kern_fork.c revision 1.32.6.1
1 /* $NetBSD: kern_fork.c,v 1.32.6.1 1997/09/08 23:09:38 thorpej 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/mount.h> 50 #include <sys/proc.h> 51 #include <sys/resourcevar.h> 52 #include <sys/vnode.h> 53 #include <sys/file.h> 54 #include <sys/acct.h> 55 #include <sys/ktrace.h> 56 #include <sys/signalvar.h> 57 58 #include <sys/syscallargs.h> 59 60 #include <vm/vm.h> 61 62 int nprocs = 1; /* process 0 */ 63 64 int fork1 __P((struct proc *, int, register_t *)); 65 66 /*ARGSUSED*/ 67 int 68 sys_fork(p, v, retval) 69 struct proc *p; 70 void *v; 71 register_t *retval; 72 { 73 74 return (fork1(p, 0, retval)); 75 } 76 77 /*ARGSUSED*/ 78 int 79 sys_vfork(p, v, retval) 80 struct proc *p; 81 void *v; 82 register_t *retval; 83 { 84 85 return (fork1(p, 1, retval)); 86 } 87 88 int 89 fork1(p1, isvfork, retval) 90 register struct proc *p1; 91 int isvfork; 92 register_t *retval; 93 { 94 register struct proc *p2; 95 register uid_t uid; 96 struct proc *newproc; 97 int count; 98 static int nextpid, pidchecked = 0; 99 100 /* 101 * Although process entries are dynamically created, we still keep 102 * a global limit on the maximum number we will create. Don't allow 103 * a nonprivileged user to use the last process; don't let root 104 * exceed the limit. The variable nprocs is the current number of 105 * processes, maxproc is the limit. 106 */ 107 uid = p1->p_cred->p_ruid; 108 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 109 tablefull("proc"); 110 return (EAGAIN); 111 } 112 113 /* 114 * Increment the count of procs running with this uid. Don't allow 115 * a nonprivileged user to exceed their current limit. 116 */ 117 count = chgproccnt(uid, 1); 118 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 119 (void)chgproccnt(uid, -1); 120 return (EAGAIN); 121 } 122 123 /* Allocate new proc. */ 124 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 125 126 /* 127 * Find an unused process ID. We remember a range of unused IDs 128 * ready to use (from nextpid+1 through pidchecked-1). 129 */ 130 nextpid++; 131 retry: 132 /* 133 * If the process ID prototype has wrapped around, 134 * restart somewhat above 0, as the low-numbered procs 135 * tend to include daemons that don't exit. 136 */ 137 if (nextpid >= PID_MAX) { 138 nextpid = 100; 139 pidchecked = 0; 140 } 141 if (nextpid >= pidchecked) { 142 int doingzomb = 0; 143 144 pidchecked = PID_MAX; 145 /* 146 * Scan the active and zombie procs to check whether this pid 147 * is in use. Remember the lowest pid that's greater 148 * than nextpid, so we can avoid checking for a while. 149 */ 150 p2 = allproc.lh_first; 151 again: 152 for (; p2 != 0; p2 = p2->p_list.le_next) { 153 while (p2->p_pid == nextpid || 154 p2->p_pgrp->pg_id == nextpid) { 155 nextpid++; 156 if (nextpid >= pidchecked) 157 goto retry; 158 } 159 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 160 pidchecked = p2->p_pid; 161 if (p2->p_pgrp->pg_id > nextpid && 162 pidchecked > p2->p_pgrp->pg_id) 163 pidchecked = p2->p_pgrp->pg_id; 164 } 165 if (!doingzomb) { 166 doingzomb = 1; 167 p2 = zombproc.lh_first; 168 goto again; 169 } 170 } 171 172 nprocs++; 173 p2 = newproc; 174 p2->p_stat = SIDL; /* protect against others */ 175 p2->p_pid = nextpid; 176 LIST_INSERT_HEAD(&allproc, p2, p_list); 177 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 178 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 179 180 /* 181 * Make a proc table entry for the new process. 182 * Start by zeroing the section of proc that is zero-initialized, 183 * then copy the section that is copied directly from the parent. 184 */ 185 bzero(&p2->p_startzero, 186 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 187 bcopy(&p1->p_startcopy, &p2->p_startcopy, 188 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 189 190 /* 191 * Duplicate sub-structures as needed. 192 * Increase reference counts on shared objects. 193 * The p_stats and p_sigacts substructs are set in vm_fork. 194 */ 195 p2->p_flag = P_INMEM | (p1->p_flag & P_SUGID); 196 p2->p_emul = p1->p_emul; 197 if (p1->p_flag & P_PROFIL) 198 startprofclock(p2); 199 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 200 M_SUBPROC, M_WAITOK); 201 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 202 p2->p_cred->p_refcnt = 1; 203 crhold(p1->p_ucred); 204 205 /* bump references to the text vnode (for procfs) */ 206 p2->p_textvp = p1->p_textvp; 207 if (p2->p_textvp) 208 VREF(p2->p_textvp); 209 210 p2->p_fd = fdcopy(p1); 211 /* 212 * If p_limit is still copy-on-write, bump refcnt, 213 * otherwise get a copy that won't be modified. 214 * (If PL_SHAREMOD is clear, the structure is shared 215 * copy-on-write.) 216 */ 217 if (p1->p_limit->p_lflags & PL_SHAREMOD) 218 p2->p_limit = limcopy(p1->p_limit); 219 else { 220 p2->p_limit = p1->p_limit; 221 p2->p_limit->p_refcnt++; 222 } 223 224 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 225 p2->p_flag |= P_CONTROLT; 226 if (isvfork) 227 p2->p_flag |= P_PPWAIT; 228 LIST_INSERT_AFTER(p1, p2, p_pglist); 229 p2->p_pptr = p1; 230 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 231 LIST_INIT(&p2->p_children); 232 233 #ifdef KTRACE 234 /* 235 * Copy traceflag and tracefile if enabled. 236 * If not inherited, these were zeroed above. 237 */ 238 if (p1->p_traceflag&KTRFAC_INHERIT) { 239 p2->p_traceflag = p1->p_traceflag; 240 if ((p2->p_tracep = p1->p_tracep) != NULL) 241 VREF(p2->p_tracep); 242 } 243 #endif 244 245 /* 246 * Set up signal actions for the new process. 247 */ 248 p2->p_sigacts = sigacts_copy(p1); 249 250 /* 251 * This begins the section where we must prevent the parent 252 * from being swapped. 253 */ 254 PHOLD(p1); 255 256 /* 257 * Finish creating the child process. It will return through a 258 * different path later. 259 */ 260 vm_fork(p1, p2); 261 262 /* 263 * Make child runnable, set start time, and add to run queue. 264 */ 265 (void) splstatclock(); 266 p2->p_stats->p_start = time; 267 p2->p_acflag = AFORK; 268 p2->p_stat = SRUN; 269 setrunqueue(p2); 270 (void) spl0(); 271 272 /* 273 * Now can be swapped. 274 */ 275 PRELE(p1); 276 277 /* 278 * Preserve synchronization semantics of vfork. If waiting for 279 * child to exec or exit, set P_PPWAIT on child, and sleep on our 280 * proc (in case of exit). 281 */ 282 if (isvfork) 283 while (p2->p_flag & P_PPWAIT) 284 tsleep(p1, PWAIT, "ppwait", 0); 285 286 /* 287 * Return child pid to parent process, 288 * marking us as parent via retval[1]. 289 */ 290 retval[0] = p2->p_pid; 291 retval[1] = 0; 292 return (0); 293 } 294
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