Re: repost: patch for 2.1.108 LDT problems

George (greerga@nidhogg.ham.muohio.edu)
Tue, 7 Jul 1998 17:47:49 -0400 (EDT)


On Tue, 7 Jul 1998, Alan Cox wrote:

>> If you do, please make it a sysctl'able option. At least on my AMD-K6-PR2/200
>> I have not experienced lockups/crashes yet.
>
>Interesting. Does this crash your K6 under 2.0.x ?
>
>On Mon, Jun 01, 1998 at 02:03:13PM +0200, Wolfgang Walter wrote:
>
>Here is how to reproduce it :
>
>$ 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>
>
>If so that indicates why we can't allow LDT usage by non root users on
>AMD components

I thought the conclusion previously was that (inadvertantly) 2.1.x prevents
this problem already by extending the segment to cover all of virtual
memory?

(Too bad I have an Intel or I'd check.)

-George

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