1 /* $OpenBSD: kern_fork.c,v 1.157 2014/02/10 01:38:07 guenther Exp $ */ 2 /* $NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $ */ 3 4 /* 5 * Copyright (c) 1982, 1986, 1989, 1991, 1993 6 * The Regents of the University of California. All rights reserved. 7 * (c) UNIX System Laboratories, Inc. 8 * All or some portions of this file are derived from material licensed 9 * to the University of California by American Telephone and Telegraph 10 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 11 * the permission of UNIX System Laboratories, Inc. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. Neither the name of the University nor the names of its contributors 22 * may be used to endorse or promote products derived from this software 23 * without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 * SUCH DAMAGE. 36 * 37 * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 38 */ 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/filedesc.h> 43 #include <sys/kernel.h> 44 #include <sys/malloc.h> 45 #include <sys/mount.h> 46 #include <sys/proc.h> 47 #include <sys/exec.h> 48 #include <sys/resourcevar.h> 49 #include <sys/signalvar.h> 50 #include <sys/vnode.h> 51 #include <sys/file.h> 52 #include <sys/acct.h> 53 #include <sys/ktrace.h> 54 #include <sys/sched.h> 55 #include <dev/rndvar.h> 56 #include <sys/pool.h> 57 #include <sys/mman.h> 58 #include <sys/ptrace.h> 59 60 #include <sys/syscallargs.h> 61 62 #include "systrace.h" 63 #include <dev/systrace.h> 64 65 #include <uvm/uvm_extern.h> 66 #include <uvm/uvm_map.h> 67 68 #ifdef __HAVE_MD_TCB 69 # include <machine/tcb.h> 70 #endif 71 72 int nprocesses = 1; /* process 0 */ 73 int nthreads = 1; /* proc 0 */ 74 int randompid; /* when set to 1, pid's go random */ 75 struct forkstat forkstat; 76 77 void fork_return(void *); 78 void tfork_child_return(void *); 79 int pidtaken(pid_t); 80 81 void process_new(struct proc *, struct process *); 82 83 void 84 fork_return(void *arg) 85 { 86 struct proc *p = (struct proc *)arg; 87 88 if (p->p_p->ps_flags & PS_TRACED) 89 psignal(p, SIGTRAP); 90 91 child_return(p); 92 } 93 94 /*ARGSUSED*/ 95 int 96 sys_fork(struct proc *p, void *v, register_t *retval) 97 { 98 int flags; 99 100 flags = FORK_FORK; 101 if (p->p_p->ps_ptmask & PTRACE_FORK) 102 flags |= FORK_PTRACE; 103 return (fork1(p, SIGCHLD, flags, NULL, 0, 104 fork_return, NULL, retval, NULL)); 105 } 106 107 /*ARGSUSED*/ 108 int 109 sys_vfork(struct proc *p, void *v, register_t *retval) 110 { 111 return (fork1(p, SIGCHLD, FORK_VFORK|FORK_PPWAIT, NULL, 0, NULL, 112 NULL, retval, NULL)); 113 } 114 115 int 116 sys___tfork(struct proc *p, void *v, register_t *retval) 117 { 118 struct sys___tfork_args /* { 119 syscallarg(const struct __tfork) *param; 120 syscallarg(size_t) psize; 121 } */ *uap = v; 122 size_t psize = SCARG(uap, psize); 123 struct __tfork param = { 0 }; 124 int flags; 125 int error; 126 127 if (psize == 0 || psize > sizeof(param)) 128 return (EINVAL); 129 if ((error = copyin(SCARG(uap, param), ¶m, psize))) 130 return (error); 131 #ifdef KTRACE 132 if (KTRPOINT(p, KTR_STRUCT)) 133 ktrstruct(p, "tfork", ¶m, sizeof(param)); 134 #endif 135 136 flags = FORK_TFORK | FORK_THREAD | FORK_SIGHAND | FORK_SHAREVM 137 | FORK_SHAREFILES; 138 139 return (fork1(p, 0, flags, param.tf_stack, param.tf_tid, 140 tfork_child_return, param.tf_tcb, retval, NULL)); 141 } 142 143 void 144 tfork_child_return(void *arg) 145 { 146 struct proc *p = curproc; 147 148 TCB_SET(p, arg); 149 child_return(p); 150 } 151 152 /* 153 * Allocate and initialize a new process. 154 */ 155 void 156 process_new(struct proc *p, struct process *parent) 157 { 158 struct process *pr; 159 160 pr = pool_get(&process_pool, PR_WAITOK); 161 pr->ps_mainproc = p; 162 163 TAILQ_INIT(&pr->ps_threads); 164 TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link); 165 pr->ps_pptr = parent; 166 LIST_INIT(&pr->ps_children); 167 pr->ps_refcnt = 1; 168 169 /* 170 * Make a process structure for the new process. 171 * Start by zeroing the section of proc that is zero-initialized, 172 * then copy the section that is copied directly from the parent. 173 */ 174 memset(&pr->ps_startzero, 0, 175 (caddr_t)&pr->ps_endzero - (caddr_t)&pr->ps_startzero); 176 memcpy(&pr->ps_startcopy, &parent->ps_startcopy, 177 (caddr_t)&pr->ps_endcopy - (caddr_t)&pr->ps_startcopy); 178 179 /* post-copy fixups */ 180 pr->ps_cred = pool_get(&pcred_pool, PR_WAITOK); 181 memcpy(pr->ps_cred, parent->ps_cred, sizeof(*pr->ps_cred)); 182 crhold(parent->ps_cred->pc_ucred); 183 pr->ps_limit->p_refcnt++; 184 185 /* bump references to the text vnode (for procfs) */ 186 pr->ps_textvp = parent->ps_textvp; 187 if (pr->ps_textvp) 188 vref(pr->ps_textvp); 189 190 timeout_set(&pr->ps_realit_to, realitexpire, pr); 191 192 pr->ps_flags = parent->ps_flags & (PS_SUGID | PS_SUGIDEXEC); 193 if (parent->ps_session->s_ttyvp != NULL && 194 parent->ps_flags & PS_CONTROLT) 195 atomic_setbits_int(&pr->ps_flags, PS_CONTROLT); 196 197 p->p_p = pr; 198 199 /* it's sufficiently inited to be globally visible */ 200 LIST_INSERT_HEAD(&allprocess, pr, ps_list); 201 } 202 203 /* print the 'table full' message once per 10 seconds */ 204 struct timeval fork_tfmrate = { 10, 0 }; 205 206 int 207 fork1(struct proc *curp, int exitsig, int flags, void *stack, pid_t *tidptr, 208 void (*func)(void *), void *arg, register_t *retval, 209 struct proc **rnewprocp) 210 { 211 struct process *curpr = curp->p_p; 212 struct process *pr; 213 struct proc *p; 214 uid_t uid; 215 struct vmspace *vm; 216 int count; 217 vaddr_t uaddr; 218 int s; 219 struct ptrace_state *newptstat = NULL; 220 #if NSYSTRACE > 0 221 void *newstrp = NULL; 222 #endif 223 224 /* sanity check some flag combinations */ 225 if (flags & FORK_THREAD) { 226 if ((flags & FORK_SIGHAND) == 0) 227 return (EINVAL); 228 } 229 if (flags & FORK_SIGHAND && (flags & FORK_SHAREVM) == 0) 230 return (EINVAL); 231 232 /* 233 * Although process entries are dynamically created, we still keep 234 * a global limit on the maximum number we will create. We reserve 235 * the last 5 processes to root. The variable nprocesses is the 236 * current number of processes, maxprocess is the limit. Similar 237 * rules for threads (struct proc): we reserve the last 5 to root; 238 * the variable nthreads is the current number of procs, maxthread is 239 * the limit. 240 */ 241 uid = curp->p_cred->p_ruid; 242 if ((nthreads >= maxthread - 5 && uid != 0) || nthreads >= maxthread) { 243 static struct timeval lasttfm; 244 245 if (ratecheck(&lasttfm, &fork_tfmrate)) 246 tablefull("proc"); 247 return (EAGAIN); 248 } 249 nthreads++; 250 251 if ((flags & FORK_THREAD) == 0) { 252 if ((nprocesses >= maxprocess - 5 && uid != 0) || 253 nprocesses >= maxprocess) { 254 static struct timeval lasttfm; 255 256 if (ratecheck(&lasttfm, &fork_tfmrate)) 257 tablefull("process"); 258 nthreads--; 259 return (EAGAIN); 260 } 261 nprocesses++; 262 263 /* 264 * Increment the count of processes running with 265 * this uid. Don't allow a nonprivileged user to 266 * exceed their current limit. 267 */ 268 count = chgproccnt(uid, 1); 269 if (uid != 0 && count > curp->p_rlimit[RLIMIT_NPROC].rlim_cur) { 270 (void)chgproccnt(uid, -1); 271 nprocesses--; 272 nthreads--; 273 return (EAGAIN); 274 } 275 } 276 277 uaddr = uvm_km_kmemalloc_pla(kernel_map, uvm.kernel_object, USPACE, 278 USPACE_ALIGN, UVM_KMF_ZERO, 279 no_constraint.ucr_low, no_constraint.ucr_high, 280 0, 0, USPACE/PAGE_SIZE); 281 if (uaddr == 0) { 282 if ((flags & FORK_THREAD) == 0) { 283 (void)chgproccnt(uid, -1); 284 nprocesses--; 285 } 286 nthreads--; 287 return (ENOMEM); 288 } 289 290 /* 291 * From now on, we're committed to the fork and cannot fail. 292 */ 293 294 /* Allocate new proc. */ 295 p = pool_get(&proc_pool, PR_WAITOK); 296 297 p->p_stat = SIDL; /* protect against others */ 298 p->p_exitsig = exitsig; 299 p->p_flag = 0; 300 p->p_xstat = 0; 301 302 if (flags & FORK_THREAD) { 303 atomic_setbits_int(&p->p_flag, P_THREAD); 304 p->p_p = pr = curpr; 305 pr->ps_refcnt++; 306 } else { 307 process_new(p, curpr); 308 pr = p->p_p; 309 } 310 311 /* 312 * Make a proc table entry for the new process. 313 * Start by zeroing the section of proc that is zero-initialized, 314 * then copy the section that is copied directly from the parent. 315 */ 316 memset(&p->p_startzero, 0, 317 (caddr_t)&p->p_endzero - (caddr_t)&p->p_startzero); 318 memcpy(&p->p_startcopy, &curp->p_startcopy, 319 (caddr_t)&p->p_endcopy - (caddr_t)&p->p_startcopy); 320 321 /* 322 * Initialize the timeouts. 323 */ 324 timeout_set(&p->p_sleep_to, endtsleep, p); 325 326 /* 327 * Duplicate sub-structures as needed. 328 * Increase reference counts on shared objects. 329 */ 330 if ((flags & FORK_THREAD) == 0) { 331 if (curpr->ps_flags & PS_PROFIL) 332 startprofclock(pr); 333 if ((flags & FORK_PTRACE) && (curpr->ps_flags & PS_TRACED)) 334 atomic_setbits_int(&pr->ps_flags, PS_TRACED); 335 if (flags & FORK_NOZOMBIE) 336 atomic_setbits_int(&pr->ps_flags, PS_NOZOMBIE); 337 } 338 339 if (flags & FORK_SHAREFILES) 340 p->p_fd = fdshare(curp); 341 else 342 p->p_fd = fdcopy(curp); 343 344 if (flags & FORK_PPWAIT) { 345 atomic_setbits_int(&pr->ps_flags, PS_PPWAIT); 346 atomic_setbits_int(&curpr->ps_flags, PS_ISPWAIT); 347 } 348 349 #ifdef KTRACE 350 /* 351 * Copy traceflag and tracefile if enabled. 352 * If not inherited, these were zeroed above. 353 */ 354 if ((flags & FORK_THREAD) == 0 && curpr->ps_traceflag & KTRFAC_INHERIT) 355 ktrsettrace(pr, curpr->ps_traceflag, curpr->ps_tracevp, 356 curpr->ps_tracecred); 357 #endif 358 359 /* 360 * set priority of child to be that of parent 361 * XXX should move p_estcpu into the region of struct proc which gets 362 * copied. 363 */ 364 scheduler_fork_hook(curp, p); 365 366 /* 367 * Create signal actions for the child process. 368 */ 369 if (flags & FORK_SIGHAND) 370 p->p_sigacts = sigactsshare(curp); 371 else 372 p->p_sigacts = sigactsinit(curp); 373 if (flags & FORK_THREAD) 374 sigstkinit(&p->p_sigstk); 375 376 /* 377 * If emulation has process fork hook, call it now. 378 */ 379 if (p->p_emul->e_proc_fork) 380 (*p->p_emul->e_proc_fork)(p, curp); 381 382 p->p_addr = (struct user *)uaddr; 383 384 /* 385 * Finish creating the child process. It will return through a 386 * different path later. 387 */ 388 uvm_fork(curp, p, ((flags & FORK_SHAREVM) ? TRUE : FALSE), stack, 389 0, func ? func : child_return, arg ? arg : p); 390 391 vm = p->p_vmspace; 392 393 if (flags & FORK_FORK) { 394 forkstat.cntfork++; 395 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 396 } else if (flags & FORK_VFORK) { 397 forkstat.cntvfork++; 398 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 399 } else if (flags & FORK_TFORK) { 400 forkstat.cnttfork++; 401 } else { 402 forkstat.cntkthread++; 403 forkstat.sizkthread += vm->vm_dsize + vm->vm_ssize; 404 } 405 406 if (pr->ps_flags & PS_TRACED && flags & FORK_FORK) 407 newptstat = malloc(sizeof(*newptstat), M_SUBPROC, M_WAITOK); 408 #if NSYSTRACE > 0 409 if (ISSET(curp->p_flag, P_SYSTRACE)) 410 newstrp = systrace_getproc(); 411 #endif 412 413 p->p_pid = allocpid(); 414 415 LIST_INSERT_HEAD(&allproc, p, p_list); 416 LIST_INSERT_HEAD(PIDHASH(p->p_pid), p, p_hash); 417 if ((flags & FORK_THREAD) == 0) { 418 LIST_INSERT_AFTER(curpr, pr, ps_pglist); 419 LIST_INSERT_HEAD(&curpr->ps_children, pr, ps_sibling); 420 421 if (pr->ps_flags & PS_TRACED) { 422 pr->ps_oppid = curpr->ps_pid; 423 if (pr->ps_pptr != curpr->ps_pptr) 424 proc_reparent(pr, curpr->ps_pptr); 425 426 /* 427 * Set ptrace status. 428 */ 429 if (flags & FORK_FORK) { 430 pr->ps_ptstat = newptstat; 431 newptstat = NULL; 432 curpr->ps_ptstat->pe_report_event = PTRACE_FORK; 433 pr->ps_ptstat->pe_report_event = PTRACE_FORK; 434 curpr->ps_ptstat->pe_other_pid = pr->ps_pid; 435 pr->ps_ptstat->pe_other_pid = curpr->ps_pid; 436 } 437 } 438 } else { 439 TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link); 440 /* 441 * if somebody else wants to take us to single threaded mode, 442 * count ourselves in. 443 */ 444 if (pr->ps_single) { 445 curpr->ps_singlecount++; 446 atomic_setbits_int(&p->p_flag, P_SUSPSINGLE); 447 } 448 } 449 450 #if NSYSTRACE > 0 451 if (newstrp) 452 systrace_fork(curp, p, newstrp); 453 #endif 454 455 if (tidptr != NULL) { 456 pid_t pid = p->p_pid + THREAD_PID_OFFSET; 457 458 if (copyout(&pid, tidptr, sizeof(pid))) 459 psignal(curp, SIGSEGV); 460 } 461 462 /* 463 * For new processes, set accounting bits 464 */ 465 if ((flags & FORK_THREAD) == 0) { 466 getnanotime(&pr->ps_start); 467 pr->ps_acflag = AFORK; 468 } 469 470 /* 471 * Make child runnable and add to run queue. 472 */ 473 if ((flags & FORK_IDLE) == 0) { 474 SCHED_LOCK(s); 475 p->p_stat = SRUN; 476 p->p_cpu = sched_choosecpu_fork(curp, flags); 477 setrunqueue(p); 478 SCHED_UNLOCK(s); 479 } else 480 p->p_cpu = arg; 481 482 if (newptstat) 483 free(newptstat, M_SUBPROC); 484 485 /* 486 * Notify any interested parties about the new process. 487 */ 488 if ((flags & FORK_THREAD) == 0) 489 KNOTE(&curpr->ps_klist, NOTE_FORK | p->p_pid); 490 491 /* 492 * Update stats now that we know the fork was successful. 493 */ 494 uvmexp.forks++; 495 if (flags & FORK_PPWAIT) 496 uvmexp.forks_ppwait++; 497 if (flags & FORK_SHAREVM) 498 uvmexp.forks_sharevm++; 499 500 /* 501 * Pass a pointer to the new process to the caller. 502 */ 503 if (rnewprocp != NULL) 504 *rnewprocp = p; 505 506 /* 507 * Preserve synchronization semantics of vfork. If waiting for 508 * child to exec or exit, set PS_PPWAIT on child and PS_ISPWAIT 509 * on ourselves, and sleep on our process for the latter flag 510 * to go away. 511 * XXX Need to stop other rthreads in the parent 512 */ 513 if (flags & FORK_PPWAIT) 514 while (curpr->ps_flags & PS_ISPWAIT) 515 tsleep(curpr, PWAIT, "ppwait", 0); 516 517 /* 518 * If we're tracing the child, alert the parent too. 519 */ 520 if ((flags & FORK_PTRACE) && (curpr->ps_flags & PS_TRACED)) 521 psignal(curp, SIGTRAP); 522 523 /* 524 * Return child pid to parent process, 525 * marking us as parent via retval[1]. 526 */ 527 if (retval != NULL) { 528 retval[0] = p->p_pid + 529 (flags & FORK_THREAD ? THREAD_PID_OFFSET : 0); 530 retval[1] = 0; 531 } 532 return (0); 533 } 534 535 /* 536 * Checks for current use of a pid, either as a pid or pgid. 537 */ 538 pid_t oldpids[100]; 539 int 540 ispidtaken(pid_t pid) 541 { 542 uint32_t i; 543 struct process *pr; 544 545 for (i = 0; i < nitems(oldpids); i++) 546 if (pid == oldpids[i]) 547 return (1); 548 549 if (pfind(pid) != NULL) 550 return (1); 551 if (pgfind(pid) != NULL) 552 return (1); 553 LIST_FOREACH(pr, &zombprocess, ps_list) { 554 if (pr->ps_pid == pid || 555 (pr->ps_pgrp && pr->ps_pgrp->pg_id == pid)) 556 return (1); 557 } 558 return (0); 559 } 560 561 /* Find an unused pid satisfying 1 <= lastpid <= PID_MAX */ 562 pid_t 563 allocpid(void) 564 { 565 static pid_t lastpid; 566 pid_t pid; 567 568 if (!randompid) { 569 /* only used early on for system processes */ 570 pid = ++lastpid; 571 } else { 572 do { 573 pid = 1 + arc4random_uniform(PID_MAX); 574 } while (ispidtaken(pid)); 575 } 576 577 return pid; 578 } 579 580 void 581 freepid(pid_t pid) 582 { 583 static uint32_t idx; 584 585 oldpids[idx++ % nitems(oldpids)] = pid; 586 } 587 588 #if defined(MULTIPROCESSOR) 589 /* 590 * XXX This is a slight hack to get newly-formed processes to 591 * XXX acquire the kernel lock as soon as they run. 592 */ 593 void 594 proc_trampoline_mp(void) 595 { 596 struct proc *p; 597 598 p = curproc; 599 600 SCHED_ASSERT_LOCKED(); 601 __mp_unlock(&sched_lock); 602 spl0(); 603 SCHED_ASSERT_UNLOCKED(); 604 KASSERT(__mp_lock_held(&kernel_lock) == 0); 605 606 KERNEL_LOCK(); 607 } 608 #endif 609