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 } 216