/* $NetBSD: semtest.c,v 1.3 2001/02/19 22:44:41 cgd Exp $ */ /*- * Copyright (c) 1999 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, * NASA Ames Research Center. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the NetBSD * Foundation, Inc. and its contributors. * 4. Neither the name of The NetBSD Foundation nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ /* * Test the SVID-compatible Semaphore facility. */ #include <sys/param.h> #include <sys/ipc.h> #include <sys/sem.h> #include <sys/wait.h> #include <err.h> #include <errno.h> #include <limits.h> #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h> #include <unistd.h> int main(int, char *[]); void print_semid_ds(struct semid_ds *, mode_t); void sigsys_handler(int); void sigchld_handler(int); void cleanup(void); void waiter(void); int sender_semid = -1; pid_t child_pid; int child_count; volatile sig_atomic_t signal_was_sigchld; key_t semkey; char keyname[] = "/tmp/msgtestXXXXXXXX"; int verbose; union mysemun { int val; /* value for SETVAL */ struct semid_ds *buf; /* buffer for IPC_{STAT,SET} */ u_short *array; /* array for GETALL & SETALL */ }; int main(argc, argv) int argc; char *argv[]; { struct sigaction sa; union mysemun sun; struct semid_ds s_ds; sigset_t sigmask; int i; int fd, ch; if ((fd = mkstemp(keyname)) < 0) err(1, "mkstemp"); close(fd); while ((ch = getopt(argc, argv, "v")) != -1) { switch (ch) { case 'v': verbose = 1; break; default: fprintf(stderr, "Usage: semtest [-v]\n"); exit(1); } } /* * Install a SIGSYS handler so that we can exit gracefully if * System V Semaphore support isn't in the kernel. */ sa.sa_handler = sigsys_handler; sigemptyset(&sa.sa_mask); sa.sa_flags = 0; if (sigaction(SIGSYS, &sa, NULL) == -1) err(1, "sigaction SIGSYS"); /* * Install and SIGCHLD handler to deal with all possible exit * conditions of the receiver. */ sa.sa_handler = sigchld_handler; sigemptyset(&sa.sa_mask); sa.sa_flags = 0; if (sigaction(SIGCHLD, &sa, NULL) == -1) err(1, "sigaction SIGCHLD"); semkey = ftok(keyname, arc4random() & INT_MAX); /* * Initialize child_pid to ourselves to that the cleanup function * works before we create the receiver. */ child_pid = getpid(); /* * Make sure that when the sender exits, the message queue is * removed. */ if (atexit(cleanup) == -1) err(1, "atexit"); sender_semid = semget(semkey, 1, IPC_CREAT | IPC_EXCL | 0640); if (sender_semid == -1) err(1, "semget"); sun.buf = &s_ds; if (semctl(sender_semid, 0, IPC_STAT, sun) == -1) err(1, "semctl IPC_STAT"); if (verbose) print_semid_ds(&s_ds, 0640); s_ds.sem_perm.mode = (s_ds.sem_perm.mode & ~0777) | 0600; sun.buf = &s_ds; if (semctl(sender_semid, 0, IPC_SET, sun) == -1) err(1, "semctl IPC_SET"); memset(&s_ds, 0, sizeof(s_ds)); sun.buf = &s_ds; if (semctl(sender_semid, 0, IPC_STAT, sun) == -1) err(1, "semctl IPC_STAT"); if ((s_ds.sem_perm.mode & 0777) != 0600) err(1, "IPC_SET of mode didn't hold"); if (verbose) print_semid_ds(&s_ds, 0600); for (child_count = 0; child_count < 5; child_count++) { switch ((child_pid = fork())) { case -1: err(1, "fork"); /* NOTREACHED */ case 0: waiter(); break; default: break; } } /* * Wait for all of the waiters to be attempting to acquire the * semaphore. */ for (;;) { i = semctl(sender_semid, 0, GETNCNT); if (i == -1) err(1, "semctl GETNCNT"); if (i == 5) break; } /* * Now set the thundering herd in motion by initializing the * semaphore to the value 1. */ sun.val = 1; if (semctl(sender_semid, 0, SETVAL, sun) == -1) err(1, "sender: semctl SETVAL to 1"); /* * Suspend forever; when we get SIGCHLD, the handler will exit. */ sigemptyset(&sigmask); for (;;) { (void) sigsuspend(&sigmask); if (signal_was_sigchld) signal_was_sigchld = 0; else break; } /* * ...and any other signal is an unexpected error. */ errx(1, "sender: received unexpected signal"); } void sigsys_handler(signo) int signo; { errx(1, "System V Semaphore support is not present in the kernel"); } void sigchld_handler(signo) int signo; { union mysemun sun; struct semid_ds s_ds; int cstatus; /* * Reap the child; if it exited successfully, then we're on the * right track! */ if (wait(&cstatus) == -1) err(1, "wait"); if (WIFEXITED(cstatus) == 0) errx(1, "receiver exited abnormally"); if (WEXITSTATUS(cstatus) != 0) errx(1, "receiver exited with status %d", WEXITSTATUS(cstatus)); /* * If we get here, the child has exited normally, and we should * decrement the child count. If the child_count reaches 0, we * should exit. */ sun.buf = &s_ds; if (semctl(sender_semid, 0, IPC_STAT, sun) == -1) err(1, "semctl IPC_STAT"); if (verbose) print_semid_ds(&s_ds, 0600); if (--child_count != 0) { signal_was_sigchld = 1; return; } exit(0); } void cleanup() { /* * If we're the sender, and it exists, remove the message queue. */ if (child_pid != 0 && sender_semid != -1) { if (semctl(sender_semid, 0, IPC_RMID) == -1) warn("semctl IPC_RMID"); } remove(keyname); } void print_semid_ds(sp, mode) struct semid_ds *sp; mode_t mode; { uid_t uid = geteuid(); gid_t gid = getegid(); printf("PERM: uid %u, gid %u, cuid %u, cgid %u, mode 0%o\n", sp->sem_perm.uid, sp->sem_perm.gid, sp->sem_perm.cuid, sp->sem_perm.cgid, sp->sem_perm.mode & 0777); printf("nsems %u\n", sp->sem_nsems); printf("otime: %s", ctime(&sp->sem_otime)); printf("ctime: %s", ctime(&sp->sem_ctime)); /* * Sanity check a few things. */ if (sp->sem_perm.uid != uid || sp->sem_perm.cuid != uid) errx(1, "uid mismatch"); if (sp->sem_perm.gid != gid || sp->sem_perm.cgid != gid) errx(1, "gid mismatch"); if ((sp->sem_perm.mode & 0777) != mode) errx(1, "mode mismatch %o != %o", (sp->sem_perm.mode & 0777), mode); } void waiter() { struct sembuf s; int semid; if ((semid = semget(semkey, 1, 0)) == -1) err(1, "waiter: semget"); /* * Attempt to acquire the semaphore. */ s.sem_num = 0; s.sem_op = -1; s.sem_flg = SEM_UNDO; if (semop(semid, &s, 1) == -1) err(1, "waiter: semop -1"); if (verbose) printf("WOO! GOT THE SEMAPHORE!\n"); sleep(1); /* * Release the semaphore and exit. */ s.sem_num = 0; s.sem_op = 1; s.sem_flg = SEM_UNDO; if (semop(semid, &s, 1) == -1) err(1, "waiter: semop +1"); exit(0); }