在汇编指令中添加变量（asm内联C示例）

Question

我想执行循环汇编代码行。 实际上我正在尝试读取内核的CPUID，需要读取CPUID的所有参数。 如果将0写入eax寄存器，则将获得制造商名称；如果将1写入eax，则将接收下一组CPUID信息。 依此类推...现在，我想执行多达15组的asm指令，以获得完整的CPUID输出。

例如：unsigned int cpuid_reg [4];

    __asm__ volatile("mov $1, %eax");
    __asm__ volatile("cpuid" : "=a" (cpuid_reg[0]), "=b" (cpuid_reg[1]), "=c" (cpuid_reg[2]), "=d" (cpuid_reg[3]));
    printf("reg[0] 0x%x , cpuid_reg[1] 0x%x, cpuid_reg[2] 0x%x, cpuid_reg[3] 0x%x\n", cpuid_reg[0], cpuid_reg[1], cpuid_reg[2], cpuid_reg[3]);


    __asm__ volatile("mov $2, %eax");
    __asm__ volatile("cpuid" : "=a" (cpuid_reg[0]), "=b" (cpuid_reg[1]), "=c" (cpuid_reg[2]), "=d" (cpuid_reg[3]));
    printf("cpuid_reg[0] 0x%x , cpuid_reg[1] 0x%x, cpuid_reg[2] 0x%x, cpuid_reg[3] 0x%x\n", cpuid_reg[0], cpuid_reg[1], cpuid_reg[2], cpuid_reg[3]);

代替这两组代码，我需要一组代码，可以在其中向eax寄存器写入0到15，以获取完整的CPUID数据。 谢谢您的帮助。

Answer 1

您可以阅读像这样和这个

static inline void cpuid(int code, uint32_t *a, uint32_t *d) {
  asm volatile("cpuid":"=a"(*a),"=d"(*d):"a"(code):"ecx","ebx");
}

/** issue a complete request, storing general registers output as a string
 */
static inline int cpuid_string(int code, uint32_t where[4]) {
  asm volatile("cpuid":"=a"(*where),"=b"(*(where+1)),
               "=c"(*(where+2)),"=d"(*(where+3)):"a"(code));
  return (int)where[0];
}