1 /* $NetBSD: kern_fork.c,v 1.25 1995/10/07 06:28:15 mycroft Exp $ */ 2 3 /* 4 * Copyright (c) 1982, 1986, 1989, 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * (c) UNIX System Laboratories, Inc. 7 * All or some portions of this file are derived from material licensed 8 * to the University of California by American Telephone and Telegraph 9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 10 * the permission of UNIX System Laboratories, Inc. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the University of 23 * California, Berkeley and its contributors. 24 * 4. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 41 */ 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/map.h> 46 #include <sys/filedesc.h> 47 #include <sys/kernel.h> 48 #include <sys/malloc.h> 49 #include <sys/proc.h> 50 #include <sys/resourcevar.h> 51 #include <sys/vnode.h> 52 #include <sys/file.h> 53 #include <sys/acct.h> 54 #include <sys/ktrace.h> 55 56 /* ARGSUSED */ 57 sys_fork(p, v, retval) 58 struct proc *p; 59 void *v; 60 register_t *retval; 61 { 62 63 return (fork1(p, 0, retval)); 64 } 65 66 /* ARGSUSED */ 67 sys_vfork(p, v, retval) 68 struct proc *p; 69 void *v; 70 register_t *retval; 71 { 72 73 return (fork1(p, 1, retval)); 74 } 75 76 int nprocs = 1; /* process 0 */ 77 78 fork1(p1, isvfork, retval) 79 register struct proc *p1; 80 int isvfork; 81 register_t *retval; 82 { 83 register struct proc *p2; 84 register uid_t uid; 85 struct proc *newproc; 86 struct proc **hash; 87 int count; 88 static int nextpid, pidchecked = 0; 89 90 /* 91 * Although process entries are dynamically created, we still keep 92 * a global limit on the maximum number we will create. Don't allow 93 * a nonprivileged user to use the last process; don't let root 94 * exceed the limit. The variable nprocs is the current number of 95 * processes, maxproc is the limit. 96 */ 97 uid = p1->p_cred->p_ruid; 98 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 99 tablefull("proc"); 100 return (EAGAIN); 101 } 102 103 /* 104 * Increment the count of procs running with this uid. Don't allow 105 * a nonprivileged user to exceed their current limit. 106 */ 107 count = chgproccnt(uid, 1); 108 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 109 (void)chgproccnt(uid, -1); 110 return (EAGAIN); 111 } 112 113 /* Allocate new proc. */ 114 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 115 116 /* 117 * Find an unused process ID. We remember a range of unused IDs 118 * ready to use (from nextpid+1 through pidchecked-1). 119 */ 120 nextpid++; 121 retry: 122 /* 123 * If the process ID prototype has wrapped around, 124 * restart somewhat above 0, as the low-numbered procs 125 * tend to include daemons that don't exit. 126 */ 127 if (nextpid >= PID_MAX) { 128 nextpid = 100; 129 pidchecked = 0; 130 } 131 if (nextpid >= pidchecked) { 132 int doingzomb = 0; 133 134 pidchecked = PID_MAX; 135 /* 136 * Scan the active and zombie procs to check whether this pid 137 * is in use. Remember the lowest pid that's greater 138 * than nextpid, so we can avoid checking for a while. 139 */ 140 p2 = allproc.lh_first; 141 again: 142 for (; p2 != 0; p2 = p2->p_list.le_next) { 143 while (p2->p_pid == nextpid || 144 p2->p_pgrp->pg_id == nextpid) { 145 nextpid++; 146 if (nextpid >= pidchecked) 147 goto retry; 148 } 149 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 150 pidchecked = p2->p_pid; 151 if (p2->p_pgrp->pg_id > nextpid && 152 pidchecked > p2->p_pgrp->pg_id) 153 pidchecked = p2->p_pgrp->pg_id; 154 } 155 if (!doingzomb) { 156 doingzomb = 1; 157 p2 = zombproc.lh_first; 158 goto again; 159 } 160 } 161 162 nprocs++; 163 p2 = newproc; 164 p2->p_stat = SIDL; /* protect against others */ 165 p2->p_pid = nextpid; 166 LIST_INSERT_HEAD(&allproc, p2, p_list); 167 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 168 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 169 170 /* 171 * Make a proc table entry for the new process. 172 * Start by zeroing the section of proc that is zero-initialized, 173 * then copy the section that is copied directly from the parent. 174 */ 175 bzero(&p2->p_startzero, 176 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 177 bcopy(&p1->p_startcopy, &p2->p_startcopy, 178 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 179 180 /* 181 * Duplicate sub-structures as needed. 182 * Increase reference counts on shared objects. 183 * The p_stats and p_sigacts substructs are set in vm_fork. 184 */ 185 p2->p_flag = P_INMEM; 186 p2->p_emul = p1->p_emul; 187 if (p1->p_flag & P_PROFIL) 188 startprofclock(p2); 189 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 190 M_SUBPROC, M_WAITOK); 191 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 192 p2->p_cred->p_refcnt = 1; 193 crhold(p1->p_ucred); 194 195 /* bump references to the text vnode (for procfs) */ 196 p2->p_textvp = p1->p_textvp; 197 if (p2->p_textvp) 198 VREF(p2->p_textvp); 199 200 p2->p_fd = fdcopy(p1); 201 /* 202 * If p_limit is still copy-on-write, bump refcnt, 203 * otherwise get a copy that won't be modified. 204 * (If PL_SHAREMOD is clear, the structure is shared 205 * copy-on-write.) 206 */ 207 if (p1->p_limit->p_lflags & PL_SHAREMOD) 208 p2->p_limit = limcopy(p1->p_limit); 209 else { 210 p2->p_limit = p1->p_limit; 211 p2->p_limit->p_refcnt++; 212 } 213 214 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 215 p2->p_flag |= P_CONTROLT; 216 if (isvfork) 217 p2->p_flag |= P_PPWAIT; 218 LIST_INSERT_AFTER(p1, p2, p_pglist); 219 p2->p_pptr = p1; 220 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 221 LIST_INIT(&p2->p_children); 222 223 #ifdef KTRACE 224 /* 225 * Copy traceflag and tracefile if enabled. 226 * If not inherited, these were zeroed above. 227 */ 228 if (p1->p_traceflag&KTRFAC_INHERIT) { 229 p2->p_traceflag = p1->p_traceflag; 230 if ((p2->p_tracep = p1->p_tracep) != NULL) 231 VREF(p2->p_tracep); 232 } 233 #endif 234 235 /* 236 * This begins the section where we must prevent the parent 237 * from being swapped. 238 */ 239 p1->p_holdcnt++; 240 /* 241 * Set return values for child before vm_fork, 242 * so they can be copied to child stack. 243 * We return parent pid, and mark as child in retval[1]. 244 * NOTE: the kernel stack may be at a different location in the child 245 * process, and thus addresses of automatic variables (including retval) 246 * may be invalid after vm_fork returns in the child process. 247 */ 248 retval[0] = p1->p_pid; 249 retval[1] = 1; 250 if (vm_fork(p1, p2, isvfork)) 251 return (0); 252 253 /* 254 * Make child runnable, set start time, and add to run queue. 255 */ 256 (void) splhigh(); 257 p2->p_stats->p_start = time; 258 p2->p_acflag = AFORK; 259 p2->p_stat = SRUN; 260 setrunqueue(p2); 261 (void) spl0(); 262 263 /* 264 * Now can be swapped. 265 */ 266 p1->p_holdcnt--; 267 268 /* 269 * Preserve synchronization semantics of vfork. If waiting for 270 * child to exec or exit, set P_PPWAIT on child, and sleep on our 271 * proc (in case of exit). 272 */ 273 if (isvfork) 274 while (p2->p_flag & P_PPWAIT) 275 tsleep(p1, PWAIT, "ppwait", 0); 276 277 /* 278 * Return child pid to parent process, 279 * marking us as parent via retval[1]. 280 */ 281 retval[0] = p2->p_pid; 282 retval[1] = 0; 283 return (0); 284 } 285