The Solaris kernel implements virtual memory watchpoints within address spaces. A watchpoint is similar to a breakpoint, except that a watchpoint stops execution when an address location is read or modified, whereas a breakpoint stops execution when an instruction is executed at a specified location. Watchpoints also provide the ability to implement breakpoints through the watchpoint interface.
You set and clear watchpoints through the /proc file system interface, by opening the control file for a process and then sending a PCWATCH command. The PCWATCH command is accompanied by a prwatch structure, which contains the address, the length of the area to be affected, and the type of watchpoint.