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Date: Thu, 8 Sep 2016 16:05:16 +0100
From: Andrew Turner <andrew@fubar.geek.nz>
To: Ed Schouten <ed@nuxi.nl>
Cc: src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
Subject: Re: svn commit: r305607 - head/sys/arm64/arm64
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On Thu, 8 Sep 2016 16:48:45 +0200
Ed Schouten <ed@nuxi.nl> wrote:

> Hi Andrew,
> 
> 2016-09-08 14:53 GMT+02:00 Andrew Turner <andrew@freebsd.org>:
> >   Trap msr/mrs instructions. These are privileged arm64
> > instructions and shouldn't normally be used.  
> 
> It depends on which system register is being used, right? System
> registers like TPIDR_EL0 are accessed by userspace all the time.
> 

Correct, the trap is only hit when userspace doesn't have permission to
access the register.

Andrew