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。
#p#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;
}
#p#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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