Blanking video memory?

[Bryan Ericson]

Hi, everyone

I have a question that I can't find the answer to, so I'm hoping
someone here will be able to help.  I'm working on a project in which
X on Linux will be used in a security-oriented environment.  When the
X server is restarted, the monitor will briefly display the contents
of the video memory left over from the previous session before the new
session takes over.  This is a concern if a confidential document was
being displayed when the previous session ended.  Note that this issue
appears to be hardware-dependent, as the behavior is different for
different video cards.

Is there a way to blank the video memory before anything is displayed
on the monitor at the beginning of a session, short of modifying the
individual drivers?  The solution could involve modifying the server
source code.  Ideally, the blanking would occur in the
device-independent layer during initialization.  We've tried using a
separate app using the Linux framebuffer to blank the screen, but
framebuffer support is not guaranteed on all hardware.

Thanks!

Bryan