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
seek_offset(IO * io)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
pos_in(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
pos_out(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