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