1 /* $NetBSD: semtest.c,v 1.3 2001/02/19 22:44:41 cgd Exp $ */ 2 3 /*- 4 * Copyright (c) 1999 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 9 * NASA Ames Research Center. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the NetBSD 22 * Foundation, Inc. and its contributors. 23 * 4. Neither the name of The NetBSD Foundation nor the names of its 24 * contributors may be used to endorse or promote products derived 25 * from this software without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37 * POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 /* 41 * Test the SVID-compatible Semaphore facility. 42 */ 43 44 #include <sys/param.h> 45 #include <sys/ipc.h> 46 #include <sys/sem.h> 47 #include <sys/wait.h> 48 49 #include <err.h> 50 #include <errno.h> 51 #include <signal.h> 52 #include <stdio.h> 53 #include <stdlib.h> 54 #include <string.h> 55 #include <time.h> 56 #include <unistd.h> 57 58 int main(int, char *[]); 59 void print_semid_ds(struct semid_ds *, mode_t); 60 void sigsys_handler(int); 61 void sigchld_handler(int); 62 void cleanup(void); 63 void waiter(void); 64 65 int sender_semid = -1; 66 pid_t child_pid; 67 int child_count; 68 volatile sig_atomic_t signal_was_sigchld; 69 70 key_t semkey; 71 72 char keyname[] = "/tmp/msgtestXXXXXXXX"; 73 74 int verbose; 75 76 union mysemun { 77 int val; /* value for SETVAL */ 78 struct semid_ds *buf; /* buffer for IPC_{STAT,SET} */ 79 u_short *array; /* array for GETALL & SETALL */ 80 }; 81 82 int 83 main(argc, argv) 84 int argc; 85 char *argv[]; 86 { 87 struct sigaction sa; 88 union mysemun sun; 89 struct semid_ds s_ds; 90 sigset_t sigmask; 91 int i; 92 93 int fd, ch; 94 95 if ((fd = mkstemp(keyname)) < 0) 96 err(1, "mkstemp"); 97 98 close(fd); 99 100 while ((ch = getopt(argc, argv, "v")) != -1) { 101 switch (ch) { 102 case 'v': 103 verbose = 1; 104 break; 105 default: 106 fprintf(stderr, "Usage: semtest [-v]\n"); 107 exit(1); 108 } 109 } 110 111 /* 112 * Install a SIGSYS handler so that we can exit gracefully if 113 * System V Semaphore support isn't in the kernel. 114 */ 115 sa.sa_handler = sigsys_handler; 116 sigemptyset(&sa.sa_mask); 117 sa.sa_flags = 0; 118 if (sigaction(SIGSYS, &sa, NULL) == -1) 119 err(1, "sigaction SIGSYS"); 120 121 /* 122 * Install and SIGCHLD handler to deal with all possible exit 123 * conditions of the receiver. 124 */ 125 sa.sa_handler = sigchld_handler; 126 sigemptyset(&sa.sa_mask); 127 sa.sa_flags = 0; 128 if (sigaction(SIGCHLD, &sa, NULL) == -1) 129 err(1, "sigaction SIGCHLD"); 130 131 semkey = ftok(keyname, 4160); 132 133 /* 134 * Initialize child_pid to ourselves to that the cleanup function 135 * works before we create the receiver. 136 */ 137 child_pid = getpid(); 138 139 /* 140 * Make sure that when the sender exits, the message queue is 141 * removed. 142 */ 143 if (atexit(cleanup) == -1) 144 err(1, "atexit"); 145 146 if ((sender_semid = semget(semkey, 1, IPC_CREAT | 0640)) == -1) 147 err(1, "semget"); 148 149 150 sun.buf = &s_ds; 151 if (semctl(sender_semid, 0, IPC_STAT, sun) == -1) 152 err(1, "semctl IPC_STAT"); 153 154 if (verbose) 155 print_semid_ds(&s_ds, 0640); 156 157 s_ds.sem_perm.mode = (s_ds.sem_perm.mode & ~0777) | 0600; 158 159 sun.buf = &s_ds; 160 if (semctl(sender_semid, 0, IPC_SET, sun) == -1) 161 err(1, "semctl IPC_SET"); 162 163 memset(&s_ds, 0, sizeof(s_ds)); 164 165 sun.buf = &s_ds; 166 if (semctl(sender_semid, 0, IPC_STAT, sun) == -1) 167 err(1, "semctl IPC_STAT"); 168 169 if ((s_ds.sem_perm.mode & 0777) != 0600) 170 err(1, "IPC_SET of mode didn't hold"); 171 172 if (verbose) 173 print_semid_ds(&s_ds, 0600); 174 175 for (child_count = 0; child_count < 5; child_count++) { 176 switch ((child_pid = fork())) { 177 case -1: 178 err(1, "fork"); 179 /* NOTREACHED */ 180 181 case 0: 182 waiter(); 183 break; 184 185 default: 186 break; 187 } 188 } 189 190 /* 191 * Wait for all of the waiters to be attempting to acquire the 192 * semaphore. 193 */ 194 for (;;) { 195 i = semctl(sender_semid, 0, GETNCNT); 196 if (i == -1) 197 err(1, "semctl GETNCNT"); 198 if (i == 5) 199 break; 200 } 201 202 /* 203 * Now set the thundering herd in motion by initializing the 204 * semaphore to the value 1. 205 */ 206 sun.val = 1; 207 if (semctl(sender_semid, 0, SETVAL, sun) == -1) 208 err(1, "sender: semctl SETVAL to 1"); 209 210 /* 211 * Suspend forever; when we get SIGCHLD, the handler will exit. 212 */ 213 sigemptyset(&sigmask); 214 for (;;) { 215 (void) sigsuspend(&sigmask); 216 if (signal_was_sigchld) 217 signal_was_sigchld = 0; 218 else 219 break; 220 } 221 222 /* 223 * ...and any other signal is an unexpected error. 224 */ 225 errx(1, "sender: received unexpected signal"); 226 } 227 228 void 229 sigsys_handler(signo) 230 int signo; 231 { 232 233 errx(1, "System V Semaphore support is not present in the kernel"); 234 } 235 236 void 237 sigchld_handler(signo) 238 int signo; 239 { 240 union mysemun sun; 241 struct semid_ds s_ds; 242 int cstatus; 243 244 /* 245 * Reap the child; if it exited successfully, then we're on the 246 * right track! 247 */ 248 if (wait(&cstatus) == -1) 249 err(1, "wait"); 250 251 if (WIFEXITED(cstatus) == 0) 252 errx(1, "receiver exited abnormally"); 253 254 if (WEXITSTATUS(cstatus) != 0) 255 errx(1, "receiver exited with status %d", 256 WEXITSTATUS(cstatus)); 257 258 /* 259 * If we get here, the child has exited normally, and we should 260 * decrement the child count. If the child_count reaches 0, we 261 * should exit. 262 */ 263 264 sun.buf = &s_ds; 265 if (semctl(sender_semid, 0, IPC_STAT, sun) == -1) 266 err(1, "semctl IPC_STAT"); 267 268 if (verbose) 269 print_semid_ds(&s_ds, 0600); 270 271 if (--child_count != 0) { 272 signal_was_sigchld = 1; 273 return; 274 } 275 276 exit(0); 277 } 278 279 void 280 cleanup() 281 { 282 283 /* 284 * If we're the sender, and it exists, remove the message queue. 285 */ 286 if (child_pid != 0 && sender_semid != -1) { 287 if (semctl(sender_semid, 0, IPC_RMID) == -1) 288 warn("semctl IPC_RMID"); 289 } 290 remove(keyname); 291 } 292 293 void 294 print_semid_ds(sp, mode) 295 struct semid_ds *sp; 296 mode_t mode; 297 { 298 uid_t uid = geteuid(); 299 gid_t gid = getegid(); 300 301 printf("PERM: uid %d, gid %d, cuid %d, cgid %d, mode 0%o\n", 302 sp->sem_perm.uid, sp->sem_perm.gid, 303 sp->sem_perm.cuid, sp->sem_perm.cgid, 304 sp->sem_perm.mode & 0777); 305 306 printf("nsems %u\n", sp->sem_nsems); 307 308 printf("otime: %s", ctime(&sp->sem_otime)); 309 printf("ctime: %s", ctime(&sp->sem_ctime)); 310 311 /* 312 * Sanity check a few things. 313 */ 314 315 if (sp->sem_perm.uid != uid || sp->sem_perm.cuid != uid) 316 errx(1, "uid mismatch"); 317 318 if (sp->sem_perm.gid != gid || sp->sem_perm.cgid != gid) 319 errx(1, "gid mismatch"); 320 321 if ((sp->sem_perm.mode & 0777) != mode) 322 errx(1, "mode mismatch %o != %o", 323 (sp->sem_perm.mode & 0777), mode); 324 } 325 326 void 327 waiter() 328 { 329 struct sembuf s; 330 int semid; 331 332 if ((semid = semget(semkey, 1, 0)) == -1) 333 err(1, "waiter: semget"); 334 335 /* 336 * Attempt to acquire the semaphore. 337 */ 338 s.sem_num = 0; 339 s.sem_op = -1; 340 s.sem_flg = SEM_UNDO; 341 342 if (semop(semid, &s, 1) == -1) 343 err(1, "waiter: semop -1"); 344 345 if (verbose) 346 printf("WOO! GOT THE SEMAPHORE!\n"); 347 sleep(1); 348 349 /* 350 * Release the semaphore and exit. 351 */ 352 s.sem_num = 0; 353 s.sem_op = 1; 354 s.sem_flg = SEM_UNDO; 355 356 if (semop(semid, &s, 1) == -1) 357 err(1, "waiter: semop +1"); 358 359 exit(0); 360 } 361