elna/source/cl.cpp

#include "elna/cl.hpp"
#include "elna/result.hpp"
#include "elna/riscv.hpp"
#include <cstddef>
#include <elfio/elfio.hpp>
#include <fstream>
#include <sstream>

namespace elna
{
    char *readSource(const char *source)
    {
        const std::size_t bufferSize = 255;

        std::ifstream input_stream{ source };
        std::stringstream buffer;
        buffer << input_stream.rdbuf();
        input_stream.close();
        std::string contents = buffer.str();
        char *result = reinterpret_cast<char *>(malloc(contents.size() + 1));
        std::copy(std::cbegin(contents), std::cend(contents), result);
        result[contents.size()] = '\0';

        return result;
    }

    int compile(const char *inFile, const char *outputFilename)
    {
        ELFIO::elfio writer;

        // You can't proceed before this function call!
        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);

        auto sourceText = readSource(inFile);
        if (sourceText == nullptr)
        {
            return 3;
        }
        CompileError *compileError = nullptr;
        size_t tokensCount{ 0 };
        auto tokens = lex(sourceText, compileError, &tokensCount);
        free(sourceText);
        if (tokens == nullptr)
        {
            printf("%lu:%lu: %s\n", compileError->line(), compileError->column(), compileError->what());
            return 1;
        }
        auto ast = parse(tokens, tokensCount);
        if (ast == nullptr)
        {
            return 2;
        }
        auto program = writeNext(ast);

        // 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);
        text_sec->set_data(reinterpret_cast<const char *>(program.text), program.length);

        // 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);
        // Add label name
        ELFIO::Elf32_Word str_index = stra.add_string("msg");

        // 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);
        ro_sec->set_data("%d\n");

        // 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 symbol table writer
        ELFIO::symbol_section_accessor syma(writer, sym_sec);
        auto label_sym = syma.add_symbol(stra, ".CL0", 0x00000000, strlen("%d\n") + 1,
                ELFIO::STB_LOCAL, ELFIO::STT_NOTYPE, 0, ro_sec->get_index());
        syma.add_symbol(stra, program.name, 0x00000000, program.length,
                ELFIO::STB_GLOBAL, ELFIO::STT_FUNC, 0, text_sec->get_index());
        auto printf_sym = syma.add_symbol(stra, "printf", 0x00000000, 0,
                ELFIO::STB_GLOBAL, ELFIO::STT_NOTYPE, 0, ELFIO::SHN_UNDEF);

        // 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 relocation table writer
        ELFIO::relocation_section_accessor rela(writer, rel_sec);
        // Add relocation entry (adjust address at offset 11)
        rela.add_entry(program.symbols[0].offset, label_sym, 26 /* ELFIO::R_RISCV_HI20 */);
        rela.add_entry(program.symbols[0].offset, label_sym, 51 /* ELFIO::R_RISCV_RELAX */);
        rela.add_entry(program.symbols[1].offset, label_sym, 27 /* ELFIO::R_RISCV_LO12_I */);
        rela.add_entry(program.symbols[1].offset, label_sym, 51 /* ELFIO::R_RISCV_RELAX */);
        rela.add_entry(program.symbols[2].offset, printf_sym, 18 /* ELFIO::R_RISCV_CALL */);
        rela.add_entry(program.symbols[2].offset, printf_sym, 51 /* ELFIO::R_RISCV_RELAX */);

        // Another method to add the same relocation entry at one step is:
        // rela.add_entry( stra, "msg",
        //                 syma, 29, 0,
        //                 ELF_ST_INFO( STB_GLOBAL, STT_OBJECT ), 0,
        //                 text_sec->get_index(),
        //                 place_to_adjust, (unsigned char)R_386_RELATIVE );

        /* We don't use local symbols here. There is no need to rearrange them.
        // But, for the completeness, we do this just prior 'save'
        syma.arrange_local_symbols([&](ELFIO::Elf_Xword first, ELFIO::Elf_Xword second) {
            rela.swap_symbols( first, second );
        }); */

        // Create ELF object file
        writer.save(outputFilename);

        return 0;
    }
}