예제 #1
0
파일: exec.c 프로젝트: chrisddom/yara
int yr_execute_code(
    YR_RULES* rules,
    EVALUATION_CONTEXT* context,
    int timeout,
    time_t start_time)
{
  int64_t r1;
  int64_t r2;
  int64_t r3;
  int64_t mem[MEM_SIZE];
  int64_t stack[STACK_SIZE];
  int32_t sp = 0;
  uint8_t* ip = rules->code_start;

  YR_RULE* rule;
  YR_STRING* string;
  YR_MATCH* match;
  YR_EXTERNAL_VARIABLE* external;

  int i;
  int found;
  int count;
  int result;
  int flags;
  int cycle = 0;
  int tidx = yr_get_tidx();

  while(1)
  {
    switch(*ip)
    {
      case HALT:
        // When the halt instruction is reached the stack
        // should be empty.
        assert(sp == 0);
        return ERROR_SUCCESS;

      case PUSH:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        push(r1);
        break;

      case POP:
        pop(r1);
        break;

      case CLEAR_M:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        mem[r1] = 0;
        break;

      case ADD_M:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        pop(r2);
        mem[r1] += r2;
        break;

      case INCR_M:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        mem[r1]++;
        break;

      case PUSH_M:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        push(mem[r1]);
        break;

      case POP_M:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        pop(mem[r1]);
        break;

      case SWAPUNDEF:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        pop(r2);
        if (r2 != UNDEFINED)
          push(r2);
        else
          push(mem[r1]);
        break;

      case JNUNDEF:
        pop(r1);
        push(r1);

        if (r1 != UNDEFINED)
        {
          ip = *(uint8_t**)(ip + 1);
          // ip will be incremented at the end of the loop,
          // decrement it here to compensate.
          ip--;
        }
        else
        {
          ip += sizeof(uint64_t);
        }
        break;

      case JLE:
        pop(r2);
        pop(r1);
        push(r1);
        push(r2);

        if (r1 <= r2)
        {
          ip = *(uint8_t**)(ip + 1);
          // ip will be incremented at the end of the loop,
          // decrement it here to compensate.
          ip--;
        }
        else
        {
          ip += sizeof(uint64_t);
        }
        break;

      case AND:
        pop(r2);
        pop(r1);
        push(r1 & r2);
        break;

      case OR:
        pop(r2);
        pop(r1);
        push(r1 | r2);
        break;

      case NOT:
        pop(r1);
        push(!r1);
        break;

      case LT:
        pop(r2);
        pop(r1);
        push(comparison(<, r1, r2));
        break;

      case GT:
        pop(r2);
        pop(r1);
        push(comparison(>, r1, r2));
        break;

      case LE:
        pop(r2);
        pop(r1);
        push(comparison(<=, r1, r2));
        break;

      case GE:
        pop(r2);
        pop(r1);
        push(comparison(>=, r1, r2));
        break;

      case EQ:
        pop(r2);
        pop(r1);
        push(comparison(==, r1, r2));
        break;

      case NEQ:
        pop(r2);
        pop(r1);
        push(comparison(!=, r1, r2));
        break;

      case ADD:
        pop(r2);
        pop(r1);
        push(operation(+, r1, r2));
        break;

      case SUB:
        pop(r2);
        pop(r1);
        push(operation(-, r1, r2));
        break;

      case MUL:
        pop(r2);
        pop(r1);
        push(operation(*, r1, r2));
        break;

      case DIV:
        pop(r2);
        pop(r1);
        push(operation(/, r1, r2));
        break;

      case MOD:
        pop(r2);
        pop(r1);
        push(operation(%, r1, r2));
        break;

      case NEG:
        pop(r1);
        push(IS_UNDEFINED(r1) ? UNDEFINED : ~r1);
        break;

      case SHR:
        pop(r2);
        pop(r1);
        push(operation(>>, r1, r2));
        break;

      case SHL:
        pop(r2);
        pop(r1);
        push(operation(<<, r1, r2));
        break;

      case XOR:
        pop(r2);
        pop(r1);
        push(operation(^, r1, r2));
        break;

      case RULE_PUSH:
        rule = *(YR_RULE**)(ip + 1);
        ip += sizeof(uint64_t);
        push(rule->t_flags[tidx] & RULE_TFLAGS_MATCH ? 1 : 0);
        break;

      case RULE_POP:
        pop(r1);
        rule = *(YR_RULE**)(ip + 1);
        ip += sizeof(uint64_t);
        if (r1)
          rule->t_flags[tidx] |= RULE_TFLAGS_MATCH;
        break;

      case EXT_INT:
        external = *(YR_EXTERNAL_VARIABLE**)(ip + 1);
        ip += sizeof(uint64_t);
        push(external->integer);
        break;

      case EXT_STR:
        external = *(YR_EXTERNAL_VARIABLE**)(ip + 1);
        ip += sizeof(uint64_t);
        push(PTR_TO_UINT64(external->string));
        break;

      case EXT_BOOL:
        external = *(YR_EXTERNAL_VARIABLE**)(ip + 1);
        ip += sizeof(uint64_t);
        if (external->type == EXTERNAL_VARIABLE_TYPE_FIXED_STRING ||
            external->type == EXTERNAL_VARIABLE_TYPE_MALLOC_STRING)
          push(external->string[0] != '\0');
        else
          push(external->integer);
        break;

      case SFOUND:
        pop(r1);
        string = UINT64_TO_PTR(YR_STRING*, r1);
        push(string->matches[tidx].tail != NULL ? 1 : 0);
        break;

      case SFOUND_AT:
        pop(r2);
        pop(r1);

        if (IS_UNDEFINED(r1))
        {
          push(0);
          break;
        }

        string = UINT64_TO_PTR(YR_STRING*, r2);
        match = string->matches[tidx].head;
        found = 0;

        while (match != NULL)
        {
          if (r1 == match->offset)
          {
            push(1);
            found = 1;
            break;
          }

          if (r1 < match->offset)
            break;

          match = match->next;
        }

        if (!found)
          push(0);

        break;

      case SFOUND_IN:
        pop(r3);
        pop(r2);
        pop(r1);

        if (IS_UNDEFINED(r1) || IS_UNDEFINED(r2))
        {
          push(0);
          break;
        }

        string = UINT64_TO_PTR(YR_STRING*, r3);
        match = string->matches[tidx].head;
        found = FALSE;

        while (match != NULL && !found)
        {
          if (match->offset >= r1 && match->offset <= r2)
          {
            push(1);
            found = TRUE;
          }

          if (match->offset > r2)
            break;

          match = match->next;
        }

        if (!found)
          push(0);

        break;

      case SCOUNT:
        pop(r1);
        string = UINT64_TO_PTR(YR_STRING*, r1);
        match = string->matches[tidx].head;
        found = 0;
        while (match != NULL)
        {
          found++;
          match = match->next;
        }
        push(found);
        break;

      case SOFFSET:
        pop(r2);
        pop(r1);

        if (IS_UNDEFINED(r1))
        {
          push(UNDEFINED);
          break;
        }

        string = UINT64_TO_PTR(YR_STRING*, r2);
        match = string->matches[tidx].head;
        i = 1;
        found = FALSE;

        while (match != NULL && !found)
        {
          if (r1 == i)
          {
            push(match->offset);
            found = TRUE;
          }

          i++;
          match = match->next;
        }

        if (!found)
          push(UNDEFINED);

        break;

      case OF:
        found = 0;
        count = 0;
        pop(r1);

        while (r1 != UNDEFINED)
        {
          string = UINT64_TO_PTR(YR_STRING*, r1);
          if (string->matches[tidx].tail != NULL)
            found++;
          count++;
          pop(r1);
        }

        pop(r2);

        if (r2 != UNDEFINED)
          push(found >= r2 ? 1 : 0);
        else
          push(found >= count ? 1 : 0);

        break;

      case SIZE:
        push(context->file_size);
        break;

      case ENTRYPOINT:
        push(context->entry_point);
        break;

      case INT8:
        pop(r1);
        push(read_int8_t(context->mem_block, r1));
        break;

      case INT16:
        pop(r1);
        push(read_int16_t(context->mem_block, r1));
        break;

      case INT32:
        pop(r1);
        push(read_int32_t(context->mem_block, r1));
        break;

      case UINT8:
        pop(r1);
        push(read_uint8_t(context->mem_block, r1));
        break;

      case UINT16:
        pop(r1);
        push(read_uint16_t(context->mem_block, r1));
        break;

      case UINT32:
        pop(r1);
        push(read_uint32_t(context->mem_block, r1));
        break;

      case CONTAINS:
        pop(r2);
        pop(r1);
        push(strstr(UINT64_TO_PTR(char*, r1),
                    UINT64_TO_PTR(char*, r2)) != NULL);
        break;

      case MATCHES:
        pop(r3);
        pop(r2);
        pop(r1);

        flags = (int) r3;
        count = strlen(UINT64_TO_PTR(char*, r1));

        if (count == 0)
        {
          push(FALSE);
          break;
        }

        result = yr_re_exec(
          UINT64_TO_PTR(uint8_t*, r2),
          UINT64_TO_PTR(uint8_t*, r1),
          count,
          flags | RE_FLAGS_SCAN,
          NULL,
          NULL);

        push(result >= 0);
        break;

      default:
        // Unknown instruction, this shouldn't happen.
        assert(FALSE);
    }

    if (timeout > 0)  // timeout == 0 means no timeout
    {
      // Check for timeout every 10 instruction cycles.

      if (++cycle == 10)
      {
        if (difftime(time(NULL), start_time) > timeout)
          return ERROR_SCAN_TIMEOUT;

        cycle = 0;
      }
    }

    ip++;
  }

  // After executing the code the stack should be empty.
  assert(sp == 0);

  return ERROR_SUCCESS;
}
예제 #2
0
파일: exec.c 프로젝트: karlhiramoto/yara
int yr_execute_code(
    YR_RULES* rules,
    YR_SCAN_CONTEXT* context,
    int timeout,
    time_t start_time)
{
  int64_t r1;
  int64_t r2;
  int64_t r3;
  int64_t mem[MEM_SIZE];
  int64_t stack[STACK_SIZE];
  int64_t args[MAX_FUNCTION_ARGS];
  int32_t sp = 0;
  uint8_t* ip = rules->code_start;

  YR_RULE* rule;
  YR_STRING* string;
  YR_MATCH* match;
  YR_OBJECT* object;
  YR_OBJECT_FUNCTION* function;

  char* identifier;
  char* args_fmt;

  int i;
  int found;
  int count;
  int result;
  int cycle = 0;
  int tidx = yr_get_tidx();

  #ifdef PROFILING_ENABLED
  clock_t start = clock();
  #endif

  while(1)
  {
    switch(*ip)
    {
      case OP_HALT:
        // When the halt instruction is reached the stack
        // should be empty.
        assert(sp == 0);
        return ERROR_SUCCESS;

      case OP_PUSH:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        push(r1);
        break;

      case OP_POP:
        pop(r1);
        break;

      case OP_CLEAR_M:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        mem[r1] = 0;
        break;

      case OP_ADD_M:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        pop(r2);
        mem[r1] += r2;
        break;

      case OP_INCR_M:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        mem[r1]++;
        break;

      case OP_PUSH_M:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        push(mem[r1]);
        break;

      case OP_POP_M:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        pop(mem[r1]);
        break;

      case OP_SWAPUNDEF:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);
        pop(r2);
        if (r2 != UNDEFINED)
          push(r2);
        else
          push(mem[r1]);
        break;

      case OP_JNUNDEF:
        pop(r1);
        push(r1);

        if (r1 != UNDEFINED)
        {
          ip = *(uint8_t**)(ip + 1);
          // ip will be incremented at the end of the loop,
          // decrement it here to compensate.
          ip--;
        }
        else
        {
          ip += sizeof(uint64_t);
        }
        break;

      case OP_JLE:
        pop(r2);
        pop(r1);
        push(r1);
        push(r2);

        if (r1 <= r2)
        {
          ip = *(uint8_t**)(ip + 1);
          // ip will be incremented at the end of the loop,
          // decrement it here to compensate.
          ip--;
        }
        else
        {
          ip += sizeof(uint64_t);
        }
        break;

      case OP_AND:
        pop(r2);
        pop(r1);
        if (IS_UNDEFINED(r1) || IS_UNDEFINED(r2))
          push(0);
        else
          push(r1 && r2);
        break;

      case OP_OR:
        pop(r2);
        pop(r1);
        if (IS_UNDEFINED(r1))
          push(r2);
        else if (IS_UNDEFINED(r2))
          push(r1);
        else
          push(r1 || r2);
        break;

      case OP_NOT:
        pop(r1);
        if (IS_UNDEFINED(r1))
          push(UNDEFINED);
        else
          push(!r1);
        break;

      case OP_LT:
        pop(r2);
        pop(r1);
        push(COMPARISON(<, r1, r2));
        break;

      case OP_GT:
        pop(r2);
        pop(r1);
        push(COMPARISON(>, r1, r2));
        break;

      case OP_LE:
        pop(r2);
        pop(r1);
        push(COMPARISON(<=, r1, r2));
        break;

      case OP_GE:
        pop(r2);
        pop(r1);
        push(COMPARISON(>=, r1, r2));
        break;

      case OP_EQ:
        pop(r2);
        pop(r1);
        push(COMPARISON(==, r1, r2));
        break;

      case OP_NEQ:
        pop(r2);
        pop(r1);
        push(COMPARISON(!=, r1, r2));
        break;

      case OP_SZ_EQ:
        pop(r2);
        pop(r1);

        if (IS_UNDEFINED(r1) || IS_UNDEFINED(r2))
          push(UNDEFINED);
        else
          push(strcmp(UINT64_TO_PTR(char*, r1),
                      UINT64_TO_PTR(char*, r2)) == 0);
        break;

      case OP_SZ_NEQ:
        pop(r2);
        pop(r1);

        if (IS_UNDEFINED(r1) || IS_UNDEFINED(r2))
          push(UNDEFINED);
        else
          push(strcmp(UINT64_TO_PTR(char*, r1),
                      UINT64_TO_PTR(char*, r2)) != 0);
        break;

      case OP_SZ_TO_BOOL:
        pop(r1);

        if (IS_UNDEFINED(r1))
          push(UNDEFINED);
        else
          push(strlen(UINT64_TO_PTR(char*, r1)) > 0);

        break;

      case OP_ADD:
        pop(r2);
        pop(r1);
        push(OPERATION(+, r1, r2));
        break;

      case OP_SUB:
        pop(r2);
        pop(r1);
        push(OPERATION(-, r1, r2));
        break;

      case OP_MUL:
        pop(r2);
        pop(r1);
        push(OPERATION(*, r1, r2));
        break;

      case OP_DIV:
        pop(r2);
        pop(r1);
        push(OPERATION(/, r1, r2));
        break;

      case OP_MOD:
        pop(r2);
        pop(r1);
        push(OPERATION(%, r1, r2));
        break;

      case OP_SHR:
        pop(r2);
        pop(r1);
        push(OPERATION(>>, r1, r2));
        break;

      case OP_SHL:
        pop(r2);
        pop(r1);
        push(OPERATION(<<, r1, r2));
        break;

      case OP_BITWISE_NOT:
        pop(r1);
        push(IS_UNDEFINED(r1) ? UNDEFINED : ~r1);
        break;

      case OP_BITWISE_AND:
        pop(r2);
        pop(r1);
        push(OPERATION(&, r1, r2));
        break;

      case OP_BITWISE_OR:
        pop(r2);
        pop(r1);
        push(OPERATION(|, r1, r2));
        break;

      case OP_BITWISE_XOR:
        pop(r2);
        pop(r1);
        push(OPERATION(^, r1, r2));
        break;

      case OP_PUSH_RULE:
        rule = *(YR_RULE**)(ip + 1);
        ip += sizeof(uint64_t);
        push(rule->t_flags[tidx] & RULE_TFLAGS_MATCH ? 1 : 0);
        break;

      case OP_MATCH_RULE:
        pop(r1);
        rule = *(YR_RULE**)(ip + 1);
        ip += sizeof(uint64_t);

        if (!IS_UNDEFINED(r1) && r1)
          rule->t_flags[tidx] |= RULE_TFLAGS_MATCH;

        #ifdef PROFILING_ENABLED
        rule->clock_ticks += clock() - start;
        start = clock();
        #endif
        break;

      case OP_OBJ_LOAD:
        identifier = *(char**)(ip + 1);
        ip += sizeof(uint64_t);

        object = (YR_OBJECT*) yr_hash_table_lookup(
            context->objects_table,
            identifier,
            NULL);

        assert(object != NULL);
        push(PTR_TO_UINT64(object));
        break;

      case OP_OBJ_FIELD:
        pop(r1);

        identifier = *(char**)(ip + 1);
        ip += sizeof(uint64_t);

        if (IS_UNDEFINED(r1))
        {
          push(UNDEFINED);
          break;
        }

        object = UINT64_TO_PTR(YR_OBJECT*, r1);
        object = yr_object_lookup_field(object, identifier);
        assert(object != NULL);
        push(PTR_TO_UINT64(object));
        break;

      case OP_OBJ_VALUE:
        pop(r1);

        if (IS_UNDEFINED(r1))
        {
          push(UNDEFINED);
          break;
        }

        object = UINT64_TO_PTR(YR_OBJECT*, r1);

        switch(object->type)
        {
          case OBJECT_TYPE_INTEGER:
            push(((YR_OBJECT_INTEGER*) object)->value);
            break;

          case OBJECT_TYPE_STRING:
            if (((YR_OBJECT_STRING*) object)->value != NULL)
              push(PTR_TO_UINT64(((YR_OBJECT_STRING*) object)->value));
            else
              push(UNDEFINED);
            break;

          default:
            assert(FALSE);
        }

        break;

      case OP_INDEX_ARRAY:
        pop(r1);  // index
        pop(r2);  // array

        if (IS_UNDEFINED(r1))
        {
          push(UNDEFINED);
          break;
        }

        object = UINT64_TO_PTR(YR_OBJECT*, r2);
        assert(object->type == OBJECT_TYPE_ARRAY);
        object = yr_object_array_get_item(object, 0, r1);

        if (object != NULL)
          push(PTR_TO_UINT64(object));
        else
          push(UNDEFINED);

        break;

      case OP_LOOKUP_DICT:
        pop(r1);  // key
        pop(r2);  // dictionary

        if (IS_UNDEFINED(r1))
        {
          push(UNDEFINED);
          break;
        }

        object = UINT64_TO_PTR(YR_OBJECT*, r2);
        assert(object->type == OBJECT_TYPE_DICTIONARY);

        object = yr_object_dict_get_item(
            object, 0, UINT64_TO_PTR(const char*, r1));

        if (object != NULL)
          push(PTR_TO_UINT64(object));
        else
          push(UNDEFINED);

        break;

      case OP_CALL:
        args_fmt = *(char**)(ip + 1);
        ip += sizeof(uint64_t);

        i = strlen(args_fmt);

        // pop arguments from stack and copy them to args array

        while (i > 0)
        {
          pop(args[i - 1]);
          i--;
        }

        pop(r2);

        function = UINT64_TO_PTR(YR_OBJECT_FUNCTION*, r2);
        result = ERROR_INTERNAL_FATAL_ERROR;

        for (i = 0; i < MAX_OVERLOADED_FUNCTIONS; i++)
        {
          if (function->prototypes[i].arguments_fmt == NULL)
            break;

          if (strcmp(function->prototypes[i].arguments_fmt, args_fmt) == 0)
          {
            result = function->prototypes[i].code(
                (void*) args,
                context,
                function);

            break;
          }
        }

        assert(i < MAX_OVERLOADED_FUNCTIONS);

        if (result == ERROR_SUCCESS)
          push(PTR_TO_UINT64(function->return_obj));
        else
          return result;

        break;

      case OP_STR_FOUND:
        pop(r1);
        string = UINT64_TO_PTR(YR_STRING*, r1);
        push(string->matches[tidx].tail != NULL ? 1 : 0);
        break;

      case OP_STR_FOUND_AT:
        pop(r2);
        pop(r1);

        if (IS_UNDEFINED(r1))
        {
          push(0);
          break;
        }

        string = UINT64_TO_PTR(YR_STRING*, r2);
        match = string->matches[tidx].head;
        found = 0;

        while (match != NULL)
        {
          if (r1 == match->base + match->offset)
          {
            push(1);
            found = 1;
            break;
          }

          if (r1 < match->base + match->offset)
            break;

          match = match->next;
        }

        if (!found)
          push(0);

        break;

      case OP_STR_FOUND_IN:
        pop(r3);
        pop(r2);
        pop(r1);

        if (IS_UNDEFINED(r1) || IS_UNDEFINED(r2))
        {
          push(UNDEFINED);
          break;
        }

        string = UINT64_TO_PTR(YR_STRING*, r3);
        match = string->matches[tidx].head;
        found = FALSE;

        while (match != NULL && !found)
        {
          if (match->base + match->offset >= r1 &&
              match->base + match->offset <= r2)
          {
            push(1);
            found = TRUE;
          }

          if (match->base + match->offset > r2)
            break;

          match = match->next;
        }

        if (!found)
          push(0);

        break;

      case OP_STR_COUNT:
        pop(r1);
        string = UINT64_TO_PTR(YR_STRING*, r1);
        push(string->matches[tidx].count);
        break;

      case OP_STR_OFFSET:
        pop(r2);
        pop(r1);

        if (IS_UNDEFINED(r1))
        {
          push(UNDEFINED);
          break;
        }

        string = UINT64_TO_PTR(YR_STRING*, r2);
        match = string->matches[tidx].head;
        i = 1;
        found = FALSE;

        while (match != NULL && !found)
        {
          if (r1 == i)
          {
            push(match->base + match->offset);
            found = TRUE;
          }

          i++;
          match = match->next;
        }

        if (!found)
          push(UNDEFINED);

        break;

      case OP_OF:
        found = 0;
        count = 0;
        pop(r1);

        while (r1 != UNDEFINED)
        {
          string = UINT64_TO_PTR(YR_STRING*, r1);
          if (string->matches[tidx].tail != NULL)
            found++;
          count++;
          pop(r1);
        }

        pop(r2);

        if (r2 != UNDEFINED)
          push(found >= r2 ? 1 : 0);
        else
          push(found >= count ? 1 : 0);

        break;

      case OP_FILESIZE:
        push(context->file_size);
        break;

      case OP_ENTRYPOINT:
        push(context->entry_point);
        break;

      case OP_INT8:
        pop(r1);
        push(read_int8_t(context->mem_block, r1));
        break;

      case OP_INT16:
        pop(r1);
        push(read_int16_t(context->mem_block, r1));
        break;

      case OP_INT32:
        pop(r1);
        push(read_int32_t(context->mem_block, r1));
        break;

      case OP_UINT8:
        pop(r1);
        push(read_uint8_t(context->mem_block, r1));
        break;

      case OP_UINT16:
        pop(r1);
        push(read_uint16_t(context->mem_block, r1));
        break;

      case OP_UINT32:
        pop(r1);
        push(read_uint32_t(context->mem_block, r1));
        break;

      case OP_CONTAINS:
        pop(r2);
        pop(r1);

        if (IS_UNDEFINED(r1) || IS_UNDEFINED(r2))
          push(UNDEFINED);
        else
          push(strstr(UINT64_TO_PTR(char*, r1),
                      UINT64_TO_PTR(char*, r2)) != NULL);
        break;

      case OP_IMPORT:
        r1 = *(uint64_t*)(ip + 1);
        ip += sizeof(uint64_t);

        FAIL_ON_ERROR(yr_modules_load(
            UINT64_TO_PTR(char*, r1),
            context));

        break;

      case OP_MATCHES:
        pop(r2);
        pop(r1);

        count = strlen(UINT64_TO_PTR(char*, r1));

        if (count == 0)
        {
          push(FALSE);
          break;
        }

        result = yr_re_exec(
          UINT64_TO_PTR(uint8_t*, r2),
          UINT64_TO_PTR(uint8_t*, r1),
          count,
          RE_FLAGS_SCAN,
          NULL,
          NULL);

        push(result >= 0);
        break;

      default:
        // Unknown instruction, this shouldn't happen.
        assert(FALSE);
    }

    if (timeout > 0)  // timeout == 0 means no timeout
    {
      // Check for timeout every 10 instruction cycles.

      if (++cycle == 10)
      {
        if (difftime(time(NULL), start_time) > timeout)
          return ERROR_SCAN_TIMEOUT;

        cycle = 0;
      }
    }

    ip++;
  }

  // After executing the code the stack should be empty.
  assert(sp == 0);

  return ERROR_SUCCESS;
}