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2b778ceb | 1 | /* Copyright (C) 2002-2021 Free Software Foundation, Inc. |
76a50749 UD |
2 | This file is part of the GNU C Library. |
3 | Contributed by Ulrich Drepper <drepper@redhat.com>, 2002. | |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
59ba27a6 | 16 | License along with the GNU C Library; if not, see |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
76a50749 | 18 | |
76a50749 | 19 | #include <fcntl.h> |
76a50749 UD |
20 | #include <semaphore.h> |
21 | #include <stdarg.h> | |
76a50749 UD |
22 | #include <unistd.h> |
23 | #include <sys/mman.h> | |
76a50749 | 24 | #include "semaphoreP.h" |
e4f639e4 | 25 | #include <shm-directory.h> |
da4aea0b | 26 | #include <sem_routines.h> |
a2f0363f | 27 | #include <futex-internal.h> |
91dd866f | 28 | #include <libc-lock.h> |
76a50749 | 29 | |
0b7d48d1 FW |
30 | #if !PTHREAD_IN_LIBC |
31 | /* The private names are not exported from libc. */ | |
32 | # define __link link | |
33 | # define __unlink unlink | |
34 | #endif | |
35 | ||
76a50749 | 36 | sem_t * |
0b7d48d1 | 37 | __sem_open (const char *name, int oflag, ...) |
76a50749 | 38 | { |
76a50749 | 39 | int fd; |
e4f639e4 | 40 | sem_t *result; |
76a50749 | 41 | |
a2f0363f TR |
42 | /* Check that shared futexes are supported. */ |
43 | int err = futex_supports_pshared (PTHREAD_PROCESS_SHARED); | |
44 | if (err != 0) | |
45 | { | |
46 | __set_errno (err); | |
47 | return SEM_FAILED; | |
48 | } | |
49 | ||
e9fed243 FW |
50 | struct shmdir_name dirname; |
51 | if (__shm_get_name (&dirname, name, true) != 0) | |
52 | { | |
53 | __set_errno (EINVAL); | |
54 | return SEM_FAILED; | |
55 | } | |
76a50749 | 56 | |
91dd866f AZ |
57 | /* Disable asynchronous cancellation. */ |
58 | #ifdef __libc_ptf_call | |
59 | int state; | |
60 | __libc_ptf_call (__pthread_setcancelstate, | |
61 | (PTHREAD_CANCEL_DISABLE, &state), 0); | |
62 | #endif | |
63 | ||
76a50749 | 64 | /* If the semaphore object has to exist simply open it. */ |
3857ca78 | 65 | if ((oflag & O_CREAT) == 0 || (oflag & O_EXCL) == 0) |
76a50749 | 66 | { |
3857ca78 | 67 | try_again: |
0b7d48d1 FW |
68 | fd = __open (dirname.name, |
69 | (oflag & ~(O_CREAT|O_ACCMODE)) | O_NOFOLLOW | O_RDWR); | |
76a50749 UD |
70 | |
71 | if (fd == -1) | |
3857ca78 UD |
72 | { |
73 | /* If we are supposed to create the file try this next. */ | |
fddfebbd | 74 | if ((oflag & O_CREAT) != 0 && errno == ENOENT) |
3857ca78 | 75 | goto try_create; |
76a50749 | 76 | |
3857ca78 UD |
77 | /* Return. errno is already set. */ |
78 | } | |
79 | else | |
dcfc8224 UD |
80 | /* Check whether we already have this semaphore mapped and |
81 | create one if necessary. */ | |
da4aea0b | 82 | result = __sem_check_add_mapping (name, fd, SEM_FAILED); |
76a50749 UD |
83 | } |
84 | else | |
85 | { | |
86 | /* We have to open a temporary file first since it must have the | |
87 | correct form before we can start using it. */ | |
76a50749 UD |
88 | mode_t mode; |
89 | unsigned int value; | |
90 | va_list ap; | |
91 | ||
3857ca78 | 92 | try_create: |
76a50749 UD |
93 | va_start (ap, oflag); |
94 | ||
95 | mode = va_arg (ap, mode_t); | |
96 | value = va_arg (ap, unsigned int); | |
97 | ||
98 | va_end (ap); | |
99 | ||
100 | if (value > SEM_VALUE_MAX) | |
101 | { | |
102 | __set_errno (EINVAL); | |
91dd866f AZ |
103 | result = SEM_FAILED; |
104 | goto out; | |
76a50749 UD |
105 | } |
106 | ||
76a50749 | 107 | /* Create the initial file content. */ |
5efe8650 UD |
108 | union |
109 | { | |
110 | sem_t initsem; | |
111 | struct new_sem newsem; | |
112 | } sem; | |
76a50749 | 113 | |
a28296e7 | 114 | __new_sem_open_init (&sem.newsem, value); |
76a50749 UD |
115 | |
116 | /* Initialize the remaining bytes as well. */ | |
5efe8650 | 117 | memset ((char *) &sem.initsem + sizeof (struct new_sem), '\0', |
3d2dd6ca | 118 | sizeof (sem_t) - sizeof (struct new_sem)); |
76a50749 | 119 | |
e9fed243 | 120 | char tmpfname[] = SHMDIR "sem.XXXXXX"; |
fddfebbd UD |
121 | int retries = 0; |
122 | #define NRETRIES 50 | |
123 | while (1) | |
124 | { | |
fddfebbd UD |
125 | /* We really want to use mktemp here. We cannot use mkstemp |
126 | since the file must be opened with a specific mode. The | |
127 | mode cannot later be set since then we cannot apply the | |
128 | file create mask. */ | |
cfa8054f | 129 | if (__mktemp (tmpfname) == NULL) |
91dd866f AZ |
130 | { |
131 | result = SEM_FAILED; | |
132 | goto out; | |
133 | } | |
fddfebbd UD |
134 | |
135 | /* Open the file. Make sure we do not overwrite anything. */ | |
0b7d48d1 | 136 | fd = __open (tmpfname, O_RDWR | O_CREAT | O_EXCL, mode); |
fddfebbd UD |
137 | if (fd == -1) |
138 | { | |
139 | if (errno == EEXIST) | |
140 | { | |
141 | if (++retries < NRETRIES) | |
e9fed243 FW |
142 | { |
143 | /* Restore the six placeholder bytes before the | |
144 | null terminator before the next attempt. */ | |
145 | memcpy (tmpfname + sizeof (tmpfname) - 7, "XXXXXX", 6); | |
146 | continue; | |
147 | } | |
fddfebbd UD |
148 | |
149 | __set_errno (EAGAIN); | |
150 | } | |
151 | ||
91dd866f AZ |
152 | result = SEM_FAILED; |
153 | goto out; | |
fddfebbd UD |
154 | } |
155 | ||
156 | /* We got a file. */ | |
157 | break; | |
158 | } | |
159 | ||
173e0ab0 | 160 | if (TEMP_FAILURE_RETRY (write (fd, &sem.initsem, sizeof (sem_t))) |
3857ca78 | 161 | == sizeof (sem_t) |
3857ca78 | 162 | /* Map the sem_t structure from the file. */ |
0b7d48d1 FW |
163 | && (result = (sem_t *) __mmap (NULL, sizeof (sem_t), |
164 | PROT_READ | PROT_WRITE, MAP_SHARED, | |
165 | fd, 0)) != MAP_FAILED) | |
76a50749 | 166 | { |
3857ca78 | 167 | /* Create the file. Don't overwrite an existing file. */ |
0b7d48d1 | 168 | if (__link (tmpfname, dirname.name) != 0) |
3857ca78 | 169 | { |
3857ca78 | 170 | /* Undo the mapping. */ |
0b7d48d1 | 171 | __munmap (result, sizeof (sem_t)); |
76a50749 | 172 | |
3857ca78 UD |
173 | /* Reinitialize 'result'. */ |
174 | result = SEM_FAILED; | |
175 | ||
176 | /* This failed. If O_EXCL is not set and the problem was | |
177 | that the file exists, try again. */ | |
178 | if ((oflag & O_EXCL) == 0 && errno == EEXIST) | |
73983ece UD |
179 | { |
180 | /* Remove the file. */ | |
0b7d48d1 | 181 | __unlink (tmpfname); |
73983ece UD |
182 | |
183 | /* Close the file. */ | |
0b7d48d1 | 184 | __close (fd); |
73983ece UD |
185 | |
186 | goto try_again; | |
187 | } | |
76a50749 | 188 | } |
fddfebbd UD |
189 | else |
190 | /* Insert the mapping into the search tree. This also | |
191 | determines whether another thread sneaked by and already | |
192 | added such a mapping despite the fact that we created it. */ | |
da4aea0b | 193 | result = __sem_check_add_mapping (name, fd, result); |
76a50749 | 194 | } |
76a50749 | 195 | |
3857ca78 UD |
196 | /* Now remove the temporary name. This should never fail. If |
197 | it fails we leak a file name. Better fix the kernel. */ | |
0b7d48d1 | 198 | __unlink (tmpfname); |
76a50749 UD |
199 | } |
200 | ||
3857ca78 UD |
201 | /* Map the mmap error to the error we need. */ |
202 | if (MAP_FAILED != (void *) SEM_FAILED && result == MAP_FAILED) | |
203 | result = SEM_FAILED; | |
204 | ||
76a50749 | 205 | /* We don't need the file descriptor anymore. */ |
73983ece | 206 | if (fd != -1) |
fddfebbd UD |
207 | { |
208 | /* Do not disturb errno. */ | |
e4f639e4 | 209 | int save = errno; |
0b7d48d1 | 210 | __close (fd); |
e4f639e4 | 211 | errno = save; |
fddfebbd | 212 | } |
76a50749 | 213 | |
91dd866f AZ |
214 | out: |
215 | #ifdef __libc_ptf_call | |
216 | __libc_ptf_call (__pthread_setcancelstate, (state, NULL), 0); | |
217 | #endif | |
218 | ||
76a50749 UD |
219 | return result; |
220 | } | |
0b7d48d1 FW |
221 | #if PTHREAD_IN_LIBC |
222 | versioned_symbol (libc, __sem_open, sem_open, GLIBC_2_34); | |
223 | # if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_1_1, GLIBC_2_34) | |
224 | compat_symbol (libpthread, __sem_open, sem_open, GLIBC_2_1_1); | |
225 | # endif | |
226 | #else /* !PTHREAD_IN_LIBC */ | |
227 | strong_alias (__sem_open, sem_open) | |
228 | #endif |