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Date: Sun, 28 Feb 2010 15:25:42 +0000
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] [Bug] qemu-system-ppc: "invalid/unsupported opcode"
	during debug session
Message-ID: <20100228152542.GA28486@shareable.org>
References: <4B3A1B9D.7010004@mail.berlios.de>
	<20100228131830.GJ10291@volta.aurel32.net>
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To: Aurelien Jarno <aurelien@aurel32.net>
Cc: QEMU Developers <qemu-devel@nongnu.org>

Aurelien Jarno wrote:
> It is not a full fix, as the OS can actually use any instruction that
> always generate a trap (even a memory access) as an instruction barrier
> to make sure the following instructions are never executed. This
> actually affects all targets, but is unlikely to happen.

I'm sure I've seen code wich intentionally accesses invalid memory,
followed by non-instruction data such as a message to print.  But I
can't think where.

> One solution for that would be to only generate an exception for an
> unsupported instruction when it is the first instruction of a TB, and
> otherwise just end the translation before this instruction.

Because that's a simple general solution for all targets, it sounds
like a good idea to me.

-- Jamie