NetBSD-5.0.2/sys/arch/i386/i386/db_memrw.c

/*	$NetBSD: db_memrw.c,v 1.24 2008/04/28 20:23:24 martin 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.
 *
 * 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>.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: db_memrw.c,v 1.24 2008/04/28 20:23:24 martin Exp $");

#include "opt_xen.h"

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

#include <uvm/uvm_extern.h>

#include <machine/db_machdep.h>
#if defined(XEN)
#include <xen/xenpmap.h>
#endif

#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 == 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, const 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 = x86_trunc_page(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;
		pmap_pte_set(pte, tmppte);
		pmap_pte_flush();
		pmap_update_pg(pgva);
		/*
		 * MULTIPROCESSOR: no shootdown required as the PTE continues to
		 * map the same page and other CPU's don't need write access.
		 */

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

		/*
		 * Restore the old PTE.
		 */
		pmap_pte_set(pte, oldpte);
		pmap_pte_flush();
#if 0 
		/*
		 * XXXSMP Not clear if this is needed for 100% correctness.
		 */
		{
			int cpumask = 0;
			/*
			 * shoot down in case other CPU mistakenly caches page.
			 */
			pmap_tlb_shootdown(pmap_kernel(), pgva, 0, PG_G);
			pmap_tlb_shootwait();
		}
#else
		pmap_update_pg(pgva);
#endif
		
	} while (size != 0);
}

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

	dst = (char *)addr;

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

	dst = (char *)addr;

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

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

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