1 /*- 2 * Copyright (c) 1991, 1993, 1994 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Keith Muller of the University of California, San Diego and Lance 7 * Visser of Convex Computer Corporation. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 #ifndef lint 35 #if 0 36 static char sccsid[] = "@(#)position.c 8.3 (Berkeley) 4/2/94"; 37 #endif 38 #endif /* not lint */ 39 #include <sys/cdefs.h> 40 __FBSDID("$FreeBSD$"); 41 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 > 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 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 ((size_t)n != out.dbsz) 211 errx(1, "%s: write failure", out.name); 212 } 213 break; 214 } 215 } 216