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Import of OpenBSD 4.2 release kernel tree with initial code to support 
Jornada 720/728, StrongARM 1110-based handheld PC.
At this point kernel roots on NFS and boots into vfs_mountroot() and traps.
What is supported:
- glass console, Jornada framebuffer (jfb) works in 16bpp direct color mode
(needs some palette tweaks for non black/white/blue colors, i think)
- saic, SA11x0 interrupt controller (needs cleanup)
- sacom, SA11x0 UART (supported only as boot console for now)
- SA11x0 GPIO controller fully supported (but can't handle multiple interrupt
handlers on one gpio pin)
- sassp, SSP port on SA11x0 that attaches spibus
- Jornada microcontroller (jmcu) to control kbd, battery, etc throught
the SPI bus (wskbd attaches on jmcu, but not tested)
- tod functions seem work
- initial code for SA-1111 (chip companion) : this is TODO

Next important steps, i think:
- gpio and intc on sa1111
- pcmcia support for sa11x0 (and sa1111 help logic)
- REAL root on nfs when we have PCMCIA support (we may use any of supported pccard NICs)
- root on wd0! (using already supported PCMCIA-ATA)

/*	$OpenBSD: db_memrw.c,v 1.3 2005/10/21 18:55:00 martin Exp $	*/
/*	$NetBSD: db_memrw.c,v 1.1 2003/04/26 18:39:27 fvdl Exp $	*/

/*-
 * Copyright (c) 1996, 2000 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Gordon W. Ross and Jason R. Thorpe.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *        This product includes software developed by the NetBSD
 *        Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

/*
 * Interface to the debugger for virtual memory read/write.
 * This file is shared by DDB and KGDB, and must work even
 * when only KGDB is included (thus no db_printf calls).
 *
 * To write in the text segment, we have to first make
 * the page writable, do the write, then restore the PTE.
 * For writes outside the text segment, and all reads,
 * just do the access -- if it causes a fault, the debugger
 * will recover with a longjmp to an appropriate place.
 *
 * ALERT!  If you want to access device registers with a
 * specific size, then the read/write functions have to
 * make sure to do the correct sized pointer access.
 *
 * Modified for i386 from hp300 version by
 * Jason R. Thorpe <thorpej@zembu.com>.
 *
 * Basic copy to amd64 by fvdl.
 */

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>

#include <uvm/uvm_extern.h>

#include <machine/db_machdep.h>

#include <ddb/db_access.h>

/*
 * Read bytes from kernel address space for debugger.
 */
void
db_read_bytes(vaddr_t addr, size_t size, char *data)
{
	char *src;

	src = (char *)addr;

	if (size == 8) {
		*((long *)data) = *((long *)src);
		return;
	}

	if (size == 4) {
		*((int *)data) = *((int *)src);
		return;
	}

	if (size == 2) {
		*((short *)data) = *((short *)src);
		return;
	}

	while (size-- > 0)
		*data++ = *src++;
}

/*
 * Write bytes somewhere in the kernel text.  Make the text
 * pages writable temporarily.
 */
static void
db_write_text(vaddr_t addr, size_t size, char *data)
{
	pt_entry_t *pte, oldpte, tmppte;
	vaddr_t pgva;
	size_t limit;
	char *dst;

	if (size == 0)
		return;

	dst = (char *)addr;

	do {
		/*
		 * Get the PTE for the page.
		 */
		pte = kvtopte(addr);
		oldpte = *pte;

		if ((oldpte & PG_V) == 0) {
			printf(" address %p not a valid page\n", dst);
			return;
		}

		/*
		 * Get the VA for the page.
		 */
		if (oldpte & PG_PS)
			pgva = (vaddr_t)dst & PG_LGFRAME;
		else
			pgva = trunc_page((vaddr_t)dst);

		/*
		 * Compute number of bytes that can be written
		 * with this mapping and subtract it from the
		 * total size.
		 */
		if (oldpte & PG_PS)
			limit = NBPD_L2 - ((vaddr_t)dst & (NBPD_L2 - 1));
		else
			limit = PAGE_SIZE - ((vaddr_t)dst & PGOFSET);
		if (limit > size)
			limit = size;
		size -= limit;

		tmppte = (oldpte & ~PG_KR) | PG_KW;
		*pte = tmppte;
		pmap_update_pg(pgva);

		/*
		 * Page is now writable.  Do as much access as we
		 * can in this page.
		 */
		for (; limit > 0; limit--)
			*dst++ = *data++;

		/*
		 * Restore the old PTE.
		 */
		*pte = oldpte;

		pmap_update_pg(pgva);
		
	} while (size != 0);
}

/*
 * Write bytes to kernel address space for debugger.
 */
void
db_write_bytes(vaddr_t addr, size_t size, char *data)
{
	extern char etext;
	char *dst;

	dst = (char *)addr;

	/* If any part is in kernel text, use db_write_text() */
	if (addr >= KERNBASE && addr < (vaddr_t)&etext) {
		db_write_text(addr, size, data);
		return;
	}

	dst = (char *)addr;

	if (size == 8) {
		*((long *)dst) = *((long *)data);
		return;
	}

	if (size == 4) {
		*((int *)dst) = *((int *)data);
		return;
	}

	if (size == 2) {
		*((short *)dst) = *((short *)data);
		return;
	}

	while (size-- > 0)
		*dst++ = *data++;
}