kern_fork.c revision 1.36
1 /* $NetBSD: kern_fork.c,v 1.36 1998/01/06 21:15:41 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/vmmeter.h> 57 58 #include <sys/syscallargs.h> 59 60 #include <vm/vm.h> 61 62 int nprocs = 1; /* process 0 */ 63 64 /*ARGSUSED*/ 65 int 66 sys_fork(p, v, retval) 67 struct proc *p; 68 void *v; 69 register_t *retval; 70 { 71 72 return (fork1(p, 0, retval, NULL)); 73 } 74 75 /* 76 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 77 * Address space is not shared, but parent is blocked until child exit. 78 */ 79 /*ARGSUSED*/ 80 int 81 sys_vfork(p, v, retval) 82 struct proc *p; 83 void *v; 84 register_t *retval; 85 { 86 87 return (fork1(p, FORK_PPWAIT, retval, NULL)); 88 } 89 90 /* 91 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 92 * semantics. Address space is shared, and parent is blocked until child exit. 93 */ 94 /*ARGSUSED*/ 95 int 96 sys___vfork14(p, v, retval) 97 struct proc *p; 98 void *v; 99 register_t *retval; 100 { 101 102 return (fork1(p, FORK_PPWAIT|FORK_SHAREVM, retval, NULL)); 103 } 104 105 int 106 fork1(p1, flags, retval, rnewprocp) 107 register struct proc *p1; 108 int flags; 109 register_t *retval; 110 struct proc **rnewprocp; 111 { 112 register struct proc *p2; 113 register uid_t uid; 114 struct proc *newproc; 115 int count; 116 static int nextpid, pidchecked = 0; 117 118 /* 119 * Although process entries are dynamically created, we still keep 120 * a global limit on the maximum number we will create. Don't allow 121 * a nonprivileged user to use the last process; don't let root 122 * exceed the limit. The variable nprocs is the current number of 123 * processes, maxproc is the limit. 124 */ 125 uid = p1->p_cred->p_ruid; 126 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 127 tablefull("proc"); 128 return (EAGAIN); 129 } 130 131 /* 132 * Increment the count of procs running with this uid. Don't allow 133 * a nonprivileged user to exceed their current limit. 134 */ 135 count = chgproccnt(uid, 1); 136 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 137 (void)chgproccnt(uid, -1); 138 return (EAGAIN); 139 } 140 141 /* Allocate new proc. */ 142 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 143 144 /* 145 * Find an unused process ID. We remember a range of unused IDs 146 * ready to use (from nextpid+1 through pidchecked-1). 147 */ 148 nextpid++; 149 retry: 150 /* 151 * If the process ID prototype has wrapped around, 152 * restart somewhat above 0, as the low-numbered procs 153 * tend to include daemons that don't exit. 154 */ 155 if (nextpid >= PID_MAX) { 156 nextpid = 100; 157 pidchecked = 0; 158 } 159 if (nextpid >= pidchecked) { 160 int doingzomb = 0; 161 162 pidchecked = PID_MAX; 163 /* 164 * Scan the active and zombie procs to check whether this pid 165 * is in use. Remember the lowest pid that's greater 166 * than nextpid, so we can avoid checking for a while. 167 */ 168 p2 = allproc.lh_first; 169 again: 170 for (; p2 != 0; p2 = p2->p_list.le_next) { 171 while (p2->p_pid == nextpid || 172 p2->p_pgrp->pg_id == nextpid) { 173 nextpid++; 174 if (nextpid >= pidchecked) 175 goto retry; 176 } 177 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 178 pidchecked = p2->p_pid; 179 if (p2->p_pgrp->pg_id > nextpid && 180 pidchecked > p2->p_pgrp->pg_id) 181 pidchecked = p2->p_pgrp->pg_id; 182 } 183 if (!doingzomb) { 184 doingzomb = 1; 185 p2 = zombproc.lh_first; 186 goto again; 187 } 188 } 189 190 nprocs++; 191 p2 = newproc; 192 p2->p_stat = SIDL; /* protect against others */ 193 p2->p_pid = nextpid; 194 LIST_INSERT_HEAD(&allproc, p2, p_list); 195 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 196 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 197 198 /* 199 * Make a proc table entry for the new process. 200 * Start by zeroing the section of proc that is zero-initialized, 201 * then copy the section that is copied directly from the parent. 202 */ 203 bzero(&p2->p_startzero, 204 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 205 bcopy(&p1->p_startcopy, &p2->p_startcopy, 206 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 207 208 /* 209 * Duplicate sub-structures as needed. 210 * Increase reference counts on shared objects. 211 * The p_stats and p_sigacts substructs are set in vm_fork. 212 */ 213 p2->p_flag = P_INMEM | (p1->p_flag & P_SUGID); 214 p2->p_emul = p1->p_emul; 215 if (p1->p_flag & P_PROFIL) 216 startprofclock(p2); 217 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 218 M_SUBPROC, M_WAITOK); 219 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 220 p2->p_cred->p_refcnt = 1; 221 crhold(p1->p_ucred); 222 223 /* bump references to the text vnode (for procfs) */ 224 p2->p_textvp = p1->p_textvp; 225 if (p2->p_textvp) 226 VREF(p2->p_textvp); 227 228 p2->p_fd = fdcopy(p1); 229 /* 230 * If p_limit is still copy-on-write, bump refcnt, 231 * otherwise get a copy that won't be modified. 232 * (If PL_SHAREMOD is clear, the structure is shared 233 * copy-on-write.) 234 */ 235 if (p1->p_limit->p_lflags & PL_SHAREMOD) 236 p2->p_limit = limcopy(p1->p_limit); 237 else { 238 p2->p_limit = p1->p_limit; 239 p2->p_limit->p_refcnt++; 240 } 241 242 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 243 p2->p_flag |= P_CONTROLT; 244 if (flags & FORK_PPWAIT) 245 p2->p_flag |= P_PPWAIT; 246 LIST_INSERT_AFTER(p1, p2, p_pglist); 247 p2->p_pptr = p1; 248 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 249 LIST_INIT(&p2->p_children); 250 251 #ifdef KTRACE 252 /* 253 * Copy traceflag and tracefile if enabled. 254 * If not inherited, these were zeroed above. 255 */ 256 if (p1->p_traceflag&KTRFAC_INHERIT) { 257 p2->p_traceflag = p1->p_traceflag; 258 if ((p2->p_tracep = p1->p_tracep) != NULL) 259 VREF(p2->p_tracep); 260 } 261 #endif 262 263 /* 264 * This begins the section where we must prevent the parent 265 * from being swapped. 266 */ 267 PHOLD(p1); 268 269 /* 270 * Finish creating the child process. It will return through a 271 * different path later. 272 */ 273 vm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); 274 275 /* 276 * Make child runnable, set start time, and add to run queue. 277 */ 278 (void) splstatclock(); 279 p2->p_stats->p_start = time; 280 p2->p_acflag = AFORK; 281 p2->p_stat = SRUN; 282 setrunqueue(p2); 283 (void) spl0(); 284 285 /* 286 * Now can be swapped. 287 */ 288 PRELE(p1); 289 290 /* 291 * Update stats now that we know the fork was successful. 292 */ 293 cnt.v_forks++; 294 if (flags & FORK_PPWAIT) 295 cnt.v_forks_ppwait++; 296 if (flags & FORK_SHAREVM) 297 cnt.v_forks_sharevm++; 298 299 /* 300 * Pass a pointer to the new process to the caller. 301 */ 302 if (rnewprocp != NULL) 303 *rnewprocp = p2; 304 305 /* 306 * Preserve synchronization semantics of vfork. If waiting for 307 * child to exec or exit, set P_PPWAIT on child, and sleep on our 308 * proc (in case of exit). 309 */ 310 if (flags & FORK_PPWAIT) 311 while (p2->p_flag & P_PPWAIT) 312 tsleep(p1, PWAIT, "ppwait", 0); 313 314 /* 315 * Return child pid to parent process, 316 * marking us as parent via retval[1]. 317 */ 318 if (retval != NULL) { 319 retval[0] = p2->p_pid; 320 retval[1] = 0; 321 } 322 return (0); 323 } 324
Indexes created Wed Sep 24 05:09:52 GMT 2025