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desmontador.c
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#include <fcntl.h>
#include <unistd.h>
#define MAX_BYTES 110000
typedef struct
{
unsigned char e_ident[16];
unsigned short e_type;
unsigned short e_machine;
unsigned int e_version;
unsigned int e_entry;
unsigned int e_phoff;
unsigned int e_shoff;
unsigned int e_flags;
unsigned short e_ehsize;
unsigned short e_phentsize;
unsigned short e_phnum;
unsigned short e_shentsize;
unsigned short e_shnum;
unsigned short e_shstrndx;
} Elf32_Ehdr;
typedef struct
{
unsigned int sh_name;
unsigned int sh_type;
unsigned int sh_flags;
unsigned int sh_addr;
unsigned int sh_offset;
unsigned int sh_size;
unsigned int sh_link;
unsigned int sh_info;
unsigned int sh_addralign;
unsigned int sh_entsize;
} Elf32_Shdr;
typedef struct
{
unsigned int st_name;
unsigned int st_value;
unsigned int st_size;
unsigned char st_info;
unsigned char st_other;
unsigned short st_shndx;
} Elf32_Sym; //cada entrada da symbol table ocupa 16 bytes
int str_len(char * str) {
int i = 0, len = 0;
while (str[i] != '\0') {
len++;
i++;
}
return len;
}
void write_dec(int num) {
char decimal_invertido[20], decimal[20];
int i = 0, negativo = 0;
if (num < 0) {
negativo = 1;
num *= -1;
}
if (num == 0) {
write(1, "0", 1);
}
else {
while (num != 0) {
decimal_invertido[i] = '0' + num % 10;
num /= 10;
i++;
}
if (negativo) {
decimal_invertido[i++] = '-';
}
for (int j=0; j<i; j++) {
decimal[j] = decimal_invertido[i-j-1];
}
write(1, decimal, i);
}
}
void write_hex_from_dec(int decimal, int mode) { //mode = 0: hex com 8 dígitos. mode = 1: hex compacto. mode = 2: hex com 2 digitos
char hex_invertido[9], hex[9];
int num_digits = 0;
while (decimal != 0) {
if (decimal % 16 >= 10) {
hex_invertido[num_digits++] = 87 + decimal % 16;
}
else {
hex_invertido[num_digits++] = '0' + decimal % 16;
}
decimal /= 16;
}
if (!mode) {
while (num_digits < 8) {
hex_invertido[num_digits++] = '0';
}
}
if (mode == 2) {
while (num_digits < 2) {
hex_invertido[num_digits++] = '0';
}
}
if (mode == 1 && num_digits == 0) {
hex_invertido[0] = '0';
num_digits++;
}
for (int j=0; j<num_digits; j++) {
hex[j] = hex_invertido[num_digits - 1 - j];
}
write(1, hex, num_digits);
}
int str_compare(char * str1, char * str2) {
if (str_len(str1) == str_len(str2)) {
for (int i = 0; i < str_len(str1); i++) {
if (str1[i] != str2[i]) {
return 0;
}
}
return 1;
}
return 0;
}
int pow2(int i) {
int result = 1;
for (int j = 0; j < i; j++) {
result *= 2;
}
return result;
}
void write_register(int registrador) {
switch (registrador) {
case 0:
write(1, "zero", 4);
break;
case 1:
write(1, "ra", 2);
break;
case 2:
write(1, "sp", 2);
break;
case 3:
write(1, "gp", 2);
break;
case 4:
write(1, "tp", 2);
break;
case 5:
write(1, "t0", 2);
break;
case 6:
write(1, "t1", 2);
break;
case 7:
write(1, "t2", 2);
break;
case 8:
write(1, "s0", 2);
break;
case 9:
write(1, "s1", 2);
break;
case 10:
write(1, "a0", 2);
break;
case 11:
write(1, "a1", 2);
break;
case 12:
write(1, "a2", 2);
break;
case 13:
write(1, "a3", 2);
break;
case 14:
write(1, "a4", 2);
break;
case 15:
write(1, "a5", 2);
break;
case 16:
write(1, "a7", 2);
break;
case 17:
write(1, "a8", 2);
break;
case 18:
write(1, "s2", 2);
break;
case 19:
write(1, "s3", 2);
break;
case 20:
write(1, "s4", 2);
break;
case 21:
write(1, "s5", 2);
break;
case 22:
write(1, "s6", 2);
break;
case 23:
write(1, "s7", 2);
break;
case 24:
write(1, "s8", 2);
break;
case 25:
write(1, "s9", 2);
break;
case 26:
write(1, "s10", 2);
break;
case 27:
write(1, "s11", 2);
break;
case 28:
write(1, "t3", 2);
break;
case 29:
write(1, "t4", 2);
break;
case 30:
write(1, "t5", 2);
break;
case 31:
write(1, "t6", 2);
break;
}
}
void write_instruction(int instruction, Elf32_Sym * symtab, int symtab_size, char * strtab, int adress) {
char bin[33], first_7[8], digits_12_to_14[4];
for (int i = 0; i < 32; i++) {
bin[i] = '0' + ((instruction >> i) & 1);
}
bin[32] = '\0';
int rd = 0, rs1 = 0, rs2 = 0;
for (int i = 0; i < 7; i++) {
first_7[6-i] = bin[i]; //pela maneira com que escrevi as strings nos ifs abaixo, lemos first 7 dessa maneira
}
first_7[7] = '\0';
for (int i = 0; i < 3; i++) {
digits_12_to_14[i] = bin[12 + i];
}
digits_12_to_14[3] = '\0';
for (int i = 0; i < 5; i++) {
rd += pow2(i) * (bin[7+i] - '0');
rs1 += pow2(i) * (bin[15+i] - '0');
rs2 += pow2(i) * (bin[20+i] - '0');
}
int im3 = instruction >> 20;
int im1 = instruction >> 12;
//im2 representa o segundo tipo de imediato da tabela
int im2_12_19 = ((instruction >> 12) & 0xff) << 12; //bits 12 ate 19
int im2_11 = ((instruction >> 20) & 0b1) << 11; //bit 11
int im2_1_10 = ((instruction >> 21) & 0b1111111111) << 1; //bits 1 ate 10
int im2_20 = ((instruction >> 31) & 0b1) << 20; //bit 20
int im2 = im2_11 | im2_12_19 | im2_1_10 | im2_20;
if (im2 >> 12 & 0b1) { //se for negativo:
im2 = (~im2 & 0xfff) + 0b1;
im2 = adress - im2;
} else {
im2 += adress;
}
//im4 representa o quarto tipo de imediato da tabela
int im4_11 = ((instruction >> 7) & 0b1) << 11; //bit 11
int im4_1_4 = ((instruction >> 8) & 0xf) << 1; //bits 1 ate 4 -> o ultimo shift coloca o bit 0 como 0
int im4_12 = ((instruction >> 31) & 0b1) << 12; //bit 12
int im4_5_10 = ((instruction >> 25) & 0b111111) << 5; //bits 5 ate 10
int im4 = im4_11 | im4_12 | im4_1_4 | im4_5_10;
if (im4 >> 12 & 0b1) { //se for negativo:
im4 = (~im4 & 0xfff) + 0b1;
im4 = adress - im4;
} else {
im4 += adress;
}
//im5 representa o quinto tipo de imediato da tabela
int im5_1 = (instruction >> 7) & 0b11111 ;
int im5_2 = ((instruction >> 25) << 5);
int im5 = im5_1 | im5_2;
if (str_compare(first_7, "0110111")) {
write(1, "lui", 3);
write(1, " ", 1);
write_register(rd);
write(1, ", ", 2);
write_dec(im1);
} else if (str_compare(first_7, "0010111")) {
write(1, "auipc", 5);
write(1, " ", 1);
write_register(rd);
write(1, ", ", 2);
write_dec(im1);
} else if (str_compare(first_7, "1101111")) {
write(1, "jal", 3);
write(1, " ", 1);
write_register(rd);
write(1, ", 0x", 4);
write_hex_from_dec(im2, 1);
write(1, " <", 2);
char * symbol_name;
for (int j = 0; j < symtab_size; j++) {
if (im2 == symtab[j].st_value) {
symbol_name = &strtab[symtab[j].st_name];
write(1, symbol_name, str_len(symbol_name));
break;
}
}
write(1, ">", 1);
} else if (str_compare(first_7, "1100111")) {
write(1, "jalr", 4);
write(1, " ", 1);
write_register(rd);
write(1, ", ", 2);
write_dec(im3);
write(1, "(", 1);
write_register(rs1);
write(1, ")", 1);
} else if (str_compare(first_7, "1100011")) {
if (str_compare(digits_12_to_14, "000")) {
write(1, "beq", 3);
} else if (str_compare(digits_12_to_14, "100")) {
write(1, "bne", 3);
} else if (str_compare(digits_12_to_14, "001")) {
write(1, "blt", 3);
} else if (str_compare(digits_12_to_14, "101")) {
write(1, "bge", 3);
} else if (str_compare(digits_12_to_14, "011")) {
write(1, "bltu", 4);
} else {
write(1, "bgeu", 4);
}
write(1, " ", 1);
write_register(rs1);
write(1, ", ", 2);
write_register(rs2);
write(1, ", ", 2);
if (str_compare(digits_12_to_14, "000") || str_compare(digits_12_to_14, "100")) {
write(1, "0x", 2);
write_hex_from_dec(im4, 1);
} else {
write_dec(im4);
}
} else if (str_compare(first_7, "0000011")) {
if (str_compare(digits_12_to_14, "000")) {
write(1, "lb", 2);
} else if (str_compare(digits_12_to_14, "100")) {
write(1, "lh", 2);
} else if (str_compare(digits_12_to_14, "010")) {
write(1, "lw", 2);
} else if (str_compare(digits_12_to_14, "001")) {
write(1, "lbu", 3);
} else {
write(1, "lhu", 3);
}
write(1, " ", 1);
write_register(rd);
write(1, ", ", 2);
write_dec(im3);
write(1, "(", 1);
write_register(rs1);
write(1, ")", 1);
} else if (str_compare(first_7, "0100011")) {
if (str_compare(digits_12_to_14, "000")) {
write(1, "sb", 2);
} else if (str_compare(digits_12_to_14, "100")) {
write(1, "sh", 2);
} else {
write(1, "sw", 2);
}
write(1, " ", 1);
write_register(rs2);
write(1, ", ", 2);
write_dec(im5);
write(1, "(", 1);
write_register(rs1);
write(1, ")", 1);
} else if (str_compare(first_7, "0010011")) {
if (str_compare(digits_12_to_14, "000")) {
write(1, "addi", 4);
} else if (str_compare(digits_12_to_14, "010")) {
write(1, "slti", 4);
} else if (str_compare(digits_12_to_14, "110")) {
write(1, "sltiu", 5);
} else if (str_compare(digits_12_to_14, "001")) {
write(1, "xori", 4);
} else if (str_compare(digits_12_to_14, "011")) {
write(1, "ori", 3);
} else if (str_compare(digits_12_to_14, "111")) {
write(1, "andi", 4);
} else if (str_compare(digits_12_to_14, "100")) {
write(1, "slli", 4);
} else if (str_compare(digits_12_to_14, "101")) {
if (bin[30] == '0') {
write(1, "srli", 4);
} else {
write(1, "srai", 4);
}
}
write(1, " ", 1);
write_register(rd);
write(1, ", ", 2);
write_register(rs1);
write(1, ", ", 2);
if (!str_compare(digits_12_to_14, "101") && !str_compare(digits_12_to_14, "100")) {
write_dec(im3);
}
else {
int shamt = (instruction >> 20) & 0b11111;
write_dec(shamt);
}
} else if (str_compare(first_7, "0110011")) {
if (str_compare(digits_12_to_14, "000")) {
if (bin[30] == '0') {
write(1, "add", 3);
} else {
write(1, "sub", 3);
}
} else if (str_compare(digits_12_to_14, "100")) {
write(1, "sll", 3);
} else if (str_compare(digits_12_to_14, "010")) {
write(1, "slt", 3);
} else if (str_compare(digits_12_to_14, "110")) {
write(1, "sltu", 4);
} else if (str_compare(digits_12_to_14, "001")) {
write(1, "xor", 3);
} else if (str_compare(digits_12_to_14, "101")) {
if (bin[30] == '0') {
write(1, "srl", 3);
} else {
write(1, "sra", 3);
}
} else if (str_compare(digits_12_to_14, "011")) {
write(1, "or", 2);
} else {
write(1, "and", 3);
}
write(1, " ", 1);
write_register(rd);
write(1, ", ", 2);
write_register(rs1);
write(1, ", ", 2);
write_register(rs2);
} else if (str_compare(first_7, "0001111")) {
if (str_compare(digits_12_to_14, "000")) {
int succ = (instruction >> 20) & 0b1111;
int pred = (instruction >> 24) & 0b1111; //iorw
write(1, "fence", 5);
write(1, " ", 1);
if ((pred >> 3) & 0b1) {
write(1, "i", 1);
}
if ((pred >> 2) & 0b1) {
write(1, "o", 1);
}
if ((pred >> 1) & 0b1) {
write(1, "r", 1);
}
if (pred & 0b1) {
write(1, "w", 1);
}
write(1, ", ", 2);
if ((succ >> 3) & 0b1) {
write(1, "i", 1);
}
if ((succ >> 2) & 0b1) {
write(1, "o", 1);
}
if ((succ >> 1) & 0b1) {
write(1, "r", 1);
}
if (succ & 0b1) {
write(1, "w", 1);
}
} else {
write(1, "fence.i", 7);
}
} else if (str_compare(first_7, "1110011")) {
int csr = instruction >> 20;
int zimm = (instruction >> 15) & 0b11111;
if (str_compare(digits_12_to_14, "000")) {
if (bin[20] == '0') {
write(1, "ecall", 5);
}
else {
write(1, "ebreak", 6);
}
} else if (str_compare(digits_12_to_14, "100")) {
write(1, "csrrw", 5);
} else if (str_compare(digits_12_to_14, "010")) {
write(1, "csrrs", 5);
} else if (str_compare(digits_12_to_14, "110")) {
write(1, "csrrc", 5);
} else if (str_compare(digits_12_to_14, "101")) {
write(1, "csrrwi", 6);
} else if (str_compare(digits_12_to_14, "110")) {
write(1, "csrrsi", 6);
} else {
write(1, "csrrci", 6);
}
write(1, " ", 1);
write_register(rd);
write(1, ", ", 2);
if (str_compare(digits_12_to_14, "100") || str_compare(digits_12_to_14, "010") || str_compare(digits_12_to_14, "110")) {
write_dec(csr);
write(1, ", ", 2);
write_register(rs1);
} else {
write_dec(csr);
write(1, ", ", 2);
write_dec(zimm);
}
} else {
write(1, "<unknown>", 9);
}
}
int main(int argc, char *argv[]) {
char elf[MAX_BYTES];
int file = open(argv[2], O_RDONLY);
read(file, elf, MAX_BYTES);
Elf32_Ehdr * p_file_header = (Elf32_Ehdr *) &elf; //ponteiro para a file header com endereço inicial dado como o do início do elf
Elf32_Shdr * section_headers = (Elf32_Shdr *) &elf[p_file_header->e_shoff]; //ponteiro para a primeira das section headers
int shstrtab_offset = section_headers[p_file_header->e_shstrndx].sh_offset; //offset da shstrtab
char * name; //ponteiro para o caractere de inicio do nome de uma section
int symtab_index, strtab_index, symtab_size;
for (int i = 0;i < p_file_header->e_shnum; i++) {
name = &elf[shstrtab_offset + section_headers[i].sh_name];
if (str_compare(name, ".symtab")) {
symtab_index = i;
}
if (str_compare(name, ".strtab")) {
strtab_index = i;
}
}
Elf32_Sym * symtab = (Elf32_Sym *) &elf[section_headers[symtab_index].sh_offset]; //ponteiro que aponta para a symbol table
symtab_size = section_headers[symtab_index].sh_size / 16;
char * symbol_name;
char * strtab = &elf[section_headers[strtab_index].sh_offset]; //ponteiro que aponta para a string table da symbol table
write(1, "\n", 1);
write(1, argv[2], str_len(argv[2]));
write(1, ": file format elf32-littleriscv\n", 32);
write(1, "\n", 1);
if (argv[1][1] == 'd') { //Dissasembly of section .text
write(1, "\n", 1);
write(1, "Disassembly of section .text:", 29);
write(1, "\n", 1);
int text_index, size;
for (int i = 0;i < p_file_header->e_shnum; i++) {
name = &elf[shstrtab_offset + section_headers[i].sh_name];
if (str_compare(name, ".text")) {
text_index = i;
}
}
size = section_headers[text_index].sh_size;
int adress;
unsigned char hex_byte;
unsigned int hex_number;
unsigned int * instruction;
for (int i = 0; i < size; i+=4) {
adress = i + section_headers[text_index].sh_addr;
instruction = (unsigned int *) &elf[section_headers[text_index].sh_offset + i];
for (int j = 0; j < symtab_size; j++) {
if (adress == symtab[j].st_value) {
symbol_name = &strtab[symtab[j].st_name];
write(1, strtab, str_len(strtab));
write(1, "\n", 1);
write_hex_from_dec(adress, 0);
write(1, " <", 2);
write(1, symbol_name, str_len(symbol_name));
write(1, ">:\n", 3);
break;
}
}
write(1, " ", 3);
write_hex_from_dec(adress, 1);
write(1, ": ", 2);
for (int j = 0; j < 4; j++) {
hex_byte = elf[i + section_headers[text_index].sh_offset + j]; //hex_byte guarda um byte que será escrito como hexadecimal
hex_number = (unsigned int) hex_byte;
write_hex_from_dec(hex_number, 2);
write(1, " ", 1);
}
write_instruction(*instruction, symtab, symtab_size, strtab, adress);
write(1, "\n", 1);
}
} else if (argv[1][1] == 't') {
write(1, "SYMBOL TABLE:\n", 14);
char binding[2];
for (int i = 1; i < symtab_size; i++) { //consideramos que a primeira linha da symtab é nula
write_hex_from_dec(symtab[i].st_value,0);
write(1, " ", 1);
binding[0] = symtab[i].st_info >> 4 ? 'g' : 'l';
binding[1] = '\0';
write(1, binding, 1);
write(1, " ", 1);
if (symtab[i].st_shndx < p_file_header->e_shnum) {
name = &elf[shstrtab_offset + section_headers[symtab[i].st_shndx].sh_name];
write(1, name, str_len(name));
}
else {
write(1, "*ABS*", 5);
}
write(1, " ", 1);
write_hex_from_dec(symtab[i].st_size, 0);
write(1, " ", 1);
symbol_name = &strtab[symtab[i].st_name];
write(1, symbol_name, str_len(symbol_name));
write(1, "\n", 1);
}
} else { //h
unsigned int size;
unsigned int vma;
write(1, "Sections:\n", 10);
write(1, "Idx Name Size VMA\n", 18);
for (int i = 0; i < p_file_header->e_shnum; i++) {
name = &elf[shstrtab_offset + section_headers[i].sh_name]; //pega automaticamente a string inteira até \0
size = section_headers[i].sh_size; //type punning
vma = section_headers[i].sh_addr;
write_dec(i);
write(1, " ", 1);
write(1, name, str_len(name));
write(1, " ", 1);
write_hex_from_dec(size, 0);
write(1, " ", 1);
write_hex_from_dec(vma, 0);
write(1, "\n", 1);
}
write(1, "\n", 1);
}
}