Linux下获取CPUID、硬盘序列号与MAC地址

在很多系统软件的开发中，需要使用一些系统的唯一性信息。所以，得到主机的CPUID、硬盘序列号及网卡的MAC地址，就成个一件很重要的应用。

本人经过一番google即自己的钻研，基本上实现了这几个功能。需要的准备知识有：

1. GCC的嵌入汇编，具体的GCC嵌入汇编知识，请参考相关手册
2. ioctl系统调用，具体的调用方法，请查看手册页

获取CPUID

按照网上提供的说明，CPUID并不是所有的Intel CPU都支持的。如果支持，汇编调用为：eax置0000_0003，调用cpuid。

以下为实现代码（在我的CPU上，并没有得到）：

#define cpuid(in,a,b,c,d)  asm("cpuid": "=a" (a), "=b" (b), "=c" (c), "=d" (d) : "a" (in));
static int
getcpuid (char *id, size_t max)
{
  int i;
  unsigned long li, maxi, maxei, ebx, ecx, edx, unused;

  cpuid (0, maxi, unused, unused, unused);
  maxi &= 0xffff;

  if (maxi < 3)
    {
      return -1;
    }

  cpuid (3, eax, ebx, ecx, edx);

  snprintf (id, max, "%08lx %08lx %08lx %08lx", eax, ebx, ecx, edx);
  fprintf (stdout, "get cpu id: %s\n", id);
  return 0;
}

获取硬盘序列号

这个的实现，采用的是读取/etc/mtab文件，找到/（即根目录）挂载的设备文件，然后打开它，再用系统调用ioctl来实现的。

ioctl第二个参数为HDIO_GET_IDENTITY, 获得指定文件描述符的标志号

ioctl的第三个参数为struct hd_driveid *，在linux/hdreg.h中，struct hd_driveid的声明有

struct hd_driveid {
 unsigned short config;  /* lots of obsolete bit flags */
 unsigned short cyls;  /* Obsolete, "physical" cyls */
 unsigned short reserved2; /* reserved (word 2) */
 unsigned short heads;  /* Obsolete, "physical" heads */
 unsigned short track_bytes; /* unformatted bytes per track */
 unsigned short sector_bytes; /* unformatted bytes per sector */
 unsigned short sectors; /* Obsolete, "physical" sectors per track */
 unsigned short vendor0; /* vendor unique */
 unsigned short vendor1; /* vendor unique */
 unsigned short vendor2; /* Retired vendor unique */
 unsigned char serial_no[20]; /* 0 = not_specified */
 unsigned short buf_type; /* Retired */
 unsigned short buf_size; /* Retired, 512 byte increments
      * 0 = not_specified
      */
        ……
};

，这其中，serial_no为硬盘的序列号。如果此项为0，则为没有提供。

思路明确了，以下为实现代码：

static int
getdiskid (char *id, size_t max)
{
  int fd;
  struct hd_driveid hid;
  FILE *fp;
  char line[0x100], *disk, *root, *p;

  fp = fopen ("/etc/mtab", "r");
  if (fp == NULL)
    {
      fprintf (stderr, "No /etc/mtab file.\n");
      return -1;
    }

  fd = -1;
  while (fgets (line, sizeof line, fp) != NULL)
    {
      disk = strtok (line, " ");
      if (disk == NULL)
 {
   continue;
 }

      root = strtok (NULL, " ");
      if (root == NULL)
 {
   continue;
 }

      if (strcmp (root, "/") == 0)
 {
   for (p = disk + strlen (disk) - 1; isdigit (*p); p --)
            {
             *p = '\0';
            }
   fd = open (disk, O_RDONLY);
   break;
 }
    }

  fclose (fp);

  if (fd < 0)
    {
      fprintf (stderr, "open hard disk device failed.\n");
      return -1;
    }

  if (ioctl (fd, HDIO_GET_IDENTITY, &hid) < 0)
    {
      fprintf (stderr, "ioctl error.\n");
      return -1;
    }

  close (fd);

  snprintf (id, max, "%s", hid.serial_no);
  fprintf (stdout, "get hard disk serial number: %s\n", id);
  return 0;
}

获取MAC地址

通过创建一个socket，然后bind特定的IP地址，就可以通过ioctl得到这个套按地绑定的网络接口名称。然后再通过网络接口名称，得到MAC地址。

如果ioctl的第二个参数为SIOCGIFNAME, 则获得指定网络接口的名称；如果ioctl的第二个参数为SIOCGIFHWADDR，则获得指定网络接口的MAC地址

ioctl的第三个参数为struct ifreq *，在linux/if.h头文件里，struct ifreq声明如下：

struct ifreq
{
#define IFHWADDRLEN 6
 union
 {
  char ifrn_name[IFNAMSIZ];  /* if name, e.g. "en0" */
 } ifr_ifrn;

 union {
  struct sockaddr ifru_addr;
  struct sockaddr ifru_dstaddr;
  struct sockaddr ifru_broadaddr;
  struct sockaddr ifru_netmask;
  struct  sockaddr ifru_hwaddr;
  short ifru_flags;
  int ifru_ivalue;
  int ifru_mtu;
  struct  ifmap ifru_map;
  char ifru_slave[IFNAMSIZ]; /* Just fits the size */
  char ifru_newname[IFNAMSIZ];
  void * ifru_data;
  struct if_settings ifru_settings;
 } ifr_ifru;
}

，其中，ifrn_name为网络接口的名称，ifr_ifru.ifru_hwaddr为网络接口的MAC地址。

#ifndef MAX_IFINDEX
# define MAX_IFINDEX    8
#endif

static int
getmacaddr (const char *ip, char *id, size_t max)
{

  int i, sockfd;
  struct sockaddr_in *loc;
  struct ifreq req[1];

  sockfd = socket (AF_INET, SOCK_DGRAM, 0);
  if (sockfd < 0)
    {
      fprintf (stderr, "Unable to create socket.\n");
      return -1;
    }

  for (i = 0; i <= MAX_IFINDEX; ++ i)
    {
      req->ifr_ifindex = i;

      if (ioctl (sockfd, SIOCGIFNAME, req) < 0)
        {
          fprintf (stderr, "ioctl error: %s\n", strerror (errno));
          continue;
        }

      if (ioctl (sockfd, SIOCGIFADDR, req) < 0)
        {
          fprintf (stderr, "ioctl interface index [%d] error: %s\n", i, strerror (errno));
          continue;
        }

      loc = (struct sockaddr_in *) (&(req->ifr_ifru.ifru_addr));
      if (loc->sin_addr.s_addr == inet_addr (ip))
        {
          fprintf (stderr, "%s bind at %s.\n", ip, req->ifr_name);
          break;
        }
    }

  if (i == MAX_IFINDEX)
    {
      fprintf (stderr, "input IP error.\n");
      close (sockfd);
      return -1;
    }

  if (ioctl (sockfd, SIOCGIFHWADDR, req) < 0)
    {
      fprintf (stderr, "ioctl error: %s\n", strerror (errno));
      close (sockfd);
      return -1;
    }

  close (sockfd);

  snprintf (id, max, "%02X%02X%02X%02X%02X%02X",
            req->ifr_hwaddr.sa_data[0] & 0xff,
            req->ifr_hwaddr.sa_data[1] & 0xff,
            req->ifr_hwaddr.sa_data[2] & 0xff,
            req->ifr_hwaddr.sa_data[3] & 0xff,
            req->ifr_hwaddr.sa_data[4] & 0xff,
            req->ifr_hwaddr.sa_data[5] & 0xff);

  fprintf (stdout, "MAC address of %s: [%s].\n", req->ifr_name, id);
  return 0;
}