1 /*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33 #include <errno.h>
34 #include <signal.h>
35 #include <stdio.h>
36 #include <stdlib.h>
37 #include <sys/stat.h>
38 #include <sys/types.h>
39 #include <unistd.h>
40
41 #include "private/ErrnoRestorer.h"
42
43 class ScopedSignalBlocker {
44 public:
ScopedSignalBlocker()45 ScopedSignalBlocker() {
46 sigset_t set;
47 sigfillset(&set);
48 sigprocmask(SIG_BLOCK, &set, &old_set_);
49 }
50
~ScopedSignalBlocker()51 ~ScopedSignalBlocker() {
52 sigprocmask(SIG_SETMASK, &old_set_, NULL);
53 }
54
55 private:
56 sigset_t old_set_;
57 };
58
__tmpfile_dir(const char * tmp_dir)59 static FILE* __tmpfile_dir(const char* tmp_dir) {
60 char buf[PATH_MAX];
61 int path_length = snprintf(buf, sizeof(buf), "%s/tmp.XXXXXXXXXX", tmp_dir);
62 if (path_length >= static_cast<int>(sizeof(buf))) {
63 return NULL;
64 }
65
66 int fd;
67 {
68 ScopedSignalBlocker ssb;
69 fd = mkstemp(buf);
70 if (fd == -1) {
71 return NULL;
72 }
73
74 // Unlink the file now so that it's removed when closed.
75 unlink(buf);
76
77 // Can we still use the file now it's unlinked?
78 // File systems without hard link support won't have the usual Unix semantics.
79 struct stat sb;
80 int rc = fstat(fd, &sb);
81 if (rc == -1) {
82 ErrnoRestorer errno_restorer;
83 close(fd);
84 return NULL;
85 }
86 }
87
88 // Turn the file descriptor into a FILE*.
89 FILE* fp = fdopen(fd, "w+");
90 if (fp != NULL) {
91 return fp;
92 }
93
94 // Failure. Clean up. We already unlinked, so we just need to close.
95 ErrnoRestorer errno_restorer;
96 close(fd);
97 return NULL;
98 }
99
tmpfile()100 FILE* tmpfile() {
101 // TODO: get this app's temporary directory from the framework ("/data/data/app/cache").
102
103 // $EXTERNAL_STORAGE turns out not to be very useful because it doesn't support hard links.
104 // This means we can't do the usual trick of calling unlink before handing the file back.
105
106 FILE* fp = __tmpfile_dir("/data/local/tmp");
107 if (fp == NULL) {
108 // P_tmpdir is "/tmp/", but POSIX explicitly says that tmpdir(3) should try P_tmpdir before
109 // giving up. This is potentially useful for bionic on the host anyway.
110 fp = __tmpfile_dir(P_tmpdir);
111 }
112 return fp;
113 }
114