elfio_section_writer::section() noexcept
    {
        return m_section;
    }

    elfio_writer::elfio_writer(ELFIO::section *text, ELFIO::section *read_only,
            ELFIO::symbol_section_accessor symbol_accessor, ELFIO::string_section_accessor string_accessor)
        : text(text), read_only(elfio_section_writer(read_only)),
        symbol_accessor(symbol_accessor), string_accessor(string_accessor)
    {
    }

    std::size_t elfio_writer::sink(const std::string& label, const std::byte *data, std::size_t size)
    {
        auto offset = text->get_size();
        text->append_data(reinterpret_cast<const char *>(data), size);

        this->symbol_accessor.add_symbol(this->string_accessor, label.data(), offset, label.size(),
                ELFIO::STB_GLOBAL, ELFIO::STT_FUNC, 0, text->get_index());

        return text->get_size();
    }

    std::string_view elfio_writer::sink(const std::byte *data, std::size_t size)
    {
        auto offset = read_only.section()->get_size();
        auto [result, inserted] = read_only(data, size);

        if (inserted)
        {
            this->symbol_accessor.add_symbol(this->string_accessor, result.data(), offset,
                result.size(), ELFIO::STB_LOCAL, ELFIO::STT_NOTYPE, 0,
                read_only.section()->get_index());
        }
        return result;
    }

    void elfio_writer::sink(const std::string& label)
    {
        this->symbol_accessor.add_symbol(this->string_accessor, "printf", 0x00000000, 0,
                ELFIO::STB_GLOBAL, ELFIO::STT_NOTYPE, 0, ELFIO::SHN_UNDEF);
    }

    std::size_t elfio_writer::size() const
    {
        return this->text->get_size();
    }

    std::ptrdiff_t lookup(ELFIO::symbol_section_accessor symbol_accessor, const std::string& label)
    {
        for (ptrdiff_t j = 0; j < symbol_accessor.get_symbols_num(); ++j)
        {
            std::string name;
            ELFIO::Elf64_Addr value;
            ELFIO::Elf_Xword size;
            unsigned char bind;
            unsigned char type;
            ELFIO::Elf_Half section_index;
            unsigned char other;

            symbol_accessor.get_symbol(j, name, value, size, bind, type, section_index, other);
            if (name == label)
            {
                return j;
            }
        }
        return -1;
    }

    void riscv32_elf(source::program *ast, const std::filesystem::path& out_file)
    {
        ELFIO::elfio writer;

        writer.create(ELFIO::ELFCLASS32, ELFIO::ELFDATA2LSB);

        writer.set_os_abi(ELFIO::ELFOSABI_NONE);
        writer.set_type(ELFIO::ET_REL);
        writer.set_machine(ELFIO::EM_RISCV);

        // Create code section
        ELFIO::section* text_sec = writer.sections.add(".text");
        text_sec->set_type(ELFIO::SHT_PROGBITS);
        text_sec->set_flags(ELFIO::SHF_ALLOC | ELFIO::SHF_EXECINSTR);
        text_sec->set_addr_align(0x1);

        // Create string table section
        ELFIO::section* str_sec = writer.sections.add(".strtab");
        str_sec->set_type(ELFIO::SHT_STRTAB);

        // Create string table writer
        ELFIO::string_section_accessor stra(str_sec);

        // Create symbol table section
        ELFIO::section* sym_sec = writer.sections.add(".symtab");
        sym_sec->set_type(ELFIO::SHT_SYMTAB);
        sym_sec->set_info(2);
        sym_sec->set_addr_align(0x4);
        sym_sec->set_entry_size(writer.get_default_entry_size(ELFIO::SHT_SYMTAB));
        sym_sec->set_link(str_sec->get_index());

        // Create relocation table section
        ELFIO::section* rel_sec = writer.sections.add(".rel.text");
        rel_sec->set_type(ELFIO::SHT_REL);
        rel_sec->set_info(text_sec->get_index());
        rel_sec->set_addr_align(0x4);
        rel_sec->set_entry_size(writer.get_default_entry_size(ELFIO::SHT_REL));
        rel_sec->set_link(sym_sec->get_index());
        rel_sec->set_flags(ELFIO::SHF_ALLOC);

        // Create read only data section
        ELFIO::section* ro_sec = writer.sections.add(".rodata");
        ro_sec->set_type(ELFIO::SHT_PROGBITS);
        ro_sec->set_flags(ELFIO::SHF_ALLOC);
        ro_sec->set_addr_align(0x4);

        // Create symbol relocation table writers
        ELFIO::symbol_section_accessor syma(writer, sym_sec);
        ELFIO::relocation_section_accessor rela(writer, rel_sec);
        auto _writer = std::make_shared<elfio_writer>(text_sec, ro_sec, syma, stra);

        visitor _visitor{ _writer };
        _visitor.visit(ast);

        syma.arrange_local_symbols();

        for (auto& reference : _visitor.references)
        {
            ELFIO::Elf_Word relocated_symbol{ 0 };

            switch (reference.target)
            {
                case address_t::high20:
                    relocated_symbol = lookup(syma, reference.name);
                    rela.add_entry(reference.offset, relocated_symbol, 26 /* ELFIO::R_RISCV_HI20 */);
                    rela.add_entry(reference.offset, relocated_symbol, 51 /* ELFIO::R_RISCV_RELAX */);
                    break;
                case address_t::lower12i:
                    relocated_symbol = lookup(syma, reference.name);
                    rela.add_entry(reference.offset, relocated_symbol, 27 /* ELFIO::R_RISCV_LO12_I */);
                    rela.add_entry(reference.offset, relocated_symbol, 51 /* ELFIO::R_RISCV_RELAX */);
                    break;
                case address_t::text:
                    relocated_symbol = lookup(syma, "printf");
                    rela.add_entry(reference.offset, relocated_symbol, 18 /* ELFIO::R_RISCV_CALL */);
                    rela.add_entry(reference.offset, relocated_symbol, 51 /* ELFIO::R_RISCV_RELAX */);
                    break;
            }
        }

        // Create ELF object file
        writer.save(out_file);
    }
}