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:
- GCC的嵌入汇编,具体的GCC嵌入汇编知识,请参考相关手册 
- 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;
}