Implementing Kernel Exception Handlers

The following information is provided to assist you in implementing kernel exception handlers.

setjmpx, longjmpx, and clrjmpx Kernel Services
The setjmpx kernel service provides a way to save the following portions of the program state at the point of a call:
Exception Handler Environment
The stacked exception handlers run in the environment in which the exception occurs. That is, an exception occurring in a process environment causes the next dispatch of the process to run the exception handler on the top of the stack of exception handlers for that process.
Restrictions on Using the setjmpx Kernel Service
Process and interrupt handler routines registering exception handlers with the setjmpx kernel service must not return to their caller before removing the saved jump buffer or buffers from the list of jump buffers.
Exception Codes
The /usr/include/sys/except.h file contains a list of code numbers corresponding to the various types of hardware exceptions. When an exception handler is invoked (the return from the setjmpx kernel service is not equal to 0), it is the responsibility of the handler to test the code to ensure that the exception is one the routine can handle.
Hardware Detection of Exceptions
Each of the exception types results in a hardware interrupt. For each such interrupt, a first-level interrupt handler (FLIH) saves the state of the executing program and calls a second-level handler (SLIH). The SLIH is passed a pointer to the machine-state save structure and a code indicating the cause of the interrupt.

Parent topic: Understanding Exception Handling