Re: Cyrix bug: freeze in hell, badboy

[aaronl () VITELUS COM (Aaron Lehmann)]

This does not seem to affect my Cyrix 6x86MX/233. In single user mode, it
just hung until I ^C'd it. Running Linux 2.2.1

/proc/cpuinfo:

processor       : 0
vendor_id       : CyrixInstead
cpu family      : 6
model           : 2
model name      : 6x86MX 2.5x Core/Bus Clock
stepping        : 7
cpu_mhz         : 187.399276
fdiv            : no
hlt             : no
sep             : no
f00f            : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu de tsc msr cx8 pge cmov mmx
bogomips        : 186.78


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On Thu, 4 Feb 1999, Ragnar Hojland Espinosa wrote:

> I emailed Cyrix a few months ago, and even managed to get a "oh, we will
> look at it" thanks to Rafael Reilova, but that was it till today.  A
> couple of people did report it, effectively, froze (most of) their Cyrix
> CPUs while running the opcodes below as non priviledged user.
>
> While I don't have the enough knowledge to assure this _is_ a CPU bug, it
> certainly looks like one to me (NO_LOCK isn't a workaround, btw).
>
> 0x804a368 <the_data>:   cwtl
> 0x804a36a <the_data+2>: orl    $0xe6ebe020,%eax
> 0x804a36f <the_data+7>: jle    0x804a368 <the_data>
>
> Here is the code (tested with linux, any version):
>
> /* Please compile without optimizations */
> unsigned char the_data[] = { 62, 152, 13, 32, 224, 235, 230, 126, 247 };
>
> void (*badboy)();
> int main (int argc, char **argv)
> {
>    badboy = (void(*)())(the_data);
>    asm ("movl badboy,%eax");
>    asm ("call *%eax");
>
>    return 0;
> }
>
> If you try it, please send me your /proc/{cpuinfo,version} and if it
> freezes or not.
> --
> ____/|  Ragnar Hojland  (ragnar () lightside ddns org)      Fingerprint  94C4B
> \ o.O|                                                   2F0D27DE025BE2302C
>  =(_)=  "Thou shalt not follow the NULL pointer for      104B78C56 B72F0822
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