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;

}

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