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