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1d498196 MD |
1 | /* |
2 | * libringbuffer/shm.c | |
3 | * | |
e92f3e28 | 4 | * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
1d498196 | 5 | * |
e92f3e28 MD |
6 | * This library is free software; you can redistribute it and/or |
7 | * modify it under the terms of the GNU Lesser General Public | |
8 | * License as published by the Free Software Foundation; only | |
9 | * version 2.1 of the License. | |
10 | * | |
11 | * This library is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | * Lesser General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU Lesser General Public | |
17 | * License along with this library; if not, write to the Free Software | |
18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
1d498196 MD |
19 | */ |
20 | ||
21 | #include "shm.h" | |
22 | #include <unistd.h> | |
23 | #include <fcntl.h> | |
24 | #include <sys/mman.h> | |
25 | #include <sys/stat.h> /* For mode constants */ | |
26 | #include <fcntl.h> /* For O_* constants */ | |
27 | #include <assert.h> | |
8da6cd6d MD |
28 | #include <stdio.h> |
29 | #include <signal.h> | |
30 | #include <dirent.h> | |
4318ae1b | 31 | #include <lttng/align.h> |
35897f8b | 32 | #include <helper.h> |
96e80018 | 33 | #include <limits.h> |
3a81f31d MD |
34 | #include <helper.h> |
35 | ||
36 | /* | |
37 | * Ensure we have the required amount of space available by writing 0 | |
38 | * into the entire buffer. Not doing so can trigger SIGBUS when going | |
39 | * beyond the available shm space. | |
40 | */ | |
41 | static | |
42 | int zero_file(int fd, size_t len) | |
43 | { | |
44 | ssize_t retlen; | |
45 | size_t written = 0; | |
46 | char *zeropage; | |
47 | long pagelen; | |
48 | int ret; | |
49 | ||
50 | pagelen = sysconf(_SC_PAGESIZE); | |
51 | if (pagelen < 0) | |
52 | return (int) pagelen; | |
53 | zeropage = calloc(pagelen, 1); | |
54 | if (!zeropage) | |
55 | return -ENOMEM; | |
56 | ||
57 | while (len > written) { | |
58 | do { | |
59 | retlen = write(fd, zeropage, | |
60 | min_t(size_t, pagelen, len - written)); | |
61 | } while (retlen == -1UL && errno == EINTR); | |
62 | if (retlen < 0) { | |
63 | ret = (int) retlen; | |
64 | goto error; | |
65 | } | |
66 | written += retlen; | |
67 | } | |
68 | ret = 0; | |
69 | error: | |
70 | free(zeropage); | |
71 | return ret; | |
72 | } | |
1d498196 MD |
73 | |
74 | struct shm_object_table *shm_object_table_create(size_t max_nb_obj) | |
75 | { | |
76 | struct shm_object_table *table; | |
77 | ||
78 | table = zmalloc(sizeof(struct shm_object_table) + | |
79 | max_nb_obj * sizeof(table->objects[0])); | |
80 | table->size = max_nb_obj; | |
81 | return table; | |
82 | } | |
83 | ||
84 | struct shm_object *shm_object_table_append(struct shm_object_table *table, | |
85 | size_t memory_map_size) | |
86 | { | |
5a61337d | 87 | int shmfd, waitfd[2], ret, i, sigblocked = 0; |
1d498196 MD |
88 | struct shm_object *obj; |
89 | char *memory_map; | |
dda4784f | 90 | char tmp_name[NAME_MAX] = "/ust-shm-tmp-XXXXXX"; |
8da6cd6d | 91 | sigset_t all_sigs, orig_sigs; |
1d498196 MD |
92 | |
93 | if (table->allocated_len >= table->size) | |
94 | return NULL; | |
7a9c21bd | 95 | obj = &table->objects[table->allocated_len]; |
1d498196 MD |
96 | |
97 | /* wait_fd: create pipe */ | |
98 | ret = pipe(waitfd); | |
99 | if (ret < 0) { | |
100 | PERROR("pipe"); | |
101 | goto error_pipe; | |
102 | } | |
103 | for (i = 0; i < 2; i++) { | |
104 | ret = fcntl(waitfd[i], F_SETFD, FD_CLOEXEC); | |
105 | if (ret < 0) { | |
106 | PERROR("fcntl"); | |
107 | goto error_fcntl; | |
108 | } | |
109 | } | |
5d61a504 MD |
110 | /* The write end of the pipe needs to be non-blocking */ |
111 | ret = fcntl(waitfd[1], F_SETFL, O_NONBLOCK); | |
112 | if (ret < 0) { | |
113 | PERROR("fcntl"); | |
114 | goto error_fcntl; | |
115 | } | |
7a9c21bd | 116 | memcpy(obj->wait_fd, waitfd, sizeof(waitfd)); |
1d498196 MD |
117 | |
118 | /* shm_fd: create shm */ | |
119 | ||
8da6cd6d MD |
120 | /* |
121 | * Theoretically, we could leak a shm if the application crashes | |
122 | * between open and unlink. Disable signals on this thread for | |
123 | * increased safety against this scenario. | |
124 | */ | |
125 | sigfillset(&all_sigs); | |
126 | ret = pthread_sigmask(SIG_BLOCK, &all_sigs, &orig_sigs); | |
127 | if (ret == -1) { | |
128 | PERROR("pthread_sigmask"); | |
129 | goto error_pthread_sigmask; | |
130 | } | |
5a61337d | 131 | sigblocked = 1; |
8da6cd6d | 132 | |
1d498196 MD |
133 | /* |
134 | * Allocate shm, and immediately unlink its shm oject, keeping | |
135 | * only the file descriptor as a reference to the object. If it | |
136 | * already exists (caused by short race window during which the | |
137 | * global object exists in a concurrent shm_open), simply retry. | |
138 | * We specifically do _not_ use the / at the beginning of the | |
139 | * pathname so that some OS implementations can keep it local to | |
140 | * the process (POSIX leaves this implementation-defined). | |
141 | */ | |
142 | do { | |
8da6cd6d MD |
143 | /* |
144 | * Using mktemp filename with O_CREAT | O_EXCL open | |
145 | * flags. | |
146 | */ | |
147 | mktemp(tmp_name); | |
148 | if (tmp_name[0] == '\0') { | |
149 | PERROR("mktemp"); | |
150 | goto error_shm_open; | |
a8803897 | 151 | } |
8da6cd6d | 152 | shmfd = shm_open(tmp_name, |
1d498196 | 153 | O_CREAT | O_EXCL | O_RDWR, 0700); |
8da6cd6d | 154 | } while (shmfd < 0 && (errno == EEXIST || errno == EACCES)); |
1d498196 MD |
155 | if (shmfd < 0) { |
156 | PERROR("shm_open"); | |
157 | goto error_shm_open; | |
158 | } | |
8da6cd6d | 159 | ret = shm_unlink(tmp_name); |
a8803897 MD |
160 | if (ret < 0 && errno != ENOENT) { |
161 | PERROR("shm_unlink"); | |
162 | goto error_shm_release; | |
163 | } | |
5a61337d | 164 | sigblocked = 0; |
8da6cd6d MD |
165 | ret = pthread_sigmask(SIG_SETMASK, &orig_sigs, NULL); |
166 | if (ret == -1) { | |
167 | PERROR("pthread_sigmask"); | |
5a61337d | 168 | goto error_sigmask_release; |
8da6cd6d | 169 | } |
3a81f31d MD |
170 | ret = zero_file(shmfd, memory_map_size); |
171 | if (ret) { | |
172 | PERROR("zero_file"); | |
173 | goto error_zero_file; | |
174 | } | |
1d498196 MD |
175 | ret = ftruncate(shmfd, memory_map_size); |
176 | if (ret) { | |
177 | PERROR("ftruncate"); | |
178 | goto error_ftruncate; | |
179 | } | |
180 | obj->shm_fd = shmfd; | |
181 | ||
182 | /* memory_map: mmap */ | |
183 | memory_map = mmap(NULL, memory_map_size, PROT_READ | PROT_WRITE, | |
184 | MAP_SHARED, shmfd, 0); | |
185 | if (memory_map == MAP_FAILED) { | |
186 | PERROR("mmap"); | |
187 | goto error_mmap; | |
188 | } | |
189 | obj->memory_map = memory_map; | |
190 | obj->memory_map_size = memory_map_size; | |
191 | obj->allocated_len = 0; | |
dc613eb9 | 192 | obj->index = table->allocated_len++; |
7a9c21bd | 193 | |
1d498196 MD |
194 | return obj; |
195 | ||
196 | error_mmap: | |
197 | error_ftruncate: | |
a8803897 | 198 | error_shm_release: |
3a81f31d | 199 | error_zero_file: |
5a61337d | 200 | error_sigmask_release: |
1d498196 MD |
201 | ret = close(shmfd); |
202 | if (ret) { | |
203 | PERROR("close"); | |
204 | assert(0); | |
205 | } | |
206 | error_shm_open: | |
5a61337d MD |
207 | if (sigblocked) { |
208 | ret = pthread_sigmask(SIG_SETMASK, &orig_sigs, NULL); | |
209 | if (ret == -1) { | |
210 | PERROR("pthread_sigmask"); | |
211 | } | |
212 | } | |
8da6cd6d | 213 | error_pthread_sigmask: |
1d498196 MD |
214 | error_fcntl: |
215 | for (i = 0; i < 2; i++) { | |
216 | ret = close(waitfd[i]); | |
217 | if (ret) { | |
218 | PERROR("close"); | |
219 | assert(0); | |
220 | } | |
221 | } | |
222 | error_pipe: | |
1d498196 MD |
223 | return NULL; |
224 | ||
225 | } | |
226 | ||
193183fb MD |
227 | struct shm_object *shm_object_table_append_shadow(struct shm_object_table *table, |
228 | int shm_fd, int wait_fd, size_t memory_map_size) | |
229 | { | |
230 | struct shm_object *obj; | |
231 | char *memory_map; | |
232 | ||
233 | if (table->allocated_len >= table->size) | |
234 | return NULL; | |
235 | obj = &table->objects[table->allocated_len]; | |
236 | ||
237 | /* wait_fd: set read end of the pipe. */ | |
238 | obj->wait_fd[0] = wait_fd; | |
239 | obj->wait_fd[1] = -1; /* write end is unset. */ | |
240 | obj->shm_fd = shm_fd; | |
241 | ||
242 | /* memory_map: mmap */ | |
243 | memory_map = mmap(NULL, memory_map_size, PROT_READ | PROT_WRITE, | |
244 | MAP_SHARED, shm_fd, 0); | |
245 | if (memory_map == MAP_FAILED) { | |
246 | PERROR("mmap"); | |
247 | goto error_mmap; | |
248 | } | |
249 | obj->memory_map = memory_map; | |
250 | obj->memory_map_size = memory_map_size; | |
251 | obj->allocated_len = memory_map_size; | |
252 | obj->index = table->allocated_len++; | |
253 | ||
254 | return obj; | |
255 | ||
256 | error_mmap: | |
257 | return NULL; | |
258 | } | |
259 | ||
1d498196 MD |
260 | static |
261 | void shmp_object_destroy(struct shm_object *obj) | |
262 | { | |
263 | int ret, i; | |
264 | ||
7a784989 MD |
265 | if (!obj->is_shadow) { |
266 | ret = munmap(obj->memory_map, obj->memory_map_size); | |
267 | if (ret) { | |
268 | PERROR("umnmap"); | |
269 | assert(0); | |
270 | } | |
271 | } | |
ef9ff354 MD |
272 | if (obj->shm_fd >= 0) { |
273 | ret = close(obj->shm_fd); | |
274 | if (ret) { | |
275 | PERROR("close"); | |
276 | assert(0); | |
277 | } | |
1d498196 MD |
278 | } |
279 | for (i = 0; i < 2; i++) { | |
824f40b8 MD |
280 | if (obj->wait_fd[i] < 0) |
281 | continue; | |
1d498196 MD |
282 | ret = close(obj->wait_fd[i]); |
283 | if (ret) { | |
284 | PERROR("close"); | |
285 | assert(0); | |
286 | } | |
287 | } | |
288 | } | |
289 | ||
290 | void shm_object_table_destroy(struct shm_object_table *table) | |
291 | { | |
292 | int i; | |
293 | ||
294 | for (i = 0; i < table->allocated_len; i++) | |
295 | shmp_object_destroy(&table->objects[i]); | |
296 | free(table); | |
297 | } | |
298 | ||
299 | /* | |
300 | * zalloc_shm - allocate memory within a shm object. | |
301 | * | |
302 | * Shared memory is already zeroed by shmget. | |
303 | * *NOT* multithread-safe (should be protected by mutex). | |
304 | * Returns a -1, -1 tuple on error. | |
305 | */ | |
306 | struct shm_ref zalloc_shm(struct shm_object *obj, size_t len) | |
307 | { | |
308 | struct shm_ref ref; | |
309 | struct shm_ref shm_ref_error = { -1, -1 }; | |
310 | ||
311 | if (obj->memory_map_size - obj->allocated_len < len) | |
312 | return shm_ref_error; | |
313 | ref.index = obj->index; | |
314 | ref.offset = obj->allocated_len; | |
315 | obj->allocated_len += len; | |
316 | return ref; | |
317 | } | |
318 | ||
319 | void align_shm(struct shm_object *obj, size_t align) | |
320 | { | |
321 | size_t offset_len = offset_align(obj->allocated_len, align); | |
322 | obj->allocated_len += offset_len; | |
323 | } |