1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93";
37 #endif /* LIBC_SCCS and not lint */
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
40
41 #include "namespace.h"
42 #include <sys/types.h>
43 #include <sys/stat.h>
44 #include <fcntl.h>
45 #include <errno.h>
46 #include <limits.h>
47 #include <unistd.h>
48 #include <stdio.h>
49 #include <stdlib.h>
50 #include "un-namespace.h"
51 #include "libc_private.h"
52 #include "local.h"
53
54 /*
55 * Re-direct an existing, open (probably) file to some other file.
56 * ANSI is written such that the original file gets closed if at
57 * all possible, no matter what.
58 */
59 FILE *
freopen(const char * __restrict file,const char * __restrict mode,FILE * __restrict fp)60 freopen(const char * __restrict file, const char * __restrict mode,
61 FILE * __restrict fp)
62 {
63 int f;
64 int dflags, flags, isopen, oflags, sverrno, wantfd;
65
66 if ((flags = __sflags(mode, &oflags)) == 0) {
67 sverrno = errno;
68 (void) fclose(fp);
69 errno = sverrno;
70 return (NULL);
71 }
72
73 FLOCKFILE_CANCELSAFE(fp);
74
75 if (!__sdidinit)
76 __sinit();
77
78 /*
79 * If the filename is a NULL pointer, the caller is asking us to
80 * re-open the same file with a different mode. We allow this only
81 * if the modes are compatible.
82 */
83 if (file == NULL) {
84 /* See comment below regarding freopen() of closed files. */
85 if (fp->_flags == 0) {
86 errno = EINVAL;
87 fp = NULL;
88 goto end;
89 }
90 if ((dflags = _fcntl(fp->_file, F_GETFL)) < 0) {
91 sverrno = errno;
92 fclose(fp);
93 errno = sverrno;
94 fp = NULL;
95 goto end;
96 }
97 /* Work around incorrect O_ACCMODE. */
98 if ((dflags & O_ACCMODE) != O_RDWR &&
99 (dflags & (O_ACCMODE | O_EXEC)) != (oflags & O_ACCMODE)) {
100 fclose(fp);
101 errno = EBADF;
102 fp = NULL;
103 goto end;
104 }
105 if (fp->_flags & __SWR)
106 (void) __sflush(fp);
107 if ((oflags ^ dflags) & O_APPEND) {
108 dflags &= ~O_APPEND;
109 dflags |= oflags & O_APPEND;
110 if (_fcntl(fp->_file, F_SETFL, dflags) < 0) {
111 sverrno = errno;
112 fclose(fp);
113 errno = sverrno;
114 fp = NULL;
115 goto end;
116 }
117 }
118 if (oflags & O_TRUNC)
119 (void) ftruncate(fp->_file, (off_t)0);
120 if (!(oflags & O_APPEND))
121 (void) _sseek(fp, (fpos_t)0, SEEK_SET);
122 if (oflags & O_CLOEXEC)
123 (void) _fcntl(fp->_file, F_SETFD, FD_CLOEXEC);
124 f = fp->_file;
125 isopen = 0;
126 wantfd = -1;
127 goto finish;
128 }
129
130 /*
131 * There are actually programs that depend on being able to "freopen"
132 * descriptors that weren't originally open. Keep this from breaking.
133 * Remember whether the stream was open to begin with, and which file
134 * descriptor (if any) was associated with it. If it was attached to
135 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
136 * should work. This is unnecessary if it was not a Unix file.
137 */
138 if (fp->_flags == 0) {
139 fp->_flags = __SEOF; /* hold on to it */
140 isopen = 0;
141 wantfd = -1;
142 } else {
143 /* flush the stream; ANSI doesn't require this. */
144 if (fp->_flags & __SWR)
145 (void) __sflush(fp);
146 /* if close is NULL, closing is a no-op, hence pointless */
147 isopen = fp->_close != NULL;
148 if ((wantfd = fp->_file) < 0 && isopen) {
149 (void) (*fp->_close)(fp->_cookie);
150 isopen = 0;
151 }
152 }
153
154 /* Get a new descriptor to refer to the new file. */
155 f = _open(file, oflags, DEFFILEMODE);
156 /* If out of fd's close the old one and try again. */
157 if (f < 0 && isopen && wantfd > STDERR_FILENO &&
158 (errno == ENFILE || errno == EMFILE)) {
159 (void) (*fp->_close)(fp->_cookie);
160 isopen = 0;
161 wantfd = -1;
162 f = _open(file, oflags, DEFFILEMODE);
163 }
164 sverrno = errno;
165
166 finish:
167 /*
168 * Finish closing fp. Even if the open succeeded above, we cannot
169 * keep fp->_base: it may be the wrong size. This loses the effect
170 * of any setbuffer calls, but stdio has always done this before.
171 *
172 * Leave the existing file descriptor open until dup2() is called
173 * below to avoid races where a concurrent open() in another thread
174 * could claim the existing descriptor.
175 */
176 if (fp->_flags & __SMBF)
177 free((char *)fp->_bf._base);
178 fp->_w = 0;
179 fp->_r = 0;
180 fp->_p = NULL;
181 fp->_bf._base = NULL;
182 fp->_bf._size = 0;
183 fp->_lbfsize = 0;
184 if (HASUB(fp))
185 FREEUB(fp);
186 fp->_ub._size = 0;
187 if (HASLB(fp))
188 FREELB(fp);
189 fp->_lb._size = 0;
190 fp->_orientation = 0;
191 memset(&fp->_mbstate, 0, sizeof(mbstate_t));
192 fp->_flags2 = 0;
193
194 if (f < 0) { /* did not get it after all */
195 if (isopen)
196 (void) (*fp->_close)(fp->_cookie);
197 fp->_flags = 0; /* set it free */
198 errno = sverrno; /* restore in case _close clobbered */
199 fp = NULL;
200 goto end;
201 }
202
203 /*
204 * If reopening something that was open before on a real file, try
205 * to maintain the descriptor. Various C library routines (perror)
206 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
207 */
208 if (wantfd >= 0) {
209 if ((oflags & O_CLOEXEC ? _fcntl(f, F_DUP2FD_CLOEXEC, wantfd) :
210 _dup2(f, wantfd)) >= 0) {
211 (void)_close(f);
212 f = wantfd;
213 } else
214 (void)_close(fp->_file);
215 }
216
217 /*
218 * File descriptors are a full int, but _file is only a short.
219 * If we get a valid file descriptor that is greater than
220 * SHRT_MAX, then the fd will get sign-extended into an
221 * invalid file descriptor. Handle this case by failing the
222 * open.
223 */
224 if (f > SHRT_MAX) {
225 fp->_flags = 0; /* set it free */
226 errno = EMFILE;
227 fp = NULL;
228 goto end;
229 }
230
231 fp->_flags = flags;
232 fp->_file = f;
233 fp->_cookie = fp;
234 fp->_read = __sread;
235 fp->_write = __swrite;
236 fp->_seek = __sseek;
237 fp->_close = __sclose;
238 /*
239 * When opening in append mode, even though we use O_APPEND,
240 * we need to seek to the end so that ftell() gets the right
241 * answer. If the user then alters the seek pointer, or
242 * the file extends, this will fail, but there is not much
243 * we can do about this. (We could set __SAPP and check in
244 * fseek and ftell.)
245 */
246 if (oflags & O_APPEND) {
247 fp->_flags2 |= __S2OAP;
248 (void) _sseek(fp, (fpos_t)0, SEEK_END);
249 }
250 end:
251 FUNLOCKFILE_CANCELSAFE();
252 return (fp);
253 }
254