Question

I need to find the architecture type of a CPU. I do not have access to /proc/cpuinfo, as the machine is running syslinux. I know there is a way to do it with inline ASM, however I believe my syntax is incorrect as my variable iedx is not being set properly.

I’m drudging along with ASM, and by no means an expert. If anyone has any tips or can point me in the right direction, I would be much obliged.

static int is64Bit(void) {
    int iedx = 0;
    asm("mov %eax, 0x80000001");
    asm("cpuid");
    asm("mov %0, %%eax" : : "a" (iedx));
    if ((iedx) && (1 << 29))
    {
        return 1;
    }
    return 0;
}

Answer 1

How many bugs can you fit in so few lines 😉

Try

static int is64bit(void) {
        int iedx = 0;
        asm volatile ("movl $0x80000001, %%eax\n"
                "cpuid\n"
        : "=d"(iedx)
        : /* No Inputs */
        : "eax", "ebx", "ecx"
        );

        if(iedx & (1 << 29))
        {
                return 1;
        }
        return 0;
}