linux-kernel - Re: Is 386 processor still supported?

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Date:	Thu, 15 Jan 2009 13:22:14 +0000 (GMT)
From:	"Maciej W. Rozycki" <macro@...ux-mips.org>
To:	Jan-Benedict Glaw <jbglaw@...-owl.de>
cc:	Ingo Molnar <mingo@...e.hu>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiri Kosina <jkosina@...e.cz>, Adam Osuchowski <adwol@...k.pl>,
	linux-kernel@...r.kernel.org, Nick Piggin <npiggin@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: Is 386 processor still supported?

On Thu, 15 Jan 2009, Jan-Benedict Glaw wrote:

>   * Debian's baseline libc is compiled to use LOCK and some other
>     newish instructions that are not available on a real i386 CPU.

 LOCK dates back to the 8086 -- it has to work with the i386.  What is not 
supported are the following i486 additions: CMPXCHG (amusingly enough 
early i486 steppings used a different opcode for this one; no idea if it 
is still possible to find such a CPU), XADD and BSWAP, the latter being 
fairly unimportant.

>   * There was a patch flying around to introduce a kernel-based
>     emulator for those instructions. However, this was (at that time)
>     neither included in Debian's kernel, nor in the upstream sources.

 UP emulation of CMPXCHG and XADD for userland should be rather trivial, 
so why not include it like with LL/SC for MIPS?

  Maciej
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