/* $OpenBSD: kern_fork.c,v 1.241 2022/07/23 22:10:58 cheloha Exp $ */ /* $NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $ */ /* * Copyright (c) 1982, 1986, 1989, 1991, 1993 * The Regents of the University of California. All rights reserved. * (c) UNIX System Laboratories, Inc. * All or some portions of this file are derived from material licensed * to the University of California by American Telephone and Telegraph * Co. or Unix System Laboratories, Inc. and are reproduced herein with * the permission of UNIX System Laboratories, Inc. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)kern_fork.c 8.6 (Berkeley) 4/8/94 */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include int nprocesses = 1; /* process 0 */ int nthreads = 1; /* proc 0 */ struct forkstat forkstat; void fork_return(void *); pid_t alloctid(void); pid_t allocpid(void); int ispidtaken(pid_t); void unveil_copy(struct process *parent, struct process *child); struct proc *thread_new(struct proc *_parent, vaddr_t _uaddr); struct process *process_new(struct proc *, struct process *, int); int fork_check_maxthread(uid_t _uid); void fork_return(void *arg) { struct proc *p = (struct proc *)arg; if (p->p_p->ps_flags & PS_TRACED) psignal(p, SIGTRAP); child_return(p); } int sys_fork(struct proc *p, void *v, register_t *retval) { void (*func)(void *) = child_return; int flags; flags = FORK_FORK; if (p->p_p->ps_ptmask & PTRACE_FORK) { flags |= FORK_PTRACE; func = fork_return; } return fork1(p, flags, func, NULL, retval, NULL); } int sys_vfork(struct proc *p, void *v, register_t *retval) { return fork1(p, FORK_VFORK|FORK_PPWAIT, child_return, NULL, retval, NULL); } int sys___tfork(struct proc *p, void *v, register_t *retval) { struct sys___tfork_args /* { syscallarg(const struct __tfork) *param; syscallarg(size_t) psize; } */ *uap = v; size_t psize = SCARG(uap, psize); struct __tfork param = { 0 }; int error; if (psize == 0 || psize > sizeof(param)) return EINVAL; if ((error = copyin(SCARG(uap, param), ¶m, psize))) return error; #ifdef KTRACE if (KTRPOINT(p, KTR_STRUCT)) ktrstruct(p, "tfork", ¶m, sizeof(param)); #endif #ifdef TCB_INVALID if (TCB_INVALID(param.tf_tcb)) return EINVAL; #endif /* TCB_INVALID */ return thread_fork(p, param.tf_stack, param.tf_tcb, param.tf_tid, retval); } /* * Allocate and initialize a thread (proc) structure, given the parent thread. */ struct proc * thread_new(struct proc *parent, vaddr_t uaddr) { struct proc *p; p = pool_get(&proc_pool, PR_WAITOK); p->p_stat = SIDL; /* protect against others */ p->p_runpri = 0; p->p_flag = 0; /* * Make a proc table entry for the new process. * Start by zeroing the section of proc that is zero-initialized, * then copy the section that is copied directly from the parent. */ memset(&p->p_startzero, 0, (caddr_t)&p->p_endzero - (caddr_t)&p->p_startzero); memcpy(&p->p_startcopy, &parent->p_startcopy, (caddr_t)&p->p_endcopy - (caddr_t)&p->p_startcopy); crhold(p->p_ucred); p->p_addr = (struct user *)uaddr; /* * Initialize the timeouts. */ timeout_set(&p->p_sleep_to, endtsleep, p); return p; } /* * Initialize common bits of a process structure, given the initial thread. */ void process_initialize(struct process *pr, struct proc *p) { /* initialize the thread links */ pr->ps_mainproc = p; TAILQ_INIT(&pr->ps_threads); TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link); pr->ps_refcnt = 1; p->p_p = pr; /* give the process the same creds as the initial thread */ pr->ps_ucred = p->p_ucred; crhold(pr->ps_ucred); /* new thread and new process */ KASSERT(p->p_ucred->cr_refcnt.r_refs >= 2); LIST_INIT(&pr->ps_children); LIST_INIT(&pr->ps_orphans); LIST_INIT(&pr->ps_ftlist); LIST_INIT(&pr->ps_sigiolst); TAILQ_INIT(&pr->ps_tslpqueue); rw_init(&pr->ps_lock, "pslock"); mtx_init(&pr->ps_mtx, IPL_HIGH); timeout_set_kclock(&pr->ps_realit_to, realitexpire, pr, KCLOCK_UPTIME, 0); timeout_set(&pr->ps_rucheck_to, rucheck, pr); } /* * Allocate and initialize a new process. */ struct process * process_new(struct proc *p, struct process *parent, int flags) { struct process *pr; pr = pool_get(&process_pool, PR_WAITOK); /* * Make a process structure for the new process. * Start by zeroing the section of proc that is zero-initialized, * then copy the section that is copied directly from the parent. */ memset(&pr->ps_startzero, 0, (caddr_t)&pr->ps_endzero - (caddr_t)&pr->ps_startzero); memcpy(&pr->ps_startcopy, &parent->ps_startcopy, (caddr_t)&pr->ps_endcopy - (caddr_t)&pr->ps_startcopy); process_initialize(pr, p); pr->ps_pid = allocpid(); lim_fork(parent, pr); /* post-copy fixups */ pr->ps_pptr = parent; pr->ps_ppid = parent->ps_pid; /* bump references to the text vnode (for sysctl) */ pr->ps_textvp = parent->ps_textvp; if (pr->ps_textvp) vref(pr->ps_textvp); /* copy unveil if unveil is active */ unveil_copy(parent, pr); pr->ps_flags = parent->ps_flags & (PS_SUGID | PS_SUGIDEXEC | PS_PLEDGE | PS_EXECPLEDGE | PS_WXNEEDED); if (parent->ps_session->s_ttyvp != NULL) pr->ps_flags |= parent->ps_flags & PS_CONTROLT; /* * Duplicate sub-structures as needed. * Increase reference counts on shared objects. */ if (flags & FORK_SHAREFILES) pr->ps_fd = fdshare(parent); else pr->ps_fd = fdcopy(parent); pr->ps_sigacts = sigactsinit(parent); if (flags & FORK_SHAREVM) pr->ps_vmspace = uvmspace_share(parent); else pr->ps_vmspace = uvmspace_fork(parent); if (parent->ps_flags & PS_PROFIL) startprofclock(pr); if (flags & FORK_PTRACE) pr->ps_flags |= parent->ps_flags & PS_TRACED; if (flags & FORK_NOZOMBIE) pr->ps_flags |= PS_NOZOMBIE; if (flags & FORK_SYSTEM) pr->ps_flags |= PS_SYSTEM; /* mark as embryo to protect against others */ pr->ps_flags |= PS_EMBRYO; /* Force visibility of all of the above changes */ membar_producer(); /* it's sufficiently inited to be globally visible */ LIST_INSERT_HEAD(&allprocess, pr, ps_list); return pr; } /* print the 'table full' message once per 10 seconds */ struct timeval fork_tfmrate = { 10, 0 }; int fork_check_maxthread(uid_t uid) { /* * Although process entries are dynamically created, we still keep * a global limit on the maximum number we will create. We reserve * the last 5 processes to root. The variable nprocesses is the * current number of processes, maxprocess is the limit. Similar * rules for threads (struct proc): we reserve the last 5 to root; * the variable nthreads is the current number of procs, maxthread is * the limit. */ if ((nthreads >= maxthread - 5 && uid != 0) || nthreads >= maxthread) { static struct timeval lasttfm; if (ratecheck(&lasttfm, &fork_tfmrate)) tablefull("thread"); return EAGAIN; } nthreads++; return 0; } static inline void fork_thread_start(struct proc *p, struct proc *parent, int flags) { struct cpu_info *ci; int s; SCHED_LOCK(s); ci = sched_choosecpu_fork(parent, flags); setrunqueue(ci, p, p->p_usrpri); SCHED_UNLOCK(s); } int fork1(struct proc *curp, int flags, void (*func)(void *), void *arg, register_t *retval, struct proc **rnewprocp) { struct process *curpr = curp->p_p; struct process *pr; struct proc *p; uid_t uid = curp->p_ucred->cr_ruid; struct vmspace *vm; int count; vaddr_t uaddr; int error; struct ptrace_state *newptstat = NULL; KASSERT((flags & ~(FORK_FORK | FORK_VFORK | FORK_PPWAIT | FORK_PTRACE | FORK_IDLE | FORK_SHAREVM | FORK_SHAREFILES | FORK_NOZOMBIE | FORK_SYSTEM)) == 0); KASSERT(func != NULL); if ((error = fork_check_maxthread(uid))) return error; if ((nprocesses >= maxprocess - 5 && uid != 0) || nprocesses >= maxprocess) { static struct timeval lasttfm; if (ratecheck(&lasttfm, &fork_tfmrate)) tablefull("process"); nthreads--; return EAGAIN; } nprocesses++; /* * Increment the count of processes running with this uid. * Don't allow a nonprivileged user to exceed their current limit. */ count = chgproccnt(uid, 1); if (uid != 0 && count > lim_cur(RLIMIT_NPROC)) { (void)chgproccnt(uid, -1); nprocesses--; nthreads--; return EAGAIN; } uaddr = uvm_uarea_alloc(); if (uaddr == 0) { (void)chgproccnt(uid, -1); nprocesses--; nthreads--; return (ENOMEM); } /* * From now on, we're committed to the fork and cannot fail. */ p = thread_new(curp, uaddr); pr = process_new(p, curpr, flags); p->p_fd = pr->ps_fd; p->p_vmspace = pr->ps_vmspace; if (pr->ps_flags & PS_SYSTEM) atomic_setbits_int(&p->p_flag, P_SYSTEM); if (flags & FORK_PPWAIT) { atomic_setbits_int(&pr->ps_flags, PS_PPWAIT); atomic_setbits_int(&curpr->ps_flags, PS_ISPWAIT); } #ifdef KTRACE /* * Copy traceflag and tracefile if enabled. * If not inherited, these were zeroed above. */ if (curpr->ps_traceflag & KTRFAC_INHERIT) ktrsettrace(pr, curpr->ps_traceflag, curpr->ps_tracevp, curpr->ps_tracecred); #endif /* * Finish creating the child thread. cpu_fork() will copy * and update the pcb and make the child ready to run. If * this is a normal user fork, the child will exit directly * to user mode via child_return() on its first time slice * and will not return here. If this is a kernel thread, * the specified entry point will be executed. */ cpu_fork(curp, p, NULL, NULL, func, arg ? arg : p); vm = pr->ps_vmspace; if (flags & FORK_FORK) { forkstat.cntfork++; forkstat.sizfork += vm->vm_dsize + vm->vm_ssize; } else if (flags & FORK_VFORK) { forkstat.cntvfork++; forkstat.sizvfork += vm->vm_dsize + vm->vm_ssize; } else { forkstat.cntkthread++; } if (pr->ps_flags & PS_TRACED && flags & FORK_FORK) newptstat = malloc(sizeof(*newptstat), M_SUBPROC, M_WAITOK); p->p_tid = alloctid(); LIST_INSERT_HEAD(&allproc, p, p_list); LIST_INSERT_HEAD(TIDHASH(p->p_tid), p, p_hash); LIST_INSERT_HEAD(PIDHASH(pr->ps_pid), pr, ps_hash); LIST_INSERT_AFTER(curpr, pr, ps_pglist); LIST_INSERT_HEAD(&curpr->ps_children, pr, ps_sibling); if (pr->ps_flags & PS_TRACED) { pr->ps_oppid = curpr->ps_pid; process_reparent(pr, curpr->ps_pptr); /* * Set ptrace status. */ if (newptstat != NULL) { pr->ps_ptstat = newptstat; newptstat = NULL; curpr->ps_ptstat->pe_report_event = PTRACE_FORK; pr->ps_ptstat->pe_report_event = PTRACE_FORK; curpr->ps_ptstat->pe_other_pid = pr->ps_pid; pr->ps_ptstat->pe_other_pid = curpr->ps_pid; } } /* * For new processes, set accounting bits and mark as complete. */ nanouptime(&pr->ps_start); pr->ps_acflag = AFORK; atomic_clearbits_int(&pr->ps_flags, PS_EMBRYO); if ((flags & FORK_IDLE) == 0) fork_thread_start(p, curp, flags); else p->p_cpu = arg; free(newptstat, M_SUBPROC, sizeof(*newptstat)); /* * Notify any interested parties about the new process. */ KNOTE(&curpr->ps_klist, NOTE_FORK | pr->ps_pid); /* * Update stats now that we know the fork was successful. */ uvmexp.forks++; if (flags & FORK_PPWAIT) uvmexp.forks_ppwait++; if (flags & FORK_SHAREVM) uvmexp.forks_sharevm++; /* * Pass a pointer to the new process to the caller. */ if (rnewprocp != NULL) *rnewprocp = p; /* * Preserve synchronization semantics of vfork. If waiting for * child to exec or exit, set PS_PPWAIT on child and PS_ISPWAIT * on ourselves, and sleep on our process for the latter flag * to go away. * XXX Need to stop other rthreads in the parent */ if (flags & FORK_PPWAIT) while (curpr->ps_flags & PS_ISPWAIT) tsleep_nsec(curpr, PWAIT, "ppwait", INFSLP); /* * If we're tracing the child, alert the parent too. */ if ((flags & FORK_PTRACE) && (curpr->ps_flags & PS_TRACED)) psignal(curp, SIGTRAP); /* * Return child pid to parent process */ if (retval != NULL) { retval[0] = pr->ps_pid; retval[1] = 0; } return (0); } int thread_fork(struct proc *curp, void *stack, void *tcb, pid_t *tidptr, register_t *retval) { struct process *pr = curp->p_p; struct proc *p; pid_t tid; vaddr_t uaddr; int s, error; if (stack == NULL) return EINVAL; if ((error = fork_check_maxthread(curp->p_ucred->cr_ruid))) return error; uaddr = uvm_uarea_alloc(); if (uaddr == 0) { nthreads--; return ENOMEM; } /* * From now on, we're committed to the fork and cannot fail. */ p = thread_new(curp, uaddr); atomic_setbits_int(&p->p_flag, P_THREAD); sigstkinit(&p->p_sigstk); /* other links */ p->p_p = pr; pr->ps_refcnt++; /* local copies */ p->p_fd = pr->ps_fd; p->p_vmspace = pr->ps_vmspace; /* * Finish creating the child thread. cpu_fork() will copy * and update the pcb and make the child ready to run. The * child will exit directly to user mode via child_return() * on its first time slice and will not return here. */ cpu_fork(curp, p, stack, tcb, child_return, p); p->p_tid = alloctid(); LIST_INSERT_HEAD(&allproc, p, p_list); LIST_INSERT_HEAD(TIDHASH(p->p_tid), p, p_hash); SCHED_LOCK(s); TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link); /* * if somebody else wants to take us to single threaded mode, * count ourselves in. */ if (pr->ps_single) { atomic_inc_int(&pr->ps_singlecount); atomic_setbits_int(&p->p_flag, P_SUSPSINGLE); } SCHED_UNLOCK(s); /* * Return tid to parent thread and copy it out to userspace */ retval[0] = tid = p->p_tid + THREAD_PID_OFFSET; retval[1] = 0; if (tidptr != NULL) { if (copyout(&tid, tidptr, sizeof(tid))) psignal(curp, SIGSEGV); } fork_thread_start(p, curp, 0); /* * Update stats now that we know the fork was successful. */ forkstat.cnttfork++; uvmexp.forks++; uvmexp.forks_sharevm++; return 0; } /* Find an unused tid */ pid_t alloctid(void) { pid_t tid; do { /* (0 .. TID_MASK+1] */ tid = 1 + (arc4random() & TID_MASK); } while (tfind(tid) != NULL); return (tid); } /* * Checks for current use of a pid, either as a pid or pgid. */ pid_t oldpids[128]; int ispidtaken(pid_t pid) { uint32_t i; for (i = 0; i < nitems(oldpids); i++) if (pid == oldpids[i]) return (1); if (prfind(pid) != NULL) return (1); if (pgfind(pid) != NULL) return (1); if (zombiefind(pid) != NULL) return (1); return (0); } /* Find an unused pid */ pid_t allocpid(void) { static int first = 1; pid_t pid; /* The first PID allocated is always 1. */ if (first) { first = 0; return 1; } /* * All subsequent PIDs are chosen randomly. We need to * find an unused PID in the range [2, PID_MAX]. */ do { pid = 2 + arc4random_uniform(PID_MAX - 1); } while (ispidtaken(pid)); return pid; } void freepid(pid_t pid) { static uint32_t idx; oldpids[idx++ % nitems(oldpids)] = pid; } #if defined(MULTIPROCESSOR) /* * XXX This is a slight hack to get newly-formed processes to * XXX acquire the kernel lock as soon as they run. */ void proc_trampoline_mp(void) { SCHED_ASSERT_LOCKED(); __mp_unlock(&sched_lock); spl0(); SCHED_ASSERT_UNLOCKED(); KERNEL_ASSERT_UNLOCKED(); KERNEL_LOCK(); } #endif