用cpuid指令读取CPU信息

#include

int main()

{

unsigned int eflags1, eflags2 = 0;

unsigned int eax = 0;

unsigned int ebx,ecx,edx;

/**

* 测试CPU是否支持CPUID指令。

* eflags寄存器的第21位，如果程序可以清楚/设置它，则说明CPU支持CPUID指令。否则不支持

*/

/* 先取eflags */

asm volatile ("pushf\n\t"

"popl %%eax"

: "=a"(eflags1)

:

: "memory"

);

printf("original eflags is %p\n", eflags1);

/* 把eflags的第21位取反，写回寄存器中 */

asm volatile ("pushl %0\n\t"

"popf"

:

: "g"(eflags1 & ~( eflags1 & (1<<21) ) )

);

/* 检查一下现在的eflags，确认第21位和最初的值相反 */

asm volatile ("pushf\n\t"

"popl %%eax"

: "=a"(eflags2)

:

: "memory"

);

printf("modified eflags is %p\n", eflags2);

/* 把原来的eflags值设置回去 */

asm volatile ("pushl %0\n\t"

"popf"

:

: "g"(eflags1)

);

/**

* FIXME: Intel文档并没有说，如果不支持CPUID的话，clear/set eflags的第21位会有什么错误。

* 它只说，在不支持CPUID指令的CPU上，如80386，执行CPUID会产生invalid opcode错误

*

* 所以，在这里我们不处理 读/写 eflags 第21比特失败的情形

*/

/**

*  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)

: "0"(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)

: "0"(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 : %p\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)

);

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;

}