/*      $OpenBSD: kern_fork.c,v 1.279 2026/04/15 18:55:54 deraadt 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 <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/acct.h>
#include <sys/ktrace.h>
#include <sys/sched.h>
#include <sys/smr.h>
#include <sys/sysctl.h>
#include <sys/pool.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <sys/atomic.h>
#include <sys/unistd.h>
#include <sys/tracepoint.h>
#include <sys/witness.h>

#include <sys/syscallargs.h>

#include <uvm/uvm_extern.h>
#include <machine/tcb.h>

int     nprocesses = 1;         /* process 0 */
int     nthreads = 1;           /* [a] 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), &param, psize)))
                return error;
#ifdef KTRACE
        if (KTRPOINT(p, KTR_STRUCT))
                ktrstruct(p, "tfork", &param, 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)
{
        refcnt_init(&pr->ps_refcnt);

        /* 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_threadcnt = 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);

        prof_fork(pr);

        LIST_INIT(&pr->ps_children);
        LIST_INIT(&pr->ps_orphans);
        LIST_INIT(&pr->ps_sigiolst);

        rw_init(&pr->ps_lock, "pslock");
        mtx_init(&pr->ps_mtx, IPL_HIGH);
        klist_init_mutex(&pr->ps_klist, &pr->ps_mtx);

        timeout_set_flags(&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_pgrp = NULL;
        pr->ps_ppid = parent->ps_pid;

        WITNESS_SETCHILD(&pr->ps_mtx.mtx_lock_obj,
            &parent->ps_mtx.mtx_lock_obj);

        /* 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_FLAGS_INHERITED_ON_FORK;
        if (parent->ps_session->s_ttyvp != NULL)
                pr->ps_flags |= parent->ps_flags & PS_CONTROLT;

        if (parent->ps_pin.pn_pins) {
                pr->ps_pin.pn_pins = mallocarray(parent->ps_pin.pn_npins,
                    sizeof(u_int), M_PINSYSCALL, M_WAITOK);
                memcpy(pr->ps_pin.pn_pins, parent->ps_pin.pn_pins,
                    parent->ps_pin.pn_npins * sizeof(u_int));
        }
        if (parent->ps_libcpin.pn_pins) {
                pr->ps_libcpin.pn_pins = mallocarray(parent->ps_libcpin.pn_npins,
                    sizeof(u_int), M_PINSYSCALL, M_WAITOK);
                memcpy(pr->ps_libcpin.pn_pins, parent->ps_libcpin.pn_pins,
                    parent->ps_libcpin.pn_npins * sizeof(u_int));
        }

        /*
         * 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)
{
        int maxthread_local, val;

        /*
         * 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.
         */
        maxthread_local = atomic_load_int(&maxthread);
        val = atomic_inc_int_nv(&nthreads);
        if ((val > maxthread_local - 5 && uid != 0) ||
            val > maxthread_local) {
                static struct timeval lasttfm;

                if (ratecheck(&lasttfm, &fork_tfmrate))
                        tablefull("thread");
                atomic_dec_int(&nthreads);
                return EAGAIN;
        }

        return 0;
}

static inline void
fork_thread_start(struct proc *p, struct proc *parent, int flags)
{
        struct cpu_info *ci;

        SCHED_LOCK();
        ci = sched_choosecpu_fork(parent, flags);
        TRACEPOINT(sched, fork, p->p_tid + THREAD_PID_OFFSET,
            p->p_p->ps_pid, CPU_INFO_UNIT(ci));
        setrunqueue(ci, p, p->p_usrpri);
        SCHED_UNLOCK();
}

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, maxprocess_local;
        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;

        maxprocess_local = atomic_load_int(&maxprocess);
        if ((nprocesses >= maxprocess_local - 5 && uid != 0) ||
            nprocesses >= maxprocess_local) {
                static struct timeval lasttfm;

                if (ratecheck(&lasttfm, &fork_tfmrate))
                        tablefull("process");
                atomic_dec_int(&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--;
                atomic_dec_int(&nthreads);
                return EAGAIN;
        }

        uaddr = uvm_uarea_alloc();
        if (uaddr == 0) {
                (void)chgproccnt(uid, -1);
                nprocesses--;
                atomic_dec_int(&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);
        pr->ps_pgrp = curpr->ps_pgrp;
        LIST_INSERT_AFTER(curpr, pr, ps_pglist);
        LIST_INSERT_HEAD(&curpr->ps_children, pr, ps_sibling);

        mtx_enter(&pr->ps_mtx);
        if (pr->ps_flags & PS_TRACED) {
                pr->ps_opptr = curpr;
                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;
                }
        }
        mtx_leave(&pr->ps_mtx);

        /*
         * 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);

        /*
         * Idle threads are just assigned to the CPU but not added
         * to any runqueue.
         */
        if ((flags & FORK_IDLE)) {
                p->p_cpu = arg;
                /* for consistency mark idle procs as pegged */
                atomic_setbits_int(&p->p_flag, P_CPUPEG);
        } else
                fork_thread_start(p, curp, flags);

        free(newptstat, M_SUBPROC, sizeof(*newptstat));

        /*
         * Notify any interested parties about the new process.
         */
        knote_processfork(curpr, 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 = pr->ps_pid;
        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 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) {
                atomic_dec_int(&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);
        memset(p->p_name, 0, sizeof p->p_name);

        /* other links */
        p->p_p = pr;

        /* 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);

        mtx_enter(&pr->ps_mtx);
        TAILQ_INSERT_TAIL(&pr->ps_threads, p, p_thr_link);
        pr->ps_threadcnt++;

        /*
         * if somebody else wants to take us to single threaded mode
         * or suspend the process, count ourselves in.
         */
        if (pr->ps_single != NULL || ISSET(pr->ps_flags, PS_STOPPING)) {
                pr->ps_suspendcnt++;
                atomic_setbits_int(&p->p_flag,
                    curp->p_flag & (P_SUSPSINGLE | P_SUSPSIG));
        }
        mtx_leave(&pr->ps_mtx);

        /*
         * Return tid to parent thread and copy it out to userspace
         */
        *retval = tid = p->p_tid + THREAD_PID_OFFSET;
        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;
}

/* Do machine independent parts of switching to a new process */
void
proc_trampoline_mi(void)
{
        struct schedstate_percpu *spc = &curcpu()->ci_schedstate;
        struct proc *p = curproc;

        SCHED_ASSERT_LOCKED();
        clear_resched(curcpu());
        mtx_leave(&sched_lock);
        spl0();

        SCHED_ASSERT_UNLOCKED();
        KERNEL_ASSERT_UNLOCKED();
        assertwaitok();
        smr_idle();

        /* Start any optional clock interrupts needed by the thread. */
        if (ISSET(p->p_p->ps_flags, PS_ITIMER)) {
                atomic_setbits_int(&spc->spc_schedflags, SPCF_ITIMER);
                clockintr_advance(&spc->spc_itimer, hardclock_period);
        }
        if (ISSET(p->p_p->ps_flags, PS_PROFIL)) {
                atomic_setbits_int(&spc->spc_schedflags, SPCF_PROFCLOCK);
                clockintr_advance(&spc->spc_profclock, profclock_period);
        }

        nanouptime(&spc->spc_runtime);
        KERNEL_LOCK();
}