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SubjectRe: Bad Illegal instruction traps on dual-Xeon (p4) Linux Dell box

Just to clarify things.

Lots of processes die from illegal op traps.. gcc, bash, make, etc... but
the instruction is ALWAYS opcode 0x55 and is part of a subroutine preamble
in every case.. You are correct... 0x55 should not generate a trap.

Bad cpu? Hmmm, Tom has 6 different CPU's ( all p4 xeons ), on three
systems, that have this EXACT same problem.

and why does this require the system to be running smp?


- jim

Kurt Garloff <kurt@garloff.de>@vger.kernel.org on 03/20/2002 03:26:10 PM

Sent by: linux-kernel-owner@vger.kernel.org


To: Tom Epperly <tepperly@llnl.gov>
cc: Linux kernel list <linux-kernel@vger.kernel.org>
Subject: Re: Bad Illegal instruction traps on dual-Xeon (p4) Linux Dell
box



On Wed, Mar 20, 2002 at 01:35:30PM -0800, Tom Epperly wrote:
> The kernel log showed me that various standard programs such as
> /bin/sh are generating bogus illegal instruction traps on a legal
> opcode (0x55) as part of a standard function preamble. After receiving
> an illegal instruction trap on opcode (0x55), the modified kernel does
> a wbinvd() to flush the cache and a __flush_tlb() to flush the TLB
> and then retries the "illegal" opcode. The retry produces a second
> illegal instruction trap on the same legal opcode (0x55). Information
> from /var/log/messages is shown below.

The CPU is what triggers the exception.
So this sounds like a defect (or overheated) CPU to me.

OTOH, the kernel logs "invalid operand". Could you run ksymoops to get a
disassembly?
AFAICS, its a push %ebp instruction, which should not be illegal. So either
your stack is overflowing or my suspicion with the defect CPU is
applicable.

Regards,
--
Kurt Garloff <kurt@garloff.de> [Eindhoven, NL]
Physics: Plasma simulations <K.Garloff@Phys.TUE.NL> [TU Eindhoven, NL]
Linux: SCSI, Security <garloff@suse.de> [SuSE Nuernberg, DE]
(See mail header or public key servers for PGP2 and GPG public keys.)

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