<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<p style="margin-bottom: 0cm; line-height: 100%"><br>
</p>
Dear Genode community,<br>
<p style="margin-bottom: 0cm; line-height: 100%"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%">I've joined Denis
Huber's project on developing a real-time checkpoint/restore
component for Genode.<br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%">(
<a class="moz-txt-link-freetext" href="https://sourceforge.net/p/genode/mailman/message/35211808/">https://sourceforge.net/p/genode/mailman/message/35211808/</a> )<br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%">In order to improve
our process of memory checkpointing we would like to distinguish
reading memory accesses from writing memory accesses.<br>
While we do not
care about reading, we are highly interested in detecting the
occurrence of writing accesses.<br>
<br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%">At the moment our
way to detect the access to a specific memory region is to detach
the
corresponding dataspace and handle<br>
the pagefault which is produced
when the component tries to access the dataspace.</p>
<p style="margin-bottom: 0cm; line-height: 100%"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%">We are aware that
it
is possible to determine whether a writing or a reading access
triggered a pagefault but we don't want to increase<br>
the amount of
pagefaults by detaching dataspaces after every time they were only
read. It would be cool if writing would cause an error<br>
which is is
not produced by reading.</p>
<p style="margin-bottom: 0cm; line-height: 100%"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%">As a solution to
this we thought of adding the possibility to make a RAM dataspace
read-only, something which is similar to „mprotect“ in Linux.<br>
With this feature we would not need to detach dataspaces but
writing
accesses would still produce faults which we could track in order
to
detect them.</p>
<p style="margin-bottom: 0cm; line-height: 100%"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%">Is such an
alteration of RAM dataspaces possible? If yes, how would you do
it?</p>
<p style="margin-bottom: 0cm; line-height: 100%">What kind of fault
would be triggered if someone tries to write to a read-only
memory? </p>
<p style="margin-bottom: 0cm; line-height: 100%">Are we able to get
information about such a fault in Genode?</p>
<p style="margin-bottom: 0cm; line-height: 100%"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%">We are using Genode
on top of the Fiasco.OC.</p>
<p style="margin-bottom: 0cm; line-height: 100%"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%">Thanks in advance!</p>
<p style="margin-bottom: 0cm; line-height: 100%"><br>
</p>
<p style="margin-bottom: 0cm; line-height: 100%">Kind Regards,</p>
<p style="margin-bottom: 0cm; line-height: 100%">David</p>
<title></title>
<meta name="generator" content="LibreOffice 4.2.8.2 (Linux)">
<style type="text/css">
<!--
@page { margin: 2cm }
p { margin-bottom: 0.25cm; line-height: 120% }
-->
</style>
</body>
</html>