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Date: Sun, 14 Sep 2008 09:34:53 +0300
From: "Blue Swirl" <blauwirbel@gmail.com>
Subject: Re: [Qemu-devel] [PATCH] SH4: Privilege check for instructions
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To: qemu-devel@nongnu.org

On 9/14/08, Shin-ichiro KAWASAKI <kawasaki@juno.dti.ne.jp> wrote:
> This patch adds check for all SH4 instructions which are
>  executed only in privileged mode.

The checks get the privileged mode status from translation context. In
theory, the same TB code block could be used in unprivileged and
privileged mode, so the status that was true at translation time may
no longer be correct at execution time. Of course normally kernel code
is not visible or executable to user processes.

The TB flags are handled in cpu-exec.c:tb_find_fast(). If I understand
the SH part correctly, the flags copied from env->flags don't contain
the privileged mode bits, isn't that in env->sr & SR_MD?

Alternatively, the check could be made at execution time, but that's
less efficient.