546 lines
17 KiB
C
546 lines
17 KiB
C
// https://docs.riscv.org/reference/isa/unpriv/rv-32-64g.html
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// https://riscv.org/wp-content/uploads/2024/12/riscv-calling.pdf
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#include "riscv64_dis.h"
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#include <gelf.h>
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#include <libelf.h>
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#define MEMORY_SIZE 20 * 1024 * 1024 // should be enough
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const char *const REGS[32] = {
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"zero", "ra", "sp", "gp", "tp", "t0", "t1", "t2", "fp", "s1", "a0",
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"a1", "a2", "a3", "a4", "a5", "a6", "a7", "s2", "s3", "s4", "s5",
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"s6", "s7", "s8", "s9", "s10", "s11", "t3", "t4", "t5", "t6"};
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Section riscv64_get_code_section(Elf *elf, GElf_Ehdr ehdr) {
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size_t str_table_index;
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if (elf_getshdrstrndx(elf, &str_table_index) != 0) {
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fprintf(stderr, "elf_getshdrstrndx failed: %s\n", elf_errmsg(-1));
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exit(1);
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}
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Elf_Scn *section = NULL;
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while ((section = elf_nextscn(elf, section)) != NULL) {
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GElf_Shdr header;
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if (gelf_getshdr(section, &header) != &header)
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continue;
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const char *name = elf_strptr(elf, str_table_index, header.sh_name);
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if (name && strcmp(name, ".text") == 0) {
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return (Section){.offset = header.sh_addr,
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.size = header.sh_size,
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.entrypoint = ehdr.e_entry};
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}
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}
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fprintf(stderr, "Failed to locate .text\n");
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exit(1);
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}
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RISCV64 riscv64_load(uint8_t *exe_bytes, size_t exe_size) {
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uint8_t *memory = calloc(MEMORY_SIZE, 1);
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Elf *elf = elf_memory((char *)exe_bytes, exe_size);
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GElf_Ehdr ehdr;
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gelf_getehdr(elf, &ehdr);
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Section text_section = riscv64_get_code_section(elf, ehdr);
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for (size_t i = 0; i < ehdr.e_phnum; i++) {
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GElf_Phdr phdr;
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gelf_getphdr(elf, i, &phdr);
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if (phdr.p_type == PT_LOAD) {
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memcpy(memory + phdr.p_vaddr, exe_bytes + phdr.p_offset, phdr.p_filesz);
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}
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}
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elf_end(elf);
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return (RISCV64){
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.memory = memory,
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.pc = text_section.offset,
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.regs = {0},
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.code_section = text_section,
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};
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}
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void riscv64_dump(const RISCV64 *r) {
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printf("REGS:");
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for (size_t i = 0; i < 32; i++) {
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printf(" %lu", r->regs[i]);
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}
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printf("\n");
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}
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void riscv64_execute(RISCV64 *r) {
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r->pc = r->code_section.entrypoint;
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r->regs[2] = MEMORY_SIZE - 1024; // set the stack pointer
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while (r->pc < r->code_section.offset + r->code_section.size) {
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r->regs[0] = 0; // clear the zero register
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uint32_t ins;
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memcpy(&ins, r->memory + r->pc, 4);
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uint16_t opcode = ins & 0b1111111;
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// https://stackoverflow.com/questions/62939410/how-can-i-find-out-the-instruction-format-of-a-risc-v-instruction
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switch (opcode) {
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case 0b1100011: {
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PARSE_B_INS(ins);
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if (funct3 == 0b000) { // beq
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if (r->regs[rs1] == r->regs[rs2]) {
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r->pc += imm;
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continue;
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}
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} else if (funct3 == 0b001) { // bne
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if (r->regs[rs1] != r->regs[rs2]) {
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r->pc += imm;
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continue;
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}
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} else if (funct3 == 0b101) { // bge
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if (r->regs[rs1] >= r->regs[rs2]) {
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r->pc += imm;
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continue;
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}
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} else if (funct3 == 0b100) { // blt
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if (r->regs[rs1] < r->regs[rs2]) {
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r->pc += imm;
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continue;
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}
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} else if (funct3 == 0b110) { // bltu
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if ((uint64_t)r->regs[rs1] < (uint64_t)r->regs[rs2]) {
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r->pc += imm;
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continue;
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}
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} else {
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fprintf(stderr, "B-type: unrecognized funct3: %03b\n", funct3);
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exit(1);
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}
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}; break;
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case 0b0010011: {
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PARSE_I_INS(ins);
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if (funct3 == 0b000) { // addi
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r->regs[rd] = r->regs[rs1] + imm;
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} else if (funct3 == 0b001) { // slli
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uint32_t shamt = (ins >> 20) & 0b111111;
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uint32_t funct6 = (ins >> 26) & 0b111111;
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if (funct6 == 0b000000) {
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r->regs[rd] = r->regs[rs1] << shamt;
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} else {
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fprintf(stderr, "I-type 1: funct3=001: unrecognized funct6: %b\n",
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funct6);
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exit(1);
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}
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} else if (funct3 == 0b011) { // sltiu
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r->regs[rd] = ((uint64_t)r->regs[rs1] < (uint64_t)(int64_t)imm) ? 1 : 0;
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} else if (funct3 == 0b100) { // xori
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r->regs[rd] = r->regs[rs1] ^ imm;
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} else if (funct3 == 0b101) {
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// of course this one just has to be different
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uint32_t shamt = (ins >> 20) & 0b111111;
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uint32_t funct6 = (ins >> 26) & 0b111111;
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if (funct6 == 0b000000) { // srli
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r->regs[rd] = (uint64_t)r->regs[rs1] >> shamt;
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} else if (funct6 == 0b010000) { // srai
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r->regs[rd] = (int64_t)r->regs[rs1] >> shamt;
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} else {
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fprintf(stderr, "I-type 1: funct3=101: unrecognized funct6: %b\n",
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funct6);
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exit(1);
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}
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} else if (funct3 == 0b111) {
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r->regs[rd] = r->regs[rs1] & imm;
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} else {
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fprintf(stderr, "I-type 1: unrecognized funct3: %03b\n", funct3);
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exit(1);
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}
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}; break;
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case 0b0000011: {
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PARSE_I_INS(ins);
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if (funct3 == 0b000) { // lb
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r->regs[rd] = (int8_t)r->memory[r->regs[rs1] + imm];
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} else if (funct3 == 0b001) { // lh
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r->regs[rd] = *(int16_t *)&r->memory[r->regs[rs1] + imm];
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} else if (funct3 == 0b010) { // lw
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r->regs[rd] = *(int32_t *)&r->memory[r->regs[rs1] + imm];
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} else if (funct3 == 0b011) { // ld
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r->regs[rd] = *(uint64_t *)&r->memory[r->regs[rs1] + imm];
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} else if (funct3 == 0b100) { // lbu
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r->regs[rd] = r->memory[r->regs[rs1] + imm];
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} else {
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fprintf(stderr, "I-type 2: unrecognized funct3: %03b\n", funct3);
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exit(1);
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}
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}; break;
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case 0b1100111: { // jalr
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PARSE_I_INS(ins);
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size_t target = (r->regs[rs1] + imm) & ~(size_t)1;
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r->regs[rd] = r->pc + 4;
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r->pc = target;
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continue;
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}; break;
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case 0b1110011: {
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PARSE_I_INS(ins);
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if (funct3 == 0b000) {
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if (imm == 0) { // ecall
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// https://jborza.com/post/2021-05-11-riscv-linux-syscalls/
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switch (r->regs[17]) {
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case 63: { // read
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if (r->regs[10] != 0) {
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fprintf(stderr, "read syscall implemented only for stdin.\n");
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exit(1);
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}
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size_t start = r->regs[11];
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size_t count = r->regs[12];
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size_t bytes_read = 0;
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for (size_t i = 0; i < count; i++) {
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int c = getchar();
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if (c == EOF)
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break;
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r->memory[start + i] = (uint8_t)c;
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bytes_read++;
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if (c == '\n')
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break;
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}
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r->regs[10] = bytes_read;
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}; break;
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case 64: { // write
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if (r->regs[10] != 1) {
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fprintf(stderr, "write syscall implemented only for stdout.\n");
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exit(1);
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}
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size_t start = r->regs[11];
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size_t end = r->regs[11] + r->regs[12];
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for (size_t i = start; i < end; i++) {
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putchar(r->memory[i]);
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}
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}; break;
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case 93: { // exit
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printf("Program exited with code %lu.\n", r->regs[10]);
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return;
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}; break;
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case 169: { // gettimeofday
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// TODO: actually return the time
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int64_t tv_addr = r->regs[10];
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int64_t tz_addr = r->regs[11];
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uint8_t tv_buf[16] = {
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0xD2, 0x02, 0x96, 0x49,
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0x00, 0x00, 0x00, 0x00, // tv_sec = 1234567890
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0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, // tv_usec = 0
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};
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memcpy(&r->memory[tv_addr], tv_buf, 16);
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memset(&r->memory[tz_addr], 0, 8);
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r->regs[10] = 0;
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}; break;
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default:
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fprintf(stderr, "Unimplemented syscall: %lu\n", r->regs[17]);
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exit(1);
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}
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break;
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} else {
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fprintf(stderr, "I-type 4: funct3=000 unrecognized imm: %b\n", imm);
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exit(1);
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};
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break;
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} else {
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fprintf(stderr, "I-type 4: unrecognized funct3: %03b\n", funct3);
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exit(1);
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}
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}; break;
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case 0b1101111: { // jal
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PARSE_J_INS(ins);
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r->regs[rd] = r->pc + 4;
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r->pc += imm;
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continue;
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}; break;
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case 0b0110011: {
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PARSE_R_INS(ins);
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if (funct3 == 0b000) {
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if (funct7 == 0b0000000) { // add
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r->regs[rd] = r->regs[rs1] + r->regs[rs2];
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} else if (funct7 == 0b0100000) { // sub
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r->regs[rd] = r->regs[rs1] - r->regs[rs2];
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} else if (funct7 == 0b0000001) { // mul
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r->regs[rd] = r->regs[rs1] * r->regs[rs2];
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} else {
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fprintf(stderr, "R-type 1: funct3=0b000: unrecognized funct7: %b\n",
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funct7);
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exit(1);
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}
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} else if (funct3 == 0b001) {
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if (funct7 == 0b0000001) { // mulh
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int64_t a_hi = r->regs[rs1] >> 32;
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int64_t b_hi = r->regs[rs2] >> 32;
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uint64_t a_lo = (uint32_t)r->regs[rs1];
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uint64_t b_lo = (uint32_t)r->regs[rs2];
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uint64_t p0 = a_lo * b_lo;
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int64_t p1 = a_hi * b_lo;
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int64_t p2 = b_hi * a_lo;
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int64_t p3 = a_hi * b_hi;
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int64_t carry = (p0 >> 32);
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int64_t mid = p1 + p2 + carry;
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r->regs[rd] = p3 + (mid >> 32);
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} else {
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fprintf(stderr, "R-type 1: funct3=0b001: unrecognized funct7: %b\n",
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funct7);
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exit(1);
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}
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} else if (funct3 == 0b010) {
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if (funct7 == 0b0000000) { // slt
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r->regs[rd] = (r->regs[rs1] < r->regs[rs2]) ? 1 : 0;
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} else {
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fprintf(stderr, "R-type 1: funct3=0b010: unrecognized funct7: %b\n",
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funct7);
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exit(1);
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}
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} else if (funct3 == 0b011) {
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if (funct7 == 0b0000000) { // sltu
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r->regs[rd] =
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((uint64_t)r->regs[rs1] < (uint64_t)r->regs[rs2]) ? 1 : 0;
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} else if (funct7 == 0b0000001) { // mulhu
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uint64_t a = r->regs[rs1];
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uint64_t b = r->regs[rs2];
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uint64_t a_lo = a & 0xffffffff;
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uint64_t a_hi = a >> 32;
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uint64_t b_lo = b & 0xffffffff;
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uint64_t b_hi = b >> 32;
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uint64_t lo_lo = a_lo * b_lo;
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uint64_t hi_lo = a_hi * b_lo;
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uint64_t lo_hi = a_lo * b_hi;
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uint64_t hi_hi = a_hi * b_hi;
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uint64_t mid =
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(lo_lo >> 32) + (hi_lo & 0xffffffff) + (lo_hi & 0xffffffff);
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r->regs[rd] = hi_hi + (hi_lo >> 32) + (lo_hi >> 32) + (mid >> 32);
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} else {
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fprintf(stderr, "R-type 1: funct3=0b011: unrecognized funct7: %b\n",
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funct7);
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exit(1);
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}
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} else if (funct3 == 0b100) {
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if (funct7 == 0b0000000) { // xor
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r->regs[rd] = r->regs[rs1] ^ r->regs[rs2];
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} else if (funct7 == 0b0000001) { // div
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if (r->regs[rs2] == 0) {
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r->regs[rd] = -1;
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} else {
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r->regs[rd] = r->regs[rs1] / r->regs[rs2];
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}
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} else {
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fprintf(stderr, "R-type 1: funct3=0b100: unrecognized funct7: %b\n",
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funct7);
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exit(1);
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}
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} else if (funct3 == 0b110) {
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if (funct7 == 0b0000001) { // rem
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if (r->regs[rs2] == 0) {
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r->regs[rd] = r->regs[rs1];
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} else {
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r->regs[rd] = r->regs[rs1] % r->regs[rs2];
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}
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} else if (funct7 == 0b0000000) { // or
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r->regs[rd] = r->regs[rs1] | r->regs[rs2];
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} else {
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fprintf(stderr, "R-type 1: funct3=0b110: unrecognized funct7: %b\n",
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funct7);
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exit(1);
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}
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} else if (funct3 == 0b111) {
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if (funct7 == 0b000) { // and
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r->regs[rd] = r->regs[rs1] & r->regs[rs2];
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} else if (funct7 == 0b001) { // remu
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if (r->regs[rs2] == 0) {
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r->regs[rd] = r->regs[rs1];
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} else {
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r->regs[rd] = (uint64_t)r->regs[rs1] % (uint64_t)r->regs[rs2];
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}
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} else {
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fprintf(stderr, "R-type 1: funct3=0b111: unrecognized funct7: %b\n",
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funct7);
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exit(1);
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}
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} else {
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fprintf(stderr, "R-type 1: unrecognized funct3: %03b\n", funct3);
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exit(1);
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}
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}; break;
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case 0b0101111: {
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fprintf(stderr, "A extension not implemented yet.\n");
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exit(1);
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}; break;
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case 0b0111011: {
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PARSE_R_INS(ins);
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if (funct3 == 0b000) {
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if (funct7 == 0b0000000) { // addw
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r->regs[rd] = (int32_t)(r->regs[rs1] + r->regs[rs2]);
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} else if (funct7 == 0b0100000) { // subw
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r->regs[rd] = (int32_t)(r->regs[rs1] - r->regs[rs2]);
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} else if (funct7 == 0b0000001) { // mulw
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r->regs[rd] = (int32_t)(r->regs[rs1] * r->regs[rs2]);
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} else {
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fprintf(stderr, "R-type 3: funct3=000: unrecognized funct7: %b\n",
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funct7);
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exit(1);
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}
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} else if (funct3 == 0b001) {
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if (funct7 == 0b0000000) { // sllw
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r->regs[rd] =
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(int32_t)(uint32_t)((uint32_t)r->regs[rs1]
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<< ((uint32_t)r->regs[rs2] & 0b11111));
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} else {
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fprintf(stderr, "R-type 3: funct3=001: unrecognized funct7: %b\n",
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funct7);
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exit(1);
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}
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} else if (funct3 == 0b100) { // divw
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int32_t a = r->regs[rs1];
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int32_t b = r->regs[rs2];
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if (b == 0) {
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r->regs[rd] = (uint64_t)(int64_t)(-1);
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} else {
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r->regs[rd] = (int64_t)(a / b);
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}
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} else if (funct3 == 0b101) {
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if (funct7 == 0b0000000) { // srlw
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r->regs[rd] = (int32_t)((uint32_t)r->regs[rs1] >>
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((uint32_t)r->regs[rs2] & 0b11111));
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} else if (funct7 == 0b0100000) { // sraw
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r->regs[rd] =
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((int32_t)r->regs[rs1]) >> ((uint32_t)r->regs[rs2] & 0b11111);
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} else if (funct7 == 0b0000001) { // divuw
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if (r->regs[rs2] == 0) {
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r->regs[rd] = -1LL;
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} else {
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r->regs[rd] =
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(int32_t)((uint32_t)r->regs[rs1] / (uint32_t)r->regs[rs2]);
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}
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} else {
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fprintf(stderr, "R-type 3: funct3=101: unrecognized funct7: %b\n",
|
|
funct7);
|
|
exit(1);
|
|
}
|
|
} else if (funct3 == 0b111) { // remuw
|
|
if (r->regs[rs2] == 0) {
|
|
r->regs[rd] = (int32_t)r->regs[rs1];
|
|
} else {
|
|
r->regs[rd] =
|
|
(int32_t)((uint32_t)r->regs[rs1] % (uint32_t)r->regs[rs2]);
|
|
}
|
|
} else {
|
|
fprintf(stderr, "R-type 3: unrecognized funct3: %03b\n", funct3);
|
|
exit(1);
|
|
}
|
|
}; break;
|
|
case 0b0011011: {
|
|
PARSE_I_INS(ins);
|
|
if (funct3 == 0b000) { // addiw
|
|
r->regs[rd] = (int32_t)r->regs[rs1] + (int32_t)imm;
|
|
} else if (funct3 == 0b001) {
|
|
uint32_t shamt = (ins >> 20) & 0b11111;
|
|
r->regs[rd] = (int32_t)r->regs[rs1] << shamt;
|
|
} else if (funct3 == 0b101) {
|
|
PARSE_R_INS(ins);
|
|
if (funct7 == 0b0000000) { // srliw
|
|
r->regs[rd] = (int32_t)((uint32_t)r->regs[rs1] >> rs2);
|
|
} else if (funct7 == 0b0100000) { // sraiw
|
|
r->regs[rd] = (int32_t)r->regs[rs1] >> rs2;
|
|
} else {
|
|
fprintf(stderr, "R-type 4: funct3=101: unrecognized funct7: %b\n",
|
|
funct7);
|
|
exit(1);
|
|
}
|
|
} else {
|
|
fprintf(stderr, "R-type 4: unrecognized funct3: %03b\n", funct3);
|
|
exit(1);
|
|
}
|
|
}; break;
|
|
case 0b0100011: {
|
|
PARSE_S_INS(ins);
|
|
|
|
if (funct3 == 0b000) { // sb
|
|
size_t addr = r->regs[rs1] + imm;
|
|
r->memory[addr] = r->regs[rs2];
|
|
} else if (funct3 == 0b001) { // sh
|
|
size_t addr = r->regs[rs1] + imm;
|
|
*(uint16_t *)(&r->memory[addr]) = r->regs[rs2];
|
|
} else if (funct3 == 0b010) { // sw
|
|
size_t addr = r->regs[rs1] + imm;
|
|
*(uint32_t *)(&r->memory[addr]) = r->regs[rs2];
|
|
} else if (funct3 == 0b011) { // sd
|
|
size_t addr = r->regs[rs1] + imm;
|
|
// take this rust
|
|
*(uint64_t *)(&r->memory[addr]) = r->regs[rs2];
|
|
} else {
|
|
fprintf(stderr, "S-type: unrecognized funct3: %03b\n", funct3);
|
|
exit(1);
|
|
}
|
|
}; break;
|
|
case 0b0110111: { // lui
|
|
PARSE_U_INS(ins);
|
|
r->regs[rd] = (int64_t)(int32_t)(imm << 12);
|
|
}; break;
|
|
case 0b0010111: { // auipc
|
|
PARSE_U_INS(ins);
|
|
r->regs[rd] = r->pc + ((int64_t)imm << 12);
|
|
}; break;
|
|
default:
|
|
fprintf(stderr, "Unrecognized opcode: %07b\n", opcode);
|
|
exit(1);
|
|
}
|
|
|
|
r->pc += 4;
|
|
}
|
|
}
|
|
|
|
int main(int argc, char *argv[]) {
|
|
if (elf_version(EV_CURRENT) == EV_NONE) {
|
|
fprintf(stderr, "Failed to initialize libelf: %s\n", elf_errmsg(-1));
|
|
return 1;
|
|
}
|
|
|
|
const char *path = NULL;
|
|
for (int i = 1; i < argc; i++) {
|
|
path = argv[i];
|
|
}
|
|
|
|
if (path == NULL) {
|
|
fprintf(stderr, "Usage: %s <path>\n", argv[0]);
|
|
return 1;
|
|
}
|
|
|
|
FILE *file = fopen(path, "rb");
|
|
if (!file) {
|
|
fprintf(stderr, "Failed to open %s\n", path);
|
|
return 1;
|
|
}
|
|
|
|
uint8_t *exe_bytes = malloc(MEMORY_SIZE);
|
|
size_t exe_size = fread(exe_bytes, 1, MEMORY_SIZE, file);
|
|
fclose(file);
|
|
|
|
RISCV64 r = riscv64_load(exe_bytes, exe_size);
|
|
free(exe_bytes);
|
|
|
|
for (r.pc = r.code_section.offset;
|
|
r.pc < r.code_section.offset + r.code_section.size; r.pc += 4) {
|
|
riscv64_disassemble_one(&r);
|
|
}
|
|
printf("END DISASSEMBLY\n");
|
|
|
|
riscv64_execute(&r);
|
|
}
|