bin/dd/position.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1991, 1993, 1994
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Keith Muller of the University of California, San Diego and Lance
   9  * Visser of Convex Computer Corporation.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  * 3. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  *
  35  * @(#)position.c       8.3 (Berkeley) 4/2/94
  36  * $FreeBSD: head/bin/dd/position.c 337865 2018-08-15 19:46:13Z kevans $
  37  */
  38
  39 #include <sys/types.h>
  40 #include <sys/mtio.h>
  41
  42 #include <err.h>
  43 #include <errno.h>
  44 #include <limits.h>
  45 #include <unistd.h>
  46
  47 #include "dd.h"
  48 #include "extern.h"
  49
  50 static off_t seek_offset(IO *);
  51
  52 static off_t
  53 seek_offset(IO *io)
  54 {
  55         off_t n;
  56         size_t sz;
  57
  58         n = io->offset;
  59         sz = io->dbsz;
  60
  61         _Static_assert(sizeof(io->offset) == sizeof(int64_t), "64-bit off_t");
  62
  63         /*
  64          * If the lseek offset will be negative, verify that this is a special
  65          * device file.  Some such files (e.g. /dev/kmem) permit "negative"
  66          * offsets.
  67          *
  68          * Bail out if the calculation of a file offset would overflow.
  69          */
  70         if ((io->flags & ISCHR) == 0 && (n < 0 || n > OFF_MAX / (ssize_t)sz))
  71                 errx(1, "seek offsets cannot be larger than %jd",
  72                     (intmax_t)OFF_MAX);
  73         else if ((io->flags & ISCHR) != 0 && (uint64_t)n > UINT64_MAX / sz)
  74                 errx(1, "seek offsets cannot be larger than %ju",
  75                     (uintmax_t)UINT64_MAX);
  76
  77         return ((off_t)( (uint64_t)n * sz ));
  78 }
  79
  80 /*
  81  * Position input/output data streams before starting the copy.  Device type
  82  * dependent.  Seekable devices use lseek, and the rest position by reading.
  83  * Seeking past the end of file can cause null blocks to be written to the
  84  * output.
  85  */
  86 void
  87 pos_in(void)
  88 {
  89         off_t cnt;
  90         int warned;
  91         ssize_t nr;
  92         size_t bcnt;
  93
  94         /* If known to be seekable, try to seek on it. */
  95         if (in.flags & ISSEEK) {
  96                 errno = 0;
  97                 if (lseek(in.fd, seek_offset(&in), SEEK_CUR) == -1 &&
  98                     errno != 0)
  99                         err(1, "%s", in.name);
 100                 return;
 101         }
 102
 103         /* Don't try to read a really weird amount (like negative). */
 104         if (in.offset < 0)
 105                 errx(1, "%s: illegal offset", "iseek/skip");
 106
 107         /*
 108          * Read the data.  If a pipe, read until satisfy the number of bytes
 109          * being skipped.  No differentiation for reading complete and partial
 110          * blocks for other devices.
 111          */
 112         for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) {
 113                 if ((nr = read(in.fd, in.db, bcnt)) > 0) {
 114                         if (in.flags & ISPIPE) {
 115                                 if (!(bcnt -= nr)) {
 116                                         bcnt = in.dbsz;
 117                                         --cnt;
 118                                 }
 119                         } else {
 120                                 --cnt;
 121                         }
 122                         if (need_summary)
 123                                 summary();
 124                         if (need_progress)
 125                                 progress();
 126                         continue;
 127                 }
 128
 129                 if (nr == 0) {
 130                         if (files_cnt > 1) {
 131                                 --files_cnt;
 132                                 continue;
 133                         }
 134                         errx(1, "skip reached end of input");
 135                 }
 136
 137                 /*
 138                  * Input error -- either EOF with no more files, or I/O error.
 139                  * If noerror not set die.  POSIX requires that the warning
 140                  * message be followed by an I/O display.
 141                  */
 142                 if (ddflags & C_NOERROR) {
 143                         if (!warned) {
 144                                 warn("%s", in.name);
 145                                 warned = 1;
 146                                 summary();
 147                         }
 148                         continue;
 149                 }
 150                 err(1, "%s", in.name);
 151         }
 152 }
 153
 154 void
 155 pos_out(void)
 156 {
 157         struct mtop t_op;
 158         off_t cnt;
 159         ssize_t n;
 160
 161         /*
 162          * If not a tape, try seeking on the file.  Seeking on a pipe is
 163          * going to fail, but don't protect the user -- they shouldn't
 164          * have specified the seek operand.
 165          */
 166         if (out.flags & (ISSEEK | ISPIPE)) {
 167                 errno = 0;
 168                 if (lseek(out.fd, seek_offset(&out), SEEK_CUR) == -1 &&
 169                     errno != 0)
 170                         err(1, "%s", out.name);
 171                 return;
 172         }
 173
 174         /* Don't try to read a really weird amount (like negative). */
 175         if (out.offset < 0)
 176                 errx(1, "%s: illegal offset", "oseek/seek");
 177
 178         /* If no read access, try using mtio. */
 179         if (out.flags & NOREAD) {
 180                 t_op.mt_op = MTFSR;
 181                 t_op.mt_count = out.offset;
 182
 183                 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
 184                         err(1, "%s", out.name);
 185                 return;
 186         }
 187
 188         /* Read it. */
 189         for (cnt = 0; cnt < out.offset; ++cnt) {
 190                 if ((n = read(out.fd, out.db, out.dbsz)) > 0)
 191                         continue;
 192
 193                 if (n == -1)
 194                         err(1, "%s", out.name);
 195
 196                 /*
 197                  * If reach EOF, fill with NUL characters; first, back up over
 198                  * the EOF mark.  Note, cnt has not yet been incremented, so
 199                  * the EOF read does not count as a seek'd block.
 200                  */
 201                 t_op.mt_op = MTBSR;
 202                 t_op.mt_count = 1;
 203                 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1)
 204                         err(1, "%s", out.name);
 205
 206                 while (cnt++ < out.offset) {
 207                         n = write(out.fd, out.db, out.dbsz);
 208                         if (n == -1)
 209                                 err(1, "%s", out.name);
 210                         if (n != out.dbsz)
 211                                 errx(1, "%s: write failure", out.name);
 212                 }
 213                 break;
 214         }
 215 }