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Re: User applications

To: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Subject: Re: User applications
From: Ralf Baechle <ralf@oss.sgi.com>
Date: Mon, 8 Jan 2001 14:05:06 -0200
Cc: "Kevin D. Kissell" <kevink@mips.com>, linux-mips@oss.sgi.com, Carsten Langgaard <carstenl@mips.com>, Michael Shmulevich <michaels@jungo.com>
In-reply-to: <Pine.GSO.3.96.1010108151854.23234G-100000@delta.ds2.pg.gda.pl>; from macro@ds2.pg.gda.pl on Mon, Jan 08, 2001 at 04:07:31PM +0100
References: <00d801c0797d$5cc410c0$0deca8c0@Ulysses> <Pine.GSO.3.96.1010108151854.23234G-100000@delta.ds2.pg.gda.pl>
Sender: owner-linux-mips@oss.sgi.com
User-agent: Mutt/1.2.5i
On Mon, Jan 08, 2001 at 04:07:31PM +0100, Maciej W. Rozycki wrote:

>  The only case caches need to be synchronized is modifying some code.  The
> ptrace syscall does it automatically for text writes -- it's needed and
> used by gdb to set breakpoints, for example.  For other code there is
> cacheflush() which allows you to flush a cache range relevant to a given
> virtual address (I see it's not implemented very well at the moment).
> 
>  Obviously, you don't want to allow unprivileged users to flush caches as
> a whole as it could lead to a DoS. 

You obviously want to allow partial cache flushes or trampolines don't work
and flushing the entire cache can be constructed from that.

  Ralf

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