Need Help on Memory Protection on a Sun 4

[Michael Lam]

I have heard that the MACH operating system has an OS feature
such that a programmer can set a trap to read/write protect
a memory segment:  make a system call using a memory address
range as argument, then any subsequent read/write operation 
into that memory range would invoke a trap to call a (probably 
C written) interrupt handler.  Examining/changing
a page's dirty bit is another thing I would like to do.

I am working on a Sun 4 environment and have heard that Sun 4 
has something similiar.  Can anyone provide me info on that.  
Please response by email.  Thanks in advance.

Michael Lam
EECS Dept.
University of Illinois at Chicago
email address: lam at uicbert.eecs.uic.edu