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Re: User applications

To: Ralf Baechle <ralf@oss.sgi.com>
Subject: Re: User applications
From: Carsten Langgaard <carstenl@mips.com>
Date: Mon, 08 Jan 2001 17:23:20 +0100
Cc: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>, "Kevin D. Kissell" <kevink@mips.com>, linux-mips@oss.sgi.com, Michael Shmulevich <michaels@jungo.com>
References: <00d801c0797d$5cc410c0$0deca8c0@Ulysses> <Pine.GSO.3.96.1010108151854.23234G-100000@delta.ds2.pg.gda.pl> <20010108140506.B886@bacchus.dhis.org>
Sender: owner-linux-mips@oss.sgi.com
Ralf Baechle wrote:

> 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.
>

What we need is a mechanism to partial invalidate the I-cache and a mechanism
to write-back and/or invalidate the D-cache.

/Carsten

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