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Re: User applications

To: "Kevin D. Kissell" <kevink@mips.com>
Subject: Re: User applications
From: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Date: Mon, 8 Jan 2001 16:07:31 +0100 (MET)
Cc: linux-mips@oss.sgi.com, Carsten Langgaard <carstenl@mips.com>, Michael Shmulevich <michaels@jungo.com>
In-reply-to: <00d801c0797d$5cc410c0$0deca8c0@Ulysses>
Organization: Technical University of Gdansk
Reply-to: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
Sender: owner-linux-mips@oss.sgi.com
On Mon, 8 Jan 2001, Kevin D. Kissell wrote:

> Back in the Ancient Old Days of System V, every architecture
> had an architecture-specific system call entry, the first parameter
> of which expressed what needed to be done.  Do we have
> such a thing in Linux?   That would be the logical place to
> things like cache flush and the atomic operations that were
> being discussed here a couple of weeks ago.

 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. 

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@ds2.pg.gda.pl, PGP key available        +


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