bborn</tt>, and is rarely used.
<LI>
(<TT>MPROTECT_VDB</tt>) By write-protecting physical pages and
catching write faults.  This is
implemented for many Unix-like systems and for win32.  It is not possible
in a few environments.
<LI>
(<TT>PROC_VDB</tt>) By retrieving dirty bit information from /proc.
(Currently only Sun's
Solaris supports this.  Though this is considerably cleaner, performance
may actually be better with mprotect and signals.)
<LI>
(<TT>PCR_VDB</tt>) By relying on an external dirty bit impl