kern_fork.c revision 1.43
1 /* $NetBSD: kern_fork.c,v 1.43 1998/06/25 21:17:16 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 8.8 (Berkeley) 2/14/95 41 */ 42 43 #include "opt_ktrace.h" 44 #include "opt_uvm.h" 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 #include <sys/map.h> 49 #include <sys/filedesc.h> 50 #include <sys/kernel.h> 51 #include <sys/malloc.h> 52 #include <sys/mount.h> 53 #include <sys/proc.h> 54 #include <sys/resourcevar.h> 55 #include <sys/vnode.h> 56 #include <sys/file.h> 57 #include <sys/acct.h> 58 #include <sys/ktrace.h> 59 #include <sys/vmmeter.h> 60 61 #include <sys/syscallargs.h> 62 63 #include <vm/vm.h> 64 #include <vm/vm_kern.h> 65 66 #if defined(UVM) 67 #include <uvm/uvm_extern.h> 68 #endif 69 70 int nprocs = 1; /* process 0 */ 71 72 /*ARGSUSED*/ 73 int 74 sys_fork(p, v, retval) 75 struct proc *p; 76 void *v; 77 register_t *retval; 78 { 79 80 return (fork1(p, 0, retval, NULL)); 81 } 82 83 /* 84 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 85 * Address space is not shared, but parent is blocked until child exit. 86 */ 87 /*ARGSUSED*/ 88 int 89 sys_vfork(p, v, retval) 90 struct proc *p; 91 void *v; 92 register_t *retval; 93 { 94 95 return (fork1(p, FORK_PPWAIT, retval, NULL)); 96 } 97 98 /* 99 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 100 * semantics. Address space is shared, and parent is blocked until child exit. 101 */ 102 /*ARGSUSED*/ 103 int 104 sys___vfork14(p, v, retval) 105 struct proc *p; 106 void *v; 107 register_t *retval; 108 { 109 110 return (fork1(p, FORK_PPWAIT|FORK_SHAREVM, retval, NULL)); 111 } 112 113 int 114 fork1(p1, flags, retval, rnewprocp) 115 register struct proc *p1; 116 int flags; 117 register_t *retval; 118 struct proc **rnewprocp; 119 { 120 register struct proc *p2; 121 register uid_t uid; 122 struct proc *newproc; 123 int count; 124 vm_offset_t uaddr; 125 static int nextpid, pidchecked = 0; 126 127 /* 128 * Although process entries are dynamically created, we still keep 129 * a global limit on the maximum number we will create. Don't allow 130 * a nonprivileged user to use the last process; don't let root 131 * exceed the limit. The variable nprocs is the current number of 132 * processes, maxproc is the limit. 133 */ 134 uid = p1->p_cred->p_ruid; 135 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 136 tablefull("proc"); 137 return (EAGAIN); 138 } 139 140 /* 141 * Increment the count of procs running with this uid. Don't allow 142 * a nonprivileged user to exceed their current limit. 143 */ 144 count = chgproccnt(uid, 1); 145 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 146 (void)chgproccnt(uid, -1); 147 return (EAGAIN); 148 } 149 150 /* 151 * Allocate virtual address space for the U-area now, while it 152 * is still easy to abort the fork operation if we're out of 153 * kernel virtual address space. The actual U-area pages will 154 * be allocated and wired in vm_fork(). 155 */ 156 #if defined(UVM) 157 uaddr = uvm_km_valloc(kernel_map, USPACE); 158 #else 159 uaddr = kmem_alloc_pageable(kernel_map, USPACE); 160 #endif 161 if (uaddr == 0) { 162 (void)chgproccnt(uid, -1); 163 return (ENOMEM); 164 } 165 166 /* 167 * We are now committed to the fork. From here on, we may 168 * block on resources, but resource allocation may NOT fail. 169 */ 170 171 /* Allocate new proc. */ 172 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 173 174 /* 175 * Find an unused process ID. We remember a range of unused IDs 176 * ready to use (from nextpid+1 through pidchecked-1). 177 */ 178 nextpid++; 179 retry: 180 /* 181 * If the process ID prototype has wrapped around, 182 * restart somewhat above 0, as the low-numbered procs 183 * tend to include daemons that don't exit. 184 */ 185 if (nextpid >= PID_MAX) { 186 nextpid = 100; 187 pidchecked = 0; 188 } 189 if (nextpid >= pidchecked) { 190 int doingzomb = 0; 191 192 pidchecked = PID_MAX; 193 /* 194 * Scan the active and zombie procs to check whether this pid 195 * is in use. Remember the lowest pid that's greater 196 * than nextpid, so we can avoid checking for a while. 197 */ 198 p2 = allproc.lh_first; 199 again: 200 for (; p2 != 0; p2 = p2->p_list.le_next) { 201 while (p2->p_pid == nextpid || 202 p2->p_pgrp->pg_id == nextpid || 203 p2->p_session->s_sid == nextpid) { 204 nextpid++; 205 if (nextpid >= pidchecked) 206 goto retry; 207 } 208 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 209 pidchecked = p2->p_pid; 210 211 if (p2->p_pgrp->pg_id > nextpid && 212 pidchecked > p2->p_pgrp->pg_id) 213 pidchecked = p2->p_pgrp->pg_id; 214 215 if (p2->p_session->s_sid > nextpid && 216 pidchecked > p2->p_session->s_sid) 217 pidchecked = p2->p_session->s_sid; 218 } 219 if (!doingzomb) { 220 doingzomb = 1; 221 p2 = zombproc.lh_first; 222 goto again; 223 } 224 } 225 226 nprocs++; 227 p2 = newproc; 228 p2->p_stat = SIDL; /* protect against others */ 229 p2->p_pid = nextpid; 230 LIST_INSERT_HEAD(&allproc, p2, p_list); 231 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 232 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 233 234 /* 235 * Make a proc table entry for the new process. 236 * Start by zeroing the section of proc that is zero-initialized, 237 * then copy the section that is copied directly from the parent. 238 */ 239 bzero(&p2->p_startzero, 240 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 241 bcopy(&p1->p_startcopy, &p2->p_startcopy, 242 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 243 244 /* 245 * Duplicate sub-structures as needed. 246 * Increase reference counts on shared objects. 247 * The p_stats and p_sigacts substructs are set in vm_fork. 248 */ 249 p2->p_flag = P_INMEM | (p1->p_flag & P_SUGID); 250 p2->p_emul = p1->p_emul; 251 if (p1->p_flag & P_PROFIL) 252 startprofclock(p2); 253 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 254 M_SUBPROC, M_WAITOK); 255 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 256 p2->p_cred->p_refcnt = 1; 257 crhold(p1->p_ucred); 258 259 /* bump references to the text vnode (for procfs) */ 260 p2->p_textvp = p1->p_textvp; 261 if (p2->p_textvp) 262 VREF(p2->p_textvp); 263 264 p2->p_fd = fdcopy(p1); 265 /* 266 * If p_limit is still copy-on-write, bump refcnt, 267 * otherwise get a copy that won't be modified. 268 * (If PL_SHAREMOD is clear, the structure is shared 269 * copy-on-write.) 270 */ 271 if (p1->p_limit->p_lflags & PL_SHAREMOD) 272 p2->p_limit = limcopy(p1->p_limit); 273 else { 274 p2->p_limit = p1->p_limit; 275 p2->p_limit->p_refcnt++; 276 } 277 278 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 279 p2->p_flag |= P_CONTROLT; 280 if (flags & FORK_PPWAIT) 281 p2->p_flag |= P_PPWAIT; 282 LIST_INSERT_AFTER(p1, p2, p_pglist); 283 p2->p_pptr = p1; 284 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 285 LIST_INIT(&p2->p_children); 286 287 #ifdef KTRACE 288 /* 289 * Copy traceflag and tracefile if enabled. 290 * If not inherited, these were zeroed above. 291 */ 292 if (p1->p_traceflag&KTRFAC_INHERIT) { 293 p2->p_traceflag = p1->p_traceflag; 294 if ((p2->p_tracep = p1->p_tracep) != NULL) 295 ktradref(p2); 296 } 297 #endif 298 299 /* 300 * This begins the section where we must prevent the parent 301 * from being swapped. 302 */ 303 PHOLD(p1); 304 305 /* 306 * Finish creating the child process. It will return through a 307 * different path later. 308 */ 309 p2->p_addr = (struct user *)uaddr; 310 #if defined(UVM) 311 uvm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); 312 #else 313 vm_fork(p1, p2, (flags & FORK_SHAREVM) ? TRUE : FALSE); 314 #endif 315 316 /* 317 * Make child runnable, set start time, and add to run queue. 318 */ 319 (void) splstatclock(); 320 p2->p_stats->p_start = time; 321 p2->p_acflag = AFORK; 322 p2->p_stat = SRUN; 323 setrunqueue(p2); 324 (void) spl0(); 325 326 /* 327 * Now can be swapped. 328 */ 329 PRELE(p1); 330 331 /* 332 * Update stats now that we know the fork was successful. 333 */ 334 #if defined(UVM) 335 uvmexp.forks++; 336 if (flags & FORK_PPWAIT) 337 uvmexp.forks_ppwait++; 338 if (flags & FORK_SHAREVM) 339 uvmexp.forks_sharevm++; 340 #else 341 cnt.v_forks++; 342 if (flags & FORK_PPWAIT) 343 cnt.v_forks_ppwait++; 344 if (flags & FORK_SHAREVM) 345 cnt.v_forks_sharevm++; 346 #endif 347 348 /* 349 * Pass a pointer to the new process to the caller. 350 */ 351 if (rnewprocp != NULL) 352 *rnewprocp = p2; 353 354 /* 355 * Preserve synchronization semantics of vfork. If waiting for 356 * child to exec or exit, set P_PPWAIT on child, and sleep on our 357 * proc (in case of exit). 358 */ 359 if (flags & FORK_PPWAIT) 360 while (p2->p_flag & P_PPWAIT) 361 tsleep(p1, PWAIT, "ppwait", 0); 362 363 /* 364 * Return child pid to parent process, 365 * marking us as parent via retval[1]. 366 */ 367 if (retval != NULL) { 368 retval[0] = p2->p_pid; 369 retval[1] = 0; 370 } 371 return (0); 372 } 373
Indexes created Mon Sep 22 10:09:38 GMT 2025