1 /* $OpenBSD: kern_fork.c,v 1.194 2017/02/08 20:58:30 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/vmmeter.h> 52 #include <sys/file.h> 53 #include <sys/acct.h> 54 #include <sys/ktrace.h> 55 #include <sys/sched.h> 56 #include <sys/sysctl.h> 57 #include <sys/pool.h> 58 #include <sys/mman.h> 59 #include <sys/ptrace.h> 60 #include <sys/atomic.h> 61 #include <sys/pledge.h> 62 #include <sys/unistd.h> 63 64 #include <sys/syscallargs.h> 65 66 #include <uvm/uvm.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 pid_t alloctid(void); 80 pid_t allocpid(void); 81 int ispidtaken(pid_t); 82 83 void process_new(struct proc *, struct process *, int); 84 85 void 86 fork_return(void *arg) 87 { 88 struct proc *p = (struct proc *)arg; 89 90 if (p->p_p->ps_flags & PS_TRACED) 91 psignal(p, SIGTRAP); 92 93 child_return(p); 94 } 95 96 int 97 sys_fork(struct proc *p, void *v, register_t *retval) 98 { 99 int flags; 100 101 flags = FORK_FORK; 102 if (p->p_p->ps_ptmask & PTRACE_FORK) 103 flags |= FORK_PTRACE; 104 return (fork1(p, flags, NULL, 0, fork_return, NULL, retval, NULL)); 105 } 106 107 int 108 sys_vfork(struct proc *p, void *v, register_t *retval) 109 { 110 return (fork1(p, FORK_VFORK|FORK_PPWAIT, NULL, 0, NULL, 111 NULL, retval, NULL)); 112 } 113 114 int 115 sys___tfork(struct proc *p, void *v, register_t *retval) 116 { 117 struct sys___tfork_args /* { 118 syscallarg(const struct __tfork) *param; 119 syscallarg(size_t) psize; 120 } */ *uap = v; 121 size_t psize = SCARG(uap, psize); 122 struct __tfork param = { 0 }; 123 int flags; 124 int error; 125 126 if (psize == 0 || psize > sizeof(param)) 127 return (EINVAL); 128 if ((error = copyin(SCARG(uap, param), ¶m, psize))) 129 return (error); 130 #ifdef KTRACE 131 if (KTRPOINT(p, KTR_STRUCT)) 132 ktrstruct(p, "tfork", ¶m, sizeof(param)); 133 #endif 134 135 flags = FORK_TFORK | FORK_THREAD | FORK_SIGHAND | FORK_SHAREVM 136 | FORK_SHAREFILES; 137 138 return (fork1(p, flags, param.tf_stack, param.tf_tid, 139 tfork_child_return, param.tf_tcb, retval, NULL)); 140 } 141 142 void 143 tfork_child_return(void *arg) 144 { 145 struct proc *p = curproc; 146 147 TCB_SET(p, arg); 148 child_return(p); 149 } 150 151 /* 152 * Initialize common bits of a process structure, given the initial thread. 153 */ 154 void 155 process_initialize(struct process *pr, struct proc *p) 156 { 157 /* initialize the thread links */ 158 pr->ps_mainproc = p; 159 TAILQ_INIT(&pr->ps_threads); 160 TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link); 161 pr->ps_refcnt = 1; 162 p->p_p = pr; 163 164 /* give the process the same creds as the initial thread */ 165 pr->ps_ucred = p->p_ucred; 166 crhold(pr->ps_ucred); 167 KASSERT(p->p_ucred->cr_ref >= 2); /* new thread and new process */ 168 169 LIST_INIT(&pr->ps_children); 170 171 timeout_set(&pr->ps_realit_to, realitexpire, pr); 172 } 173 174 175 /* 176 * Allocate and initialize a new process. 177 */ 178 void 179 process_new(struct proc *p, struct process *parent, int flags) 180 { 181 struct process *pr; 182 183 pr = pool_get(&process_pool, PR_WAITOK); 184 185 /* 186 * Make a process structure for the new process. 187 * Start by zeroing the section of proc that is zero-initialized, 188 * then copy the section that is copied directly from the parent. 189 */ 190 memset(&pr->ps_startzero, 0, 191 (caddr_t)&pr->ps_endzero - (caddr_t)&pr->ps_startzero); 192 memcpy(&pr->ps_startcopy, &parent->ps_startcopy, 193 (caddr_t)&pr->ps_endcopy - (caddr_t)&pr->ps_startcopy); 194 195 process_initialize(pr, p); 196 pr->ps_pid = allocpid(); 197 198 /* post-copy fixups */ 199 pr->ps_pptr = parent; 200 pr->ps_limit->p_refcnt++; 201 202 /* bump references to the text vnode (for sysctl) */ 203 pr->ps_textvp = parent->ps_textvp; 204 if (pr->ps_textvp) 205 vref(pr->ps_textvp); 206 207 pr->ps_flags = parent->ps_flags & 208 (PS_SUGID | PS_SUGIDEXEC | PS_PLEDGE | PS_WXNEEDED); 209 if (parent->ps_session->s_ttyvp != NULL) 210 pr->ps_flags |= parent->ps_flags & PS_CONTROLT; 211 212 /* 213 * Duplicate sub-structures as needed. 214 * Increase reference counts on shared objects. 215 */ 216 if (flags & FORK_SHAREFILES) 217 pr->ps_fd = fdshare(parent); 218 else 219 pr->ps_fd = fdcopy(parent); 220 if (flags & FORK_SIGHAND) 221 pr->ps_sigacts = sigactsshare(parent); 222 else 223 pr->ps_sigacts = sigactsinit(parent); 224 if (flags & FORK_SHAREVM) 225 pr->ps_vmspace = uvmspace_share(parent); 226 else 227 pr->ps_vmspace = uvmspace_fork(parent); 228 229 if (pr->ps_pledgepaths) 230 pr->ps_pledgepaths->wl_ref++; 231 232 if (parent->ps_flags & PS_PROFIL) 233 startprofclock(pr); 234 if (flags & FORK_PTRACE) 235 pr->ps_flags |= parent->ps_flags & PS_TRACED; 236 if (flags & FORK_NOZOMBIE) 237 pr->ps_flags |= PS_NOZOMBIE; 238 if (flags & FORK_SYSTEM) 239 pr->ps_flags |= PS_SYSTEM; 240 241 /* mark as embryo to protect against others */ 242 pr->ps_flags |= PS_EMBRYO; 243 244 /* Force visibility of all of the above changes */ 245 membar_producer(); 246 247 /* it's sufficiently inited to be globally visible */ 248 LIST_INSERT_HEAD(&allprocess, pr, ps_list); 249 } 250 251 /* print the 'table full' message once per 10 seconds */ 252 struct timeval fork_tfmrate = { 10, 0 }; 253 254 int 255 fork1(struct proc *curp, int flags, void *stack, pid_t *tidptr, 256 void (*func)(void *), void *arg, register_t *retval, 257 struct proc **rnewprocp) 258 { 259 struct process *curpr = curp->p_p; 260 struct process *pr; 261 struct proc *p; 262 uid_t uid; 263 struct vmspace *vm; 264 int count; 265 vaddr_t uaddr; 266 int s; 267 struct ptrace_state *newptstat = NULL; 268 269 /* sanity check some flag combinations */ 270 if (flags & FORK_THREAD) { 271 if ((flags & FORK_SHAREFILES) == 0 || 272 (flags & FORK_SIGHAND) == 0 || 273 (flags & FORK_SYSTEM) != 0) 274 return (EINVAL); 275 } 276 if (flags & FORK_SIGHAND && (flags & FORK_SHAREVM) == 0) 277 return (EINVAL); 278 279 /* 280 * Although process entries are dynamically created, we still keep 281 * a global limit on the maximum number we will create. We reserve 282 * the last 5 processes to root. The variable nprocesses is the 283 * current number of processes, maxprocess is the limit. Similar 284 * rules for threads (struct proc): we reserve the last 5 to root; 285 * the variable nthreads is the current number of procs, maxthread is 286 * the limit. 287 */ 288 uid = curp->p_ucred->cr_ruid; 289 if ((nthreads >= maxthread - 5 && uid != 0) || nthreads >= maxthread) { 290 static struct timeval lasttfm; 291 292 if (ratecheck(&lasttfm, &fork_tfmrate)) 293 tablefull("proc"); 294 return (EAGAIN); 295 } 296 nthreads++; 297 298 if ((flags & FORK_THREAD) == 0) { 299 if ((nprocesses >= maxprocess - 5 && uid != 0) || 300 nprocesses >= maxprocess) { 301 static struct timeval lasttfm; 302 303 if (ratecheck(&lasttfm, &fork_tfmrate)) 304 tablefull("process"); 305 nthreads--; 306 return (EAGAIN); 307 } 308 nprocesses++; 309 310 /* 311 * Increment the count of processes running with 312 * this uid. Don't allow a nonprivileged user to 313 * exceed their current limit. 314 */ 315 count = chgproccnt(uid, 1); 316 if (uid != 0 && count > curp->p_rlimit[RLIMIT_NPROC].rlim_cur) { 317 (void)chgproccnt(uid, -1); 318 nprocesses--; 319 nthreads--; 320 return (EAGAIN); 321 } 322 } 323 324 uaddr = uvm_uarea_alloc(); 325 if (uaddr == 0) { 326 if ((flags & FORK_THREAD) == 0) { 327 (void)chgproccnt(uid, -1); 328 nprocesses--; 329 } 330 nthreads--; 331 return (ENOMEM); 332 } 333 334 /* 335 * From now on, we're committed to the fork and cannot fail. 336 */ 337 338 /* Allocate new proc. */ 339 p = pool_get(&proc_pool, PR_WAITOK); 340 341 p->p_stat = SIDL; /* protect against others */ 342 p->p_flag = 0; 343 344 /* 345 * Make a proc table entry for the new process. 346 * Start by zeroing the section of proc that is zero-initialized, 347 * then copy the section that is copied directly from the parent. 348 */ 349 memset(&p->p_startzero, 0, 350 (caddr_t)&p->p_endzero - (caddr_t)&p->p_startzero); 351 memcpy(&p->p_startcopy, &curp->p_startcopy, 352 (caddr_t)&p->p_endcopy - (caddr_t)&p->p_startcopy); 353 crhold(p->p_ucred); 354 355 /* 356 * Initialize the timeouts. 357 */ 358 timeout_set(&p->p_sleep_to, endtsleep, p); 359 360 if (flags & FORK_THREAD) { 361 atomic_setbits_int(&p->p_flag, P_THREAD); 362 p->p_p = pr = curpr; 363 pr->ps_refcnt++; 364 } else { 365 process_new(p, curpr, flags); 366 pr = p->p_p; 367 } 368 p->p_fd = pr->ps_fd; 369 p->p_vmspace = pr->ps_vmspace; 370 if (pr->ps_flags & PS_SYSTEM) 371 atomic_setbits_int(&p->p_flag, P_SYSTEM); 372 373 if (flags & FORK_PPWAIT) { 374 atomic_setbits_int(&pr->ps_flags, PS_PPWAIT); 375 atomic_setbits_int(&curpr->ps_flags, PS_ISPWAIT); 376 } 377 378 #ifdef KTRACE 379 /* 380 * Copy traceflag and tracefile if enabled. 381 * If not inherited, these were zeroed above. 382 */ 383 if ((flags & FORK_THREAD) == 0 && curpr->ps_traceflag & KTRFAC_INHERIT) 384 ktrsettrace(pr, curpr->ps_traceflag, curpr->ps_tracevp, 385 curpr->ps_tracecred); 386 #endif 387 388 /* 389 * set priority of child to be that of parent 390 * XXX should move p_estcpu into the region of struct proc which gets 391 * copied. 392 */ 393 scheduler_fork_hook(curp, p); 394 395 if (flags & FORK_THREAD) 396 sigstkinit(&p->p_sigstk); 397 398 p->p_addr = (struct user *)uaddr; 399 400 /* 401 * Finish creating the child thread. cpu_fork() will copy 402 * and update the pcb and make the child ready to run. If 403 * this is a normal user fork, the child will exit directly 404 * to user mode via child_return() on its first time slice 405 * and will not return here. If this is a kernel thread, 406 * the specified entry point will be executed. 407 */ 408 cpu_fork(curp, p, stack, 0, func ? func : child_return, arg ? arg : p); 409 410 vm = pr->ps_vmspace; 411 412 if (flags & FORK_FORK) { 413 forkstat.cntfork++; 414 forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; 415 } else if (flags & FORK_VFORK) { 416 forkstat.cntvfork++; 417 forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; 418 } else if (flags & FORK_TFORK) { 419 forkstat.cnttfork++; 420 } else { 421 forkstat.cntkthread++; 422 forkstat.sizkthread += vm->vm_dsize + vm->vm_ssize; 423 } 424 425 if (pr->ps_flags & PS_TRACED && flags & FORK_FORK) 426 newptstat = malloc(sizeof(*newptstat), M_SUBPROC, M_WAITOK); 427 428 p->p_tid = alloctid(); 429 430 LIST_INSERT_HEAD(&allproc, p, p_list); 431 LIST_INSERT_HEAD(TIDHASH(p->p_tid), p, p_hash); 432 if ((flags & FORK_THREAD) == 0) { 433 LIST_INSERT_HEAD(PIDHASH(pr->ps_pid), pr, ps_hash); 434 LIST_INSERT_AFTER(curpr, pr, ps_pglist); 435 LIST_INSERT_HEAD(&curpr->ps_children, pr, ps_sibling); 436 437 if (pr->ps_flags & PS_TRACED) { 438 pr->ps_oppid = curpr->ps_pid; 439 if (pr->ps_pptr != curpr->ps_pptr) 440 proc_reparent(pr, curpr->ps_pptr); 441 442 /* 443 * Set ptrace status. 444 */ 445 if (flags & FORK_FORK) { 446 pr->ps_ptstat = newptstat; 447 newptstat = NULL; 448 curpr->ps_ptstat->pe_report_event = PTRACE_FORK; 449 pr->ps_ptstat->pe_report_event = PTRACE_FORK; 450 curpr->ps_ptstat->pe_other_pid = pr->ps_pid; 451 pr->ps_ptstat->pe_other_pid = curpr->ps_pid; 452 } 453 } 454 } else { 455 TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link); 456 /* 457 * if somebody else wants to take us to single threaded mode, 458 * count ourselves in. 459 */ 460 if (pr->ps_single) { 461 curpr->ps_singlecount++; 462 atomic_setbits_int(&p->p_flag, P_SUSPSINGLE); 463 } 464 } 465 466 if (tidptr != NULL) { 467 pid_t tid = p->p_tid + THREAD_PID_OFFSET; 468 469 if (copyout(&tid, tidptr, sizeof(tid))) 470 psignal(curp, SIGSEGV); 471 } 472 473 /* 474 * For new processes, set accounting bits and mark as complete. 475 */ 476 if ((flags & FORK_THREAD) == 0) { 477 getnanotime(&pr->ps_start); 478 pr->ps_acflag = AFORK; 479 atomic_clearbits_int(&pr->ps_flags, PS_EMBRYO); 480 } 481 482 /* 483 * Make child runnable and add to run queue. 484 */ 485 if ((flags & FORK_IDLE) == 0) { 486 SCHED_LOCK(s); 487 p->p_stat = SRUN; 488 p->p_cpu = sched_choosecpu_fork(curp, flags); 489 setrunqueue(p); 490 SCHED_UNLOCK(s); 491 } else 492 p->p_cpu = arg; 493 494 if (newptstat) 495 free(newptstat, M_SUBPROC, sizeof(*newptstat)); 496 497 /* 498 * Notify any interested parties about the new process. 499 */ 500 if ((flags & FORK_THREAD) == 0) 501 KNOTE(&curpr->ps_klist, NOTE_FORK | pr->ps_pid); 502 503 /* 504 * Update stats now that we know the fork was successful. 505 */ 506 uvmexp.forks++; 507 if (flags & FORK_PPWAIT) 508 uvmexp.forks_ppwait++; 509 if (flags & FORK_SHAREVM) 510 uvmexp.forks_sharevm++; 511 512 /* 513 * Pass a pointer to the new process to the caller. 514 */ 515 if (rnewprocp != NULL) 516 *rnewprocp = p; 517 518 /* 519 * Preserve synchronization semantics of vfork. If waiting for 520 * child to exec or exit, set PS_PPWAIT on child and PS_ISPWAIT 521 * on ourselves, and sleep on our process for the latter flag 522 * to go away. 523 * XXX Need to stop other rthreads in the parent 524 */ 525 if (flags & FORK_PPWAIT) 526 while (curpr->ps_flags & PS_ISPWAIT) 527 tsleep(curpr, PWAIT, "ppwait", 0); 528 529 /* 530 * If we're tracing the child, alert the parent too. 531 */ 532 if ((flags & FORK_PTRACE) && (curpr->ps_flags & PS_TRACED)) 533 psignal(curp, SIGTRAP); 534 535 /* 536 * Return child pid to parent process, 537 * marking us as parent via retval[1]. 538 */ 539 if (retval != NULL) { 540 retval[0] = (flags & FORK_THREAD) == 0 ? pr->ps_pid : 541 (p->p_tid + THREAD_PID_OFFSET); 542 retval[1] = 0; 543 } 544 return (0); 545 } 546 547 /* Find an unused tid */ 548 pid_t 549 alloctid(void) 550 { 551 pid_t tid; 552 553 do { 554 /* (0 .. TID_MASK+1] */ 555 tid = 1 + (arc4random() & TID_MASK); 556 } while (tfind(tid) != NULL); 557 558 return (tid); 559 } 560 561 /* 562 * Checks for current use of a pid, either as a pid or pgid. 563 */ 564 pid_t oldpids[128]; 565 int 566 ispidtaken(pid_t pid) 567 { 568 uint32_t i; 569 570 for (i = 0; i < nitems(oldpids); i++) 571 if (pid == oldpids[i]) 572 return (1); 573 574 if (prfind(pid) != NULL) 575 return (1); 576 if (pgfind(pid) != NULL) 577 return (1); 578 if (zombiefind(pid) != NULL) 579 return (1); 580 return (0); 581 } 582 583 /* Find an unused pid */ 584 pid_t 585 allocpid(void) 586 { 587 static pid_t lastpid; 588 pid_t pid; 589 590 if (!randompid) { 591 /* only used early on for system processes */ 592 pid = ++lastpid; 593 } else { 594 /* Find an unused pid satisfying lastpid < pid <= PID_MAX */ 595 do { 596 pid = arc4random_uniform(PID_MAX - lastpid) + 1 + 597 lastpid; 598 } while (ispidtaken(pid)); 599 } 600 601 return pid; 602 } 603 604 void 605 freepid(pid_t pid) 606 { 607 static uint32_t idx; 608 609 oldpids[idx++ % nitems(oldpids)] = pid; 610 } 611 612 #if defined(MULTIPROCESSOR) 613 /* 614 * XXX This is a slight hack to get newly-formed processes to 615 * XXX acquire the kernel lock as soon as they run. 616 */ 617 void 618 proc_trampoline_mp(void) 619 { 620 SCHED_ASSERT_LOCKED(); 621 __mp_unlock(&sched_lock); 622 spl0(); 623 SCHED_ASSERT_UNLOCKED(); 624 KERNEL_ASSERT_UNLOCKED(); 625 626 KERNEL_LOCK(); 627 } 628 #endif 629