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* SUPPORT, LICENSE: New files. * Numerous files touched as part of merging the 4.5 branch onto the mainline development trunk and ensuring that the script that cuts snapshots and releases works on the documentation.
82 lines
2.8 KiB
Perl
82 lines
2.8 KiB
Perl
@c
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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 $Id$
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@c
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@chapter Ada95 Interrupt Support
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@section Introduction
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This chapter describes what is required to enable Ada interrupt
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and error exception handling when using GNAT over RTEMS.
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The GNAT Ada95 interrupt support RTEMS was developed by
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Jiri Gaisler <jgais@@ws.estec.esa.nl> who also wrote this
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chapter.
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@section Mapping Interrupts to POSIX Signals
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In Ada95, interrupts can be attached with the interrupt_attach pragma.
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For most systems, the gnat run-time will use POSIX signal to implement
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the interrupt handling, mapping one signal per interrupt. For interrupts
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to be propagated to the attached Ada handler, the corresponding signal
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must be raised when the interrupt occurs.
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The same mechanism is used to generate Ada error exceptions.
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Three error exceptions are defined: program, constraint and storage
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error. These are generated by raising the predefined signals: SIGILL,
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SIGFPE and SIGSEGV. These signals should be raised when a spurious
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or erroneous trap occurs.
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To enable gnat interrupt and error exception support for a particular
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bsp, the following has to be done:
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@enumerate
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@item Write an interrupt/trap handler that will raise the corresponding
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signal depending on the interrupt/trap number.
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@item Install the interrupt handler for all interrupts/traps that will be
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handled by gnat (including spurious).
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@item At startup, gnat calls @code{__gnat_install_handler()}. The bsp
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must provide this function which installs the interrupt/trap handlers.
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@end enumerate
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Which cpu-interrupt will generate which signal is implementation
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defined. There are 32 POSIX signals (1 - 32), and all except the
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three error signals (SIGILL, SIGFPE and SIGSEGV) can be used. I
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would suggest to use the upper 16 (17 - 32) which do not
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have an assigned POSIX name.
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Note that the pragma interrupt_attach will only bind a signal
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to a particular Ada handler - it will not unmask the
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interrupt or do any other things to enable it. This have to be
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done separately, typically by writing various device register.
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@section Example Ada95 Interrupt Program
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An example program (@code{irq_test}) is included in the
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Ada examples package to show how interrupts can be handled
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in Ada95. Note that generation of the test interrupt
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(@code{irqforce.c}) is bsp specific and must be edited.
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NOTE: The @code{irq_test} example was written for the SPARC/ERC32
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BSP.
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@section Version Requirements
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With RTEMS 4.0, a patch was required to psignal.c in RTEMS
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sources (to correct a bug associated to the default action of
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signals 15-32). The SPARC/ERC32 RTEMS BSP includes the
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@code{gnatsupp} subdirectory that can be used as an example
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for other BSPs.
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With GNAT 3.11p, a patch is required for @code{a-init.c} to invoke
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the BSP specific routine that installs the exception handlers.
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