linux获取Cpu信息

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利用cpuid获取cpu信息，包括序列号，类型名等，还有另一种方法就是dmidecode的源码来实现，需要root权限，读取dev/mem
这里只列出cpuid的方法：
嵌入式汇编的说明：
例子：
asm volatile ("cpuid"
: "=a"(eax)
: "a"(1)
);
其中嵌入式汇编代码中，“a”(1)和"0"(1)是相同的，均表示eax = 1，即数字代表下标，英文字母为定义的变量，如“=a”(eax)，其下标为0；
完整代码如下：
#include <stdio.h>//其中嵌入式汇编代码中，“a”(1)和"0"(1)是相同的，均表示eax = 1，即数字代表下标，英文字母为定义的变量，如“=a”(eax)，其下标为0//int main(){    unsigned int eflags1, eflags2 = 0;    unsigned int eax = 0;    unsigned int ebx,ecx,edx;    /**     *  eax == 1，则在eax中返回Family/Model/Stepping等信息     *  [0:3]    stepping     *  [4:7]    model     *  [8:11]    family     *  [12:13]    processor type     *  [16:19]    extended model ID     *  [20:27]    extended family ID     */    asm volatile ("cpuid"              : "=a"(eax)              : "a"(1)              );    // printf("eax is %p/n", eax);    printf("Extended Family\t: %d\n", (0xff00000 & eax) >> 20);    printf("Extended Model\t: %d\n", (0xf0000 & eax) >> 16);    printf("Processor type\t: %d\n", (0x3000 & eax) >> 12);    printf("Family\t\t: %d\n", (0xf00 & eax) >> 8);    printf("Model\t\t: %d\n", (0xf0 & eax) >> 4);    printf("Stepping:\t: %d\n", (0xf & eax));    printf("/n");        /**     * eax == 0x800000000     * 如果CPU支持Brand String，则在EAX中返 >= 0x80000004的值。     */    asm volatile ("cpuid"              : "=a"(eax)              : "a"(0x80000000)              );    printf("Is CPU support Brand String? %s\n", eax >= 0x80000004? "yes":"no");    printf("/n");    /**     * 如果支持Brand String，则EAX从0x80000002到0x80000004，每次增1，CPUID指令返回：     * EAX    : Processor Brand String     * EBX    : Processor Brand String Continued     * ECX    : Processor Brand String Continued     * EDX    : Processor Brand String Continued     */    if(eax >= 0x80000004) {        unsigned int brands[4]; //每次的eax、ebx、ecx、edx        unsigned int i;        printf("Brand String/t: ");        for (i = 0x80000002; i <= 0x80000004; i++) {            asm volatile ("cpuid"                      : "=a"(brands[0]), "=b"(brands[1]), "=c"(brands[2]), "=d"(brands[3])                      : "0" (i)                      );            printf("%s", (char *)brands);        }        //FIXME: 打出来的字符串是：In^Htel(R) Pentium(R^H) D CPU 2.80GHz        //其中^H是个不可见字符，会把它前一个吃掉        printf("\n");    }    /**     * eax == 0     * eax    : cpuid指令允许的最大eax输入值     * ebx    : "Genu"     * ecx    : "ntel"     * edx    : "inel"     */    asm volatile ("cpuid"              : "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx)              : "0"(0) );    printf("Maximum CPUID Input EAX : %d\n", eax);    char string[128];    snprintf(string, 5, "%s", (char *)&ebx);    snprintf(string + 4, 5, "%s", (char *)&edx);    snprintf(string + 8, 5, "%s", (char *)&ecx);    printf("Vendor\t\t: %s\n", string);    printf("\n");    /**     * eax == 1,      * edx的第18比特为1，则CPU支持serial number     *         为0，则不支持，或者被disabled     * 序列号有96位，其中最高32位即是eax的输出值。应当把它保存下来，然后     * 再设置eax==3, 取剩下的64位     */    asm volatile ("cpuid"              : "=a"(eax), "=d"(edx)              : "a"(1)              );    printf("%08x:%08x\n",ecx,edx);    printf("%08x:%08x\n",eax,edx);    if ( edx & (1 << 18) ) {        /* serial number supported */        /* edx输出中间32位的序列号，ecx输出最低32位的序列号 */        asm volatile ("cpuid"                  : "=c"(ecx), "=d"(edx)                  : "a"(3)                  );        printf("Serial Number\t : %x-%x-%x-%x-%x-%x\n",                 eax >> 16, eax << 16, edx >> 16, edx << 16, ecx >> 16, ecx << 16);    } else         printf("Serial Number not supported.\n");    printf("/n");    /**     * eax == 80000006h，返回L2 Cache的信息     *      * ecx[31:16]    : L2 Cache size, in Kbytes     * ecx[15:12]    : L2 Cache Associativity     *           00h disabled     *           01h direct mapped     *           02h 2-Way     *           04h 4-Way     *           06h 8-Way     *           08h 16-Way     *           0Fh Fully associative     * ecx[7:0]    : L2 Cache Line size in bytes     */    asm volatile ("cpuid"              : "=c"(ecx)              : "a"(0x80000006)              );    printf("L2 Cache Size\t : %dKbytes\n", ( ecx >> 16 ) );    printf("L2 Cache Line Size\t : %dbytes\n", (ecx & 0xff));    printf("L2 Cache Associativity\t : ");    switch ( (ecx & 0xf000) >> 12 )    {        case 0x00:            printf("%s\n", "disabled");            break;        case 0x01:            printf("%s\n", "direct mapped");            break;        case 0x02:            printf("%s\n", "2-Way");            break;        case 0x04:            printf("%s\n", "4-Way");            break;        case 0x06:            printf("%s\n", "8-Way");            break;        case 0x08:            printf("%s\n", "16-Way");            break;        case 0x0f:            printf("Fully associative");            break;        default:            printf("No such entry..\n");    }    printf("\n");    /**     * Input : eax == 4 && ecx == 0     *     * (eax[31:26] + 1) 是该物理处理器package上实现的core CPUs数目     */    asm volatile ("cpuid"              : "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx)              : "0"(4), "2"(0)              );    printf("Number of Cores on this physical package\t : %d\n", (eax >> 27) + 1 );    printf("\n");    /**     * Input : eax == 1，则edx返回feature flag     *     */    return 0;}
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