[ANNOUNCE] Linux Hardened Device Drivers Project

From: Rhoads, Rob (rob.rhoads@intel.com)
Date: Fri Sep 20 2002 - 19:26:47 EST

Project Announcement:
We've started a new project on sourceforge.net w/ focus
on hardening Linux device drivers for highly available
systems. This project is being worked on with folks from
OSDL's CGL and DCL projects as well.

Initially we've created a specification, a few kernel modules
that implement a set of driver programming interfaces, and
a sample device driver that demonstrates those interfaces.

We are actively soliciting involvement with others in the
Linux developer community. We need your help to make this
project relevant and useful.

Below I've included an overview of the hardened driver project.
By no means is this complete or final. It's just our initial
attempt at defining what is meant by the term hardened driver
and the areas we want to focus on.

For additional info, please checkout the links at the bottom
of this message and the Hardened Drivers web site at

Hardened Driver Project Overview:
Device drivers have traditionally been a significant source
of software faults. For this reason, they are of key concern
in improving the availability and stability of the operating
system. A critical element in creating Highly Available (HA)
environment is to reduce the likelihood of faults in key
drivers, a methodology called driver hardening.

A device driver is typically implemented with emphasis on
the proper operation of the hardware. Attention to how it
will function in the event of hardware faults is often
minimal. Hardened drivers, on the other hand, are designed
with the assumption that the underlying hardware that they
control will fail. They need to respond to such failures by
handling faults gracefully, limiting the impact on the overall
system. Hardened device drivers must continue to operate when
the hardware has failed (e.g. allow device fail-over), and
must not allow the propagation of corrupt data from a failed
device to other components of the system.

Hardened device drivers must also be active participants in
the recovery of detected faults, by locally recovering them or
by reporting them to higher-level system management software
that subsequently instructs the driver to take a specific

The goal of a hardened driver is to provide an environment
in which hardware and software failures are transparent to
the applications using their services, where possible. The
way to effectively achieve this goal is to analyze a
driver's software design and implement appropriate changes
to improve stability, reliability and availability, and
to provide instrumentation for management middleware.

We believe that improving driver stability and reliability
includes such measures as ensuring that all wait loops are
limited with a timeout, validating input and output data and
structuring the driver to anticipate hardware errors.
Improving availability includes adding support for device
hot swapping and validating the driver with fault injection.
Instrumentation for management middleware includes functions
such as reporting of statistical indicators and logging of
pertinent events to enable postmortem analysis in the event
of a failure.

To minimize instability contributed by device drivers and to
enhance the availability of HA systems, we've attempted to
define a set of requirements that a device driver should
adhere to in order to be considered a hardened driver. We
then define different hardening traits and the required
programming interfaces to support these hardening traits.

We've identified four areas in which drivers can be hardened:
o Hardening with code robustness
o Hardening with event logging
o Hardening with diagnostics
o Hardening with resource monitoring and statistics

We've also identified some key areas we feel are most critical
to overall system stability and plan to focus initial hardening
efforts on drivers for network interface cards, physical storage,
and logical storage.

Project Links:
o The Driver Hardening website:

o The SourceForge project related info:

o Hardened Drivers Mailing List Info (subscribe here):

Rob Rhoads mailto:rob.rhoads@intel.com
Staff Software Engineer office: 503-677-5498
Telecom Software Platforms
Intel Communications Group

This email message solely contains my own personal views, and not
necessarily those of my employer.

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