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Re: O2 RM7000 Issues

To: Sergey Rogozhkin <rogozhkin@niisi.msk.ru>
Subject: Re: O2 RM7000 Issues
From: Ralf Baechle <ralf@linux-mips.org>
Date: Tue, 17 Jul 2007 11:14:26 +0100
Cc: Linux MIPS List <linux-mips@linux-mips.org>, "Gleb O. Raiko" <raiko@niisi.msk.ru>, Kumba <kumba@gentoo.org>
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On Tue, Jul 17, 2007 at 01:04:00PM +0400, Sergey Rogozhkin wrote:

> Are you really sure RM7000 has this bug? Workaround mentioned above 
> breaks gcc signal frame unwinding mechanism: it search for sigcontext 
> struct at fixed offset from signal trampoline.

Sigh.  Yes, I am certain - this is information right from the CPU designers.
When I did modify the signal frame for PMC's E9000 core I knew some
software such as debuggers was likely to break, so I was careful to only
use the mechanism if absolutly necessary that is on E9000 cores.  The
problem semmed to strike rather frequently on E9000 but there had been no
reports of application crashes matching the problem's fingerprint on RM7000
so the issue felt as if it was rather theoretical on RM7000.  So I choose to
not enable the workaround for RM7000 until recently.

  Ralf

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