Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fork.c
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1 /* $NetBSD: kern_fork.c,v 1.229 2022/07/01 09:54:36 prlw1 Exp $ */ 2 3 /*- 4 * Copyright (c) 1999, 2001, 2004, 2006, 2007, 2008, 2019 5 * The NetBSD Foundation, Inc. 6 * All rights reserved. 7 * 8 * This code is derived from software contributed to The NetBSD Foundation 9 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 10 * NASA Ames Research Center, by Charles M. Hannum, and by Andrew Doran. 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 * 21 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 23 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 24 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 25 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 26 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 27 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 28 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 29 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 30 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 31 * POSSIBILITY OF SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 1982, 1986, 1989, 1991, 1993 36 * The Regents of the University of California. All rights reserved. 37 * (c) UNIX System Laboratories, Inc. 38 * All or some portions of this file are derived from material licensed 39 * to the University of California by American Telephone and Telegraph 40 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 41 * the permission of UNIX System Laboratories, Inc. 42 * 43 * Redistribution and use in source and binary forms, with or without 44 * modification, are permitted provided that the following conditions 45 * are met: 46 * 1. Redistributions of source code must retain the above copyright 47 * notice, this list of conditions and the following disclaimer. 48 * 2. Redistributions in binary form must reproduce the above copyright 49 * notice, this list of conditions and the following disclaimer in the 50 * documentation and/or other materials provided with the distribution. 51 * 3. Neither the name of the University nor the names of its contributors 52 * may be used to endorse or promote products derived from this software 53 * without specific prior written permission. 54 * 55 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 56 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 57 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 58 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 59 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 60 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 61 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 62 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 63 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 64 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 65 * SUCH DAMAGE. 66 * 67 * @(#)kern_fork.c 8.8 (Berkeley) 2/14/95 68 */ 69 70 #include <sys/cdefs.h> 71 __KERNEL_RCSID(0, "$NetBSD: kern_fork.c,v 1.229 2022/07/01 09:54:36 prlw1 Exp $"); 72 73 #include "opt_ktrace.h" 74 #include "opt_dtrace.h" 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/filedesc.h> 79 #include <sys/kernel.h> 80 #include <sys/pool.h> 81 #include <sys/mount.h> 82 #include <sys/proc.h> 83 #include <sys/ras.h> 84 #include <sys/resourcevar.h> 85 #include <sys/vnode.h> 86 #include <sys/file.h> 87 #include <sys/acct.h> 88 #include <sys/ktrace.h> 89 #include <sys/sched.h> 90 #include <sys/signalvar.h> 91 #include <sys/syscall.h> 92 #include <sys/kauth.h> 93 #include <sys/atomic.h> 94 #include <sys/syscallargs.h> 95 #include <sys/uidinfo.h> 96 #include <sys/sdt.h> 97 #include <sys/ptrace.h> 98 99 /* 100 * DTrace SDT provider definitions 101 */ 102 SDT_PROVIDER_DECLARE(proc); 103 SDT_PROBE_DEFINE3(proc, kernel, , create, 104 "struct proc *", /* new process */ 105 "struct proc *", /* parent process */ 106 "int" /* flags */); 107 108 u_int nprocs __cacheline_aligned = 1; /* process 0 */ 109 110 /* 111 * Number of ticks to sleep if fork() would fail due to process hitting 112 * limits. Exported in miliseconds to userland via sysctl. 113 */ 114 int forkfsleep = 0; 115 116 int 117 sys_fork(struct lwp *l, const void *v, register_t *retval) 118 { 119 120 return fork1(l, 0, SIGCHLD, NULL, 0, NULL, NULL, retval); 121 } 122 123 /* 124 * vfork(2) system call compatible with 4.4BSD (i.e. BSD with Mach VM). 125 * Address space is not shared, but parent is blocked until child exit. 126 */ 127 int 128 sys_vfork(struct lwp *l, const void *v, register_t *retval) 129 { 130 131 return fork1(l, FORK_PPWAIT, SIGCHLD, NULL, 0, NULL, NULL, 132 retval); 133 } 134 135 /* 136 * New vfork(2) system call for NetBSD, which implements original 3BSD vfork(2) 137 * semantics. Address space is shared, and parent is blocked until child exit. 138 */ 139 int 140 sys___vfork14(struct lwp *l, const void *v, register_t *retval) 141 { 142 143 return fork1(l, FORK_PPWAIT|FORK_SHAREVM, SIGCHLD, NULL, 0, 144 NULL, NULL, retval); 145 } 146 147 /* 148 * Linux-compatible __clone(2) system call. 149 */ 150 int 151 sys___clone(struct lwp *l, const struct sys___clone_args *uap, 152 register_t *retval) 153 { 154 /* { 155 syscallarg(int) flags; 156 syscallarg(void *) stack; 157 } */ 158 int flags, sig; 159 160 /* 161 * We don't support the CLONE_PTRACE flag. 162 */ 163 if (SCARG(uap, flags) & (CLONE_PTRACE)) 164 return EINVAL; 165 166 /* 167 * Linux enforces CLONE_VM with CLONE_SIGHAND, do same. 168 */ 169 if (SCARG(uap, flags) & CLONE_SIGHAND 170 && (SCARG(uap, flags) & CLONE_VM) == 0) 171 return EINVAL; 172 173 flags = 0; 174 175 if (SCARG(uap, flags) & CLONE_VM) 176 flags |= FORK_SHAREVM; 177 if (SCARG(uap, flags) & CLONE_FS) 178 flags |= FORK_SHARECWD; 179 if (SCARG(uap, flags) & CLONE_FILES) 180 flags |= FORK_SHAREFILES; 181 if (SCARG(uap, flags) & CLONE_SIGHAND) 182 flags |= FORK_SHARESIGS; 183 if (SCARG(uap, flags) & CLONE_VFORK) 184 flags |= FORK_PPWAIT; 185 186 sig = SCARG(uap, flags) & CLONE_CSIGNAL; 187 if (sig < 0 || sig >= _NSIG) 188 return EINVAL; 189 190 /* 191 * Note that the Linux API does not provide a portable way of 192 * specifying the stack area; the caller must know if the stack 193 * grows up or down. So, we pass a stack size of 0, so that the 194 * code that makes this adjustment is a noop. 195 */ 196 return fork1(l, flags, sig, SCARG(uap, stack), 0, 197 NULL, NULL, retval); 198 } 199 200 /* 201 * Print the 'table full' message once per 10 seconds. 202 */ 203 static struct timeval fork_tfmrate = { 10, 0 }; 204 205 /* 206 * Check if a process is traced and shall inform about FORK events. 207 */ 208 static inline bool 209 tracefork(struct proc *p, int flags) 210 { 211 212 return (p->p_slflag & (PSL_TRACEFORK|PSL_TRACED)) == 213 (PSL_TRACEFORK|PSL_TRACED) && (flags & FORK_PPWAIT) == 0; 214 } 215 216 /* 217 * Check if a process is traced and shall inform about VFORK events. 218 */ 219 static inline bool 220 tracevfork(struct proc *p, int flags) 221 { 222 223 return (p->p_slflag & (PSL_TRACEVFORK|PSL_TRACED)) == 224 (PSL_TRACEVFORK|PSL_TRACED) && (flags & FORK_PPWAIT) != 0; 225 } 226 227 /* 228 * Check if a process is traced and shall inform about VFORK_DONE events. 229 */ 230 static inline bool 231 tracevforkdone(struct proc *p, int flags) 232 { 233 234 return (p->p_slflag & (PSL_TRACEVFORK_DONE|PSL_TRACED)) == 235 (PSL_TRACEVFORK_DONE|PSL_TRACED) && (flags & FORK_PPWAIT); 236 } 237 238 /* 239 * General fork call. Note that another LWP in the process may call exec() 240 * or exit() while we are forking. It's safe to continue here, because 241 * neither operation will complete until all LWPs have exited the process. 242 */ 243 int 244 fork1(struct lwp *l1, int flags, int exitsig, void *stack, size_t stacksize, 245 void (*func)(void *), void *arg, register_t *retval) 246 { 247 struct proc *p1, *p2, *parent; 248 struct plimit *p1_lim; 249 uid_t uid; 250 struct lwp *l2; 251 int count; 252 vaddr_t uaddr; 253 int tnprocs; 254 int error = 0; 255 256 p1 = l1->l_proc; 257 uid = kauth_cred_getuid(l1->l_cred); 258 tnprocs = atomic_inc_uint_nv(&nprocs); 259 260 /* 261 * Although process entries are dynamically created, we still keep 262 * a global limit on the maximum number we will create. 263 */ 264 if (__predict_false(tnprocs >= maxproc)) 265 error = -1; 266 else 267 error = kauth_authorize_process(l1->l_cred, 268 KAUTH_PROCESS_FORK, p1, KAUTH_ARG(tnprocs), NULL, NULL); 269 270 if (error) { 271 static struct timeval lasttfm; 272 atomic_dec_uint(&nprocs); 273 if (ratecheck(&lasttfm, &fork_tfmrate)) 274 tablefull("proc", "increase kern.maxproc or NPROC"); 275 if (forkfsleep) 276 kpause("forkmx", false, forkfsleep, NULL); 277 return EAGAIN; 278 } 279 280 /* 281 * Enforce limits. 282 */ 283 count = chgproccnt(uid, 1); 284 if (__predict_false(count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) { 285 if (kauth_authorize_process(l1->l_cred, KAUTH_PROCESS_RLIMIT, 286 p1, KAUTH_ARG(KAUTH_REQ_PROCESS_RLIMIT_BYPASS), 287 &p1->p_rlimit[RLIMIT_NPROC], KAUTH_ARG(RLIMIT_NPROC)) != 0) { 288 (void)chgproccnt(uid, -1); 289 atomic_dec_uint(&nprocs); 290 if (forkfsleep) 291 kpause("forkulim", false, forkfsleep, NULL); 292 return EAGAIN; 293 } 294 } 295 296 /* 297 * Allocate virtual address space for the U-area now, while it 298 * is still easy to abort the fork operation if we're out of 299 * kernel virtual address space. 300 */ 301 uaddr = uvm_uarea_alloc(); 302 if (__predict_false(uaddr == 0)) { 303 (void)chgproccnt(uid, -1); 304 atomic_dec_uint(&nprocs); 305 return ENOMEM; 306 } 307 308 /* Allocate new proc. */ 309 p2 = proc_alloc(); 310 if (p2 == NULL) { 311 /* We were unable to allocate a process ID. */ 312 uvm_uarea_free(uaddr); 313 mutex_enter(p1->p_lock); 314 uid = kauth_cred_getuid(p1->p_cred); 315 (void)chgproccnt(uid, -1); 316 mutex_exit(p1->p_lock); 317 atomic_dec_uint(&nprocs); 318 return EAGAIN; 319 } 320 321 /* 322 * We are now committed to the fork. From here on, we may 323 * block on resources, but resource allocation may NOT fail. 324 */ 325 326 /* 327 * Make a proc table entry for the new process. 328 * Start by zeroing the section of proc that is zero-initialized, 329 * then copy the section that is copied directly from the parent. 330 */ 331 memset(&p2->p_startzero, 0, 332 (unsigned) ((char *)&p2->p_endzero - (char *)&p2->p_startzero)); 333 memcpy(&p2->p_startcopy, &p1->p_startcopy, 334 (unsigned) ((char *)&p2->p_endcopy - (char *)&p2->p_startcopy)); 335 336 TAILQ_INIT(&p2->p_sigpend.sp_info); 337 338 LIST_INIT(&p2->p_lwps); 339 LIST_INIT(&p2->p_sigwaiters); 340 341 /* 342 * Duplicate sub-structures as needed. 343 * Increase reference counts on shared objects. 344 * Inherit flags we want to keep. The flags related to SIGCHLD 345 * handling are important in order to keep a consistent behaviour 346 * for the child after the fork. If we are a 32-bit process, the 347 * child will be too. 348 */ 349 p2->p_flag = 350 p1->p_flag & (PK_SUGID | PK_NOCLDWAIT | PK_CLDSIGIGN | PK_32); 351 p2->p_emul = p1->p_emul; 352 p2->p_execsw = p1->p_execsw; 353 354 if (flags & FORK_SYSTEM) { 355 /* 356 * Mark it as a system process. Set P_NOCLDWAIT so that 357 * children are reparented to init(8) when they exit. 358 * init(8) can easily wait them out for us. 359 */ 360 p2->p_flag |= (PK_SYSTEM | PK_NOCLDWAIT); 361 } 362 363 mutex_init(&p2->p_stmutex, MUTEX_DEFAULT, IPL_HIGH); 364 mutex_init(&p2->p_auxlock, MUTEX_DEFAULT, IPL_NONE); 365 rw_init(&p2->p_reflock); 366 cv_init(&p2->p_waitcv, "wait"); 367 cv_init(&p2->p_lwpcv, "lwpwait"); 368 369 /* 370 * Share a lock between the processes if they are to share signal 371 * state: we must synchronize access to it. 372 */ 373 if (flags & FORK_SHARESIGS) { 374 p2->p_lock = p1->p_lock; 375 mutex_obj_hold(p1->p_lock); 376 } else 377 p2->p_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE); 378 379 kauth_proc_fork(p1, p2); 380 381 p2->p_raslist = NULL; 382 #if defined(__HAVE_RAS) 383 ras_fork(p1, p2); 384 #endif 385 386 /* bump references to the text vnode (for procfs) */ 387 p2->p_textvp = p1->p_textvp; 388 if (p2->p_textvp) 389 vref(p2->p_textvp); 390 if (p1->p_path) 391 p2->p_path = kmem_strdupsize(p1->p_path, NULL, KM_SLEEP); 392 else 393 p2->p_path = NULL; 394 395 if (flags & FORK_SHAREFILES) 396 fd_share(p2); 397 else if (flags & FORK_CLEANFILES) 398 p2->p_fd = fd_init(NULL); 399 else 400 p2->p_fd = fd_copy(); 401 402 /* XXX racy */ 403 p2->p_mqueue_cnt = p1->p_mqueue_cnt; 404 405 if (flags & FORK_SHARECWD) 406 cwdshare(p2); 407 else 408 p2->p_cwdi = cwdinit(); 409 410 /* 411 * Note: p_limit (rlimit stuff) is copy-on-write, so normally 412 * we just need increase pl_refcnt. 413 */ 414 p1_lim = p1->p_limit; 415 if (!p1_lim->pl_writeable) { 416 lim_addref(p1_lim); 417 p2->p_limit = p1_lim; 418 } else { 419 p2->p_limit = lim_copy(p1_lim); 420 } 421 422 if (flags & FORK_PPWAIT) { 423 /* Mark ourselves as waiting for a child. */ 424 p2->p_lflag = PL_PPWAIT; 425 l1->l_vforkwaiting = true; 426 p2->p_vforklwp = l1; 427 } else { 428 p2->p_lflag = 0; 429 l1->l_vforkwaiting = false; 430 } 431 p2->p_sflag = 0; 432 p2->p_slflag = 0; 433 parent = (flags & FORK_NOWAIT) ? initproc : p1; 434 p2->p_pptr = parent; 435 p2->p_ppid = parent->p_pid; 436 LIST_INIT(&p2->p_children); 437 438 p2->p_aio = NULL; 439 440 #ifdef KTRACE 441 /* 442 * Copy traceflag and tracefile if enabled. 443 * If not inherited, these were zeroed above. 444 */ 445 if (p1->p_traceflag & KTRFAC_INHERIT) { 446 mutex_enter(&ktrace_lock); 447 p2->p_traceflag = p1->p_traceflag; 448 if ((p2->p_tracep = p1->p_tracep) != NULL) 449 ktradref(p2); 450 mutex_exit(&ktrace_lock); 451 } 452 #endif 453 454 /* 455 * Create signal actions for the child process. 456 */ 457 p2->p_sigacts = sigactsinit(p1, flags & FORK_SHARESIGS); 458 mutex_enter(p1->p_lock); 459 p2->p_sflag |= 460 (p1->p_sflag & (PS_STOPFORK | PS_STOPEXEC | PS_NOCLDSTOP)); 461 sched_proc_fork(p1, p2); 462 mutex_exit(p1->p_lock); 463 464 p2->p_stflag = p1->p_stflag; 465 466 /* 467 * p_stats. 468 * Copy parts of p_stats, and zero out the rest. 469 */ 470 p2->p_stats = pstatscopy(p1->p_stats); 471 472 /* 473 * Set up the new process address space. 474 */ 475 uvm_proc_fork(p1, p2, (flags & FORK_SHAREVM) ? true : false); 476 477 /* 478 * Finish creating the child process. 479 * It will return through a different path later. 480 */ 481 lwp_create(l1, p2, uaddr, (flags & FORK_PPWAIT) ? LWP_VFORK : 0, 482 stack, stacksize, (func != NULL) ? func : child_return, arg, &l2, 483 l1->l_class, &l1->l_sigmask, &l1->l_sigstk); 484 485 /* 486 * Inherit l_private from the parent. 487 * Note that we cannot use lwp_setprivate() here since that 488 * also sets the CPU TLS register, which is incorrect if the 489 * process has changed that without letting the kernel know. 490 */ 491 l2->l_private = l1->l_private; 492 493 /* 494 * If emulation has a process fork hook, call it now. 495 */ 496 if (p2->p_emul->e_proc_fork) 497 (*p2->p_emul->e_proc_fork)(p2, l1, flags); 498 499 /* 500 * ...and finally, any other random fork hooks that subsystems 501 * might have registered. 502 */ 503 doforkhooks(p2, p1); 504 505 SDT_PROBE(proc, kernel, , create, p2, p1, flags, 0, 0); 506 507 /* 508 * It's now safe for the scheduler and other processes to see the 509 * child process. 510 */ 511 mutex_enter(&proc_lock); 512 513 if (p1->p_session->s_ttyvp != NULL && p1->p_lflag & PL_CONTROLT) 514 p2->p_lflag |= PL_CONTROLT; 515 516 LIST_INSERT_HEAD(&parent->p_children, p2, p_sibling); 517 p2->p_exitsig = exitsig; /* signal for parent on exit */ 518 519 /* 520 * Trace fork(2) and vfork(2)-like events on demand in a debugger. 521 */ 522 if (tracefork(p1, flags) || tracevfork(p1, flags)) { 523 proc_changeparent(p2, p1->p_pptr); 524 SET(p2->p_slflag, PSL_TRACEDCHILD); 525 } 526 527 p2->p_oppid = p1->p_pid; /* Remember the original parent id. */ 528 529 LIST_INSERT_AFTER(p1, p2, p_pglist); 530 LIST_INSERT_HEAD(&allproc, p2, p_list); 531 532 p2->p_trace_enabled = trace_is_enabled(p2); 533 #ifdef __HAVE_SYSCALL_INTERN 534 (*p2->p_emul->e_syscall_intern)(p2); 535 #endif 536 537 /* 538 * Update stats now that we know the fork was successful. 539 */ 540 KPREEMPT_DISABLE(l1); 541 CPU_COUNT(CPU_COUNT_FORKS, 1); 542 if (flags & FORK_PPWAIT) 543 CPU_COUNT(CPU_COUNT_FORKS_PPWAIT, 1); 544 if (flags & FORK_SHAREVM) 545 CPU_COUNT(CPU_COUNT_FORKS_SHAREVM, 1); 546 KPREEMPT_ENABLE(l1); 547 548 if (ktrpoint(KTR_EMUL)) 549 p2->p_traceflag |= KTRFAC_TRC_EMUL; 550 551 /* 552 * Notify any interested parties about the new process. 553 */ 554 if (!SLIST_EMPTY(&p1->p_klist)) { 555 mutex_exit(&proc_lock); 556 knote_proc_fork(p1, p2); 557 mutex_enter(&proc_lock); 558 } 559 560 /* 561 * Make child runnable, set start time, and add to run queue except 562 * if the parent requested the child to start in SSTOP state. 563 */ 564 mutex_enter(p2->p_lock); 565 566 /* 567 * Start profiling. 568 */ 569 if ((p2->p_stflag & PST_PROFIL) != 0) { 570 mutex_spin_enter(&p2->p_stmutex); 571 startprofclock(p2); 572 mutex_spin_exit(&p2->p_stmutex); 573 } 574 575 getmicrotime(&p2->p_stats->p_start); 576 p2->p_acflag = AFORK; 577 lwp_lock(l2); 578 KASSERT(p2->p_nrlwps == 1); 579 KASSERT(l2->l_stat == LSIDL); 580 if (p2->p_sflag & PS_STOPFORK) { 581 p2->p_nrlwps = 0; 582 p2->p_stat = SSTOP; 583 p2->p_waited = 0; 584 p1->p_nstopchild++; 585 l2->l_stat = LSSTOP; 586 KASSERT(l2->l_wchan == NULL); 587 lwp_unlock(l2); 588 } else { 589 p2->p_nrlwps = 1; 590 p2->p_stat = SACTIVE; 591 setrunnable(l2); 592 /* LWP now unlocked */ 593 } 594 595 /* 596 * Return child pid to parent process, 597 * marking us as parent via retval[1]. 598 */ 599 if (retval != NULL) { 600 retval[0] = p2->p_pid; 601 retval[1] = 0; 602 } 603 604 mutex_exit(p2->p_lock); 605 606 /* 607 * Let the parent know that we are tracing its child. 608 */ 609 if (tracefork(p1, flags) || tracevfork(p1, flags)) { 610 mutex_enter(p1->p_lock); 611 eventswitch(TRAP_CHLD, 612 tracefork(p1, flags) ? PTRACE_FORK : PTRACE_VFORK, 613 retval[0]); 614 mutex_enter(&proc_lock); 615 } 616 617 /* 618 * Preserve synchronization semantics of vfork. If waiting for 619 * child to exec or exit, sleep until it clears p_vforkwaiting. 620 */ 621 while (l1->l_vforkwaiting) 622 cv_wait(&l1->l_waitcv, &proc_lock); 623 624 /* 625 * Let the parent know that we are tracing its child. 626 */ 627 if (tracevforkdone(p1, flags)) { 628 mutex_enter(p1->p_lock); 629 eventswitch(TRAP_CHLD, PTRACE_VFORK_DONE, retval[0]); 630 } else 631 mutex_exit(&proc_lock); 632 633 return 0; 634 } 635 636 /* 637 * MI code executed in each newly spawned process before returning to userland. 638 */ 639 void 640 child_return(void *arg) 641 { 642 struct lwp *l = curlwp; 643 struct proc *p = l->l_proc; 644 645 if ((p->p_slflag & (PSL_TRACED|PSL_TRACEDCHILD)) == 646 (PSL_TRACED|PSL_TRACEDCHILD)) { 647 eventswitchchild(p, TRAP_CHLD, 648 ISSET(p->p_lflag, PL_PPWAIT) ? PTRACE_VFORK : PTRACE_FORK); 649 } 650 651 md_child_return(l); 652 653 /* 654 * Return SYS_fork for all fork types, including vfork(2) and clone(2). 655 * 656 * This approach simplifies the code and avoids extra locking. 657 */ 658 ktrsysret(SYS_fork, 0, 0); 659 }
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