xnu-1228.0.2.tar.gz

[apple/xnu.git] / bsd / kern / kern_fork.c

/*
 * Copyright (c) 2000-2007 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995, 1997 Apple Computer, Inc. All Rights Reserved */
/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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 8.8 (Berkeley) 2/14/95
 */
/*
 * NOTICE: This file was modified by McAfee Research in 2004 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

#include <kern/assert.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/user.h>
#include <sys/resourcevar.h>
#include <sys/vnode_internal.h>
#include <sys/file_internal.h>
#include <sys/acct.h>
#include <sys/codesign.h>
#include <sys/sysproto.h>
#if CONFIG_DTRACE
/* Do not include dtrace.h, it redefines kmem_[alloc/free] */
extern void dtrace_fasttrap_fork(proc_t, proc_t);
extern void (*dtrace_helpers_fork)(proc_t, proc_t);
extern void dtrace_lazy_dofs_duplicate(proc_t, proc_t);

#include <sys/dtrace_ptss.h>
#endif

#include <bsm/audit_kernel.h>

#include <mach/mach_types.h>
#include <kern/kern_types.h>
#include <kern/kalloc.h>
#include <kern/mach_param.h>
#include <kern/task.h>
#include <kern/thread_call.h>
#include <kern/zalloc.h>

#include <machine/spl.h>

#if CONFIG_MACF
#include <security/mac.h>
#include <security/mac_mach_internal.h>
#endif

#include <vm/vm_map.h>
#include <vm/vm_protos.h>
#include <vm/vm_shared_region.h>

#include <sys/shm_internal.h>   /* for shmfork() */
#include <mach/task.h>          /* for thread_create() */
#include <mach/thread_act.h>    /* for thread_resume() */

#include <sys/sdt.h>

/* XXX routines which should have Mach prototypes, but don't */
void thread_set_parent(thread_t parent, int pid);
extern void act_thread_catt(void *ctx);
void thread_set_child(thread_t child, int pid);
void *act_thread_csave(void);


thread_t cloneproc(proc_t, int); 
proc_t forkproc(proc_t, int);
void forkproc_free(proc_t, int);
thread_t procdup(proc_t parent, proc_t child);
thread_t fork_create_child(task_t parent_task, proc_t child, int inherit_memory, int is64bit);

#define DOFORK  0x1     /* fork() system call */
#define DOVFORK 0x2     /* vfork() system call */


/*
 * vfork
 *
 * Description: vfork system call
 *
 * Parameters:  void                    [no arguments]
 *
 * Retval:      0                       (to child process)
 *              !0                      pid of child (to parent process)
 *              -1                      error (see "Returns:")
 *
 * Returns:     EAGAIN                  Administrative limit reached
 *              EINVAL                  vfork() caled during vfork()
 *              ENOMEM                  Failed to allocate new process
 *
 * Note:        After a successful call to this function, the parent process
 *              has its task, thread, and uthread lent to the child process,
 *              and control is returned to the caller; if this function is
 *              invoked as a system call, the return is to user space, and
 *              is effectively running on the child process.
 *
 *              Subsequent calls that operate on process state are permitted,
 *              though discouraged, and will operate on the child process; any
 *              operations on the task, thread, or uthread will result in
 *              changes in the parent state, and, if inheritable, the child
 *              state, when a task, thread, and uthread are realized for the
 *              child process at execve() time, will also be effected.  Given
 *              this, it's recemmended that people use the posix_spawn() call
 *              instead.
 */
int
vfork(proc_t parent, __unused struct vfork_args *uap, register_t *retval)
{
        proc_t child;
        uid_t uid;
        thread_t cur_act = (thread_t)current_thread();
        int count;
        uthread_t ut;
#if CONFIG_MACF
        int err;
#endif

        /*
         * Although process entries are dynamically created, we still keep
         * a global limit on the maximum number we will create.  Don't allow
         * a nonprivileged user to use the last process; don't let root
         * exceed the limit. The variable nprocs is the current number of
         * processes, maxproc is the limit.
         */
        uid = kauth_cred_get()->cr_ruid;
        proc_list_lock();
        if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) {
                proc_list_unlock();
                tablefull("proc");
                retval[1] = 0;
                return (EAGAIN);
        }
        proc_list_unlock();

        /*
         * Increment the count of procs running with this uid. Don't allow
         * a nonprivileged user to exceed their current limit, which is
         * always less than what an rlim_t can hold.
         * (locking protection is provided by list lock held in chgproccnt)
         */
        count = chgproccnt(uid, 1);
        if (uid != 0 &&
            (rlim_t)count > parent->p_rlimit[RLIMIT_NPROC].rlim_cur) {
                (void)chgproccnt(uid, -1);
                return (EAGAIN);
        }

        ut = (uthread_t)get_bsdthread_info(cur_act);
        if (ut->uu_flag & UT_VFORK) {
                printf("vfork called recursively by %s\n", parent->p_comm);
                (void)chgproccnt(uid, -1);
                return (EINVAL);
        }

#if CONFIG_MACF
        /*
         * Determine if MAC policies applied to the process will allow
         * it to fork.
         */
        err = mac_proc_check_fork(parent);
        if (err  != 0) {
                (void)chgproccnt(uid, -1);
                return (err);
        }
#endif

        proc_lock(parent);
        parent->p_lflag  |= P_LVFORK;
        parent->p_vforkcnt++;
        proc_unlock(parent);

        /* The newly created process comes with signal lock held */
        if ((child = forkproc(parent,1)) == NULL) {
                /* Failed to allocate new process */
                (void)chgproccnt(uid, -1);
                /*
                 * XXX kludgy, but necessary without a full flags audit...
                 * XXX these are inherited by the child, which depends on
                 * XXX P_VFORK being set.
                 */
                proc_lock(parent);
                parent->p_lflag &= ~P_LVFORK;
                parent->p_vforkcnt--;
                proc_unlock(parent);
                return (ENOMEM);
        }

#if CONFIG_MACF
        /* allow policies to associate the credential/label  */
        /* that we referenced from the parent ... with the child */
        /* JMM - this really isn't safe, as we can drop that */
        /*       association without informing the policy in other */
        /*       situations (keep long enough to get policies changed) */
        mac_cred_label_associate_fork(child->p_ucred, child);
#endif

        AUDIT_ARG(pid, child->p_pid);

        child->task = parent->task;

        /* make child visible */
        pinsertchild(parent, child);

        child->p_lflag  |= P_LINVFORK;
        child->p_vforkact = cur_act;
        child->p_stat = SRUN;

        ut->uu_flag |= UT_VFORK;
        ut->uu_proc = child;
        ut->uu_userstate = (void *)act_thread_csave();
        ut->uu_vforkmask = ut->uu_sigmask;

        /* temporarily drop thread-set-id state */
        if (ut->uu_flag & UT_SETUID) {
                ut->uu_flag |= UT_WASSETUID;
                ut->uu_flag &= ~UT_SETUID;
        }
        
        thread_set_child(cur_act, child->p_pid);

        microtime(&child->p_start);
        microtime(&child->p_stats->p_start); /* for compat sake */
        child->p_acflag = AFORK;

        /*
         * Preserve synchronization semantics of vfork.  If waiting for
         * child to exec or exit, set P_PPWAIT on child, and sleep on our
         * proc (in case of exit).
         */
        child->p_lflag |= P_LPPWAIT;

        /* drop the signal lock on the child */
        proc_signalend(child, 0);
        proc_transend(child, 0);

        retval[0] = child->p_pid;
        retval[1] = 1;                  /* flag child return for user space */

        DTRACE_PROC1(create, proc_t, child);

        return (0);
}

/*
 * vfork_return
 *
 * Description: "Return" to parent vfork thread() following execve/_exit;
 *              this is done by reassociating the parent process structure
 *              with the task, thread, and uthread.
 *
 * Parameters:  child                   Child process
 *              retval                  System call return value array
 *              rval                    Return value to present to parent
 *
 * Returns:     void
 *
 * Note:        The caller resumes or exits the parent, as appropriate, after
 *              callling this function.
 */
void
vfork_return(proc_t child, register_t *retval, int rval)
{
        proc_t parent = child->p_pptr;
        thread_t cur_act = (thread_t)current_thread();
        uthread_t ut;
        
        ut = (uthread_t)get_bsdthread_info(cur_act);

        act_thread_catt(ut->uu_userstate);

        /* Make sure only one at this time */
        proc_lock(parent);
        parent->p_vforkcnt--;
        if (parent->p_vforkcnt <0)
                panic("vfork cnt is -ve");
        if (parent->p_vforkcnt <=0)
                parent->p_lflag  &= ~P_LVFORK;
        proc_unlock(parent);
        ut->uu_userstate = 0;
        ut->uu_flag &= ~UT_VFORK;
        /* restore thread-set-id state */
        if (ut->uu_flag & UT_WASSETUID) {
                ut->uu_flag |= UT_SETUID;
                ut->uu_flag &= UT_WASSETUID;
        }
        ut->uu_proc = 0;
        ut->uu_sigmask = ut->uu_vforkmask;
        child->p_lflag  &= ~P_LINVFORK;
        child->p_vforkact = (void *)0;

        thread_set_parent(cur_act, rval);

        if (retval) {
                retval[0] = rval;
                retval[1] = 0;                  /* mark parent */
        }

        return;
}


/*
 * fork_create_child
 *
 * Description: Common operations associated with the creation of a child
 *              process
 *
 * Parameters:  parent_task             parent task
 *              child                   child process
 *              inherit_memory          TRUE, if the parents address space is
 *                                      to be inherited by the child
 *              is64bit                 TRUE, if the child being created will
 *                                      be associated with a 64 bit process
 *                                      rather than a 32 bit process
 *
 * Note:        This code is called in the fork() case, from the execve() call
 *              graph, if implementing an execve() following a vfork(), from
 *              the posix_spawn() call graph (which implicitly includes a
 *              vfork() equivalent call, and in the system bootstrap case.
 *
 *              It creates a new task and thread (and as a side effect of the
 *              thread creation, a uthread), which is then associated with the
 *              process 'child'.  If the parent process address space is to
 *              be inherited, then a flag indicates that the newly created
 *              task should inherit this from the child task.
 *
 *              As a special concession to bootstrapping the initial process
 *              in the system, it's possible for 'parent_task' to be TASK_NULL;
 *              in this case, 'inherit_memory' MUST be FALSE.
 */
thread_t
fork_create_child(task_t parent_task, proc_t child, int inherit_memory, int is64bit)
{
        thread_t        child_thread = NULL;
        task_t          child_task;
        kern_return_t   result;

        /* Create a new task for the child process */
        result = task_create_internal(parent_task,
                                        inherit_memory,
                                        is64bit,
                                        &child_task);
        if (result != KERN_SUCCESS) {
                printf("execve: task_create_internal failed.  Code: %d\n", result);
                goto bad;
        }

        /* Set the child task to the new task */
        child->task = child_task;

        /* Set child task proc to child proc */
        set_bsdtask_info(child_task, child);

        /* Propagate CPU limit timer from parent */
        if (timerisset(&child->p_rlim_cpu))
                task_vtimer_set(child_task, TASK_VTIMER_RLIM);

        /* Set/clear 64 bit vm_map flag */
        if (is64bit)
                vm_map_set_64bit(get_task_map(child_task));
        else
                vm_map_set_32bit(get_task_map(child_task));

#if CONFIG_MACF
        /* Update task for MAC framework */
        /* valid to use p_ucred as child is still not running ... */
        mac_task_label_update_cred(child->p_ucred, child_task);
#endif

        /* Set child scheduler priority if nice value inherited from parent */
        if (child->p_nice != 0)
                resetpriority(child);

        /* Create a new thread for the child process */
        result = thread_create(child_task, &child_thread);
        if (result != KERN_SUCCESS) {
                printf("execve: thread_create failed. Code: %d\n", result);
                task_deallocate(child_task);
                child_task = NULL;
        }
bad:
        thread_yield_internal(1);

        return(child_thread);
}


/*
 * procdup
 *
 * Description: Givben a parent process, provide a duplicate task and thread
 *              for a child process of that parent.
 *
 * Parameters:  parent                  Parent process to use as the template
 *              child                   Child process to duplicate into
 *
 * Returns:     !NULL                   Child process thread pointer
 *              NULL                    Failure (unspecified)
 *
 * Note:        Most of the heavy lifting is done by fork_create_child(); this
 *              function exists more or less to deal with the 64 bit commpage,
 *              which requires explicit inheritance, the x86 commpage, which
 *              should not need explicit mapping any more, but apparently does,
 *              and to be variant for the bootstrap process.
 *
 *              There is a special case where the system is being bootstraped,
 *              where this function will be called from cloneproc(), called in
 *              turn from bsd_utaskbootstrap().  In this case, we are acting
 *              to create a task and thread (and uthread) for the benefit of
 *              the kernel process - the first process in the system (PID 0).
 *
 *              In that specific case, we will *not* pass a parent task, since
 *              there is *not* parent task present to pass.
 *
 * XXX:         This function should go away; the variance can moved into
 * XXX:         cloneproc(), and the 64bit commpage code can be moved into
 * XXX:         fork_create_child(), after the x86 commpage inheritance is
 * XXX:         corrected.
 */
thread_t
procdup(proc_t parent, proc_t child)
{
        thread_t                child_thread;
        task_t                  child_task;

        if (parent->task == kernel_task)
                child_thread = fork_create_child(TASK_NULL, child, FALSE, FALSE);
        else
                child_thread = fork_create_child(parent->task, child, TRUE, (parent->p_flag & P_LP64));

        if (child_thread != NULL) {
                child_task = get_threadtask(child_thread);
                if (parent->p_flag & P_LP64) {
                        task_set_64bit(child_task, TRUE);
                        OSBitOrAtomic(P_LP64, (UInt32 *)&child->p_flag);
#ifdef __ppc__
                        /* LP64todo - clean up hacked mapping of commpage */
                        /* 
                         * PPC51: ppc64 is limited to 51-bit addresses.
                         * Memory above that limit is handled specially at
                         * the pmap level.
                         */
                         pmap_map_sharedpage(child_task, get_map_pmap(get_task_map(child_task)));
#endif /* __ppc__ */
                } else {
                        task_set_64bit(child_task, FALSE);
                        OSBitAndAtomic(~((uint32_t)P_LP64), (UInt32 *)&child->p_flag);
                }
        }

        return(child_thread);
}


/*
 * fork
 *
 * Description: fork system call.
 *
 * Parameters:  parent                  Parent process to fork
 *              uap (void)              [unused]
 *              retval                  Return value
 *
 * Returns:     0                       Success
 *              EAGAIN                  Resource unavailable, try again
 */
int
fork(proc_t parent, __unused struct fork_args *uap, register_t *retval)
{
        proc_t child;
        uid_t uid;
        thread_t newth;
        int count;
        task_t t;
#if CONFIG_MACF
        int err;
#endif

        /*
         * Although process entries are dynamically created, we still keep
         * a global limit on the maximum number we will create.  Don't allow
         * a nonprivileged user to use the last process; don't let root
         * exceed the limit. The variable nprocs is the current number of
         * processes, maxproc is the limit.
         */
        uid = kauth_cred_get()->cr_ruid;
        proc_list_lock();
        if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) {
                proc_list_unlock();
                tablefull("proc");
                retval[1] = 0;
                return (EAGAIN);
        }
        proc_list_unlock();

        /*
         * Increment the count of procs running with this uid. Don't allow
         * a nonprivileged user to exceed their current limit, which is
         * always less than what an rlim_t can hold.
         * (locking protection is provided by list lock held in chgproccnt)
         */
        count = chgproccnt(uid, 1);
        if (uid != 0 &&
            (rlim_t)count > parent->p_rlimit[RLIMIT_NPROC].rlim_cur) {
                (void)chgproccnt(uid, -1);
                return (EAGAIN);
        }

#if CONFIG_MACF
        /*
         * Determine if MAC policies applied to the process will allow
         * it to fork.
         */
        err = mac_proc_check_fork(parent);
        if (err != 0) {
                (void)chgproccnt(uid, -1);
                return (err);
        }
#endif

        /* The newly created process comes with signal lock held */
        if ((newth = cloneproc(parent, 1)) == NULL) {
                /* Failed to create thread */
                (void)chgproccnt(uid, -1);
                return (EAGAIN);
        }

        thread_dup(newth);
        /* child = newth->task->proc; */
        child = (proc_t)(get_bsdtask_info(get_threadtask(newth)));

#if CONFIG_MACF
        /* inform policies of new process sharing this cred/label */
        /* safe to use p_ucred here since child is not running */
        /* JMM - unsafe to assume the association will stay - as */
        /*        there are other ways it can be dropped without */
        /*        informing the policies. */
        mac_cred_label_associate_fork(child->p_ucred, child);
#endif

        /* propogate change of PID - may get new cred if auditing */
        set_security_token(child);

        AUDIT_ARG(pid, child->p_pid);

        thread_set_child(newth, child->p_pid);

        microtime(&child->p_start);
        microtime(&child->p_stats->p_start);    /* for compat sake */
        child->p_acflag = AFORK;

#if CONFIG_DTRACE
        /*
         * APPLE NOTE: Solaris does a sprlock() and drops the proc_lock
         * here. We're cheating a bit and only taking the p_dtrace_sprlock
         * lock. A full sprlock would task_suspend the parent.
         */
        lck_mtx_lock(&parent->p_dtrace_sprlock);

        /*
         * Remove all DTrace tracepoints from the child process. We
         * need to do this _before_ duplicating USDT providers since
         * any associated probes may be immediately enabled.
         */
        if (parent->p_dtrace_count > 0) {
                dtrace_fasttrap_fork(parent, child);
        }

        lck_mtx_unlock(&parent->p_dtrace_sprlock);

        /*
         * Duplicate any lazy dof(s). This must be done while NOT
         * holding the parent sprlock! Lock ordering is dtrace_dof_mode_lock,
         * then sprlock. It is imperative we always call
         * dtrace_lazy_dofs_duplicate, rather than null check and
         * call if !NULL. If we NULL test, during lazy dof faulting
         * we can race with the faulting code and proceed from here to
         * beyond the helpers copy. The lazy dof faulting will then
         * fail to copy the helpers to the child process.
         */
        dtrace_lazy_dofs_duplicate(parent, child);
        
        /*
         * Duplicate any helper actions and providers. The SFORKING
         * we set above informs the code to enable USDT probes that
         * sprlock() may fail because the child is being forked.
         */
        /*
         * APPLE NOTE: As best I can tell, Apple's sprlock() equivalent
         * never fails to find the child. We do not set SFORKING.
         */
        if (parent->p_dtrace_helpers != NULL && dtrace_helpers_fork) {
                (*dtrace_helpers_fork)(parent, child);
        }

#endif

        /* drop the signal lock on the child */
        proc_signalend(child, 0);
        proc_transend(child, 0);

        /* "Return" to the child */
        (void)thread_resume(newth);

        /* drop the extra references we got during the creation */
        if ((t = (task_t)get_threadtask(newth)) != NULL) {
                task_deallocate(t);
        }
        thread_deallocate(newth);

        proc_knote(parent, NOTE_FORK | child->p_pid);

        retval[0] = child->p_pid;
        retval[1] = 0;                  /* flag parent */

        DTRACE_PROC1(create, proc_t, child);

        return (0);
}

/*
 * cloneproc
 *
 * Description: Create a new process from a specified process.
 *
 * Parameters:  parent                  The parent process of the process to
 *                                      be cloned
 *              lock                    Whether or not the signal lock was held
 *                                      when calling cloneproc().
 *
 * Returns:     !NULL                   pointer to new child thread
 *              NULL                    Failure (unspecified)
 *
 * Note:        On return newly created child process has signal lock held
 *              to block delivery of signal to it if called with lock set.
 *              fork() code needs to explicity remove this lock before
 *              signals can be delivered
 *
 *              In the case of bootstrap, this function can be called from
 *              bsd_utaskbootstrap() in order to bootstrap the first process;
 *              the net effect is to provide a uthread structure for the
 *              kernel process associated with the kernel task.  This results
 *              in a side effect in procdup(), which is why the code is more
 *              complicated at the top of that function.
 */
thread_t
cloneproc(proc_t parent, int lock)
{
        proc_t child;
        thread_t th = NULL;

        if ((child = forkproc(parent,lock)) == NULL) {
                /* Failed to allocate new process */
                goto bad;
        }

        if ((th = procdup(parent, child)) == NULL) {
                /*
                 * Failed to create thread; now we must deconstruct the new
                 * process previously obtained from forkproc().
                 */
                forkproc_free(child, lock);
                goto bad;
        }

        /* make child visible */
        pinsertchild(parent, child);

        /*
         * Make child runnable, set start time.
         */
        child->p_stat = SRUN;

bad:
        return(th);
}

/*
 * Destroy a process structure that resulted from a call to forkproc(), but
 * which must be returned to the system because of a subsequent failure
 * preventing it from becoming active.
 *
 * Parameters:  p                       The incomplete process from forkproc()
 *              lock                    Whether or not the signal lock was held
 *                                      when calling forkproc().
 *
 * Returns:     (void)
 *
 * Note:        This function should only be used in an error handler following
 *              a call to forkproc().  The 'lock' paramenter should be the same
 *              as the lock parameter passed to forkproc().
 *
 *              Operations occur in reverse order of those in forkproc().
 */
void
forkproc_free(proc_t p, int lock)
{

        /* Drop the signal lock, if it was held */
        if (lock) {
                proc_signalend(p, 0);
                proc_transend(p, 0);
        }

        /*
         * If we have our own copy of the resource limits structure, we
         * need to free it.  If it's a shared copy, we need to drop our
         * reference on it.
         */
        proc_limitdrop(p, 0);
        p->p_limit = NULL;

#if SYSV_SHM
        /* Need to drop references to the shared memory segment(s), if any */
        if (p->vm_shm) {
                /*
                 * Use shmexec(): we have no address space, so no mappings
                 *
                 * XXX Yes, the routine is badly named.
                 */
                shmexec(p);
        }
#endif

        /* Need to undo the effects of the fdcopy(), if any */
        fdfree(p);

        /*
         * Drop the reference on a text vnode pointer, if any
         * XXX This code is broken in forkproc(); see <rdar://4256419>;
         * XXX if anyone ever uses this field, we will be extremely unhappy.
         */
        if (p->p_textvp) {
                vnode_rele(p->p_textvp);
                p->p_textvp = NULL;
        }

        /* Stop the profiling clock */
        stopprofclock(p);

        /* Release the credential reference */
        kauth_cred_unref(&p->p_ucred);

        proc_list_lock();
        /* Decrement the count of processes in the system */
        nprocs--;
        proc_list_unlock();

        thread_call_free(p->p_rcall);

        /* Free allocated memory */
        FREE_ZONE(p->p_sigacts, sizeof *p->p_sigacts, M_SIGACTS);
        FREE_ZONE(p->p_stats, sizeof *p->p_stats, M_PSTATS);
        proc_checkdeadrefs(p);
        FREE_ZONE(p, sizeof *p, M_PROC);
}


/*
 * forkproc
 *
 * Description: Create a new process structure, given a parent process
 *              structure.
 *
 * Parameters:  parent                  The parent process
 *              lock                    If the signal lock should be taken on
 *                                      the newly created process.
 *
 * Returns:     !NULL                   The new process structure
 *              NULL                    Error (insufficient free memory)
 *
 * Note:        When successful, the newly created process structure is
 *              partially initialized; if a caller needs to deconstruct the
 *              returned structure, they must call forkproc_free() to do so.
 */
proc_t
forkproc(proc_t parent, int lock)
{
        struct proc *  child;   /* Our new process */
        static int nextpid = 0, pidwrap = 0;
        int error = 0;
        struct session *sessp;
        uthread_t uth_parent = (uthread_t)get_bsdthread_info(current_thread());

        MALLOC_ZONE(child, proc_t , sizeof *child, M_PROC, M_WAITOK);
        if (child == NULL) {
                printf("forkproc: M_PROC zone exhausted\n");
                goto bad;
        }
        /* zero it out as we need to insert in hash */
        bzero(child, sizeof *child);

        MALLOC_ZONE(child->p_stats, struct pstats *,
                        sizeof *child->p_stats, M_PSTATS, M_WAITOK);
        if (child->p_stats == NULL) {
                printf("forkproc: M_SUBPROC zone exhausted (p_stats)\n");
                FREE_ZONE(child, sizeof *child, M_PROC);
                child = NULL;
                goto bad;
        }
        MALLOC_ZONE(child->p_sigacts, struct sigacts *,
                        sizeof *child->p_sigacts, M_SIGACTS, M_WAITOK);
        if (child->p_sigacts == NULL) {
                printf("forkproc: M_SUBPROC zone exhausted (p_sigacts)\n");
                FREE_ZONE(child->p_stats, sizeof *child->p_stats, M_PSTATS);
                FREE_ZONE(child, sizeof *child, M_PROC);
                child = NULL;
                goto bad;
        }
        child->p_rcall = thread_call_allocate((thread_call_func_t)realitexpire, child);
        if (child->p_rcall == NULL) {
                FREE_ZONE(child->p_sigacts, sizeof *child->p_sigacts, M_SIGACTS);
                FREE_ZONE(child->p_stats, sizeof *child->p_stats, M_PSTATS);
                FREE_ZONE(child, sizeof *child, M_PROC);
                child = NULL;
                goto bad;
        }


        /*
         * Find an unused PID.  
         */

        proc_list_lock();

        nextpid++;
retry:
        /*
         * If the process ID prototype has wrapped around,
         * restart somewhat above 0, as the low-numbered procs
         * tend to include daemons that don't exit.
         */
        if (nextpid >= PID_MAX) {
                nextpid = 100;
                pidwrap = 1;
        }
        if (pidwrap != 0) {

                /* if the pid stays in hash both for zombie and runniing state */
                if  (pfind_locked(nextpid) != PROC_NULL) {
                        nextpid++;
                        goto retry;
                }

                if (pgfind_internal(nextpid) != PGRP_NULL) {
                        nextpid++;
                        goto retry;
                }       
                if (session_find_internal(nextpid) != SESSION_NULL) {
                        nextpid++;
                        goto retry;
                }       
        }
        nprocs++;
        child->p_pid = nextpid;
#if 1
        if (child->p_pid != 0) {
                if (pfind_locked(child->p_pid) != PROC_NULL)
                        panic("proc in the list already\n");
        }
#endif
        /* Insert in the hash */
        child->p_listflag |= (P_LIST_INHASH | P_LIST_INCREATE);
        LIST_INSERT_HEAD(PIDHASH(child->p_pid), child, p_hash);
        proc_list_unlock();


        /*
         * We've identified the PID we are going to use; initialize the new
         * process structure.
         */
        child->p_stat = SIDL;
        child->p_pgrpid = PGRPID_DEAD;

        /*
         * The zero'ing of the proc was at the allocation time due to need for insertion
         * to hash. Copy the section that is to be copied directly from the parent.
         */
        bcopy(&parent->p_startcopy, &child->p_startcopy,
            (unsigned) ((caddr_t)&child->p_endcopy - (caddr_t)&child->p_startcopy));

        /*
         * Some flags are inherited from the parent.
         * Duplicate sub-structures as needed.
         * Increase reference counts on shared objects.
         * The p_stats and p_sigacts substructs are set in vm_fork.
         */
        child->p_flag = (parent->p_flag & (P_LP64 | P_TRANSLATED | P_AFFINITY));
        if (parent->p_flag & P_PROFIL)
                startprofclock(child);
        /*
         * Note that if the current thread has an assumed identity, this
         * credential will be granted to the new process.
         */
        child->p_ucred = kauth_cred_get_with_ref();

        lck_mtx_init(&child->p_mlock, proc_lck_grp, proc_lck_attr);
        lck_mtx_init(&child->p_fdmlock, proc_lck_grp, proc_lck_attr);
#if CONFIG_DTRACE
        lck_mtx_init(&child->p_dtrace_sprlock, proc_lck_grp, proc_lck_attr);
#endif
        lck_spin_init(&child->p_slock, proc_lck_grp, proc_lck_attr);
        klist_init(&child->p_klist);

        if (child->p_textvp != NULLVP) {
                /* bump references to the text vnode */
                /* Need to hold iocount across the ref call */
                if (vnode_getwithref(child->p_textvp) == 0) {
                        error = vnode_ref(child->p_textvp);
                        vnode_put(child->p_textvp);
                        if (error != 0)
                                child->p_textvp = NULLVP;
                }
        }

        /* XXX may fail to copy descriptors to child */
        child->p_fd = fdcopy(parent, uth_parent->uu_cdir);

#if SYSV_SHM
        if (parent->vm_shm) {
                /* XXX may fail to attach shm to child */
                (void)shmfork(parent,child);
        }
#endif
        /*
         * inherit the limit structure to child
         */
        proc_limitfork(parent, child);

        if (child->p_limit->pl_rlimit[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
                uint64_t rlim_cur = child->p_limit->pl_rlimit[RLIMIT_CPU].rlim_cur;
                child->p_rlim_cpu.tv_sec = (rlim_cur > __INT_MAX__) ? __INT_MAX__ : rlim_cur;
        }

        bzero(&child->p_stats->pstat_startzero,
            (unsigned) ((caddr_t)&child->p_stats->pstat_endzero -
            (caddr_t)&child->p_stats->pstat_startzero));

        bzero(&child->p_stats->user_p_prof, sizeof(struct user_uprof));

        if (parent->p_sigacts != NULL)
                (void)memcpy(child->p_sigacts,
                                parent->p_sigacts, sizeof *child->p_sigacts);
        else
                (void)memset(child->p_sigacts, 0, sizeof *child->p_sigacts);

        sessp = proc_session(parent);
        if (sessp->s_ttyvp != NULL && parent->p_flag & P_CONTROLT)
                OSBitOrAtomic(P_CONTROLT, (UInt32 *)&child->p_flag);
        session_rele(sessp);

        /* block all signals to reach the process */
        if (lock) {
                proc_signalstart(child, 0);
                proc_transstart(child, 0);
        }

        TAILQ_INIT(&child->p_uthlist);
        TAILQ_INIT(&child->aio_activeq);
        TAILQ_INIT(&child->aio_doneq);
        /* Inherit the parent flags for code sign */
        child->p_csflags = parent->p_csflags;
        child->p_wqthread = parent->p_wqthread;
        child->p_threadstart = parent->p_threadstart;
        child->p_pthsize = parent->p_pthsize;
        workqueue_init_lock(child);

#if CONFIG_LCTX
        child->p_lctx = NULL;
        /* Add new process to login context (if any). */
        if (parent->p_lctx != NULL) {
                LCTX_LOCK(parent->p_lctx);
                enterlctx(child, parent->p_lctx, 0);
        }
#endif

bad:
        return(child);
}

void
proc_lock(proc_t p)
{
        lck_mtx_lock(&p->p_mlock);
}

void
proc_unlock(proc_t p)
{
        lck_mtx_unlock(&p->p_mlock);
}

void
proc_spinlock(proc_t p)
{
        lck_spin_lock(&p->p_slock);
}

void
proc_spinunlock(proc_t p)
{
        lck_spin_unlock(&p->p_slock);
}

void 
proc_list_lock(void)
{
        lck_mtx_lock(proc_list_mlock);
}

void 
proc_list_unlock(void)
{
        lck_mtx_unlock(proc_list_mlock);
}

#include <kern/zalloc.h>

struct zone     *uthread_zone;
static int uthread_zone_inited = 0;

static void
uthread_zone_init(void)
{
        if (!uthread_zone_inited) {
                uthread_zone = zinit(sizeof(struct uthread),
                                        THREAD_MAX * sizeof(struct uthread),
                                        THREAD_CHUNK * sizeof(struct uthread),
                                        "uthreads");
                uthread_zone_inited = 1;
        }
}

void *
uthread_alloc(task_t task, thread_t thread)
{
        proc_t p;
        uthread_t uth;
        uthread_t uth_parent;
        void *ut;

        if (!uthread_zone_inited)
                uthread_zone_init();

        ut = (void *)zalloc(uthread_zone);
        bzero(ut, sizeof(struct uthread));

        p = (proc_t) get_bsdtask_info(task);
        uth = (uthread_t)ut;

        /*
         * Thread inherits credential from the creating thread, if both
         * are in the same task.
         *
         * If the creating thread has no credential or is from another
         * task we can leave the new thread credential NULL.  If it needs
         * one later, it will be lazily assigned from the task's process.
         */
        uth_parent = (uthread_t)get_bsdthread_info(current_thread());
        if (task == current_task() && 
            uth_parent != NULL &&
            IS_VALID_CRED(uth_parent->uu_ucred)) {
                /*
                 * XXX The new thread is, in theory, being created in context
                 * XXX of parent thread, so a direct reference to the parent
                 * XXX is OK.
                 */
                kauth_cred_ref(uth_parent->uu_ucred);
                uth->uu_ucred = uth_parent->uu_ucred;
                /* the credential we just inherited is an assumed credential */
                if (uth_parent->uu_flag & UT_SETUID)
                        uth->uu_flag |= UT_SETUID;
        } else {
                uth->uu_ucred = NOCRED;
        }

        
        if ((task != kernel_task) && p) {
                
                proc_lock(p);
                if (uth_parent) {
                        if (uth_parent->uu_flag & UT_SAS_OLDMASK)
                                uth->uu_sigmask = uth_parent->uu_oldmask;
                        else
                                uth->uu_sigmask = uth_parent->uu_sigmask;
                }
                uth->uu_context.vc_thread = thread;
                TAILQ_INSERT_TAIL(&p->p_uthlist, uth, uu_list);
                proc_unlock(p);

#if CONFIG_DTRACE
                if (p->p_dtrace_ptss_pages != NULL) {
                        uth->t_dtrace_scratch = dtrace_ptss_claim_entry(p);
                }
#endif
        }

        return (ut);
}


/* 
 * This routine frees all the BSD context in uthread except the credential.
 * It does not free the uthread structure as well
 */
void
uthread_cleanup(task_t task, void *uthread, void * bsd_info)
{
        struct _select *sel;
        uthread_t uth = (uthread_t)uthread;
        proc_t p = (proc_t)bsd_info;

        /*
         * Per-thread audit state should never last beyond system
         * call return.  Since we don't audit the thread creation/
         * removal, the thread state pointer should never be
         * non-NULL when we get here.
         */
        assert(uth->uu_ar == NULL);

        sel = &uth->uu_select;
        /* cleanup the select bit space */
        if (sel->nbytes) {
                FREE(sel->ibits, M_TEMP);
                FREE(sel->obits, M_TEMP);
                sel->nbytes = 0;
        }

        if (uth->uu_cdir) {
                vnode_rele(uth->uu_cdir);
                uth->uu_cdir = NULLVP;
        }

        if (uth->uu_allocsize && uth->uu_wqset){
                kfree(uth->uu_wqset, uth->uu_allocsize);
                sel->count = 0;
                uth->uu_allocsize = 0;
                uth->uu_wqset = 0;
                sel->wql = 0;
        }


        if ((task != kernel_task) && p) {

                if (((uth->uu_flag & UT_VFORK) == UT_VFORK) && (uth->uu_proc != PROC_NULL))  {
                        vfork_exit_internal(uth->uu_proc, 0, 1);
                }
                if (get_bsdtask_info(task) == p) { 
                        proc_lock(p);
                        TAILQ_REMOVE(&p->p_uthlist, uth, uu_list);
                        proc_unlock(p);
                }
#if CONFIG_DTRACE
                if (uth->t_dtrace_scratch != NULL) {
                        dtrace_ptss_release_entry(p, uth->t_dtrace_scratch);
                }
#endif
        }
}

/* This routine releases the credential stored in uthread */
void
uthread_cred_free(void *uthread)
{
        uthread_t uth = (uthread_t)uthread;

        /* and free the uthread itself */
        if (IS_VALID_CRED(uth->uu_ucred)) {
                kauth_cred_t oldcred = uth->uu_ucred;
                uth->uu_ucred = NOCRED;
                kauth_cred_unref(&oldcred);
        }
}

/* This routine frees the uthread structure held in thread structure */
void
uthread_zone_free(void *uthread)
{
        /* and free the uthread itself */
        zfree(uthread_zone, uthread);
}