// SPDX-License-Identifier: GPL-2.0+
/*******************************************************************************
 * QtMips - MIPS 32-bit Architecture Subset Simulator
 *
 * Implemented to support following courses:
 *
 *   B35APO - Computer Architectures
 *   https://cw.fel.cvut.cz/wiki/courses/b35apo
 *
 *   B4M35PAP - Advanced Computer Architectures
 *   https://cw.fel.cvut.cz/wiki/courses/b4m35pap/start
 *
 * Copyright (c) 2017-2019 Karel Koci<cynerd@email.cz>
 * Copyright (c) 2019      Pavel Pisa <pisa@cmp.felk.cvut.cz>
 *
 * Faculty of Electrical Engineering (http://www.fel.cvut.cz)
 * Czech Technical University        (http://www.cvut.cz/)
 *
 * This program 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 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA  02110-1301, USA.
 *
 ******************************************************************************/

#include "programloader.h"
#include <exception>
#include <unistd.h>
#include <fcntl.h>
#include <cerrno>
#include <cstring>
#include "qtmipsexception.h"

#ifndef O_BINARY
#define O_BINARY 0
#endif

using namespace machine;

ProgramLoader::ProgramLoader(const char *file) {
    const GElf_Ehdr *elf_ehdr;
    // Initialize elf library
    if (elf_version(EV_CURRENT) == EV_NONE)
        throw QTMIPS_EXCEPTION(Input, "Elf library initialization failed", elf_errmsg(-1));
    // Open source file
    if ((this->fd = open(file, O_RDONLY | O_BINARY, 0)) < 0)
        throw QTMIPS_EXCEPTION(Input, QString("Can't open input elf file for reading (") + QString(file) + QString(")"), std::strerror(errno));
    // Initialize elf
    if (!(this->elf = elf_begin(this->fd, ELF_C_READ, NULL)))
        throw QTMIPS_EXCEPTION(Input, "Elf read begin failed", elf_errmsg(-1));
    // Check elf kind
    if (elf_kind(this->elf) != ELF_K_ELF)
        throw QTMIPS_EXCEPTION(Input, "Invalid input file elf format, plain elf file expected", "");

    elf_ehdr = gelf_getehdr(this->elf, &this->hdr);
    if (!elf_ehdr)
        throw QTMIPS_EXCEPTION(Input, "Getting elf file header failed", elf_errmsg(-1));
    executable_entry = elf_ehdr->e_entry;
    // Check elf file format, executable expected, nothing else.
    if (this->hdr.e_type != ET_EXEC)
        throw QTMIPS_EXCEPTION(Input, "Invalid input file type", "");
    // Check elf file architecture, of course only mips is supported.
    // Note: This also checks that this is big endian as EM_MIPS is suppose to be: MIPS R3000 big-endian
    if (this->hdr.e_machine != EM_MIPS)
        throw QTMIPS_EXCEPTION(Input, "Invalid input file architecture", "");
    // Check elf file class, only 32bit architecture is supported.
    int elf_class;
    if ((elf_class = gelf_getclass(this->elf)) == ELFCLASSNONE)
        throw QTMIPS_EXCEPTION(Input, "Getting elf class failed", elf_errmsg(-1));
    if (elf_class != ELFCLASS32)
        throw QTMIPS_EXCEPTION(Input, "Only supported architecture is 32bit", "");

    // Get number of program sections in elf file
    if (elf_getphdrnum(this->elf, &this->n_secs))
        throw QTMIPS_EXCEPTION(Input, "Elf program sections count query failed", elf_errmsg(-1));
    // Get program sections headers
    if (!(this->phdrs = elf32_getphdr(this->elf)))
        throw QTMIPS_EXCEPTION(Input, "Elf program sections get failed", elf_errmsg(-1));
    // We want only LOAD sections so we create map of those sections
    for (unsigned i = 0; i < this->n_secs; i++) {
        if (phdrs[i].p_type != PT_LOAD)
            continue;
        this->map.push_back(i);
    }
    // TODO instead of direct access should we be using sections and elf_data? And if so how to link program header and section?
}

ProgramLoader::ProgramLoader(QString file) : ProgramLoader(file.toStdString().c_str()) { }

ProgramLoader::~ProgramLoader() {
    // Close elf
    elf_end(this->elf);
    // Close file
    close(this->fd);
}

void ProgramLoader::to_memory(Memory *mem) {
    // Load program to memory (just dump it byte by byte)
    for (int i = 0; i < this->map.size(); i++) {
        std::uint32_t base_address = this->phdrs[this->map[i]].p_vaddr;
        char *f = elf_rawfile(this->elf, NULL);
        size_t phdrs_i = this->map[i];
        for (unsigned y = 0; y < this->phdrs[phdrs_i].p_filesz; y++) {
            mem->write_byte(base_address + y, (std::uint8_t) f[this->phdrs[phdrs_i].p_offset + y]);
        }
    }
}

std::uint32_t ProgramLoader::end() {
    std::uint32_t last = 0;
    // Go trough all sections and found out last one
    for (int i = 0; i < this->map.size(); i++) {
        Elf32_Phdr *phdr = &(this->phdrs[this->map[i]]);
        if ((phdr->p_vaddr + phdr->p_filesz) > last)
            last = phdr->p_vaddr + phdr->p_filesz;
    }
    return last + 0x10; // We add offset so we are sure that also pipeline is empty
}

std::uint32_t ProgramLoader::get_executable_entry() {
    return executable_entry;
}

SymbolTable *ProgramLoader::get_symbol_table() {
    SymbolTable *p_st = new SymbolTable();
    Elf_Scn     *scn = NULL;
    GElf_Shdr   shdr;
    Elf_Data    *data;
    int          count, ii;

    elf_version(EV_CURRENT);

    while (1) {
        if ((scn = elf_nextscn(this->elf, scn)) == NULL)
            return p_st;
        gelf_getshdr(scn, &shdr);
        if (shdr.sh_type == SHT_SYMTAB) {
            /* found a symbol table, go print it. */
            break;
        }
    }

    data = elf_getdata(scn, NULL);
    count = shdr.sh_size / shdr.sh_entsize;

    /* rettrieve the symbol names */
    for (ii = 0; ii < count; ++ii) {
        GElf_Sym sym;
        gelf_getsym(data, ii, &sym);
        p_st->add_symbol(elf_strptr(elf, shdr.sh_link, sym.st_name),
                        sym.st_value, sym.st_size, sym.st_info, sym.st_other);
    }

    return p_st;
}