Introduce --min-complete.
[dss.git] / ipc.c
1 #include <sys/wait.h>
2 #include <stdio.h>
3 #include <inttypes.h>
4 #include <stdlib.h>
5 #include <unistd.h>
6 #include <errno.h>
7 #include <sys/types.h>
8 #include <sys/ipc.h>
9 #include <sys/sem.h>
10 #include <string.h>
11 #include <assert.h>
12 #include <sys/stat.h>
13 #include <stddef.h>
14 #include <limits.h>
15 #include <sys/param.h>
16
17 #include "gcc-compat.h"
18 #include "str.h"
19 #include "log.h"
20 #include "gcc-compat.h"
21 #include "err.h"
22 #include "ipc.h"
23
24 #if (defined(__GNUC__) && defined(__i386__))
25 #define get16bits(d) (*((const uint16_t *) (d)))
26 #else
27 #define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
28 +(uint32_t)(((const uint8_t *)(d))[0]) )
29 #endif
30
31 /*
32 * SuperFastHash, by Paul Hsieh.
33 * http://www.azillionmonkeys.com/qed/hash.html
34 */
35 static uint32_t super_fast_hash(const uint8_t *data, uint32_t len, uint32_t hash)
36 {
37 uint32_t tmp;
38 int rem = len & 3;
39
40 len >>= 2;
41
42 for (;len > 0; len--) {
43 hash += get16bits (data);
44 tmp = (get16bits (data+2) << 11) ^ hash;
45 hash = (hash << 16) ^ tmp;
46 data += 2*sizeof (uint16_t);
47 hash += hash >> 11;
48 }
49
50 /* Handle end cases */
51 switch (rem) {
52 case 3:
53 hash += get16bits (data);
54 hash ^= hash << 16;
55 hash ^= data[sizeof (uint16_t)] << 18;
56 hash += hash >> 11;
57 break;
58 case 2:
59 hash += get16bits (data);
60 hash ^= hash << 11;
61 hash += hash >> 17;
62 break;
63 case 1:
64 hash += *data;
65 hash ^= hash << 10;
66 hash += hash >> 1;
67 }
68 /* Force "avalanching" of final 127 bits */
69 hash ^= hash << 3;
70 hash += hash >> 5;
71 hash ^= hash << 4;
72 hash += hash >> 17;
73 hash ^= hash << 25;
74 hash += hash >> 6;
75 return hash;
76 }
77
78 /*
79 * Return the canonical absolute name of a given file name.
80 *
81 * Slightly modified version of glibc's realpath, Copyright (C)
82 * 1996-2002,2004,2005,2006,2008 Free Software Foundation, Inc.
83 *
84 * A canonical name does not contain any `.', `..' components nor any repeated
85 * path separators ('/') or symlinks. All path components must exist. The
86 * result is malloc'd and must be freed by the caller.
87 */
88 static int dss_realpath(const char *name, char **resolved_path)
89 {
90 char *rpath = NULL, *dest, *extra_buf = NULL;
91 const char *start, *end, *rpath_limit;
92 long int path_max;
93 int ret, num_links = 0;
94
95 if (name[0] == '\0') {
96 /*
97 * As per Single Unix Specification V2 we must return an error
98 * if the name argument points to an empty string.
99 */
100 ret = -ERRNO_TO_DSS_ERROR(ENOENT);
101 goto error;
102 }
103 #ifdef PATH_MAX
104 path_max = PATH_MAX;
105 #else
106 /*
107 * From realpath(3): Asking pathconf(3) does not really help, since on
108 * the one hand POSIX warns that the result of pathconf(3) may be
109 * huge and unsuitable for mallocing memory. And on the other hand
110 * pathconf(3) may return -1 to signify that PATH_MAX is not bounded.
111 */
112 path_max = pathconf(name, _PC_PATH_MAX);
113 if (path_max <= 0 || path_max >= 4096)
114 path_max = 4096;
115 #endif
116 rpath = dss_malloc(path_max);
117 rpath_limit = rpath + path_max;
118
119 if (name[0] != '/') {
120 if (!getcwd(rpath, path_max)) {
121 ret = -ERRNO_TO_DSS_ERROR(errno);
122 goto error;
123 }
124 dest = memchr(rpath, '\0', path_max);
125 } else {
126 rpath[0] = '/';
127 dest = rpath + 1;
128 }
129
130 for (start = end = name; *start; start = end) {
131 struct stat st;
132 int n;
133
134 /* Skip sequence of multiple path-separators. */
135 while (*start == '/')
136 ++start;
137
138 /* Find end of path component. */
139 for (end = start; *end && *end != '/'; ++end)
140 /* Nothing. */ ;
141
142 if (end - start == 0)
143 break;
144 else if (end - start == 1 && start[0] == '.')
145 /* nothing */ ;
146 else if (end - start == 2 && start[0] == '.' && start[1] == '.') {
147 /* Back up to previous component, ignore if at root already. */
148 if (dest > rpath + 1)
149 while ((--dest)[-1] != '/') ;
150 } else {
151 size_t new_size;
152
153 if (dest[-1] != '/')
154 *dest++ = '/';
155
156 if (dest + (end - start) >= rpath_limit) {
157 ptrdiff_t dest_offset = dest - rpath;
158
159 new_size = rpath_limit - rpath;
160 if (end - start + 1 > path_max)
161 new_size += end - start + 1;
162 else
163 new_size += path_max;
164 rpath = dss_realloc(rpath, new_size);
165 rpath_limit = rpath + new_size;
166 dest = rpath + dest_offset;
167 }
168
169 memcpy(dest, start, end - start);
170 dest += end - start;
171 *dest = '\0';
172
173 if (stat(rpath, &st) < 0) {
174 ret = -ERRNO_TO_DSS_ERROR(errno);
175 goto error;
176 }
177
178 if (S_ISLNK(st.st_mode)) {
179 char *buf = alloca(path_max);
180 size_t len;
181
182 if (++num_links > MAXSYMLINKS) {
183 ret = -ERRNO_TO_DSS_ERROR(ELOOP);
184 goto error;
185 }
186
187 n = readlink(rpath, buf, path_max - 1);
188 if (n < 0) {
189 ret = -ERRNO_TO_DSS_ERROR(errno);
190 goto error;
191 }
192 buf[n] = '\0';
193
194 if (!extra_buf)
195 extra_buf = alloca(path_max);
196
197 len = strlen(end);
198 if ((long int) (n + len) >= path_max) {
199 ret = -ERRNO_TO_DSS_ERROR(ENAMETOOLONG);
200 goto error;
201 }
202
203 /* Careful here, end may be a pointer into extra_buf... */
204 memmove(&extra_buf[n], end, len + 1);
205 name = end = memcpy(extra_buf, buf, n);
206
207 if (buf[0] == '/') /* It's an absolute symlink */
208 dest = rpath + 1;
209 else /* Back up to previous component, ignore if at root already: */
210 if (dest > rpath + 1)
211 while ((--dest)[-1] != '/')
212 ; /* nothing */
213 } else if (!S_ISDIR(st.st_mode) && *end != '\0') {
214 ret = -ERRNO_TO_DSS_ERROR(ENOTDIR);
215 goto error;
216 }
217 }
218 }
219 if (dest > rpath + 1 && dest[-1] == '/')
220 --dest;
221 *dest = '\0';
222 *resolved_path = rpath;
223 return 1;
224 error:
225 free(rpath);
226 *resolved_path = NULL;
227 return ret;
228 }
229
230 static inline int get_key_or_die(char *config_file)
231 {
232 int ret;
233 struct stat statbuf;
234 char *rpath;
235
236 assert(config_file);
237 if (stat(config_file, &statbuf) == 0) {
238 ret = dss_realpath(config_file, &rpath);
239 if (ret < 0) {
240 DSS_EMERG_LOG(("could not resolve path %s: %s\n", config_file,
241 dss_strerror(-ret)));
242 exit(EXIT_FAILURE);
243 }
244 DSS_DEBUG_LOG(("resolved path: %s\n", rpath));
245 } else
246 /*
247 * This happens if the user did not specify a config file, and
248 * the default config file does not exist. Another (unlikely)
249 * possibility is that the config file was removed between
250 * startup and this call. We don't care about these corner
251 * cases too much and just use the unresolved path in this
252 * case.
253 */
254 rpath = dss_strdup(config_file);
255 ret = super_fast_hash((uint8_t *)rpath, strlen(rpath), 0) >> 1;
256 free(rpath);
257 return ret;
258 }
259
260 static int mutex_get(int key, int flags)
261 {
262 int ret;
263
264 DSS_DEBUG_LOG(("getting semaphore 0x%x\n", key));
265 ret = semget(key, 2, flags);
266 if (ret < 0)
267 return -ERRNO_TO_DSS_ERROR(errno);
268 return ret;
269 }
270
271 static int do_semop(int id, struct sembuf *sops, int num)
272 {
273 int ret;
274
275 DSS_DEBUG_LOG(("calling semop\n"));
276 do {
277 ret = semop(id, sops, num);
278 if (ret >= 0)
279 return 1;
280 } while (errno == EINTR);
281 return -ERRNO_TO_DSS_ERROR(errno);
282 }
283
284 static int mutex_lock(int id)
285 {
286 struct sembuf sops[4];
287 int ret;
288
289 DSS_DEBUG_LOG(("locking\n"));
290
291 sops[0].sem_num = 0;
292 sops[0].sem_op = 0;
293 sops[0].sem_flg = SEM_UNDO | IPC_NOWAIT;
294
295 sops[1].sem_num = 0;
296 sops[1].sem_op = 1;
297 sops[1].sem_flg = SEM_UNDO | IPC_NOWAIT;
298
299 sops[2].sem_num = 1;
300 sops[2].sem_op = 0;
301 sops[2].sem_flg = SEM_UNDO | IPC_NOWAIT;
302
303 sops[3].sem_num = 1;
304 sops[3].sem_op = 1;
305 sops[3].sem_flg = SEM_UNDO | IPC_NOWAIT;
306
307 ret = do_semop(id, sops, 4);
308 if (ret < 0)
309 return -ERRNO_TO_DSS_ERROR(errno);
310 return 1;
311 }
312
313 static int mutex_try_lock(int id)
314 {
315 struct sembuf sops[2];
316 int ret;
317
318 DSS_DEBUG_LOG(("trying to lock\n"));
319
320 sops[0].sem_num = 0;
321 sops[0].sem_op = 0;
322 sops[0].sem_flg = SEM_UNDO | IPC_NOWAIT;
323
324 sops[1].sem_num = 0;
325 sops[1].sem_op = 1;
326 sops[1].sem_flg = SEM_UNDO | IPC_NOWAIT;
327
328 ret = do_semop(id, sops, 2);
329 if (ret < 0)
330 return -ERRNO_TO_DSS_ERROR(errno);
331 return 1;
332 }
333
334 int lock_dss(char *config_file)
335 {
336 int ret, key = get_key_or_die(config_file);
337
338 ret = mutex_get(key, IPC_CREAT | 0600);
339 if (ret < 0)
340 return ret;
341 return mutex_lock(ret);
342 }
343
344 int get_dss_pid(char *config_file, pid_t *pid)
345 {
346 int ret, semid, key = get_key_or_die(config_file);
347
348 ret = mutex_get(key, 0);
349 if (ret < 0)
350 return ret;
351 semid = ret;
352 ret = semctl(semid, 1, GETPID);
353 if (ret < 0)
354 return -E_NOT_RUNNING;
355 *pid = ret;
356 ret = mutex_try_lock(semid);
357 if (ret >= 0)
358 return -E_NOT_RUNNING;
359 return 1;
360 }