Code Alignment Problem

From: Ken Allen (kendrhyd_at_sympatico.ca)
Date: 02/04/05 

Date: Fri, 04 Feb 2005 14:59:13 -0500

We have an odd problem with one of our device drivers, and it seems to
be associated with the placement and size of the code, but we cannot
determine the exact cause or the correct resolution.

First, I need to be clear that this is an older set of code, and it is
being compiled with the VS 6 C++ compiler. The driver environment was
hacked to permit the use of C++ code in the kernel, and so the
environment is even more strange.

There is one aspect of the driver that attempts to access the contents
of a mountable file system during the boot process. Normally this works
fine, as the attempt to open a file in that file system causes an
auto-mount, and the file is accessed. We did notice that in debug mode
the code was failing, and it turned out that the call to open the file
was returning a "device not ready" error, which normally indicates that
the file system could not be mounted.

As we started to debug the cause of the problem, by adding extra debug
information, the problem 'disappeared'! After several hours of
experimenting with the code, we found that if we added or removed some
code, we could cause the problem to occur or disappear! The actual code
being added or removed does not seem to matter, as it is typically debug
statements anyway, and in no way affects the algorithm.

Does anyone have any suggestions on how we could go about isolating the
cause for this problem and avoiding it in the future -- aside from
rewriting the driver in the standard and latest DDK environment?

-Ken

Relevant Pages

  • Re: Code Alignment Problem
    ... Maxim Shatskih, Windows DDK MVP ... The driver environment was ... > of a mountable file system during the boot process. ... We did notice that in debug mode ...
    (microsoft.public.development.device.drivers)
  • Re: Code Alignment Problem
    ... > of a mountable file system during the boot process. ... We did notice that in debug mode ... we could cause the problem to occur or disappear! ... > rewriting the driver in the standard and latest DDK environment? ...
    (microsoft.public.development.device.drivers)
  • Re: Code Alignment Problem
    ... That makes it sound more like a timing bug than an alignment bug. ... >> of a mountable file system during the boot process. ... >> As we started to debug the cause of the problem, ... >> rewriting the driver in the standard and latest DDK environment? ...
    (microsoft.public.development.device.drivers)
  • Re: [SLE] Re: And another 10.1 showstopper
    ... someone has to debug it. ... in 10.1, in trying to use the radeon driver built by the kernel developers, the driver hung my entire system everytime it switched into graphics. ... I can't say that open source, including device drivers, is better just because it is open source. ...
    (SuSE)
  • newbie asks orienting questions about file system drivers
    ... I'm very new to device drivers. ... I would like to write a file system driver, preferrably in managed code ... I need to obtain the Installable File System Kit ... Is the User-Mode Driver ...
    (microsoft.public.development.device.drivers)