/* intboiexit.s - VxMicro spurious interrupt support for IA-32 architecture */

/*
 * Copyright (c) 2010-2014 Wind River Systems, Inc.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 */

/*
DESCRIPTION
This module implements the single interrupt handling routine _IntBoiExit().
This routine is used by some interrupt controller drivers (e.g. the Intel
8259A driver) to short circuit the execution of normal interrupt stub
processing when a spurious interrupt is detected.

When a spurious interrupt condition is detected by the interrupt controller's
"beginning of interrupt" (BOI) handler it forces a return to _IntBoiExit()
rather than returning back to the interrupt stub.  The _IntBoiExit() routine
then pops the parameter passed to the BOI handler and branches to _IntExit(),
thereby circumventing execution of the "application" ISR and the interrupt
controller driver's "end of interrupt" (EOI) handler (if present).

\INTERNAL
The _IntBoiExit() routine is provided in a separate module so that it gets
included in the final image only if an interrupt controller driver utilizing
_IntBoiExit() is present.

*/

#define _ASMLANGUAGE
#include <arch/x86/asm.h>
#include <offsets.h>		/* nanokernel structure offset definitions */


	/* exports (internal APIs) */

	GTEXT(_IntBoiExit)

 	/* externs */

	GTEXT(_IntExit)

/*******************************************************************************
*
* _IntBoiExit - exit interrupt handler stub without invoking ISR
*
* This routine exits an interrupt handler stub without invoking the associated
* ISR handler (or the EOI handler, if present).  It should only be jumped to
* by an interrupt controller driver's BOI routine, and only if the BOI routine
* is passed a single parameter by the interrupt stub.
*
* \INTERNAL
* A BOI routine that has no parameters can jump directly to _IntExit().
*/

SECTION_FUNC(TEXT, _IntBoiExit)
        addl    $4, %esp		/* pop off the $BoiParameter */
        jmp     FUNC(_IntExit)		/* exit via kernel */