kern_fork.c revision 1.38
1 /* $NetBSD: kern_fork.c,v 1.38 1998/02/10 14:09:30 mrg 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 "opt_uvm.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/map.h> 48 #include <sys/filedesc.h> 49 #include <sys/kernel.h> 50 #include <sys/malloc.h> 51 #include <sys/mount.h> 52 #include <sys/proc.h> 53 #include <sys/resourcevar.h> 54 #include <sys/vnode.h> 55 #include <sys/file.h> 56 #include <sys/acct.h> 57 #include <sys/ktrace.h> 58 #include <sys/vmmeter.h> 59 60 #include <sys/syscallargs.h> 61 62 #include <vm/vm.h> 63 64 #if defined(UVM) 65 #include <uvm/uvm_extern.h> 66 #endif 67 68 int nprocs = 1; /* process 0 */ 69 70 /*ARGSUSED*/ 71 int 72 sys_fork(p, v, retval) 73 struct proc *p; 74 void *v; 75 register_t *retval; 76 { 77 78 return (fork1(p, 0, retval, NULL)); 79 } 80 81 /* 82 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 83 * Address space is not shared, but parent is blocked until child exit. 84 */ 85 /*ARGSUSED*/ 86 int 87 sys_vfork(p, v, retval) 88 struct proc *p; 89 void *v; 90 register_t *retval; 91 { 92 93 return (fork1(p, FORK_PPWAIT, retval, NULL)); 94 } 95 96 /* 97 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 98 * semantics. Address space is shared, and parent is blocked until child exit. 99 */ 100 /*ARGSUSED*/ 101 int 102 sys___vfork14(p, v, retval) 103 struct proc *p; 104 void *v; 105 register_t *retval; 106 { 107 108 return (fork1(p, FORK_PPWAIT|FORK_SHAREVM, retval, NULL)); 109 } 110 111 int 112 fork1(p1, flags, retval, rnewprocp) 113 register struct proc *p1; 114 int flags; 115 register_t *retval; 116 struct proc **rnewprocp; 117 { 118 register struct proc *p2; 119 register uid_t uid; 120 struct proc *newproc; 121 int count; 122 static int nextpid, pidchecked = 0; 123 124 /* 125 * Although process entries are dynamically created, we still keep 126 * a global limit on the maximum number we will create. Don't allow 127 * a nonprivileged user to use the last process; don't let root 128 * exceed the limit. The variable nprocs is the current number of 129 * processes, maxproc is the limit. 130 */ 131 uid = p1->p_cred->p_ruid; 132 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 133 tablefull("proc"); 134 return (EAGAIN); 135 } 136 137 /* 138 * Increment the count of procs running with this uid. Don't allow 139 * a nonprivileged user to exceed their current limit. 140 */ 141 count = chgproccnt(uid, 1); 142 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 143 (void)chgproccnt(uid, -1); 144 return (EAGAIN); 145 } 146 147 /* Allocate new proc. */ 148 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 149 150 /* 151 * Find an unused process ID. We remember a range of unused IDs 152 * ready to use (from nextpid+1 through pidchecked-1). 153 */ 154 nextpid++; 155 retry: 156 /* 157 * If the process ID prototype has wrapped around, 158 * restart somewhat above 0, as the low-numbered procs 159 * tend to include daemons that don't exit. 160 */ 161 if (nextpid >= PID_MAX) { 162 nextpid = 100; 163 pidchecked = 0; 164 } 165 if (nextpid >= pidchecked) { 166 int doingzomb = 0; 167 168 pidchecked = PID_MAX; 169 /* 170 * Scan the active and zombie procs to check whether this pid 171 * is in use. Remember the lowest pid that's greater 172 * than nextpid, so we can avoid checking for a while. 173 */ 174 p2 = allproc.lh_first; 175 again: 176 for (; p2 != 0; p2 = p2->p_list.le_next) { 177 while (p2->p_pid == nextpid || 178 p2->p_pgrp->pg_id == nextpid) { 179 nextpid++; 180 if (nextpid >= pidchecked) 181 goto retry; 182 } 183 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 184 pidchecked = p2->p_pid; 185 if (p2->p_pgrp->pg_id > nextpid && 186 pidchecked > p2->p_pgrp->pg_id) 187 pidchecked = p2->p_pgrp->pg_id; 188 } 189 if (!doingzomb) { 190 doingzomb = 1; 191 p2 = zombproc.lh_first; 192 goto again; 193 } 194 } 195 196 nprocs++; 197 p2 = newproc; 198 p2->p_stat = SIDL; /* protect against others */ 199 p2->p_pid = nextpid; 200 LIST_INSERT_HEAD(&allproc, p2, p_list); 201 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 202 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 203 204 /* 205 * Make a proc table entry for the new process. 206 * Start by zeroing the section of proc that is zero-initialized, 207 * then copy the section that is copied directly from the parent. 208 */ 209 bzero(&p2->p_startzero, 210 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 211 bcopy(&p1->p_startcopy, &p2->p_startcopy, 212 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 213 214 /* 215 * Duplicate sub-structures as needed. 216 * Increase reference counts on shared objects. 217 * The p_stats and p_sigacts substructs are set in vm_fork. 218 */ 219 p2->p_flag = P_INMEM | (p1->p_flag & P_SUGID); 220 p2->p_emul = p1->p_emul; 221 if (p1->p_flag & P_PROFIL) 222 startprofclock(p2); 223 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 224 M_SUBPROC, M_WAITOK); 225 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 226 p2->p_cred->p_refcnt = 1; 227 crhold(p1->p_ucred); 228 229 /* bump references to the text vnode (for procfs) */ 230 p2->p_textvp = p1->p_textvp; 231 if (p2->p_textvp) 232 VREF(p2->p_textvp); 233 234 p2->p_fd = fdcopy(p1); 235 /* 236 * If p_limit is still copy-on-write, bump refcnt, 237 * otherwise get a copy that won't be modified. 238 * (If PL_SHAREMOD is clear, the structure is shared 239 * copy-on-write.) 240 */ 241 if (p1->p_limit->p_lflags & PL_SHAREMOD) 242 p2->p_limit = limcopy(p1->p_limit); 243 else { 244 p2->p_limit = p1->p_limit; 245 p2->p_limit->p_refcnt++; 246 } 247 248 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 249 p2->p_flag |= P_CONTROLT; 250 if (flags & FORK_PPWAIT) 251 p2->p_flag |= P_PPWAIT; 252 LIST_INSERT_AFTER(p1, p2, p_pglist); 253 p2->p_pptr = p1; 254 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 255 LIST_INIT(&p2->p_children); 256 257 #ifdef KTRACE 258 /* 259 * Copy traceflag and tracefile if enabled. 260 * If not inherited, these were zeroed above. 261 */ 262 if (p1->p_traceflag&KTRFAC_INHERIT) { 263 p2->p_traceflag = p1->p_traceflag; 264 if ((p2->p_tracep = p1->p_tracep) != NULL) 265 VREF(p2->p_tracep); 266 } 267 #endif 268 269 /* 270 * This begins the section where we must prevent the parent 271 * from being swapped. 272 */ 273 PHOLD(p1); 274 275 /* 276 * Finish creating the child process. It will return through a 277 * different path later. 278 */ 279 #if defined(UVM) 280 uvm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); 281 #else 282 vm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); 283 #endif 284 285 /* 286 * Make child runnable, set start time, and add to run queue. 287 */ 288 (void) splstatclock(); 289 p2->p_stats->p_start = time; 290 p2->p_acflag = AFORK; 291 p2->p_stat = SRUN; 292 setrunqueue(p2); 293 (void) spl0(); 294 295 /* 296 * Now can be swapped. 297 */ 298 PRELE(p1); 299 300 /* 301 * Update stats now that we know the fork was successful. 302 */ 303 #if defined(UVM) 304 uvmexp.forks++; 305 if (flags & FORK_PPWAIT) 306 uvmexp.forks_ppwait++; 307 if (flags & FORK_SHAREVM) 308 uvmexp.forks_sharevm++; 309 #else 310 cnt.v_forks++; 311 if (flags & FORK_PPWAIT) 312 cnt.v_forks_ppwait++; 313 if (flags & FORK_SHAREVM) 314 cnt.v_forks_sharevm++; 315 #endif 316 317 /* 318 * Pass a pointer to the new process to the caller. 319 */ 320 if (rnewprocp != NULL) 321 *rnewprocp = p2; 322 323 /* 324 * Preserve synchronization semantics of vfork. If waiting for 325 * child to exec or exit, set P_PPWAIT on child, and sleep on our 326 * proc (in case of exit). 327 */ 328 if (flags & FORK_PPWAIT) 329 while (p2->p_flag & P_PPWAIT) 330 tsleep(p1, PWAIT, "ppwait", 0); 331 332 /* 333 * Return child pid to parent process, 334 * marking us as parent via retval[1]. 335 */ 336 if (retval != NULL) { 337 retval[0] = p2->p_pid; 338 retval[1] = 0; 339 } 340 return (0); 341 } 342
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