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  • From: Rainer Desor <renkaba AT gmx.de>
  • To: baslinux AT lists.ibiblio.org
  • Subject: Re: [BL] ifconfig illegal instruction on 386ex
  • Date: Fri, 19 May 2006 20:36:23 +0200

On Thu, 18 May 2006 08:15:17 -0700, David Moberg <davidjmoberg AT gmail.com> wrote:


Perhaps the busybox binary contains 486 instructions, which the 386
does not know how to execute. I wonder if the following kernel feature
would help? If I built a kernel with it, would you be willing to test
it?

CONFIG_CPU_EMU486
When used on a 386, Linux can emulate 3 instructions from the 486 set.
This allows user space programs compiled for 486 to run on a 386
without crashing with a SIGILL [Illegal instruction]. As any emulation,
performance will be very low, but since these instruction are not often
used, this might not hurt. The emulated instructions are:
- bswap (does the same as htonl())
- cmpxchg (used in multi-threading, mutex locking)
- xadd (rarely used)


Hi David,

I guess you are right. Especially internet related commands create 'illegal instruction' error.
AFAIK the instruction BSWAP is not part of the 386 instruction set and might be used
by buysbox to change byte-order from pc to network. Usually htonl() is used, but BSWAP
might be faster or smaller code. Would be nice to have busybox for 386 instead of replace parts with slackware.

regards

Rainer


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--
Rainer Desor / Bovenden / Germany




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