/* idtEnt.h - IA-32 IDT Entry code */

/*
 * Copyright (c) 2012-2014, Wind River Systems, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1) Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2) Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3) Neither the name of Wind River Systems nor the names of its contributors
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
DESCRIPTION
This header file provides code for constructing an IA-32 interrupt descriptor.

 */

#ifndef _IDTENT_H
#define _IDTENT_H

#ifdef __cplusplus
extern"C"
	{
#endif

/*
 * Bitmask used to determine which exceptions result in an error code being
 * pushed onto the stack.  The following exception vectors push an error code:
 *
 *  Vector    Mnemonic    Description
 *  ------    -------     ----------------------
 *    8       #DF         Double Fault
 *    10      #TS         Invalid TSS
 *    11      #NP         Segment Not Present
 *    12      #SS         Stack Segment Fault
 *    13      #GP         General Protection Fault
 *    14      #PF         Page Fault
 *    17      #AC         Alignment Check
 */

#define _EXC_ERROR_CODE_FAULTS	0x27d00


/*
 * Interrupt Descriptor Table (IDT) entry structure
 *
 * (This is taken from Intel documentation, so don't try to interpret it
 * too deeply.)
 */

typedef struct idtEntry {
	unsigned short	lowOffset;
	unsigned short	segmentSelector;
	unsigned short	reserved:5;
	unsigned short	intGateIndicator:8;
	unsigned short	descPrivLevel:2;
	unsigned short	present:1;
	unsigned short	hiOffset;
	} __packed IDT_ENTRY;

/**
 *
 * @brief Create an IDT entry
 *
 * This routine creates an interrupt-gate descriptor at the location defined by
 * <pIdtEntry>. The entry is created such that <routine> is invoked when an
 * interrupt vector is asserted.  The <dpl> argument specifies the privilege
 * level for the interrupt-gate descriptor; (hardware) interrupts and exceptions
 * should specify a level of 0, whereas handlers for user-mode software generated
 * interrupts should specify 3.
 *
 * @return N/A
 *
 * INTERNAL
 * This is a shared routine between the IA-32 nanokernel runtime code and the
 * genIdt host tool code. It is done this way to keep the two sides in sync.
 *
 * The runtime passes a pointer directly to the IDT entry to update whereas the
 * host side simply passes a pointer to a local variable.
 *
 */

static inline void _IdtEntCreate
	(
	unsigned long long *pIdtEntry,      /* Pointer to where the entry is be built */
	void (*routine)(void *),	    /* Routine to call when interrupt occurs  */
	unsigned int dpl		    /* priv level for interrupt descriptor    */
	)
	{
	unsigned long *pIdtEntry32 = (unsigned long *)pIdtEntry;

	pIdtEntry32[0] = (KERNEL_CODE_SEG_SELECTOR << 16) |
			((unsigned short)(unsigned int)routine);

    /*
     * The constant 0x8e00 results from the following:
     *
     * Segment Present = 1
     *
     * Descriptor Privilege Level (DPL) = 0  (dpl arg will be or'ed in)
     *
     * Interrupt Gate Indicator = 0xE
     *    The _IntEnt() and _ExcEnt() stubs assume that an interrupt-gate
     *    descriptor is used, and thus they do not issue a 'cli' instruction
     *    given that the processor automatically clears the IF flag when
     *    accessing the interrupt/exception handler via an interrupt-gate.
     *
     * Size of Gate (D) = 1
     *
     * Reserved = 0
     */

	pIdtEntry32[1] = ((unsigned int) routine & 0xffff0000) |
				    (0x8e00 | (dpl << 13));
	}

#ifdef __cplusplus
	}
#endif

#endif /* _IDTENT_H */