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AIX Version 4.3 Kernel and Subsystems Technical Reference, Volume 1

uexadd Kernel Service


Adds a systemwide exception handler for catching user-mode process exceptions.


#include <sys/types.h>
#include <sys/errno.h>
#include <sys/except.h>
void uexadd (exp)
struct uexcepth *exp;


exp Points to an exception handler structure. This structure must be pinned and is used for registering user-mode process exception handlers. The uexcepth structure is defined in the /usr/include/sys/except.h file.


The uexadd kernel service is typically used to install a systemwide exception handler to catch exceptions occurring during execution of a process in user mode. The uexadd kernel service adds the exception handler structure specified by the exp parameter, to the chain of exception handlers to be called if an exception occurs while a process is executing in user mode. The last exception handler registered is the first exception handler called for a user-mode exception.

The uexcepth structure has:

Additional exception handler-dependent information can be added to the end of the structure, but must be pinned.

Attention: The uexcepth structure must be pinned when the uexadd kernel service is called. It must remain pinned and unmodified until after the call to the uexdel kernel service to delete the specified exception handler. Otherwise, the system may crash.

Execution Environment

The uexadd kernel service can be called from the process environment only.

Return Values

The uexadd kernel service has no return values.

Implementation Specifics

The uexadd kernel service is part of Base Operating System (BOS) Runtime.

Related Information

The uexdel kernel service and User-Mode Exception Handler for the uexadd Kernel Service.

User-Mode Exception Handling and Kernel Extension and Device Driver Management Services in AIX Kernel Extensions and Device Support Programming Concepts.

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