Page Fault and Segmentation Fault Mechanism
To report exceptions that occur in the 386 memory management hardware, they must be caught and routed to the proper portion of the kernel. UNIX places these exceptions in two categories: Faults signaled to the user process, which terminates the process if it is not interested in the exception, and "resource not present" faults sent to the virtual memory system to request a missing page.
The 386 also signals a variety of segment exceptions, almost all of which result in dire consequences for the process that invokes them. A single page fault exception encodes both "page not present" as well as "protection violation" events. These page faults, along with the fault address, are recorded in processor special register cr2 and should be carefully examined to determine the precise nature of each exception.
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