bsd/kern/kern_physio.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*-
  23  * Copyright (c) 1982, 1986, 1990, 1993
  24  *      The Regents of the University of California.  All rights reserved.
  25  * (c) UNIX System Laboratories, Inc.
  26  * All or some portions of this file are derived from material licensed
  27  * to the University of California by American Telephone and Telegraph
  28  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
  29  * the permission of UNIX System Laboratories, Inc.
  30  *
  31  * Redistribution and use in source and binary forms, with or without
  32  * modification, are permitted provided that the following conditions
  33  * are met:
  34  * 1. Redistributions of source code must retain the above copyright
  35  *    notice, this list of conditions and the following disclaimer.
  36  * 2. Redistributions in binary form must reproduce the above copyright
  37  *    notice, this list of conditions and the following disclaimer in the
  38  *    documentation and/or other materials provided with the distribution.
  39  * 3. All advertising materials mentioning features or use of this software
  40  *    must display the following acknowledgement:
  41  *      This product includes software developed by the University of
  42  *      California, Berkeley and its contributors.
  43  * 4. Neither the name of the University nor the names of its contributors
  44  *    may be used to endorse or promote products derived from this software
  45  *    without specific prior written permission.
  46  *
  47  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  48  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  49  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  50  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  51  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  52  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  53  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  54  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  55  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  56  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  57  * SUCH DAMAGE.
  58  *
  59  *      from: @(#)kern_physio.c 8.1 (Berkeley) 6/10/93
  60  */
  61 /*
  62  * HISTORY
  63  * 27-July-97  Umesh Vaishampayan  (umeshv@apple.com)
  64  *      Allow physio() to kernel space.
  65  */
  66
  67 #include <sys/param.h>
  68 #include <sys/systm.h>
  69 #include <sys/buf.h>
  70 #include <sys/conf.h>
  71 #include <sys/proc.h>
  72
  73 int
  74 physio(strategy, bp, dev, flags, minphys, uio, blocksize)
  75         void (*strategy)();
  76         struct buf *bp;
  77         dev_t dev;
  78         int flags;
  79         u_int (*minphys)();
  80         struct uio *uio;
  81         int blocksize;
  82 {
  83         struct iovec *iovp;
  84         struct proc *p = current_proc();
  85         int error, done, i, nobuf, s, todo;
  86
  87         error = 0;
  88         flags &= B_READ | B_WRITE;
  89
  90         /*
  91          * [check user read/write access to the data buffer]
  92          *
  93          * Check each iov one by one.  Note that we know if we're reading or
  94          * writing, so we ignore the uio's rw parameter.  Also note that if
  95          * we're doing a read, that's a *write* to user-space.
  96          */
  97         for (i = 0; i < uio->uio_iovcnt; i++) {
  98                 if(uio->uio_segflg != UIO_SYSSPACE) {
  99                         if (!useracc(uio->uio_iov[i].iov_base,
 100                                 uio->uio_iov[i].iov_len,
 101                                 (flags == B_READ) ? B_WRITE : B_READ))
 102                         return (EFAULT);
 103                 }
 104         }
 105         /* Make sure we have a buffer, creating one if necessary. */
 106         if (nobuf = (bp == NULL)) {
 107 //              bp = getphysbuf();
 108                 panic("physio: null buf pointer\n");
 109                 }
 110
 111         /* [raise the processor priority level to splbio;] */
 112         s = splbio();
 113
 114         /* [while the buffer is marked busy] */
 115         while (bp->b_flags & B_BUSY) {
 116                 /* [mark the buffer wanted] */
 117                 bp->b_flags |= B_WANTED;
 118                 /* [wait until the buffer is available] */
 119                 tsleep((caddr_t)bp, PRIBIO+1, "physbuf", 0);
 120         }
 121
 122         /* Mark it busy, so nobody else will use it. */
 123         bp->b_flags |= B_BUSY;
 124
 125         /* [lower the priority level] */
 126         splx(s);
 127
 128         /* [set up the fixed part of the buffer for a transfer] */
 129         bp->b_dev = dev;
 130         bp->b_error = 0;
 131         bp->b_proc = p;
 132
 133         /*
 134          * [while there are data to transfer and no I/O error]
 135          * Note that I/O errors are handled with a 'goto' at the bottom
 136          * of the 'while' loop.
 137          */
 138         for (i = 0; i < uio->uio_iovcnt; i++) {
 139                 iovp = &uio->uio_iov[i];
 140                 while (iovp->iov_len > 0) {
 141                         /*
 142                          * [mark the buffer busy for physical I/O]
 143                          * (i.e. set B_PHYS (because it's an I/O to user
 144                          * memory, and B_RAW, because B_RAW is to be
 145                          * "Set by physio for raw transfers.", in addition
 146                          * to the "busy" and read/write flag.)
 147                          */
 148                         s = splbio();
 149                         bp->b_flags = B_BUSY | B_PHYS | B_RAW | flags;
 150                         splx(s);
 151
 152                         /* [set up the buffer for a maximum-sized transfer] */
 153                         bp->b_blkno = uio->uio_offset / blocksize;
 154                         bp->b_bcount = iovp->iov_len;
 155                         bp->b_data = iovp->iov_base;
 156
 157                         /*
 158                          * [call minphys to bound the tranfer size]
 159                          * and remember the amount of data to transfer,
 160                          * for later comparison.
 161                          */
 162                         (*minphys)(bp);
 163                         todo = bp->b_bcount;
 164
 165                         /*
 166                          * [lock the part of the user address space involved
 167                          *    in the transfer]
 168                          * Beware vmapbuf(); it clobbers b_data and
 169                          * saves it in b_saveaddr.  However, vunmapbuf()
 170                          * restores it.
 171                          */
 172
 173                         if(uio->uio_segflg != UIO_SYSSPACE)
 174                                 vslock(bp->b_data, todo);
 175
 176 #if 0
 177                         vmapbuf(bp, todo);
 178 #endif /* 0 */
 179                         /* [call strategy to start the transfer] */
 180                         (*strategy)(bp);
 181
 182                         /*
 183                          * Note that the raise/wait/lower/get error
 184                          * steps below would be done by biowait(), but
 185                          * we want to unlock the address space before
 186                          * we lower the priority.
 187                          *
 188                          * [raise the priority level to splbio]
 189                          */
 190                         s = splbio();
 191
 192                         /* [wait for the transfer to complete] */
 193                         while ((bp->b_flags & B_DONE) == 0)
 194                                 tsleep((caddr_t) bp, PRIBIO + 1, "physio", 0);
 195
 196                         /*
 197                          * [unlock the part of the address space previously
 198                          *    locked]
 199                          */
 200 #if 0
 201                         vunmapbuf(bp, todo);
 202 #endif /* 0 */
 203                         if(uio->uio_segflg != UIO_SYSSPACE)
 204                                 vsunlock(bp->b_data, todo);
 205
 206                         /* remember error value (save a splbio/splx pair) */
 207                         if (bp->b_flags & B_ERROR)
 208                                 error = (bp->b_error ? bp->b_error : EIO);
 209
 210                         /* [lower the priority level] */
 211                         splx(s);
 212
 213                         /*
 214                          * [deduct the transfer size from the total number
 215                          *    of data to transfer]
 216                          */
 217                         done = bp->b_bcount - bp->b_resid;
 218                         iovp->iov_len -= done;
 219                         iovp->iov_base += done;
 220                         uio->uio_offset += done;
 221                         uio->uio_resid -= done;
 222
 223                         /*
 224                          * Now, check for an error.
 225                          * Also, handle weird end-of-disk semantics.
 226                          */
 227                         if (error || done < todo)
 228                                 goto done;
 229                 }
 230         }
 231
 232 done:
 233         /*
 234          * [clean up the state of the buffer]
 235          * Remember if somebody wants it, so we can wake them up below.
 236          * Also, if we had to steal it, give it back.
 237          */
 238         s = splbio();
 239         bp->b_flags &= ~(B_BUSY | B_PHYS | B_RAW);
 240 #if 0
 241         if (nobuf)
 242                 putphysbuf(bp);
 243
 244         else
 245 #endif /* 0 */
 246                 {
 247                 /*
 248                  * [if another process is waiting for the raw I/O buffer,
 249                  *    wake up processes waiting to do physical I/O;
 250                  */
 251                 if (bp->b_flags & B_WANTED) {
 252                         bp->b_flags &= ~B_WANTED;
 253                         wakeup(bp);
 254                 }
 255         }
 256         splx(s);
 257
 258         return (error);
 259 }
 260
 261 /*
 262  * Leffler, et al., says on p. 231:
 263  * "The minphys() routine is called by physio() to adjust the
 264  * size of each I/O transfer before the latter is passed to
 265  * the strategy routine..."
 266  *
 267  * so, just adjust the buffer's count accounting to MAXPHYS here,
 268  * and return the new count;
 269  */
 270 u_int
 271 minphys(bp)
 272         struct buf *bp;
 273 {
 274
 275         bp->b_bcount = min(MAXPHYS, bp->b_bcount);
 276         return bp->b_bcount;
 277 }
 278
 279 /*
 280  * Do a read on a device for a user process.
 281  */
 282 rawread(dev, uio)
 283         dev_t dev;
 284         struct uio *uio;
 285 {
 286         return (physio(cdevsw[major(dev)].d_strategy, (struct buf *)NULL,
 287             dev, B_READ, minphys, uio, DEV_BSIZE));
 288 }
 289
 290 /*
 291  * Do a write on a device for a user process.
 292  */
 293 rawwrite(dev, uio)
 294         dev_t dev;
 295         struct uio *uio;
 296 {
 297         return (physio(cdevsw[major(dev)].d_strategy, (struct buf *)NULL,
 298             dev, B_WRITE, minphys, uio, DEV_BSIZE));
 299 }