/* * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009 * The President and Fellows of Harvard College. * * 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. Neither the name of the University 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 UNIVERSITY 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 UNIVERSITY 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. */ /* * forktest - test fork(). * * This should work correctly when fork is implemented. * * It should also continue to work after subsequent assignments, most * notably after implementing the virtual memory system. */ #include <unistd.h> #include <string.h> #include <stdlib.h> #include <stdio.h> #include <err.h> /* * This is used by all processes, to try to help make sure all * processes have a distinct address space. */ static volatile int mypid; /* * Helper function for fork that prints a warning on error. */ static int dofork(void) { int pid; pid = fork(); if (pid < 0) { warn("fork"); } return pid; } /* * Check to make sure each process has its own address space. Write * the pid into the data segment and read it back repeatedly, making * sure it's correct every time. */ static void check(void) { int i; mypid = getpid(); /* Make sure each fork has its own address space. */ for (i=0; i<800; i++) { volatile int seenpid; seenpid = mypid; if (seenpid != getpid()) { errx(1, "pid mismatch (%d, should be %d) " "- your vm is broken!", seenpid, getpid()); } } } /* * Wait for a child process. * * This assumes dowait is called the same number of times as dofork * and passed its results in reverse order. Any forks that fail send * us -1 and are ignored. The first 0 we see indicates the fork that * generated the current process; that means it's time to exit. Only * the parent of all the processes returns from the chain of dowaits. */ static void dowait(int nowait, int pid) { int x; if (pid<0) { /* fork in question failed; just return */ return; } if (pid==0) { /* in the fork in question we were the child; exit */ exit(0); } if (!nowait) { if (waitpid(pid, &x, 0)<0) { warn("waitpid"); } else if (WIFSIGNALED(x)) { warnx("pid %d: signal %d", pid, WTERMSIG(x)); } else if (WEXITSTATUS(x) != 0) { warnx("pid %d: exit %d", pid, WEXITSTATUS(x)); } } } /* * Actually run the test. */ static void test(int nowait) { int pid0, pid1, pid2, pid3; /* * Caution: This generates processes geometrically. * * It is unrolled to encourage gcc to registerize the pids, * to prevent wait/exit problems if fork corrupts memory. */ pid0 = dofork(); putchar('0'); check(); pid1 = dofork(); putchar('1'); check(); pid2 = dofork(); putchar('2'); check(); pid3 = dofork(); putchar('3'); check(); /* * These must be called in reverse order to avoid waiting * improperly. */ dowait(nowait, pid3); dowait(nowait, pid2); dowait(nowait, pid1); dowait(nowait, pid0); putchar('\n'); } int main(int argc, char *argv[]) { static const char expected[] = "|----------------------------|\n"; int nowait=0; if (argc==2 && !strcmp(argv[1], "-w")) { nowait=1; } else if (argc!=1 && argc!=0) { warnx("usage: forktest [-w]"); return 1; } warnx("Starting. Expect this many:"); write(STDERR_FILENO, expected, strlen(expected)); test(nowait); warnx("Complete."); return 0; }