sys/kern/kern__physio.c

/*
 * Copyright (c) 1989, 1990, 1991, 1992 William F. Jolitz, TeleMuse
 * All rights reserved.
 *
 * 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 software is a component of "386BSD" developed by
        William F. Jolitz, TeleMuse.
 * 4. Neither the name of the developer nor the name "386BSD"
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS A COMPONENT OF 386BSD DEVELOPED BY WILLIAM F. JOLITZ
 * AND IS INTENDED FOR RESEARCH AND EDUCATIONAL PURPOSES ONLY. THIS
 * SOFTWARE SHOULD NOT BE CONSIDERED TO BE A COMMERCIAL PRODUCT.
 * THE DEVELOPER URGES THAT USERS WHO REQUIRE A COMMERCIAL PRODUCT
 * NOT MAKE USE THIS WORK.
 *
 * FOR USERS WHO WISH TO UNDERSTAND THE 386BSD SYSTEM DEVELOPED
 * BY WILLIAM F. JOLITZ, WE RECOMMEND THE USER STUDY WRITTEN
 * REFERENCES SUCH AS THE  "PORTING UNIX TO THE 386" SERIES
 * (BEGINNING JANUARY 1991 "DR. DOBBS JOURNAL", USA AND BEGINNING
 * JUNE 1991 "UNIX MAGAZIN", GERMANY) BY WILLIAM F. JOLITZ AND
 * LYNNE GREER JOLITZ, AS WELL AS OTHER BOOKS ON UNIX AND THE
 * ON-LINE 386BSD USER MANUAL BEFORE USE. A BOOK DISCUSSING THE INTERNALS
 * OF 386BSD ENTITLED "386BSD FROM THE INSIDE OUT" WILL BE AVAILABLE LATE 1992.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPER ``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 DEVELOPER 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.
 *
 *      $Id: kern__physio.c,v 1.6 1994/01/14 16:24:47 davidg Exp $
 */

#include "param.h"
#include "systm.h"
#include "buf.h"
#include "conf.h"
#include "proc.h"
#include "malloc.h"
#include "vnode.h"
#include "vm/vm.h"
#include "specdev.h"

/*
 * Driver interface to do "raw" I/O in the address space of a
 * user process directly for read and write operations..
 */

int
rawread(dev, uio)
        dev_t dev; struct uio *uio;
{
        return (uioapply(physio, (caddr_t) cdevsw[major(dev)].d_strategy,
                                 (caddr_t) (u_long) dev, uio));
}

int
rawwrite(dev, uio)
        dev_t dev; struct uio *uio;
{
        return (uioapply(physio, (caddr_t) cdevsw[major(dev)].d_strategy,
                                (caddr_t) (u_long) dev, uio));
}


int physio(strat, dev, bp, off, rw, base, len, p)
        d_strategy_t strat;
        dev_t dev;
        struct buf *bp;
        int rw, off;
        caddr_t base;
        int *len;
        struct proc *p;
{
        int amttodo = *len;
        int error, amtdone;
        vm_prot_t ftype;
        vm_offset_t v, lastv;
        caddr_t adr;
        int oldflags;
        int s;

        int bp_alloc = (bp == 0);

/*
 * keep the process from being swapped
 */
        oldflags = p->p_flag;
        p->p_flag |= SPHYSIO;

        rw = rw == UIO_READ ? B_READ : 0;

        /* create and build a buffer header for a transfer */

        if (bp_alloc) {
                bp = (struct buf *)getpbuf();
                bzero((char *)bp, sizeof(*bp));                 /* 09 Sep 92*/
        } else {
                s = splbio();
                while (bp->b_flags & B_BUSY) {
                        bp->b_flags |= B_WANTED;
                        tsleep((caddr_t)bp, PRIBIO, "physbw", 0);
                }
                bp->b_flags |= B_BUSY;
                splx(s);
        }

        bp->b_flags = B_BUSY | B_PHYS | rw;
        bp->b_proc = p;
        bp->b_dev = dev;
        bp->b_error = 0;
        bp->b_blkno = off/DEV_BSIZE;
        amtdone = 0;

        /* iteratively do I/O on as large a chunk as possible */
        do {
                bp->b_flags &= ~B_DONE;
                bp->b_un.b_addr = base;
                /* XXX limit */
                bp->b_bcount = min (256*1024, amttodo);

                /* first, check if accessible */
                if (rw == B_READ && !useracc(base, bp->b_bcount, B_WRITE)) {
                        error = EFAULT;
                        goto errrtn;
                }
                if (rw == B_WRITE && !useracc(base, bp->b_bcount, B_READ)) {
                        error = EFAULT;
                        goto errrtn;
                }

                /* update referenced and dirty bits, handle copy objects */
                if (rw == B_READ)
                        ftype = VM_PROT_READ | VM_PROT_WRITE;
                else
                        ftype = VM_PROT_READ;

                lastv = 0;
                for (adr = (caddr_t)trunc_page(base); adr < base + bp->b_bcount;
                        adr += NBPG) {

/*
 * make sure that the pde is valid and wired
 */
                        v = trunc_page(((vm_offset_t)vtopte(adr)));
                        if (v != lastv) {
                                vm_map_pageable(&p->p_vmspace->vm_map, v,
                                        round_page(v+1), FALSE);
                                lastv = v;
                        }

/*
 * do the vm_fault if needed, do the copy-on-write thing when
 * reading stuff off device into memory.
 */
                        if (ftype & VM_PROT_WRITE) {
                                /*
                                 * properly handle copy-on-write
                                 */
                                *(volatile int *) adr += 0;
                        }
#if 0
                        else {
                                /*
                                 * this clause is not really necessary because
                                 * vslock does a vm_map_pageable FALSE.
                                 * It is not optimally efficient to reference the
                                 * page with the possiblity of it being paged out, but
                                 * if this page is faulted here, it will be placed on the
                                 * active queue, with the probability of it being paged
                                 * out being very very low.  This is here primarily for
                                 * "symmetry".
                                 */
                                *(volatile int *) adr;
                        }
#endif
                }
/*
 * if the process has been blocked by the wiring of the page table pages
 * above or faults of other pages, then the vm_map_pageable contained in the
 * vslock will fault the pages back in if they have been paged out since
 * being referenced in the loop above. (vm_map_pageable calls vm_fault_wire
 * which calls vm_fault to get the pages if needed.)
 */

                /* lock in core (perform vm_map_pageable, FALSE) */
                vslock (base, bp->b_bcount);

                /* perform transfer */
                physstrat(bp, strat, PRIBIO);

                /* unlock (perform vm_map_pageable, TRUE) */
                vsunlock (base, bp->b_bcount, 0);

                lastv = 0;

/*
 * unwire the pde
 */
                for (adr = (caddr_t)trunc_page(base); adr < base + bp->b_bcount;
                        adr += NBPG) {
                        v = trunc_page(((vm_offset_t)vtopte(adr)));
                        if (v != lastv) {
                                vm_map_pageable(&p->p_vmspace->vm_map, v, round_page(v+1), TRUE);
                                lastv = v;
                        }
                }


                amtdone = bp->b_bcount - bp->b_resid;
                amttodo -= amtdone;
                base += amtdone;
                bp->b_blkno += amtdone/DEV_BSIZE;
        } while (amttodo && (bp->b_flags & B_ERROR) == 0 && amtdone > 0);

        error = bp->b_error;
errrtn:
        if (bp_alloc) {
                relpbuf(bp);
        } else {
                bp->b_flags &= ~B_BUSY;
                wakeup((caddr_t)bp);
        }
        *len = amttodo;

/*
 * allow the process to be swapped
 */
        p->p_flag &= ~SPHYSIO;
        p->p_flag |= (oldflags & SPHYSIO);

        return (error);
}