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 36 #ifndef lint 37 #if 0 38 static char sccsid[] = "@(#)position.c 8.3 (Berkeley) 4/2/94"; 39 #endif 40 #endif /* not lint */ 41 #include <sys/cdefs.h> 42 #include <sys/types.h> 43 #include <sys/mtio.h> 44 45 #include <err.h> 46 #include <errno.h> 47 #include <inttypes.h> 48 #include <limits.h> 49 #include <signal.h> 50 #include <unistd.h> 51 52 #include "dd.h" 53 #include "extern.h" 54 55 static off_t 56 seek_offset(IO *io) 57 { 58 off_t n; 59 size_t sz; 60 61 n = io->offset; 62 sz = io->dbsz; 63 64 _Static_assert(sizeof(io->offset) == sizeof(int64_t), "64-bit off_t"); 65 66 /* 67 * If the lseek offset will be negative, verify that this is a special 68 * device file. Some such files (e.g. /dev/kmem) permit "negative" 69 * offsets. 70 * 71 * Bail out if the calculation of a file offset would overflow. 72 */ 73 if ((io->flags & ISCHR) == 0 && (n < 0 || n > OFF_MAX / (ssize_t)sz)) 74 errx(1, "seek offsets cannot be larger than %jd", 75 (intmax_t)OFF_MAX); 76 else if ((io->flags & ISCHR) != 0 && (uint64_t)n > UINT64_MAX / sz) 77 errx(1, "seek offsets cannot be larger than %ju", 78 (uintmax_t)UINT64_MAX); 79 80 return ((off_t)( (uint64_t)n * sz )); 81 } 82 83 /* 84 * Position input/output data streams before starting the copy. Device type 85 * dependent. Seekable devices use lseek, and the rest position by reading. 86 * Seeking past the end of file can cause null blocks to be written to the 87 * output. 88 */ 89 void 90 pos_in(void) 91 { 92 off_t cnt; 93 int warned; 94 ssize_t nr; 95 size_t bcnt; 96 97 /* If known to be seekable, try to seek on it. */ 98 if (in.flags & ISSEEK) { 99 errno = 0; 100 if (lseek(in.fd, seek_offset(&in), SEEK_CUR) == -1 && 101 errno != 0) 102 err(1, "%s", in.name); 103 return; 104 } 105 106 /* Don't try to read a really weird amount (like negative). */ 107 if (in.offset < 0) 108 errx(1, "%s: illegal offset", "iseek/skip"); 109 110 /* 111 * Read the data. If a pipe, read until satisfy the number of bytes 112 * being skipped. No differentiation for reading complete and partial 113 * blocks for other devices. 114 */ 115 for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) { 116 if ((nr = read(in.fd, in.db, bcnt)) > 0) { 117 if (in.flags & ISPIPE) { 118 if (!(bcnt -= nr)) { 119 bcnt = in.dbsz; 120 --cnt; 121 } 122 } else 123 --cnt; 124 if (need_summary) 125 summary(); 126 if (need_progress) 127 progress(); 128 continue; 129 } 130 131 if (nr == 0) { 132 if (files_cnt > 1) { 133 --files_cnt; 134 continue; 135 } 136 errx(1, "skip reached end of input"); 137 } 138 139 /* 140 * Input error -- either EOF with no more files, or I/O error. 141 * If noerror not set die. POSIX requires that the warning 142 * message be followed by an I/O display. 143 */ 144 if (ddflags & C_NOERROR) { 145 if (!warned) { 146 warn("%s", in.name); 147 warned = 1; 148 summary(); 149 } 150 continue; 151 } 152 err(1, "%s", in.name); 153 } 154 } 155 156 void 157 pos_out(void) 158 { 159 struct mtop t_op; 160 off_t cnt; 161 ssize_t n; 162 163 /* 164 * If not a tape, try seeking on the file. Seeking on a pipe is 165 * going to fail, but don't protect the user -- they shouldn't 166 * have specified the seek operand. 167 */ 168 if (out.flags & (ISSEEK | ISPIPE)) { 169 errno = 0; 170 if (lseek(out.fd, seek_offset(&out), SEEK_CUR) == -1 && 171 errno != 0) 172 err(1, "%s", out.name); 173 return; 174 } 175 176 /* Don't try to read a really weird amount (like negative). */ 177 if (out.offset < 0) 178 errx(1, "%s: illegal offset", "oseek/seek"); 179 180 /* If no read access, try using mtio. */ 181 if (out.flags & NOREAD) { 182 t_op.mt_op = MTFSR; 183 t_op.mt_count = out.offset; 184 185 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 186 err(1, "%s", out.name); 187 return; 188 } 189 190 /* Read it. */ 191 for (cnt = 0; cnt < out.offset; ++cnt) { 192 before_io(); 193 n = read(out.fd, out.db, out.dbsz); 194 after_io(); 195 if (n > 0) 196 continue; 197 if (n == -1) 198 err(1, "%s", out.name); 199 200 /* 201 * If reach EOF, fill with NUL characters; first, back up over 202 * the EOF mark. Note, cnt has not yet been incremented, so 203 * the EOF read does not count as a seek'd block. 204 */ 205 t_op.mt_op = MTBSR; 206 t_op.mt_count = 1; 207 if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) 208 err(1, "%s", out.name); 209 210 while (cnt++ < out.offset) { 211 before_io(); 212 n = write(out.fd, out.db, out.dbsz); 213 after_io(); 214 if (n == -1) 215 err(1, "%s", out.name); 216 if (n != out.dbsz) 217 errx(1, "%s: write failure", out.name); 218 } 219 break; 220 } 221 } 222