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Date: Wed, 12 Nov 1997 20:30:53 -0800 (PST)
From: Shawn Ramsey <shawn@luke.cpl.net>
To: Mike Jeays <jeays@statcan.ca>
cc: freebsd-questions@FreeBSD.ORG
Subject: Re: Pentium hardware bug
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> machines under various operating systems. This was done on a Pentium
> 120, running FreeBSD 2.2.1.
> 
> The program is trapped with an illegal instruction, as shown below.
> Running gdb on the resulting core dump gives the message shown below,
> but any attempt to run the program *under gdb* results in a complete
> system crash.  So FreeBSD survives the test well - but gdb doesn't!
> 
> /home/mike/c/crash% cat crash1.c
>  unsigned char hang[] = { 0xf0, 0x0f, 0xc7, 0xc8 };
> 
>   int main()
>   {
>     void (*kill)();
>     kill = hang;
>     kill(); 
>     /* return can be omitted as there is none */
>   }
> 
> /home/mike/c/crash% gcc crash1.c -o crash1
> crash1.c: In function `main':
> crash1.c:6: warning: assignment from incompatible pointer type
> /home/mike/c/crash% crash1
> Illegal instruction (core dumped)
> /home/mike/c/crash% d
> total 162
> -rwxrwxr-x  1 mike     wheel        8826 Nov 12 1997 22:08 crash1
> -rw-r--r--  1 mike     wheel         173 Nov 12 1997 22:06 crash1..c
> -rw-------  1 mike     wheel      143360 Nov 12 1997 22:09 crash1.core
>  
> /home/mike/c/crash% gdb crash1 crash1.core
> GDB is free software and you are welcome to distribute copies of it
>  under certain conditions; type "show copying" to see the conditions.
> There is absolutely no warranty for GDB; type "show warranty" for details.
> GDB 4.16 (i386-unknown-freebsd), Copyright 1996 Free Software Foundation,
> Inc...
> (no debugging symbols found)...
> Core was generated by `crash1'.
> Program terminated with signal 4, Illegal instruction.
> #0  0x208c in hang ()
> (gdb) 
> 
> (Typing 'r' here results in an immediate and very complete crash!)
> 
> Any comments, more explanation, other experiences?
> 
> 

This vicious piece of code locks my P233 up tight as a drum. I would hate
to by an ISP providing shell access to hundreds of users on a P5, when any
user could compile this code and lock the machine up! :(

If I run this on an AMD 5x86-133 I get this :

Illegal instruction (core dump)

Havent done anything with gdb as I am not familar with it...