mem.c

早期freebsd实现

/*
 * Copyright (c) 1988 University of Utah.
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department and Ralph Campbell.
 *
 * 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 University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
 *
 * from: Utah $Hdr: mem.c 1.14 90/10/12$
 *
 *	@(#)mem.c	8.2 (Berkeley) 3/28/94
 */

/*
 * Memory special file
 */

#include <sys/param.h>
#include <sys/conf.h>
#include <sys/buf.h>
#include <sys/systm.h>
#include <sys/malloc.h>

#include <machine/cpu.h>

#include <vm/vm_param.h>
#include <vm/lock.h>
#include <vm/vm_prot.h>
#include <vm/pmap.h>

/*ARGSUSED*/
mmrw(dev, uio, flags)
	dev_t dev;
	struct uio *uio;
	int flags;
{
	register u_long v;
	register u_int c;
	register struct iovec *iov;
	int error = 0;
	caddr_t zbuf = NULL;
	extern vm_offset_t avail_end;

	while (uio->uio_resid > 0 && error == 0) {
		iov = uio->uio_iov;
		if (iov->iov_len == 0) {
			uio->uio_iov++;
			uio->uio_iovcnt--;
			if (uio->uio_iovcnt < 0)
				panic("mmrw");
			continue;
		}
		switch (minor(dev)) {

/* minor device 0 is physical memory */
		case 0:
			v = (u_long)uio->uio_offset;
			c = iov->iov_len;
			if (v + c <= btoc(physmem))
				v += MACH_CACHED_MEMORY_ADDR;
			else
				return (EFAULT);
			error = uiomove((caddr_t)v, (int)c, uio);
			continue;

/* minor device 1 is kernel memory */
		case 1:
			v = (u_long)uio->uio_offset;
			if (v < MACH_CACHED_MEMORY_ADDR)
				return (EFAULT);
			c = iov->iov_len;
			if (v + c <= MACH_PHYS_TO_CACHED(avail_end) ||
			    v >= MACH_KSEG2_ADDR && kernacc((caddr_t)v, c,
			    uio->uio_rw == UIO_READ ? B_READ : B_WRITE)) {
				error = uiomove((caddr_t)v, (int)c, uio);
				continue;
			}
			return (EFAULT);

/* minor device 2 is EOF/RATHOLE */
		case 2:
			if (uio->uio_rw == UIO_WRITE)
				uio->uio_resid = 0;
			return (0);

/* minor device 12 (/dev/zero) is source of nulls on read, rathole on write */
		case 12:
			if (uio->uio_rw == UIO_WRITE) {
				c = iov->iov_len;
				break;
			}
			if (zbuf == NULL) {
				zbuf = (caddr_t)
				    malloc(CLBYTES, M_TEMP, M_WAITOK);
				bzero(zbuf, CLBYTES);
			}
			c = min(iov->iov_len, CLBYTES);
			error = uiomove(zbuf, (int)c, uio);
			continue;

		default:
			return (ENXIO);
		}
		if (error)
			break;
		iov->iov_base += c;
		iov->iov_len -= c;
		uio->uio_offset += c;
		uio->uio_resid -= c;
	}
	if (zbuf)
		free(zbuf, M_TEMP);
	return (error);
}