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@c COPYRIGHT (c) 1988-2002.
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@c On-Line Applications Research Corporation (OAR).
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@c All rights reserved.
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@c
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@c fatal.t,v 1.15 2002/01/17 21:47:47 joel Exp
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@c
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@chapter Fatal Error Manager
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@cindex fatal errors
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@section Introduction
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The fatal error manager processes all fatal or
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irrecoverable errors. The directive provided by the fatal error
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manager is:
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@itemize @bullet
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@item @code{@value{DIRPREFIX}fatal_error_occurred} - Invoke the fatal error handler
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@end itemize
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@section Background
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@cindex fatal error detection
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@cindex fatal error processing
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@cindex fatal error user extension
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The fatal error manager is called upon detection of
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an irrecoverable error condition by either RTEMS or the
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application software. Fatal errors can be detected from three
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sources:
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@itemize @bullet
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@item the executive (RTEMS)
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@item user system code
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@item user application code
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@end itemize
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RTEMS automatically invokes the fatal error manager
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upon detection of an error it considers to be fatal. Similarly,
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the user should invoke the fatal error manager upon detection of
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a fatal error.
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Each status or dynamic user extension set may include
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a fatal error handler. The fatal error handler in the static
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extension set can be used to provide access to debuggers and
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monitors which may be present on the target hardware. If any
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user-supplied fatal error handlers are installed, the fatal
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error manager will invoke them. If no user handlers are
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configured or if all the user handler return control to the
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fatal error manager, then the RTEMS default fatal error handler
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is invoked. If the default fatal error handler is invoked, then
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the system state is marked as failed.
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Although the precise behavior of the default fatal
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error handler is processor specific, in general, it will disable
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all maskable interrupts, place the error code in a known
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processor dependent place (generally either on the stack or in a
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register), and halt the processor. The precise actions of the
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RTEMS fatal error are discussed in the Default Fatal Error
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Processing chapter of the Applications Supplement document for
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a specific target processor.
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@section Operations
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@subsection Announcing a Fatal Error
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@findex _Internal_errors_What_happened
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The @code{@value{DIRPREFIX}fatal_error_occurred} directive is invoked when a
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fatal error is detected. Before invoking any user-supplied
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fatal error handlers or the RTEMS fatal error handler, the
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@code{@value{DIRPREFIX}fatal_error_occurred}
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directive stores useful information in the
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variable @code{_Internal_errors_What_happened}. This @value{STRUCTURE}
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contains three pieces of information:
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@itemize @bullet
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@item the source of the error (API or executive core),
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@item whether the error was generated internally by the
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executive, and a
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@item a numeric code to indicate the error type.
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@end itemize
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The error type indicator is dependent on the source
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of the error and whether or not the error was internally
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generated by the executive. If the error was generated
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from an API, then the error code will be of that API's
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error or status codes. The status codes for the RTEMS
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API are in c/src/exec/rtems/headers/status.h. Those
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for the POSIX API can be found in .
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The @code{@value{DIRPREFIX}fatal_error_occurred} directive is responsible
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for invoking an optional user-supplied fatal error handler
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and/or the RTEMS fatal error handler. All fatal error handlers
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are passed an error code to describe the error detected.
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Occasionally, an application requires more
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sophisticated fatal error processing such as passing control to
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a debugger. For these cases, a user-supplied fatal error
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handler can be specified in the RTEMS configuration table. The
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User Extension Table field fatal contains the address of the
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fatal error handler to be executed when the
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@code{@value{DIRPREFIX}fatal_error_occurred}
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directive is called. If the field is set to NULL or if the
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configured fatal error handler returns to the executive, then
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the default handler provided by RTEMS is executed. This default
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handler will halt execution on the processor where the error
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occurred.
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@section Directives
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This section details the fatal error manager's
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directives. A subsection is dedicated to each of this manager's
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directives and describes the calling sequence, related
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constants, usage, and status codes.
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@c
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@c
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@c
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@page
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@subsection FATAL_ERROR_OCCURRED - Invoke the fatal error handler
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@cindex announce fatal error
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@cindex fatal error, announce
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@subheading CALLING SEQUENCE:
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@ifset is-C
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@findex rtems_fatal_error_occurred
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@example
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void volatile rtems_fatal_error_occurred(
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rtems_unsigned32 the_error
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);
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@end example
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@end ifset
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@ifset is-Ada
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@example
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procedure Fatal_Error_Occurred (
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The_Error : in RTEMS.Unsigned32
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);
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@end example
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@end ifset
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@subheading DIRECTIVE STATUS CODES
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NONE
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@subheading DESCRIPTION:
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This directive processes fatal errors. If the FATAL
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error extension is defined in the configuration table, then the
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user-defined error extension is called. If configured and the
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provided FATAL error extension returns, then the RTEMS default
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error handler is invoked. This directive can be invoked by
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RTEMS or by the user's application code including initialization
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tasks, other tasks, and ISRs.
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@subheading NOTES:
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This directive supports local operations only.
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Unless the user-defined error extension takes special
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actions such as restarting the calling task, this directive WILL
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NOT RETURN to the caller.
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The user-defined extension for this directive may
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wish to initiate a global shutdown.
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