numatop: %{optflags} fail the 32bit build

[Florian Weimer]

On 09/12/2013 02:53 PM, Florian Weimer wrote:

> By the way, we could generate much better code if the registers were
> passed as an array or struct, so that they are in consecutive memory:
>
> struct regs {
>    unsigned eax, ebx, ecx, edx;
> };
>
> void
> cpuid(struct regs *r)
> {
>    __asm volatile
>      ("push %%ebx\n\t"
>       "cpuid\n\t"
>       "mov %%eax, (%0)\n\t"
>       "mov %%ebx, 4(%0)\n\t"
>       "mov %%ecx, 8(%0)\n\t"
>       "mov %%edx, 12(%0)\n\t"
>       "pop %%ebx"
>       :
>       : "S" (r)
>       : "eax", "ecx", "edx", "memory");
> }

Okay, I forgot to load the %eax register.  This version has actually 
been tested (on x86_64):

void
cpuid(struct regs *r)
{
   __asm volatile
     ("mov (%0), %%eax\n\t"
      "push %%rbx\n\t"
      "cpuid\n\t"
      "mov %%eax, (%0)\n\t"
      "mov %%ebx, 4(%0)\n\t"
      "mov %%ecx, 8(%0)\n\t"
      "mov %%edx, 12(%0)\n\t"
      "pop %%rbx"
      :
      : "D" (r)
      : "eax", "ecx", "edx", "memory");
}

"D" picks the %edi register, which saves another move because it 
contains the first function parameter on x86_64.

For the i386 version, replace %rbx with %ebx.

-- 
Florian Weimer / Red Hat Product Security Team