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Fatal Error Manager

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.. index:: fatal errors

Introduction

The fatal error manager processes all fatal or irrecoverable errors and other sources of system termination (for example after exit()). The directives provided by the fatal error manager are:

  • rtems.fatal_error_occurred - Invoke the fatal error handler
  • rtems.fatal - Invoke the fatal error handler with error source

Background

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.. index:: fatal error detection
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.. index:: fatal error processing
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.. index:: fatal error user extension

The fatal error manager is called upon detection of an irrecoverable error condition by either RTEMS or the application software. Fatal errors can be detected from three sources:

  • the executive (RTEMS)
  • user system code
  • user application code

RTEMS automatically invokes the fatal error manager upon detection of an error it considers to be fatal. Similarly, the user should invoke the fatal error manager upon detection of a fatal error.

Each static or dynamic user extension set may include a fatal error handler. The fatal error handler in the static extension set can be used to provide access to debuggers and monitors which may be present on the target hardware. If any user-supplied fatal error handlers are installed, the fatal error manager will invoke them. If no user handlers are configured or if all the user handler return control to the fatal error manager, then the RTEMS default fatal error handler is invoked. If the default fatal error handler is invoked, then the system state is marked as failed.

Although the precise behavior of the default fatal error handler is processor specific, in general, it will disable all maskable interrupts, place the error code in a known processor dependent place (generally either on the stack or in a register), and halt the processor. The precise actions of the RTEMS fatal error are discussed in the Default Fatal Error Processing chapter of the Applications Supplement document for a specific target processor.

Operations

Announcing a Fatal Error

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.. index:: _Internal_errors_What_happened

The rtems.fatal_error_occurred directive is invoked when a fatal error is detected. Before invoking any user-supplied fatal error handlers or the RTEMS fatal error handler, the``rtems.fatal_error_occurred`` directive stores useful information in the variable _Internal_errors_What_happened. This record contains three pieces of information:

  • the source of the error (API or executive core),
  • whether the error was generated internally by the executive, and a
  • a numeric code to indicate the error type.

The error type indicator is dependent on the source of the error and whether or not the error was internally generated by the executive. If the error was generated from an API, then the error code will be of that API’s error or status codes. The status codes for the RTEMS API are in cpukit/rtems/include/rtems/rtems/status.h. Those for the POSIX API can be found in <errno.h>.

The rtems.fatal_error_occurred directive is responsible for invoking an optional user-supplied fatal error handler and/or the RTEMS fatal error handler. All fatal error handlers are passed an error code to describe the error detected.

Occasionally, an application requires more sophisticated fatal error processing such as passing control to a debugger. For these cases, a user-supplied fatal error handler can be specified in the RTEMS configuration table. The User Extension Table field fatal contains the address of the fatal error handler to be executed when the``rtems.fatal_error_occurred`` directive is called. If the field is set to NULL or if the configured fatal error handler returns to the executive, then the default handler provided by RTEMS is executed. This default handler will halt execution on the processor where the error occurred.

Directives

This section details the fatal error manager’s directives. A subsection is dedicated to each of this manager’s directives and describes the calling sequence, related constants, usage, and status codes.

FATAL_ERROR_OCCURRED - Invoke the fatal error handler

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.. index:: announce fatal error
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.. index:: fatal error, announce

CALLING SEQUENCE:

procedure Fatal_Error_Occurred (
The_Error : in     RTEMS.Unsigned32
);

DIRECTIVE STATUS CODES

NONE

DESCRIPTION:

This directive processes fatal errors. If the FATAL error extension is defined in the configuration table, then the user-defined error extension is called. If configured and the provided FATAL error extension returns, then the RTEMS default error handler is invoked. This directive can be invoked by RTEMS or by the user’s application code including initialization tasks, other tasks, and ISRs.

NOTES:

This directive supports local operations only.

Unless the user-defined error extension takes special actions such as restarting the calling task, this directive WILL NOT RETURN to the caller.

The user-defined extension for this directive may wish to initiate a global shutdown.

FATAL - Invoke the fatal error handler with error source

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.. index:: announce fatal error
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.. index:: fatal error, announce

CALLING SEQUENCE:

DIRECTIVE STATUS CODES

NONE

DESCRIPTION:

This directive invokes the internal error handler with is internal set to false. See also rtems.fatal_error_occurred.

EXCEPTION_FRAME_PRINT - Prints the exception frame

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.. index:: exception frame

CALLING SEQUENCE:

DIRECTIVE STATUS CODES

NONE

DESCRIPTION:

Prints the exception frame via printk().

FATAL_SOURCE_TEXT - Returns a text for a fatal source

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.. index:: fatal error

CALLING SEQUENCE:

DIRECTIVE STATUS CODES

The fatal source text or "?" in case the passed fatal source is invalid.

DESCRIPTION:

Returns a text for a fatal source. The text for fatal source is the enumerator constant.

INTERNAL_ERROR_TEXT - Returns a text for an internal error code

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.. index:: fatal error

CALLING SEQUENCE:

DIRECTIVE STATUS CODES

The error code text or "?" in case the passed error code is invalid.

DESCRIPTION:

Returns a text for an internal error code. The text for each internal error code is the enumerator constant.

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