disasm.cc

// Copyright 2020, VIXL authors
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#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "code-buffer-vixl.h"
#include "aarch64/decoder-aarch64.h"
#include "aarch64/disasm-aarch64.h"

// This example is interactive, and isn't tested systematically.
#ifndef TEST_EXAMPLES

using namespace vixl;
using namespace vixl::aarch64;

void PrintUsage(char const* name) {
  printf("Usage: %s [OPTION]... <INSTRUCTION>...\n", name);
  printf("\n");
  printf("Disassemble ad-hoc A64 instructions.\n");
  printf("\n");
  printf(
      "Options:\n"
      "  --start-at <address>\n"
      "    Start disassembling from <address> Any signed 64-bit value\n"
      "    accepted by strtoll can be specified. The address is printed\n"
      "    alongside each instruction, and it is also used to decode\n"
      "    PC-relative offsets.\n"
      "\n"
      "    Defaults to 0.\n"
      "\n");
  printf(
      "<instruction>\n"
      "  A hexadecimal representation of an A64 instruction. The leading '0x'\n"
      "  (or '0X') is optional.\n"
      "\n"
      "  Multiple instructions can be provided; they will be disassembled as\n"
      "  if they were read sequentially from memory.\n"
      "\n");
  printf("Examples:\n");
  printf("  $ %s d2824685\n", name);
  printf("   0x0000000000000000:  d2824685  movz x5, #0x1234\n");
  printf("\n");
  printf("  $ %s --start-at -4 0x10fffe85 0xd61f00a0\n", name);
  printf("  -0x0000000000000004:  10fffe85  adr x5, #-0x30 (addr -0x34)\n");
  printf("   0x0000000000000000:  d61f00a0  br x5\n");
}

Instr ParseInstr(char const* arg) {
  // TODO: Error handling for out-of-range inputs.
  return (Instr)strtoul(arg, NULL, 16);
}

int64_t ParseInt64(char const* arg) {
  // TODO: Error handling for out-of-range inputs.
  return (int64_t)strtoll(arg, NULL, 0);
}

int main(int argc, char* argv[]) {
  for (int i = 1; i < argc; i++) {
    char const* arg = argv[i];
    if ((strcmp(arg, "--help") == 0) || (strcmp(arg, "-h") == 0)) {
      PrintUsage(argv[0]);
      return 0;
    }
  }

  // Assume an address of 0, unless otherwise specified.
  int64_t start_address = 0;
  // Allocate space for one instruction per argument.
  CodeBuffer buffer((argc - 1) * kInstructionSize);

  bool expect_start_at = false;
  for (int i = 1; i < argc; i++) {
    char* arg = argv[i];
    if (expect_start_at) {
      start_address = ParseInt64(arg);
      expect_start_at = false;
    } else if (strcmp(arg, "--start-at") == 0) {
      expect_start_at = true;
    } else {
      // Assume that everything else is an instruction.
      buffer.Emit(ParseInstr(arg));
    }
  }
  buffer.SetClean();

  if (expect_start_at) {
    printf("No address given. Use: --start-at <address>\n");
    return 1;
  }

  if (buffer.GetSizeInBytes() == 0) {
    printf("Nothing to disassemble.\n");
    return 0;
  }

  // Disassemble the buffer.
  const Instruction* start = buffer.GetStartAddress<Instruction*>();
  const Instruction* end = buffer.GetEndAddress<Instruction*>();
  vixl::aarch64::PrintDisassembler disasm(stdout);
  disasm.PrintSignedAddresses(true);
  disasm.MapCodeAddress(start_address, start);
  disasm.DisassembleBuffer(start, end);

  return 0;
}

#endif  // TEST_EXAMPLES