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Re: NetBSD/i386 7.0 hangs booting 486

In article <>,
Felix Deichmann  <> wrote:
>Am 20.11.2015 um 22:04 schrieb Christos Zoulas:
>> change:
>> __get_cpuid_max() to always return 0 immediately and then we can debug it :-)
>I could finally get 7.0 to boot on the 486 machine successfully to login 
>prompt after several release builds and installations (no fun):
>The above patch alone is not enough. __get_cpuid() also needed a 
>work-around, as it seems to be called with __level == 0, so 
>__get_cpuid() will not return before another cpuid instruction in it is 
>   if (__get_cpuid_max (__ext, 0) < __level)
>     return 0;
>   __cpuid (__level, *__eax, *__ebx, *__ecx, *__edx);
>   return 1;
>I think finding a suitable bugfix is out of my league now, but can 
>assist with testing of course.

Can you please compile and run this and tell me what it prints?


#include <stdio.h>

#define __cpuid(level, a, b, c, d)                      \
  __asm__ ("xchg{l}\t{%%}ebx, %k1\n\t"                  \
           "cpuid\n\t"                                  \
           "xchg{l}\t{%%}ebx, %k1\n\t"                  \
           : "=a" (a), "=&r" (b), "=c" (c), "=d" (d)    \
           : "0" (level))

static __inline unsigned int              
__get_cpuid_max (unsigned int __ext, unsigned int *__sig)
  unsigned int __eax, __ebx, __ecx, __edx;

  /* See if we can use cpuid.  On AMD64 we always can.  */
  __asm__ ("pushf{l|d}\n\t"
           "mov{l}\t{%0, %1|%1, %0}\n\t"
           "xor{l}\t{%2, %0|%0, %2}\n\t"
           : "=&r" (__eax), "=&r" (__ebx) 
           : "i" (0x00200000));
  if (!((__eax ^ __ebx) & 0x00200000))
    return 0;

printf("run %x %x\n", __eax, __ebx);
  /* Host supports cpuid.  Return highest supported cpuid input value.  */
  __cpuid (__ext, __eax, __ebx, __ecx, __edx);

  if (__sig)
    *__sig = __ebx;

  return __eax;

        printf("%x\n", __get_cpuid_max(0, NULL));

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