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

/*
 * Copyright (c) 1995-2016 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) 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_sig.c  8.7 (Berkeley) 4/18/94
 */
/*
 * 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.
 */

#define SIGPROP         /* include signal properties table */
#include <sys/param.h>
#include <sys/resourcevar.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/systm.h>
#include <sys/timeb.h>
#include <sys/times.h>
#include <sys/acct.h>
#include <sys/file_internal.h>
#include <sys/kernel.h>
#include <sys/wait.h>
#include <sys/signalvar.h>
#include <sys/syslog.h>
#include <sys/stat.h>
#include <sys/lock.h>
#include <sys/kdebug.h>
#include <sys/reason.h>

#include <sys/mount.h>
#include <sys/sysproto.h>

#include <security/audit/audit.h>

#include <kern/cpu_number.h>

#include <sys/vm.h>
#include <sys/user.h>           /* for coredump */
#include <kern/ast.h>           /* for APC support */
#include <kern/kalloc.h>
#include <kern/task.h>          /* extern void   *get_bsdtask_info(task_t); */
#include <kern/thread.h>
#include <kern/sched_prim.h>
#include <kern/thread_call.h>
#include <kern/policy_internal.h>

#include <mach/exception.h>
#include <mach/task.h>
#include <mach/thread_act.h>
#include <libkern/OSAtomic.h>

#include <sys/sdt.h>
#include <sys/codesign.h>
#include <sys/random.h>
#include <libkern/section_keywords.h>

#if CONFIG_MACF
#include <security/mac_framework.h>
#endif

/*
 * Missing prototypes that Mach should export
 *
 * +++
 */
extern int thread_enable_fpe(thread_t act, int onoff);
extern kern_return_t get_signalact(task_t, thread_t *, int);
extern unsigned int get_useraddr(void);
extern boolean_t task_did_exec(task_t task);
extern boolean_t task_is_exec_copy(task_t task);
extern void vm_shared_region_reslide_stale(void);

/*
 * ---
 */

extern void doexception(int exc, mach_exception_code_t code,
    mach_exception_subcode_t sub);

static void stop(proc_t, proc_t);
static int cansignal_nomac(proc_t, kauth_cred_t, proc_t, int);
int cansignal(proc_t, kauth_cred_t, proc_t, int);
int killpg1(proc_t, int, int, int, int);
kern_return_t do_bsdexception(int, int, int);
void __posix_sem_syscall_return(kern_return_t);
char *proc_name_address(void *p);

/* implementations in osfmk/kern/sync_sema.c. We do not want port.h in this scope, so void * them  */
kern_return_t semaphore_timedwait_signal_trap_internal(mach_port_name_t, mach_port_name_t, unsigned int, clock_res_t, void (*)(kern_return_t));
kern_return_t semaphore_timedwait_trap_internal(mach_port_name_t, unsigned int, clock_res_t, void (*)(kern_return_t));
kern_return_t semaphore_wait_signal_trap_internal(mach_port_name_t, mach_port_name_t, void (*)(kern_return_t));
kern_return_t semaphore_wait_trap_internal(mach_port_name_t, void (*)(kern_return_t));

static int      filt_sigattach(struct knote *kn, struct kevent_qos_s *kev);
static void     filt_sigdetach(struct knote *kn);
static int      filt_signal(struct knote *kn, long hint);
static int      filt_signaltouch(struct knote *kn, struct kevent_qos_s *kev);
static int      filt_signalprocess(struct knote *kn, struct kevent_qos_s *kev);

SECURITY_READ_ONLY_EARLY(struct filterops) sig_filtops = {
        .f_attach = filt_sigattach,
        .f_detach = filt_sigdetach,
        .f_event = filt_signal,
        .f_touch = filt_signaltouch,
        .f_process = filt_signalprocess,
};

/* structures  and fns for killpg1 iterartion callback and filters */
struct killpg1_filtargs {
        bool posix;
        proc_t curproc;
};

struct killpg1_iterargs {
        proc_t curproc;
        kauth_cred_t uc;
        int signum;
        int nfound;
};

static int killpg1_allfilt(proc_t p, void * arg);
static int killpg1_pgrpfilt(proc_t p, __unused void * arg);
static int killpg1_callback(proc_t p, void * arg);

static int pgsignal_filt(proc_t p, void * arg);
static int pgsignal_callback(proc_t p, void * arg);
static kern_return_t get_signalthread(proc_t, int, thread_t *);


/* flags for psignal_internal */
#define PSIG_LOCKED     0x1
#define PSIG_VFORK      0x2
#define PSIG_THREAD     0x4
#define PSIG_TRY_THREAD 0x8

static os_reason_t build_signal_reason(int signum, const char *procname);
static void psignal_internal(proc_t p, task_t task, thread_t thread, int flavor, int signum, os_reason_t signal_reason);

/*
 * NOTE: Source and target may *NOT* overlap! (target is smaller)
 */
static void
sigaltstack_kern_to_user32(struct kern_sigaltstack *in, struct user32_sigaltstack *out)
{
        out->ss_sp          = CAST_DOWN_EXPLICIT(user32_addr_t, in->ss_sp);
        out->ss_size    = CAST_DOWN_EXPLICIT(user32_size_t, in->ss_size);
        out->ss_flags   = in->ss_flags;
}

static void
sigaltstack_kern_to_user64(struct kern_sigaltstack *in, struct user64_sigaltstack *out)
{
        out->ss_sp          = in->ss_sp;
        out->ss_size    = in->ss_size;
        out->ss_flags   = in->ss_flags;
}

/*
 * NOTE: Source and target may are permitted to overlap! (source is smaller);
 * this works because we copy fields in order from the end of the struct to
 * the beginning.
 */
static void
sigaltstack_user32_to_kern(struct user32_sigaltstack *in, struct kern_sigaltstack *out)
{
        out->ss_flags   = in->ss_flags;
        out->ss_size    = in->ss_size;
        out->ss_sp              = CAST_USER_ADDR_T(in->ss_sp);
}
static void
sigaltstack_user64_to_kern(struct user64_sigaltstack *in, struct kern_sigaltstack *out)
{
        out->ss_flags   = in->ss_flags;
        out->ss_size    = (user_size_t)in->ss_size;
        out->ss_sp      = (user_addr_t)in->ss_sp;
}

static void
sigaction_kern_to_user32(struct kern_sigaction *in, struct user32_sigaction *out)
{
        /* This assumes 32 bit __sa_handler is of type sig_t */
        out->__sigaction_u.__sa_handler = CAST_DOWN_EXPLICIT(user32_addr_t, in->__sigaction_u.__sa_handler);
        out->sa_mask = in->sa_mask;
        out->sa_flags = in->sa_flags;
}
static void
sigaction_kern_to_user64(struct kern_sigaction *in, struct user64_sigaction *out)
{
        /* This assumes 32 bit __sa_handler is of type sig_t */
        out->__sigaction_u.__sa_handler = in->__sigaction_u.__sa_handler;
        out->sa_mask = in->sa_mask;
        out->sa_flags = in->sa_flags;
}

static void
__sigaction_user32_to_kern(struct __user32_sigaction *in, struct __kern_sigaction *out)
{
        out->__sigaction_u.__sa_handler = CAST_USER_ADDR_T(in->__sigaction_u.__sa_handler);
        out->sa_tramp = CAST_USER_ADDR_T(in->sa_tramp);
        out->sa_mask = in->sa_mask;
        out->sa_flags = in->sa_flags;

        kern_return_t kr;
        kr = machine_thread_function_pointers_convert_from_user(current_thread(),
            &out->sa_tramp, 1);
        assert(kr == KERN_SUCCESS);
}

static void
__sigaction_user64_to_kern(struct __user64_sigaction *in, struct __kern_sigaction *out)
{
        out->__sigaction_u.__sa_handler = (user_addr_t)in->__sigaction_u.__sa_handler;
        out->sa_tramp = (user_addr_t)in->sa_tramp;
        out->sa_mask = in->sa_mask;
        out->sa_flags = in->sa_flags;

        kern_return_t kr;
        kr = machine_thread_function_pointers_convert_from_user(current_thread(),
            &out->sa_tramp, 1);
        assert(kr == KERN_SUCCESS);
}

#if SIGNAL_DEBUG
void ram_printf(int);
int ram_debug = 0;
unsigned int rdebug_proc = 0;
void
ram_printf(int x)
{
        printf("x is %d", x);
}
#endif /* SIGNAL_DEBUG */


void
signal_setast(thread_t sig_actthread)
{
        act_set_astbsd(sig_actthread);
}

static int
cansignal_nomac(proc_t src, kauth_cred_t uc_src, proc_t dst, int signum)
{
        /* you can signal yourself */
        if (src == dst) {
                return 1;
        }

        /* you can't send the init proc SIGKILL, even if root */
        if (signum == SIGKILL && dst == initproc) {
                return 0;
        }

        /* otherwise, root can always signal */
        if (kauth_cred_issuser(uc_src)) {
                return 1;
        }

        /* processes in the same session can send SIGCONT to each other */
        {
                struct session *sess_src = SESSION_NULL;
                struct session *sess_dst = SESSION_NULL;

                /* The session field is protected by the list lock. */
                proc_list_lock();
                if (src->p_pgrp != PGRP_NULL) {
                        sess_src = src->p_pgrp->pg_session;
                }
                if (dst->p_pgrp != PGRP_NULL) {
                        sess_dst = dst->p_pgrp->pg_session;
                }
                proc_list_unlock();

                /* allow SIGCONT within session and for processes without session */
                if (signum == SIGCONT && sess_src == sess_dst) {
                        return 1;
                }
        }

        /* the source process must be authorized to signal the target */
        {
                int allowed = 0;
                kauth_cred_t uc_dst = NOCRED, uc_ref = NOCRED;

                uc_dst = uc_ref = kauth_cred_proc_ref(dst);

                /*
                 * If the real or effective UID of the sender matches the real or saved
                 * UID of the target, allow the signal to be sent.
                 */
                if (kauth_cred_getruid(uc_src) == kauth_cred_getruid(uc_dst) ||
                    kauth_cred_getruid(uc_src) == kauth_cred_getsvuid(uc_dst) ||
                    kauth_cred_getuid(uc_src) == kauth_cred_getruid(uc_dst) ||
                    kauth_cred_getuid(uc_src) == kauth_cred_getsvuid(uc_dst)) {
                        allowed = 1;
                }

                if (uc_ref != NOCRED) {
                        kauth_cred_unref(&uc_ref);
                        uc_ref = NOCRED;
                }

                return allowed;
        }
}

/*
 * Can process `src`, with ucred `uc_src`, send the signal `signum` to process
 * `dst`?  The ucred is referenced by the caller so internal fileds can be used
 * safely.
 */
int
cansignal(proc_t src, kauth_cred_t uc_src, proc_t dst, int signum)
{
#if CONFIG_MACF
        if (mac_proc_check_signal(src, dst, signum)) {
                return 0;
        }
#endif

        return cansignal_nomac(src, uc_src, dst, signum);
}

/*
 * <rdar://problem/21952708> Some signals can be restricted from being handled,
 * forcing the default action for that signal. This behavior applies only to
 * non-root (EUID != 0) processes, and is configured with the "sigrestrict=x"
 * bootarg:
 *
 *   0 (default): Disallow use of restricted signals. Trying to register a handler
 *              returns ENOTSUP, which userspace may use to take special action (e.g. abort).
 *   1: As above, but return EINVAL. Restricted signals behave similarly to SIGKILL.
 *   2: Usual POSIX semantics.
 */
unsigned sigrestrict_arg = 0;

#if PLATFORM_WatchOS
static int
sigrestrictmask(void)
{
        if (kauth_getuid() != 0 && sigrestrict_arg != 2) {
                return SIGRESTRICTMASK;
        }
        return 0;
}

static int
signal_is_restricted(proc_t p, int signum)
{
        if (sigmask(signum) & sigrestrictmask()) {
                if (sigrestrict_arg == 0 &&
                    task_get_apptype(p->task) == TASK_APPTYPE_APP_DEFAULT) {
                        return ENOTSUP;
                } else {
                        return EINVAL;
                }
        }
        return 0;
}

#else

static inline int
signal_is_restricted(proc_t p, int signum)
{
        (void)p;
        (void)signum;
        return 0;
}
#endif /* !PLATFORM_WatchOS */

/*
 * Returns:     0                       Success
 *              EINVAL
 *      copyout:EFAULT
 *      copyin:EFAULT
 *
 * Notes:       Uses current thread as a parameter to inform PPC to enable
 *              FPU exceptions via setsigvec(); this operation is not proxy
 *              safe!
 */
/* ARGSUSED */
int
sigaction(proc_t p, struct sigaction_args *uap, __unused int32_t *retval)
{
        struct kern_sigaction vec;
        struct __kern_sigaction __vec;

        struct kern_sigaction *sa = &vec;
        struct sigacts *ps = p->p_sigacts;

        int signum;
        int bit, error = 0;
        uint32_t sigreturn_validation = PS_SIGRETURN_VALIDATION_DEFAULT;

        signum = uap->signum;
        if (signum <= 0 || signum >= NSIG ||
            signum == SIGKILL || signum == SIGSTOP) {
                return EINVAL;
        }

        if (uap->nsa) {
                if (IS_64BIT_PROCESS(p)) {
                        struct __user64_sigaction       __vec64;
                        error = copyin(uap->nsa, &__vec64, sizeof(__vec64));
                        __sigaction_user64_to_kern(&__vec64, &__vec);
                } else {
                        struct __user32_sigaction       __vec32;
                        error = copyin(uap->nsa, &__vec32, sizeof(__vec32));
                        __sigaction_user32_to_kern(&__vec32, &__vec);
                }
                if (error) {
                        return error;
                }

                sigreturn_validation = (__vec.sa_flags & SA_VALIDATE_SIGRETURN_FROM_SIGTRAMP) ?
                    PS_SIGRETURN_VALIDATION_ENABLED : PS_SIGRETURN_VALIDATION_DISABLED;
                __vec.sa_flags &= SA_USERSPACE_MASK; /* Only pass on valid sa_flags */

                if ((__vec.sa_flags & SA_SIGINFO) || __vec.sa_handler != SIG_DFL) {
                        if ((error = signal_is_restricted(p, signum))) {
                                if (error == ENOTSUP) {
                                        printf("%s(%d): denied attempt to register action for signal %d\n",
                                            proc_name_address(p), proc_pid(p), signum);
                                }
                                return error;
                        }
                }
        }

        if (uap->osa) {
                sa->sa_handler = ps->ps_sigact[signum];
                sa->sa_mask = ps->ps_catchmask[signum];
                bit = sigmask(signum);
                sa->sa_flags = 0;
                if ((ps->ps_sigonstack & bit) != 0) {
                        sa->sa_flags |= SA_ONSTACK;
                }
                if ((ps->ps_sigintr & bit) == 0) {
                        sa->sa_flags |= SA_RESTART;
                }
                if (ps->ps_siginfo & bit) {
                        sa->sa_flags |= SA_SIGINFO;
                }
                if (ps->ps_signodefer & bit) {
                        sa->sa_flags |= SA_NODEFER;
                }
                if ((signum == SIGCHLD) && (p->p_flag & P_NOCLDSTOP)) {
                        sa->sa_flags |= SA_NOCLDSTOP;
                }
                if ((signum == SIGCHLD) && (p->p_flag & P_NOCLDWAIT)) {
                        sa->sa_flags |= SA_NOCLDWAIT;
                }

                if (IS_64BIT_PROCESS(p)) {
                        struct user64_sigaction vec64 = {};
                        sigaction_kern_to_user64(sa, &vec64);
                        error = copyout(&vec64, uap->osa, sizeof(vec64));
                } else {
                        struct user32_sigaction vec32 = {};
                        sigaction_kern_to_user32(sa, &vec32);
                        error = copyout(&vec32, uap->osa, sizeof(vec32));
                }
                if (error) {
                        return error;
                }
        }

        if (uap->nsa) {
                uint32_t old_sigreturn_validation = atomic_load_explicit(
                        &ps->ps_sigreturn_validation, memory_order_relaxed);
                if (old_sigreturn_validation == PS_SIGRETURN_VALIDATION_DEFAULT) {
                        atomic_compare_exchange_strong_explicit(&ps->ps_sigreturn_validation,
                            &old_sigreturn_validation, sigreturn_validation,
                            memory_order_relaxed, memory_order_relaxed);
                }
                error = setsigvec(p, current_thread(), signum, &__vec, FALSE);
        }

        return error;
}

/* Routines to manipulate bits on all threads */
int
clear_procsiglist(proc_t p, int bit, boolean_t in_signalstart)
{
        struct uthread * uth;
        thread_t thact;

        proc_lock(p);
        if (!in_signalstart) {
                proc_signalstart(p, 1);
        }

        if ((p->p_lflag & P_LINVFORK) && p->p_vforkact) {
                thact = p->p_vforkact;
                uth = (struct uthread *)get_bsdthread_info(thact);
                if (uth) {
                        uth->uu_siglist &= ~bit;
                }
                if (!in_signalstart) {
                        proc_signalend(p, 1);
                }
                proc_unlock(p);
                return 0;
        }

        TAILQ_FOREACH(uth, &p->p_uthlist, uu_list) {
                uth->uu_siglist &= ~bit;
        }
        p->p_siglist &= ~bit;
        if (!in_signalstart) {
                proc_signalend(p, 1);
        }
        proc_unlock(p);

        return 0;
}


static int
unblock_procsigmask(proc_t p, int bit)
{
        struct uthread * uth;
        thread_t thact;

        proc_lock(p);
        proc_signalstart(p, 1);

        if ((p->p_lflag & P_LINVFORK) && p->p_vforkact) {
                thact = p->p_vforkact;
                uth = (struct uthread *)get_bsdthread_info(thact);
                if (uth) {
                        uth->uu_sigmask &= ~bit;
                }
                p->p_sigmask &= ~bit;
                proc_signalend(p, 1);
                proc_unlock(p);
                return 0;
        }
        TAILQ_FOREACH(uth, &p->p_uthlist, uu_list) {
                uth->uu_sigmask &= ~bit;
        }
        p->p_sigmask &= ~bit;

        proc_signalend(p, 1);
        proc_unlock(p);
        return 0;
}

static int
block_procsigmask(proc_t p, int bit)
{
        struct uthread * uth;
        thread_t thact;

        proc_lock(p);
        proc_signalstart(p, 1);

        if ((p->p_lflag & P_LINVFORK) && p->p_vforkact) {
                thact = p->p_vforkact;
                uth = (struct uthread *)get_bsdthread_info(thact);
                if (uth) {
                        uth->uu_sigmask |= bit;
                }
                p->p_sigmask |=  bit;
                proc_signalend(p, 1);
                proc_unlock(p);
                return 0;
        }
        TAILQ_FOREACH(uth, &p->p_uthlist, uu_list) {
                uth->uu_sigmask |= bit;
        }
        p->p_sigmask |=  bit;

        proc_signalend(p, 1);
        proc_unlock(p);
        return 0;
}

int
set_procsigmask(proc_t p, int bit)
{
        struct uthread * uth;
        thread_t thact;

        proc_lock(p);
        proc_signalstart(p, 1);

        if ((p->p_lflag & P_LINVFORK) && p->p_vforkact) {
                thact = p->p_vforkact;
                uth = (struct uthread *)get_bsdthread_info(thact);
                if (uth) {
                        uth->uu_sigmask = bit;
                }
                p->p_sigmask =  bit;
                proc_signalend(p, 1);
                proc_unlock(p);
                return 0;
        }
        TAILQ_FOREACH(uth, &p->p_uthlist, uu_list) {
                uth->uu_sigmask = bit;
        }
        p->p_sigmask =  bit;
        proc_signalend(p, 1);
        proc_unlock(p);

        return 0;
}

/* XXX should be static? */
/*
 * Notes:       The thread parameter is used in the PPC case to select the
 *              thread on which the floating point exception will be enabled
 *              or disabled.  We can't simply take current_thread(), since
 *              this is called from posix_spawn() on the not currently running
 *              process/thread pair.
 *
 *              We mark thread as unused to alow compilation without warning
 *              on non-PPC platforms.
 */
int
setsigvec(proc_t p, __unused thread_t thread, int signum, struct __kern_sigaction *sa, boolean_t in_sigstart)
{
        struct sigacts *ps = p->p_sigacts;
        int bit;

        assert(signum < NSIG);

        if ((signum == SIGKILL || signum == SIGSTOP) &&
            sa->sa_handler != SIG_DFL) {
                return EINVAL;
        }
        bit = sigmask(signum);
        /*
         * Change setting atomically.
         */
        ps->ps_sigact[signum] = sa->sa_handler;
        ps->ps_trampact[signum] = sa->sa_tramp;
        ps->ps_catchmask[signum] = sa->sa_mask & ~sigcantmask;
        if (sa->sa_flags & SA_SIGINFO) {
                ps->ps_siginfo |= bit;
        } else {
                ps->ps_siginfo &= ~bit;
        }
        if ((sa->sa_flags & SA_RESTART) == 0) {
                ps->ps_sigintr |= bit;
        } else {
                ps->ps_sigintr &= ~bit;
        }
        if (sa->sa_flags & SA_ONSTACK) {
                ps->ps_sigonstack |= bit;
        } else {
                ps->ps_sigonstack &= ~bit;
        }
        if (sa->sa_flags & SA_RESETHAND) {
                ps->ps_sigreset |= bit;
        } else {
                ps->ps_sigreset &= ~bit;
        }
        if (sa->sa_flags & SA_NODEFER) {
                ps->ps_signodefer |= bit;
        } else {
                ps->ps_signodefer &= ~bit;
        }
        if (signum == SIGCHLD) {
                if (sa->sa_flags & SA_NOCLDSTOP) {
                        OSBitOrAtomic(P_NOCLDSTOP, &p->p_flag);
                } else {
                        OSBitAndAtomic(~((uint32_t)P_NOCLDSTOP), &p->p_flag);
                }
                if ((sa->sa_flags & SA_NOCLDWAIT) || (sa->sa_handler == SIG_IGN)) {
                        OSBitOrAtomic(P_NOCLDWAIT, &p->p_flag);
                } else {
                        OSBitAndAtomic(~((uint32_t)P_NOCLDWAIT), &p->p_flag);
                }
        }

        /*
         * Set bit in p_sigignore for signals that are set to SIG_IGN,
         * and for signals set to SIG_DFL where the default is to ignore.
         * However, don't put SIGCONT in p_sigignore,
         * as we have to restart the process.
         */
        if (sa->sa_handler == SIG_IGN ||
            (sigprop[signum] & SA_IGNORE && sa->sa_handler == SIG_DFL)) {
                clear_procsiglist(p, bit, in_sigstart);
                if (signum != SIGCONT) {
                        p->p_sigignore |= bit;  /* easier in psignal */
                }
                p->p_sigcatch &= ~bit;
        } else {
                p->p_sigignore &= ~bit;
                if (sa->sa_handler == SIG_DFL) {
                        p->p_sigcatch &= ~bit;
                } else {
                        p->p_sigcatch |= bit;
                }
        }
        return 0;
}

/*
 * Initialize signal state for process 0;
 * set to ignore signals that are ignored by default.
 */
void
siginit(proc_t p)
{
        int i;

        for (i = 1; i < NSIG; i++) {
                if (sigprop[i] & SA_IGNORE && i != SIGCONT) {
                        p->p_sigignore |= sigmask(i);
                }
        }
}

/*
 * Reset signals for an exec of the specified process.
 */
void
execsigs(proc_t p, thread_t thread)
{
        struct sigacts *ps = p->p_sigacts;
        int nc, mask;
        struct uthread *ut;

        ut = (struct uthread *)get_bsdthread_info(thread);

        /*
         * transfer saved signal states from the process
         * back to the current thread.
         *
         * NOTE: We do this without the process locked,
         * because we are guaranteed to be single-threaded
         * by this point in exec and the p_siglist is
         * only accessed by threads inside the process.
         */
        ut->uu_siglist |= p->p_siglist;
        p->p_siglist = 0;

        /*
         * Reset caught signals.  Held signals remain held
         * through p_sigmask (unless they were caught,
         * and are now ignored by default).
         */
        while (p->p_sigcatch) {
                nc = ffs((unsigned int)p->p_sigcatch);
                mask = sigmask(nc);
                p->p_sigcatch &= ~mask;
                if (sigprop[nc] & SA_IGNORE) {
                        if (nc != SIGCONT) {
                                p->p_sigignore |= mask;
                        }
                        ut->uu_siglist &= ~mask;
                }
                ps->ps_sigact[nc] = SIG_DFL;
        }

        atomic_store_explicit(&ps->ps_sigreturn_validation,
            PS_SIGRETURN_VALIDATION_DEFAULT, memory_order_relaxed);
        /* Generate random token value used to validate sigreturn arguments */
        read_random(&ps->ps_sigreturn_token, sizeof(ps->ps_sigreturn_token));

        /*
         * Reset stack state to the user stack.
         * Clear set of signals caught on the signal stack.
         */
        /* thread */
        ut->uu_sigstk.ss_flags = SA_DISABLE;
        ut->uu_sigstk.ss_size = 0;
        ut->uu_sigstk.ss_sp = USER_ADDR_NULL;
        ut->uu_flag &= ~UT_ALTSTACK;
        /* process */
        ps->ps_sigonstack = 0;
}

/*
 * Manipulate signal mask.
 * Note that we receive new mask, not pointer,
 * and return old mask as return value;
 * the library stub does the rest.
 */
int
sigprocmask(proc_t p, struct sigprocmask_args *uap, __unused int32_t *retval)
{
        int error = 0;
        sigset_t oldmask, nmask;
        user_addr_t omask = uap->omask;
        struct uthread *ut;

        ut = (struct uthread *)get_bsdthread_info(current_thread());
        oldmask  = ut->uu_sigmask;

        if (uap->mask == USER_ADDR_NULL) {
                /* just want old mask */
                goto out;
        }
        error = copyin(uap->mask, &nmask, sizeof(sigset_t));
        if (error) {
                goto out;
        }

        switch (uap->how) {
        case SIG_BLOCK:
                block_procsigmask(p, (nmask & ~sigcantmask));
                signal_setast(current_thread());
                break;

        case SIG_UNBLOCK:
                unblock_procsigmask(p, (nmask & ~sigcantmask));
                signal_setast(current_thread());
                break;

        case SIG_SETMASK:
                set_procsigmask(p, (nmask & ~sigcantmask));
                signal_setast(current_thread());
                break;

        default:
                error = EINVAL;
                break;
        }
out:
        if (!error && omask != USER_ADDR_NULL) {
                copyout(&oldmask, omask, sizeof(sigset_t));
        }
        return error;
}

int
sigpending(__unused proc_t p, struct sigpending_args *uap, __unused int32_t *retval)
{
        struct uthread *ut;
        sigset_t pendlist;

        ut = (struct uthread *)get_bsdthread_info(current_thread());
        pendlist = ut->uu_siglist;

        if (uap->osv) {
                copyout(&pendlist, uap->osv, sizeof(sigset_t));
        }
        return 0;
}

/*
 * Suspend process until signal, providing mask to be set
 * in the meantime.  Note nonstandard calling convention:
 * libc stub passes mask, not pointer, to save a copyin.
 */

static int
sigcontinue(__unused int error)
{
//      struct uthread *ut = get_bsdthread_info(current_thread());
        unix_syscall_return(EINTR);
}

int
sigsuspend(proc_t p, struct sigsuspend_args *uap, int32_t *retval)
{
        __pthread_testcancel(1);
        return sigsuspend_nocancel(p, (struct sigsuspend_nocancel_args *)uap, retval);
}

int
sigsuspend_nocancel(proc_t p, struct sigsuspend_nocancel_args *uap, __unused int32_t *retval)
{
        struct uthread *ut;

        ut = (struct uthread *)get_bsdthread_info(current_thread());

        /*
         * When returning from sigpause, we want
         * the old mask to be restored after the
         * signal handler has finished.  Thus, we
         * save it here and mark the sigacts structure
         * to indicate this.
         */
        ut->uu_oldmask = ut->uu_sigmask;
        ut->uu_flag |= UT_SAS_OLDMASK;
        ut->uu_sigmask = (uap->mask & ~sigcantmask);
        (void) tsleep0((caddr_t) p, PPAUSE | PCATCH, "pause", 0, sigcontinue);
        /* always return EINTR rather than ERESTART... */
        return EINTR;
}


int
__disable_threadsignal(__unused proc_t p,
    __unused struct __disable_threadsignal_args *uap,
    __unused int32_t *retval)
{
        struct uthread *uth;

        uth = (struct uthread *)get_bsdthread_info(current_thread());

        /* No longer valid to have any signal delivered */
        uth->uu_flag |= (UT_NO_SIGMASK | UT_CANCELDISABLE);

        return 0;
}

void
__pthread_testcancel(int presyscall)
{
        thread_t self = current_thread();
        struct uthread * uthread;

        uthread = (struct uthread *)get_bsdthread_info(self);


        uthread->uu_flag &= ~UT_NOTCANCELPT;

        if ((uthread->uu_flag & (UT_CANCELDISABLE | UT_CANCEL | UT_CANCELED)) == UT_CANCEL) {
                if (presyscall != 0) {
                        unix_syscall_return(EINTR);
                        /* NOTREACHED */
                } else {
                        thread_abort_safely(self);
                }
        }
}



int
__pthread_markcancel(__unused proc_t p,
    struct __pthread_markcancel_args *uap, __unused int32_t *retval)
{
        thread_act_t target_act;
        int error = 0;
        struct uthread *uth;

        target_act = (thread_act_t)port_name_to_thread(uap->thread_port,
            PORT_TO_THREAD_IN_CURRENT_TASK);

        if (target_act == THR_ACT_NULL) {
                return ESRCH;
        }

        uth = (struct uthread *)get_bsdthread_info(target_act);

        /* if the thread is in vfork do not cancel */
        if ((uth->uu_flag & (UT_VFORK | UT_CANCEL | UT_CANCELED)) == 0) {
                uth->uu_flag |= (UT_CANCEL | UT_NO_SIGMASK);
                if (((uth->uu_flag & UT_NOTCANCELPT) == 0)
                    && ((uth->uu_flag & UT_CANCELDISABLE) == 0)) {
                        thread_abort_safely(target_act);
                }
        }

        thread_deallocate(target_act);
        return error;
}

/* if action =0 ; return the cancellation state ,
 *      if marked for cancellation, make the thread canceled
 * if action = 1 ; Enable the cancel handling
 * if action = 2; Disable the cancel handling
 */
int
__pthread_canceled(__unused proc_t p,
    struct __pthread_canceled_args *uap, __unused int32_t *retval)
{
        thread_act_t thread;
        struct uthread *uth;
        int action = uap->action;

        thread = current_thread();
        uth = (struct uthread *)get_bsdthread_info(thread);

        switch (action) {
        case 1:
                uth->uu_flag &= ~UT_CANCELDISABLE;
                return 0;
        case 2:
                uth->uu_flag |= UT_CANCELDISABLE;
                return 0;
        case 0:
        default:
                /* if the thread is in vfork do not cancel */
                if ((uth->uu_flag & (UT_CANCELDISABLE | UT_CANCEL | UT_CANCELED)) == UT_CANCEL) {
                        uth->uu_flag &= ~UT_CANCEL;
                        uth->uu_flag |= (UT_CANCELED | UT_NO_SIGMASK);
                        return 0;
                }
                return EINVAL;
        }
        return EINVAL;
}

__attribute__((noreturn))
void
__posix_sem_syscall_return(kern_return_t kern_result)
{
        int error = 0;

        if (kern_result == KERN_SUCCESS) {
                error = 0;
        } else if (kern_result == KERN_ABORTED) {
                error = EINTR;
        } else if (kern_result == KERN_OPERATION_TIMED_OUT) {
                error = ETIMEDOUT;
        } else {
                error = EINVAL;
        }
        unix_syscall_return(error);
        /* does not return */
}

#if OLD_SEMWAIT_SIGNAL
/*
 * Returns:     0                       Success
 *              EINTR
 *              ETIMEDOUT
 *              EINVAL
 *      EFAULT if timespec is NULL
 */
int
__old_semwait_signal(proc_t p, struct __old_semwait_signal_args *uap,
    int32_t *retval)
{
        __pthread_testcancel(0);
        return __old_semwait_signal_nocancel(p, (struct __old_semwait_signal_nocancel_args *)uap, retval);
}

int
__old_semwait_signal_nocancel(proc_t p, struct __old_semwait_signal_nocancel_args *uap,
    __unused int32_t *retval)
{
        kern_return_t kern_result;
        int error;
        mach_timespec_t then;
        struct timespec now;
        struct user_timespec ts;
        boolean_t truncated_timeout = FALSE;

        if (uap->timeout) {
                if (IS_64BIT_PROCESS(p)) {
                        struct user64_timespec ts64;
                        error = copyin(uap->ts, &ts64, sizeof(ts64));
                        ts.tv_sec = (user_time_t)ts64.tv_sec;
                        ts.tv_nsec = (user_long_t)ts64.tv_nsec;
                } else {
                        struct user32_timespec ts32;
                        error = copyin(uap->ts, &ts32, sizeof(ts32));
                        ts.tv_sec = ts32.tv_sec;
                        ts.tv_nsec = ts32.tv_nsec;
                }

                if (error) {
                        return error;
                }

                if ((ts.tv_sec & 0xFFFFFFFF00000000ULL) != 0) {
                        ts.tv_sec = 0xFFFFFFFF;
                        ts.tv_nsec = 0;
                        truncated_timeout = TRUE;
                }

                if (uap->relative) {
                        then.tv_sec = (unsigned int)ts.tv_sec;
                        then.tv_nsec = (clock_res_t)ts.tv_nsec;
                } else {
                        nanotime(&now);

                        /* if time has elapsed, set time to null timepsec to bailout rightaway */
                        if (now.tv_sec == ts.tv_sec ?
                            now.tv_nsec > ts.tv_nsec :
                            now.tv_sec > ts.tv_sec) {
                                then.tv_sec = 0;
                                then.tv_nsec = 0;
                        } else {
                                then.tv_sec = (unsigned int)(ts.tv_sec - now.tv_sec);
                                then.tv_nsec = (clock_res_t)(ts.tv_nsec - now.tv_nsec);
                                if (then.tv_nsec < 0) {
                                        then.tv_nsec += NSEC_PER_SEC;
                                        then.tv_sec--;
                                }
                        }
                }

                if (uap->mutex_sem == 0) {
                        kern_result = semaphore_timedwait_trap_internal((mach_port_name_t)uap->cond_sem, then.tv_sec, then.tv_nsec, __posix_sem_syscall_return);
                } else {
                        kern_result = semaphore_timedwait_signal_trap_internal(uap->cond_sem, uap->mutex_sem, then.tv_sec, then.tv_nsec, __posix_sem_syscall_return);
                }
        } else {
                if (uap->mutex_sem == 0) {
                        kern_result = semaphore_wait_trap_internal(uap->cond_sem, __posix_sem_syscall_return);
                } else {
                        kern_result = semaphore_wait_signal_trap_internal(uap->cond_sem, uap->mutex_sem, __posix_sem_syscall_return);
                }
        }

        if (kern_result == KERN_SUCCESS && !truncated_timeout) {
                return 0;
        } else if (kern_result == KERN_SUCCESS && truncated_timeout) {
                return EINTR; /* simulate an exceptional condition because Mach doesn't support a longer timeout */
        } else if (kern_result == KERN_ABORTED) {
                return EINTR;
        } else if (kern_result == KERN_OPERATION_TIMED_OUT) {
                return ETIMEDOUT;
        } else {
                return EINVAL;
        }
}
#endif /* OLD_SEMWAIT_SIGNAL*/

/*
 * Returns:     0                       Success
 *              EINTR
 *              ETIMEDOUT
 *              EINVAL
 *      EFAULT if timespec is NULL
 */
int
__semwait_signal(proc_t p, struct __semwait_signal_args *uap,
    int32_t *retval)
{
        __pthread_testcancel(0);
        return __semwait_signal_nocancel(p, (struct __semwait_signal_nocancel_args *)uap, retval);
}

int
__semwait_signal_nocancel(__unused proc_t p, struct __semwait_signal_nocancel_args *uap,
    __unused int32_t *retval)
{
        kern_return_t kern_result;
        mach_timespec_t then;
        struct timespec now;
        struct user_timespec ts;
        boolean_t truncated_timeout = FALSE;

        if (uap->timeout) {
                ts.tv_sec = (user_time_t)uap->tv_sec;
                ts.tv_nsec = uap->tv_nsec;

                if ((ts.tv_sec & 0xFFFFFFFF00000000ULL) != 0) {
                        ts.tv_sec = 0xFFFFFFFF;
                        ts.tv_nsec = 0;
                        truncated_timeout = TRUE;
                }

                if (uap->relative) {
                        then.tv_sec = (unsigned int)ts.tv_sec;
                        then.tv_nsec = (clock_res_t)ts.tv_nsec;
                } else {
                        nanotime(&now);

                        /* if time has elapsed, set time to null timepsec to bailout rightaway */
                        if (now.tv_sec == ts.tv_sec ?
                            now.tv_nsec > ts.tv_nsec :
                            now.tv_sec > ts.tv_sec) {
                                then.tv_sec = 0;
                                then.tv_nsec = 0;
                        } else {
                                then.tv_sec = (unsigned int)(ts.tv_sec - now.tv_sec);
                                then.tv_nsec = (clock_res_t)(ts.tv_nsec - now.tv_nsec);
                                if (then.tv_nsec < 0) {
                                        then.tv_nsec += NSEC_PER_SEC;
                                        then.tv_sec--;
                                }
                        }
                }

                if (uap->mutex_sem == 0) {
                        kern_result = semaphore_timedwait_trap_internal((mach_port_name_t)uap->cond_sem, then.tv_sec, then.tv_nsec, __posix_sem_syscall_return);
                } else {
                        kern_result = semaphore_timedwait_signal_trap_internal(uap->cond_sem, uap->mutex_sem, then.tv_sec, then.tv_nsec, __posix_sem_syscall_return);
                }
        } else {
                if (uap->mutex_sem == 0) {
                        kern_result = semaphore_wait_trap_internal(uap->cond_sem, __posix_sem_syscall_return);
                } else {
                        kern_result = semaphore_wait_signal_trap_internal(uap->cond_sem, uap->mutex_sem, __posix_sem_syscall_return);
                }
        }

        if (kern_result == KERN_SUCCESS && !truncated_timeout) {
                return 0;
        } else if (kern_result == KERN_SUCCESS && truncated_timeout) {
                return EINTR; /* simulate an exceptional condition because Mach doesn't support a longer timeout */
        } else if (kern_result == KERN_ABORTED) {
                return EINTR;
        } else if (kern_result == KERN_OPERATION_TIMED_OUT) {
                return ETIMEDOUT;
        } else {
                return EINVAL;
        }
}


int
__pthread_kill(__unused proc_t p, struct __pthread_kill_args *uap,
    __unused int32_t *retval)
{
        thread_t target_act;
        int error = 0;
        int signum = uap->sig;
        struct uthread *uth;

        target_act = (thread_t)port_name_to_thread(uap->thread_port,
            PORT_TO_THREAD_NONE);

        if (target_act == THREAD_NULL) {
                return ESRCH;
        }
        if ((u_int)signum >= NSIG) {
                error = EINVAL;
                goto out;
        }

        uth = (struct uthread *)get_bsdthread_info(target_act);

        if (uth->uu_flag & UT_NO_SIGMASK) {
                error = ESRCH;
                goto out;
        }

        if ((thread_get_tag(target_act) & THREAD_TAG_WORKQUEUE) && !uth->uu_workq_pthread_kill_allowed) {
                error = ENOTSUP;
                goto out;
        }

        if (signum) {
                psignal_uthread(target_act, signum);
        }
out:
        thread_deallocate(target_act);
        return error;
}


int
__pthread_sigmask(__unused proc_t p, struct __pthread_sigmask_args *uap,
    __unused int32_t *retval)
{
        user_addr_t set = uap->set;
        user_addr_t oset = uap->oset;
        sigset_t nset;
        int error = 0;
        struct uthread *ut;
        sigset_t  oldset;

        ut = (struct uthread *)get_bsdthread_info(current_thread());
        oldset = ut->uu_sigmask;

        if (set == USER_ADDR_NULL) {
                /* need only old mask */
                goto out;
        }

        error = copyin(set, &nset, sizeof(sigset_t));
        if (error) {
                goto out;
        }

        switch (uap->how) {
        case SIG_BLOCK:
                ut->uu_sigmask |= (nset & ~sigcantmask);
                break;

        case SIG_UNBLOCK:
                ut->uu_sigmask &= ~(nset);
                signal_setast(current_thread());
                break;

        case SIG_SETMASK:
                ut->uu_sigmask = (nset & ~sigcantmask);
                signal_setast(current_thread());
                break;

        default:
                error = EINVAL;
        }
out:
        if (!error && oset != USER_ADDR_NULL) {
                copyout(&oldset, oset, sizeof(sigset_t));
        }

        return error;
}

/*
 * Returns:     0                       Success
 *              EINVAL
 *      copyin:EFAULT
 *      copyout:EFAULT
 */
int
__sigwait(proc_t p, struct __sigwait_args *uap, int32_t *retval)
{
        __pthread_testcancel(1);
        return __sigwait_nocancel(p, (struct __sigwait_nocancel_args *)uap, retval);
}

int
__sigwait_nocancel(proc_t p, struct __sigwait_nocancel_args *uap, __unused int32_t *retval)
{
        struct uthread *ut;
        struct uthread *uth;
        int error = 0;
        sigset_t mask;
        sigset_t siglist;
        sigset_t sigw = 0;
        int signum;

        ut = (struct uthread *)get_bsdthread_info(current_thread());

        if (uap->set == USER_ADDR_NULL) {
                return EINVAL;
        }

        error = copyin(uap->set, &mask, sizeof(sigset_t));
        if (error) {
                return error;
        }

        siglist = (mask & ~sigcantmask);

        if (siglist == 0) {
                return EINVAL;
        }

        proc_lock(p);
        if ((p->p_lflag & P_LINVFORK) && p->p_vforkact) {
                proc_unlock(p);
                return EINVAL;
        } else {
                proc_signalstart(p, 1);
                TAILQ_FOREACH(uth, &p->p_uthlist, uu_list) {
                        if ((sigw = uth->uu_siglist & siglist)) {
                                break;
                        }
                }
                proc_signalend(p, 1);
        }

        if (sigw) {
                /* The signal was pending on a thread */
                goto sigwait1;
        }
        /*
         * When returning from sigwait, we want
         * the old mask to be restored after the
         * signal handler has finished.  Thus, we
         * save it here and mark the sigacts structure
         * to indicate this.
         */
        uth = ut;               /* wait for it to be delivered to us */
        ut->uu_oldmask = ut->uu_sigmask;
        ut->uu_flag |= UT_SAS_OLDMASK;
        if (siglist == (sigset_t)0) {
                proc_unlock(p);
                return EINVAL;
        }
        /* SIGKILL and SIGSTOP are not maskable as well */
        ut->uu_sigmask = ~(siglist | sigcantmask);
        ut->uu_sigwait = siglist;

        /* No Continuations for now */
        error =  msleep((caddr_t)&ut->uu_sigwait, &p->p_mlock, PPAUSE | PCATCH, "pause", 0);

        if (error == ERESTART) {
                error = 0;
        }

        sigw = (ut->uu_sigwait & siglist);
        ut->uu_sigmask = ut->uu_oldmask;
        ut->uu_oldmask = 0;
        ut->uu_flag &= ~UT_SAS_OLDMASK;
sigwait1:
        ut->uu_sigwait = 0;
        if (!error) {
                signum = ffs((unsigned int)sigw);
                if (!signum) {
                        panic("sigwait with no signal wakeup");
                }
                /* Clear the pending signal in the thread it was delivered */
                uth->uu_siglist &= ~(sigmask(signum));

#if CONFIG_DTRACE
                DTRACE_PROC2(signal__clear, int, signum, siginfo_t *, &(ut->t_dtrace_siginfo));
#endif

                proc_unlock(p);
                if (uap->sig != USER_ADDR_NULL) {
                        error = copyout(&signum, uap->sig, sizeof(int));
                }
        } else {
                proc_unlock(p);
        }

        return error;
}

int
sigaltstack(__unused proc_t p, struct sigaltstack_args *uap, __unused int32_t *retval)
{
        struct kern_sigaltstack ss;
        struct kern_sigaltstack *pstk;
        int error;
        struct uthread *uth;
        int onstack;

        uth = (struct uthread *)get_bsdthread_info(current_thread());

        pstk = &uth->uu_sigstk;
        if ((uth->uu_flag & UT_ALTSTACK) == 0) {
                uth->uu_sigstk.ss_flags |= SA_DISABLE;
        }
        onstack = pstk->ss_flags & SA_ONSTACK;
        if (uap->oss) {
                if (IS_64BIT_PROCESS(p)) {
                        struct user64_sigaltstack ss64 = {};
                        sigaltstack_kern_to_user64(pstk, &ss64);
                        error = copyout(&ss64, uap->oss, sizeof(ss64));
                } else {
                        struct user32_sigaltstack ss32 = {};
                        sigaltstack_kern_to_user32(pstk, &ss32);
                        error = copyout(&ss32, uap->oss, sizeof(ss32));
                }
                if (error) {
                        return error;
                }
        }
        if (uap->nss == USER_ADDR_NULL) {
                return 0;
        }
        if (IS_64BIT_PROCESS(p)) {
                struct user64_sigaltstack ss64;
                error = copyin(uap->nss, &ss64, sizeof(ss64));
                sigaltstack_user64_to_kern(&ss64, &ss);
        } else {
                struct user32_sigaltstack ss32;
                error = copyin(uap->nss, &ss32, sizeof(ss32));
                sigaltstack_user32_to_kern(&ss32, &ss);
        }
        if (error) {
                return error;
        }
        if ((ss.ss_flags & ~SA_DISABLE) != 0) {
                return EINVAL;
        }

        if (ss.ss_flags & SA_DISABLE) {
                /* if we are here we are not in the signal handler ;so no need to check */
                if (uth->uu_sigstk.ss_flags & SA_ONSTACK) {
                        return EINVAL;
                }
                uth->uu_flag &= ~UT_ALTSTACK;
                uth->uu_sigstk.ss_flags = ss.ss_flags;
                return 0;
        }
        if (onstack) {
                return EPERM;
        }
/* The older stacksize was 8K, enforce that one so no compat problems */
#define OLDMINSIGSTKSZ 8*1024
        if (ss.ss_size < OLDMINSIGSTKSZ) {
                return ENOMEM;
        }
        uth->uu_flag |= UT_ALTSTACK;
        uth->uu_sigstk = ss;
        return 0;
}

int
kill(proc_t cp, struct kill_args *uap, __unused int32_t *retval)
{
        proc_t p;
        kauth_cred_t uc = kauth_cred_get();
        int posix = uap->posix;         /* !0 if posix behaviour desired */

        AUDIT_ARG(pid, uap->pid);
        AUDIT_ARG(signum, uap->signum);

        if ((u_int)uap->signum >= NSIG) {
                return EINVAL;
        }
        if (uap->pid > 0) {
                /* kill single process */
                if ((p = proc_find(uap->pid)) == NULL) {
                        if ((p = pzfind(uap->pid)) != NULL) {
                                /*
                                 * POSIX 1003.1-2001 requires returning success when killing a
                                 * zombie; see Rationale for kill(2).
                                 */
                                return 0;
                        }
                        return ESRCH;
                }
                AUDIT_ARG(process, p);
                if (!cansignal(cp, uc, p, uap->signum)) {
                        proc_rele(p);
                        return EPERM;
                }
                if (uap->signum) {
                        psignal(p, uap->signum);
                }
                proc_rele(p);
                return 0;
        }
        switch (uap->pid) {
        case -1: /* broadcast signal */
                return killpg1(cp, uap->signum, 0, 1, posix);
        case 0: /* signal own process group */
                return killpg1(cp, uap->signum, 0, 0, posix);
        default: /* negative explicit process group */
                return killpg1(cp, uap->signum, -(uap->pid), 0, posix);
        }
        /* NOTREACHED */
}

os_reason_t
build_userspace_exit_reason(uint32_t reason_namespace, uint64_t reason_code, user_addr_t payload, uint32_t payload_size,
    user_addr_t reason_string, uint64_t reason_flags)
{
        os_reason_t exit_reason = OS_REASON_NULL;

        int error = 0;
        int num_items_to_copy = 0;
        uint32_t user_data_to_copy = 0;
        char *reason_user_desc = NULL;
        size_t reason_user_desc_len = 0;

        exit_reason = os_reason_create(reason_namespace, reason_code);
        if (exit_reason == OS_REASON_NULL) {
                printf("build_userspace_exit_reason: failed to allocate exit reason\n");
                return exit_reason;
        }

        exit_reason->osr_flags |= OS_REASON_FLAG_FROM_USERSPACE;

        /*
         * Only apply flags that are allowed to be passed from userspace.
         */
        exit_reason->osr_flags |= (reason_flags & OS_REASON_FLAG_MASK_ALLOWED_FROM_USER);
        if ((reason_flags & OS_REASON_FLAG_MASK_ALLOWED_FROM_USER) != reason_flags) {
                printf("build_userspace_exit_reason: illegal flags passed from userspace (some masked off) 0x%llx, ns: %u, code 0x%llx\n",
                    reason_flags, reason_namespace, reason_code);
        }

        if (!(exit_reason->osr_flags & OS_REASON_FLAG_NO_CRASH_REPORT)) {
                exit_reason->osr_flags |= OS_REASON_FLAG_GENERATE_CRASH_REPORT;
        }

        if (payload != USER_ADDR_NULL) {
                if (payload_size == 0) {
                        printf("build_userspace_exit_reason: exit reason with namespace %u, nonzero payload but zero length\n",
                            reason_namespace);
                        exit_reason->osr_flags |= OS_REASON_FLAG_BAD_PARAMS;
                        payload = USER_ADDR_NULL;
                } else {
                        num_items_to_copy++;

                        if (payload_size > EXIT_REASON_PAYLOAD_MAX_LEN) {
                                exit_reason->osr_flags |= OS_REASON_FLAG_PAYLOAD_TRUNCATED;
                                payload_size = EXIT_REASON_PAYLOAD_MAX_LEN;
                        }

                        user_data_to_copy += payload_size;
                }
        }

        if (reason_string != USER_ADDR_NULL) {
                reason_user_desc = kheap_alloc(KHEAP_TEMP,
                    EXIT_REASON_USER_DESC_MAX_LEN, Z_WAITOK);

                if (reason_user_desc != NULL) {
                        error = copyinstr(reason_string, (void *) reason_user_desc,
                            EXIT_REASON_USER_DESC_MAX_LEN, &reason_user_desc_len);

                        if (error == 0) {
                                num_items_to_copy++;
                                user_data_to_copy += reason_user_desc_len;
                        } else if (error == ENAMETOOLONG) {
                                num_items_to_copy++;
                                reason_user_desc[EXIT_REASON_USER_DESC_MAX_LEN - 1] = '\0';
                                user_data_to_copy += reason_user_desc_len;
                        } else {
                                exit_reason->osr_flags |= OS_REASON_FLAG_FAILED_DATA_COPYIN;
                                kheap_free(KHEAP_TEMP, reason_user_desc,
                                    EXIT_REASON_USER_DESC_MAX_LEN);
                                reason_user_desc = NULL;
                                reason_user_desc_len = 0;
                        }
                }
        }

        if (num_items_to_copy != 0) {
                uint32_t reason_buffer_size_estimate = 0;
                mach_vm_address_t data_addr = 0;

                reason_buffer_size_estimate = kcdata_estimate_required_buffer_size(num_items_to_copy, user_data_to_copy);

                error = os_reason_alloc_buffer(exit_reason, reason_buffer_size_estimate);
                if (error != 0) {
                        printf("build_userspace_exit_reason: failed to allocate signal reason buffer\n");
                        goto out_failed_copyin;
                }

                if (reason_user_desc != NULL && reason_user_desc_len != 0) {
                        if (KERN_SUCCESS == kcdata_get_memory_addr(&exit_reason->osr_kcd_descriptor,
                            EXIT_REASON_USER_DESC,
                            (uint32_t)reason_user_desc_len,
                            &data_addr)) {
                                kcdata_memcpy(&exit_reason->osr_kcd_descriptor, (mach_vm_address_t) data_addr,
                                    reason_user_desc, (uint32_t)reason_user_desc_len);
                        } else {
                                printf("build_userspace_exit_reason: failed to allocate space for reason string\n");
                                goto out_failed_copyin;
                        }
                }

                if (payload != USER_ADDR_NULL) {
                        if (KERN_SUCCESS ==
                            kcdata_get_memory_addr(&exit_reason->osr_kcd_descriptor,
                            EXIT_REASON_USER_PAYLOAD,
                            payload_size,
                            &data_addr)) {
                                error = copyin(payload, (void *) data_addr, payload_size);
                                if (error) {
                                        printf("build_userspace_exit_reason: failed to copy in payload data with error %d\n", error);
                                        goto out_failed_copyin;
                                }
                        } else {
                                printf("build_userspace_exit_reason: failed to allocate space for payload data\n");
                                goto out_failed_copyin;
                        }
                }
        }

        if (reason_user_desc != NULL) {
                kheap_free(KHEAP_TEMP, reason_user_desc, EXIT_REASON_USER_DESC_MAX_LEN);
                reason_user_desc = NULL;
                reason_user_desc_len = 0;
        }

        return exit_reason;

out_failed_copyin:

        if (reason_user_desc != NULL) {
                kheap_free(KHEAP_TEMP, reason_user_desc, EXIT_REASON_USER_DESC_MAX_LEN);
                reason_user_desc = NULL;
                reason_user_desc_len = 0;
        }

        exit_reason->osr_flags |= OS_REASON_FLAG_FAILED_DATA_COPYIN;
        os_reason_alloc_buffer(exit_reason, 0);
        return exit_reason;
}

static int
terminate_with_payload_internal(struct proc *cur_proc, int target_pid, uint32_t reason_namespace,
    uint64_t reason_code, user_addr_t payload, uint32_t payload_size,
    user_addr_t reason_string, uint64_t reason_flags)
{
        proc_t target_proc = PROC_NULL;
        kauth_cred_t cur_cred = kauth_cred_get();

        os_reason_t signal_reason = OS_REASON_NULL;

        AUDIT_ARG(pid, target_pid);
        if ((target_pid <= 0)) {
                return EINVAL;
        }

        target_proc = proc_find(target_pid);
        if (target_proc == PROC_NULL) {
                return ESRCH;
        }

        AUDIT_ARG(process, target_proc);

        if (!cansignal(cur_proc, cur_cred, target_proc, SIGKILL)) {
                proc_rele(target_proc);
                return EPERM;
        }

        if (target_pid != cur_proc->p_pid) {
                /*
                 * FLAG_ABORT should only be set on terminate_with_reason(getpid()) that
                 * was a fallback from an unsuccessful abort_with_reason(). In that case
                 * caller's pid matches the target one. Otherwise remove the flag.
                 */
                reason_flags &= ~((typeof(reason_flags))OS_REASON_FLAG_ABORT);
        }

        KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_PROC, BSD_PROC_EXITREASON_CREATE) | DBG_FUNC_NONE,
            target_proc->p_pid, reason_namespace,
            reason_code, 0, 0);

        signal_reason = build_userspace_exit_reason(reason_namespace, reason_code, payload, payload_size,
            reason_string, (reason_flags | OS_REASON_FLAG_NO_CRASHED_TID));

        if (target_pid == cur_proc->p_pid) {
                /*
                 * psignal_thread_with_reason() will pend a SIGKILL on the specified thread or
                 * return if the thread and/or task are already terminating. Either way, the
                 * current thread won't return to userspace.
                 */
                psignal_thread_with_reason(target_proc, current_thread(), SIGKILL, signal_reason);
        } else {
                psignal_with_reason(target_proc, SIGKILL, signal_reason);
        }

        proc_rele(target_proc);

        return 0;
}

int
terminate_with_payload(struct proc *cur_proc, struct terminate_with_payload_args *args,
    __unused int32_t *retval)
{
        return terminate_with_payload_internal(cur_proc, args->pid, args->reason_namespace, args->reason_code, args->payload,
                   args->payload_size, args->reason_string, args->reason_flags);
}

static int
killpg1_allfilt(proc_t p, void * arg)
{
        struct killpg1_filtargs * kfargp = (struct killpg1_filtargs *)arg;

        /*
         * Don't signal initproc, a system process, or the current process if POSIX
         * isn't specified.
         */
        return p->p_pid > 1 && !(p->p_flag & P_SYSTEM) &&
               (kfargp->posix ? true : p != kfargp->curproc);
}

static int
killpg1_pgrpfilt(proc_t p, __unused void * arg)
{
        /* XXX shouldn't this allow signalling zombies? */
        return p->p_pid > 1 && !(p->p_flag & P_SYSTEM) && p->p_stat != SZOMB;
}

static int
killpg1_callback(proc_t p, void *arg)
{
        struct killpg1_iterargs *kargp = (struct killpg1_iterargs *)arg;
        int signum = kargp->signum;

        if ((p->p_listflag & P_LIST_EXITED) == P_LIST_EXITED) {
                /*
                 * Count zombies as found for the purposes of signalling, since POSIX
                 * 1003.1-2001 sees signalling zombies as successful.  If killpg(2) or
                 * kill(2) with pid -1 only finds zombies that can be signalled, it
                 * shouldn't return ESRCH.  See the Rationale for kill(2).
                 *
                 * Don't call into MAC -- it's not expecting signal checks for exited
                 * processes.
                 */
                if (cansignal_nomac(kargp->curproc, kargp->uc, p, signum)) {
                        kargp->nfound++;
                }
        } else if (cansignal(kargp->curproc, kargp->uc, p, signum)) {
                kargp->nfound++;

                if (signum != 0) {
                        psignal(p, signum);
                }
        }

        return PROC_RETURNED;
}

/*
 * Common code for kill process group/broadcast kill.
 */
int
killpg1(proc_t curproc, int signum, int pgid, int all, int posix)
{
        kauth_cred_t uc;
        struct pgrp *pgrp;
        int error = 0;

        uc = kauth_cred_proc_ref(curproc);
        struct killpg1_iterargs karg = {
                .curproc = curproc, .uc = uc, .nfound = 0, .signum = signum
        };

        if (all) {
                /*
                 * Broadcast to all processes that the user can signal (pid was -1).
                 */
                struct killpg1_filtargs kfarg = {
                        .posix = posix, .curproc = curproc
                };
                proc_iterate(PROC_ALLPROCLIST | PROC_ZOMBPROCLIST, killpg1_callback,
                    &karg, killpg1_allfilt, &kfarg);
        } else {
                if (pgid == 0) {
                        /*
                         * Send to current the current process' process group.
                         */
                        pgrp = proc_pgrp(curproc);
                } else {
                        pgrp = pgfind(pgid);
                        if (pgrp == NULL) {
                                error = ESRCH;
                                goto out;
                        }
                }

                /* PGRP_DROPREF drops the pgrp refernce */
                pgrp_iterate(pgrp, PGRP_DROPREF, killpg1_callback, &karg,
                    killpg1_pgrpfilt, NULL);
        }
        error = (karg.nfound > 0 ? 0 : (posix ? EPERM : ESRCH));
out:
        kauth_cred_unref(&uc);
        return error;
}

/*
 * Send a signal to a process group.
 */
void
gsignal(int pgid, int signum)
{
        struct pgrp *pgrp;

        if (pgid && (pgrp = pgfind(pgid))) {
                pgsignal(pgrp, signum, 0);
                pg_rele(pgrp);
        }
}

/*
 * Send a signal to a process group.  If checkctty is 1,
 * limit to members which have a controlling terminal.
 */

static int
pgsignal_filt(proc_t p, void * arg)
{
        int checkctty = *(int*)arg;

        if ((checkctty == 0) || p->p_flag & P_CONTROLT) {
                return 1;
        } else {
                return 0;
        }
}


static int
pgsignal_callback(proc_t p, void * arg)
{
        int  signum = *(int*)arg;

        psignal(p, signum);
        return PROC_RETURNED;
}


void
pgsignal(struct pgrp *pgrp, int signum, int checkctty)
{
        if (pgrp != PGRP_NULL) {
                pgrp_iterate(pgrp, 0, pgsignal_callback, &signum, pgsignal_filt, &checkctty);
        }
}


void
tty_pgsignal(struct tty *tp, int signum, int checkctty)
{
        struct pgrp * pg;

        pg = tty_pgrp(tp);
        if (pg != PGRP_NULL) {
                pgrp_iterate(pg, 0, pgsignal_callback, &signum, pgsignal_filt, &checkctty);
                pg_rele(pg);
        }
}
/*
 * Send a signal caused by a trap to a specific thread.
 */
void
threadsignal(thread_t sig_actthread, int signum, mach_exception_code_t code, boolean_t set_exitreason)
{
        struct uthread *uth;
        struct task * sig_task;
        proc_t p;
        int mask;

        if ((u_int)signum >= NSIG || signum == 0) {
                return;
        }

        mask = sigmask(signum);
        if ((mask & threadmask) == 0) {
                return;
        }
        sig_task = get_threadtask(sig_actthread);
        p = (proc_t)(get_bsdtask_info(sig_task));

        uth = get_bsdthread_info(sig_actthread);
        if (uth->uu_flag & UT_VFORK) {
                p = uth->uu_proc;
        }

        proc_lock(p);
        if (!(p->p_lflag & P_LTRACED) && (p->p_sigignore & mask)) {
                proc_unlock(p);
                return;
        }

        uth->uu_siglist |= mask;
        uth->uu_code = code;

        /* Attempt to establish whether the signal will be fatal (mirrors logic in psignal_internal()) */
        if (set_exitreason && ((p->p_lflag & P_LTRACED) || (!(uth->uu_sigwait & mask)
            && !(uth->uu_sigmask & mask) && !(p->p_sigcatch & mask))) &&
            !(mask & stopsigmask) && !(mask & contsigmask)) {
                if (uth->uu_exit_reason == OS_REASON_NULL) {
                        KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_PROC, BSD_PROC_EXITREASON_CREATE) | DBG_FUNC_NONE,
                            p->p_pid, OS_REASON_SIGNAL, signum, 0, 0);

                        os_reason_t signal_reason = build_signal_reason(signum, "exc handler");

                        set_thread_exit_reason(sig_actthread, signal_reason, TRUE);

                        /* We dropped/consumed the reference in set_thread_exit_reason() */
                        signal_reason = OS_REASON_NULL;
                }
        }

        proc_unlock(p);

        /* mark on process as well */
        signal_setast(sig_actthread);
}

/* Called with proc locked */
static void
set_thread_extra_flags(struct uthread *uth, os_reason_t reason)
{
        extern int vm_shared_region_reslide_restrict;
        assert(uth != NULL);
        /*
         * Check whether the userland fault address falls within the shared
         * region and notify userland if so. This allows launchd to apply
         * special policies around this fault type.
         */
        if (reason->osr_namespace == OS_REASON_SIGNAL &&
            reason->osr_code == SIGSEGV) {
                mach_vm_address_t fault_address = uth->uu_subcode;

#if defined(__arm64__)
                /* taken from osfmk/arm/misc_protos.h */
                #define TBI_MASK           0xff00000000000000
                #define tbi_clear(addr)    ((addr) & ~(TBI_MASK))
                fault_address = tbi_clear(fault_address);
#endif /* __arm64__ */

                if (fault_address >= SHARED_REGION_BASE &&
                    fault_address <= SHARED_REGION_BASE + SHARED_REGION_SIZE) {
                        /*
                         * Always report whether the fault happened within the shared cache
                         * region, but only stale the slide if the resliding is extended
                         * to all processes or if the process faulting is a platform one.
                         */
                        reason->osr_flags |= OS_REASON_FLAG_SHAREDREGION_FAULT;

#if __has_feature(ptrauth_calls)
                        if (!vm_shared_region_reslide_restrict || csproc_get_platform_binary(current_proc())) {
                                vm_shared_region_reslide_stale();
                        }
#endif /* __has_feature(ptrauth_calls) */
                }
        }
}

void
set_thread_exit_reason(void *th, void *reason, boolean_t proc_locked)
{
        struct uthread *targ_uth = get_bsdthread_info(th);
        struct task *targ_task = NULL;
        proc_t targ_proc = NULL;

        os_reason_t exit_reason = (os_reason_t)reason;

        if (exit_reason == OS_REASON_NULL) {
                return;
        }

        if (!proc_locked) {
                targ_task = get_threadtask(th);
                targ_proc = (proc_t)(get_bsdtask_info(targ_task));

                proc_lock(targ_proc);
        }

        set_thread_extra_flags(targ_uth, exit_reason);

        if (targ_uth->uu_exit_reason == OS_REASON_NULL) {
                targ_uth->uu_exit_reason = exit_reason;
        } else {
                /* The caller expects that we drop a reference on the exit reason */
                os_reason_free(exit_reason);
        }

        if (!proc_locked) {
                assert(targ_proc != NULL);
                proc_unlock(targ_proc);
        }
}

/*
 * get_signalthread
 *
 * Picks an appropriate thread from a process to target with a signal.
 *
 * Called with proc locked.
 * Returns thread with BSD ast set.
 *
 * We attempt to deliver a proc-wide signal to the first thread in the task.
 * This allows single threaded applications which use signals to
 * be able to be linked with multithreaded libraries.
 */
static kern_return_t
get_signalthread(proc_t p, int signum, thread_t * thr)
{
        struct uthread *uth;
        sigset_t mask = sigmask(signum);
        thread_t sig_thread;
        struct task * sig_task = p->task;
        kern_return_t kret;
        bool skip_wqthreads = true;

        *thr = THREAD_NULL;

        if ((p->p_lflag & P_LINVFORK) && p->p_vforkact) {
                sig_thread = p->p_vforkact;
                kret = check_actforsig(sig_task, sig_thread, 1);
                if (kret == KERN_SUCCESS) {
                        *thr = sig_thread;
                        return KERN_SUCCESS;
                } else {
                        return KERN_FAILURE;
                }
        }

again:
        TAILQ_FOREACH(uth, &p->p_uthlist, uu_list) {
                if (((uth->uu_flag & UT_NO_SIGMASK) == 0) &&
                    (((uth->uu_sigmask & mask) == 0) || (uth->uu_sigwait & mask))) {
                        thread_t th = uth->uu_context.vc_thread;
                        if (skip_wqthreads && (thread_get_tag(th) & THREAD_TAG_WORKQUEUE)) {
                                /* Workqueue threads may be parked in the kernel unable to
                                 * deliver signals for an extended period of time, so skip them
                                 * in favor of pthreads in a first pass. (rdar://50054475). */
                        } else if (check_actforsig(p->task, th, 1) == KERN_SUCCESS) {
                                *thr = th;
                                return KERN_SUCCESS;
                        }
                }
        }
        if (skip_wqthreads) {
                skip_wqthreads = false;
                goto again;
        }
        if (get_signalact(p->task, thr, 1) == KERN_SUCCESS) {
                return KERN_SUCCESS;
        }

        return KERN_FAILURE;
}

static os_reason_t
build_signal_reason(int signum, const char *procname)
{
        os_reason_t signal_reason = OS_REASON_NULL;
        proc_t sender_proc = current_proc();
        uint32_t reason_buffer_size_estimate = 0, proc_name_length = 0;
        const char *default_sender_procname = "unknown";
        mach_vm_address_t data_addr;
        int ret;

        signal_reason = os_reason_create(OS_REASON_SIGNAL, signum);
        if (signal_reason == OS_REASON_NULL) {
                printf("build_signal_reason: unable to allocate signal reason structure.\n");
                return signal_reason;
        }

        reason_buffer_size_estimate = kcdata_estimate_required_buffer_size(2, sizeof(sender_proc->p_name) +
            sizeof(sender_proc->p_pid));

        ret = os_reason_alloc_buffer_noblock(signal_reason, reason_buffer_size_estimate);
        if (ret != 0) {
                printf("build_signal_reason: unable to allocate signal reason buffer.\n");
                return signal_reason;
        }

        if (KERN_SUCCESS == kcdata_get_memory_addr(&signal_reason->osr_kcd_descriptor, KCDATA_TYPE_PID,
            sizeof(sender_proc->p_pid), &data_addr)) {
                kcdata_memcpy(&signal_reason->osr_kcd_descriptor, data_addr, &sender_proc->p_pid,
                    sizeof(sender_proc->p_pid));
        } else {
                printf("build_signal_reason: exceeded space in signal reason buf, unable to log PID\n");
        }

        proc_name_length = sizeof(sender_proc->p_name);
        if (KERN_SUCCESS == kcdata_get_memory_addr(&signal_reason->osr_kcd_descriptor, KCDATA_TYPE_PROCNAME,
            proc_name_length, &data_addr)) {
                if (procname) {
                        char truncated_procname[proc_name_length];
                        strncpy((char *) &truncated_procname, procname, proc_name_length);
                        truncated_procname[proc_name_length - 1] = '\0';

                        kcdata_memcpy(&signal_reason->osr_kcd_descriptor, data_addr, truncated_procname,
                            (uint32_t)strlen((char *) &truncated_procname));
                } else if (*sender_proc->p_name) {
                        kcdata_memcpy(&signal_reason->osr_kcd_descriptor, data_addr, &sender_proc->p_name,
                            sizeof(sender_proc->p_name));
                } else {
                        kcdata_memcpy(&signal_reason->osr_kcd_descriptor, data_addr, &default_sender_procname,
                            (uint32_t)strlen(default_sender_procname) + 1);
                }
        } else {
                printf("build_signal_reason: exceeded space in signal reason buf, unable to log procname\n");
        }

        return signal_reason;
}

/*
 * Send the signal to the process.  If the signal has an action, the action
 * is usually performed by the target process rather than the caller; we add
 * the signal to the set of pending signals for the process.
 *
 * Always drops a reference on a signal_reason if one is provided, whether via
 * passing it to a thread or deallocating directly.
 *
 * Exceptions:
 *   o When a stop signal is sent to a sleeping process that takes the
 *     default action, the process is stopped without awakening it.
 *   o SIGCONT restarts stopped processes (or puts them back to sleep)
 *     regardless of the signal action (eg, blocked or ignored).
 *
 * Other ignored signals are discarded immediately.
 */
static void
psignal_internal(proc_t p, task_t task, thread_t thread, int flavor, int signum, os_reason_t signal_reason)
{
        int prop;
        user_addr_t action = USER_ADDR_NULL;
        proc_t                  sig_proc;
        thread_t                sig_thread;
        task_t                  sig_task;
        int                     mask;
        struct uthread          *uth;
        kern_return_t           kret;
        uid_t                   r_uid;
        proc_t                  pp;
        kauth_cred_t            my_cred;
        char                    *launchd_exit_reason_desc = NULL;
        boolean_t               update_thread_policy = FALSE;

        if ((u_int)signum >= NSIG || signum == 0) {
                panic("psignal: bad signal number %d", signum);
        }

        mask = sigmask(signum);
        prop = sigprop[signum];

#if SIGNAL_DEBUG
        if (rdebug_proc && (p != PROC_NULL) && (p == rdebug_proc)) {
                ram_printf(3);
        }
#endif /* SIGNAL_DEBUG */

        /* catch unexpected initproc kills early for easier debuggging */
        if (signum == SIGKILL && p == initproc) {
                if (signal_reason == NULL) {
                        panic_plain("unexpected SIGKILL of %s %s (no reason provided)",
                            (p->p_name[0] != '\0' ? p->p_name : "initproc"),
                            ((p->p_csflags & CS_KILLED) ? "(CS_KILLED)" : ""));
                } else {
                        launchd_exit_reason_desc = launchd_exit_reason_get_string_desc(signal_reason);
                        panic_plain("unexpected SIGKILL of %s %s with reason -- namespace %d code 0x%llx description %." LAUNCHD_PANIC_REASON_STRING_MAXLEN "s",
                            (p->p_name[0] != '\0' ? p->p_name : "initproc"),
                            ((p->p_csflags & CS_KILLED) ? "(CS_KILLED)" : ""),
                            signal_reason->osr_namespace, signal_reason->osr_code,
                            launchd_exit_reason_desc ? launchd_exit_reason_desc : "none");
                }
        }

        /*
         *      We will need the task pointer later.  Grab it now to
         *      check for a zombie process.  Also don't send signals
         *      to kernel internal tasks.
         */
        if (flavor & PSIG_VFORK) {
                sig_task = task;
                sig_thread = thread;
                sig_proc = p;
        } else if (flavor & PSIG_THREAD) {
                sig_task = get_threadtask(thread);
                sig_thread = thread;
                sig_proc = (proc_t)get_bsdtask_info(sig_task);
        } else if (flavor & PSIG_TRY_THREAD) {
                assert((thread == current_thread()) && (p == current_proc()));
                sig_task = p->task;
                sig_thread = thread;
                sig_proc = p;
        } else {
                sig_task = p->task;
                sig_thread = THREAD_NULL;
                sig_proc = p;
        }

        if ((sig_task == TASK_NULL) || is_kerneltask(sig_task)) {
                os_reason_free(signal_reason);
                return;
        }

        /*
         * do not send signals to the process that has the thread
         * doing a reboot(). Not doing so will mark that thread aborted
         * and can cause IO failures wich will cause data loss.  There's
         * also no need to send a signal to a process that is in the middle
         * of being torn down.
         */
        if (ISSET(sig_proc->p_flag, P_REBOOT) || ISSET(sig_proc->p_lflag, P_LEXIT)) {
                DTRACE_PROC3(signal__discard, thread_t, sig_thread, proc_t, sig_proc, int, signum);
                os_reason_free(signal_reason);
                return;
        }

        if ((flavor & (PSIG_VFORK | PSIG_THREAD)) == 0) {
                proc_knote(sig_proc, NOTE_SIGNAL | signum);
        }

        if ((flavor & PSIG_LOCKED) == 0) {
                proc_signalstart(sig_proc, 0);
        }

        /* Don't send signals to a process that has ignored them. */
        if (((flavor & PSIG_VFORK) == 0) && ((sig_proc->p_lflag & P_LTRACED) == 0) && (sig_proc->p_sigignore & mask)) {
                DTRACE_PROC3(signal__discard, thread_t, sig_thread, proc_t, sig_proc, int, signum);
                goto sigout_unlocked;
        }

        /*
         * The proc_lock prevents the targeted thread from being deallocated
         * or handling the signal until we're done signaling it.
         *
         * Once the proc_lock is dropped, we have no guarantee the thread or uthread exists anymore.
         *
         * XXX: What if the thread goes inactive after the thread passes bsd ast point?
         */
        proc_lock(sig_proc);

        if (flavor & PSIG_VFORK) {
                action = SIG_DFL;
                act_set_astbsd(sig_thread);
                kret = KERN_SUCCESS;
        } else if (flavor & PSIG_TRY_THREAD) {
                uth = get_bsdthread_info(sig_thread);
                if (((uth->uu_flag & UT_NO_SIGMASK) == 0) &&
                    (((uth->uu_sigmask & mask) == 0) || (uth->uu_sigwait & mask)) &&
                    ((kret = check_actforsig(sig_proc->task, sig_thread, 1)) == KERN_SUCCESS)) {
                        /* deliver to specified thread */
                } else {
                        /* deliver to any willing thread */
                        kret = get_signalthread(sig_proc, signum, &sig_thread);
                }
        } else if (flavor & PSIG_THREAD) {
                /* If successful return with ast set */
                kret = check_actforsig(sig_task, sig_thread, 1);
        } else {
                /* If successful return with ast set */
                kret = get_signalthread(sig_proc, signum, &sig_thread);
        }

        if (kret != KERN_SUCCESS) {
                DTRACE_PROC3(signal__discard, thread_t, sig_thread, proc_t, sig_proc, int, signum);
                proc_unlock(sig_proc);
                goto sigout_unlocked;
        }

        uth = get_bsdthread_info(sig_thread);

        /*
         * If proc is traced, always give parent a chance.
         */

        if ((flavor & PSIG_VFORK) == 0) {
                if (sig_proc->p_lflag & P_LTRACED) {
                        action = SIG_DFL;
                } else {
                        /*
                         * If the signal is being ignored,
                         * then we forget about it immediately.
                         * (Note: we don't set SIGCONT in p_sigignore,
                         * and if it is set to SIG_IGN,
                         * action will be SIG_DFL here.)
                         */
                        if (sig_proc->p_sigignore & mask) {
                                goto sigout_locked;
                        }

                        if (uth->uu_sigwait & mask) {
                                action = KERN_SIG_WAIT;
                        } else if (uth->uu_sigmask & mask) {
                                action = KERN_SIG_HOLD;
                        } else if (sig_proc->p_sigcatch & mask) {
                                action = KERN_SIG_CATCH;
                        } else {
                                action = SIG_DFL;
                        }
                }
        }

        /* TODO: p_nice isn't hooked up to the scheduler... */
        if (sig_proc->p_nice > NZERO && action == SIG_DFL && (prop & SA_KILL) &&
            (sig_proc->p_lflag & P_LTRACED) == 0) {
                sig_proc->p_nice = NZERO;
        }

        if (prop & SA_CONT) {
                uth->uu_siglist &= ~stopsigmask;
        }

        if (prop & SA_STOP) {
                struct pgrp *pg;
                /*
                 * If sending a tty stop signal to a member of an orphaned
                 * process group, discard the signal here if the action
                 * is default; don't stop the process below if sleeping,
                 * and don't clear any pending SIGCONT.
                 */
                pg = proc_pgrp(sig_proc);
                if (prop & SA_TTYSTOP && pg->pg_jobc == 0 &&
                    action == SIG_DFL) {
                        pg_rele(pg);
                        goto sigout_locked;
                }
                pg_rele(pg);
                uth->uu_siglist &= ~contsigmask;
        }

        uth->uu_siglist |= mask;

        /*
         * Defer further processing for signals which are held,
         * except that stopped processes must be continued by SIGCONT.
         */
        /* vfork will not go thru as action is SIG_DFL */
        if ((action == KERN_SIG_HOLD) && ((prop & SA_CONT) == 0 || sig_proc->p_stat != SSTOP)) {
                goto sigout_locked;
        }

        /*
         *      SIGKILL priority twiddling moved here from above because
         *      it needs sig_thread.  Could merge it into large switch
         *      below if we didn't care about priority for tracing
         *      as SIGKILL's action is always SIG_DFL.
         *
         *      TODO: p_nice isn't hooked up to the scheduler...
         */
        if ((signum == SIGKILL) && (sig_proc->p_nice > NZERO)) {
                sig_proc->p_nice = NZERO;
        }

        /*
         *      Process is traced - wake it up (if not already
         *      stopped) so that it can discover the signal in
         *      issig() and stop for the parent.
         */
        if (sig_proc->p_lflag & P_LTRACED) {
                if (sig_proc->p_stat != SSTOP) {
                        goto runlocked;
                } else {
                        goto sigout_locked;
                }
        }

        if ((flavor & PSIG_VFORK) != 0) {
                goto runlocked;
        }

        if (action == KERN_SIG_WAIT) {
#if CONFIG_DTRACE
                /*
                 * DTrace proc signal-clear returns a siginfo_t. Collect the needed info.
                 */
                r_uid = kauth_getruid(); /* per thread credential; protected by our thread context */

                bzero((caddr_t)&(uth->t_dtrace_siginfo), sizeof(uth->t_dtrace_siginfo));

                uth->t_dtrace_siginfo.si_signo = signum;
                uth->t_dtrace_siginfo.si_pid = current_proc()->p_pid;
                uth->t_dtrace_siginfo.si_status = W_EXITCODE(signum, 0);
                uth->t_dtrace_siginfo.si_uid = r_uid;
                uth->t_dtrace_siginfo.si_code = 0;
#endif
                uth->uu_sigwait = mask;
                uth->uu_siglist &= ~mask;
                wakeup(&uth->uu_sigwait);
                /* if it is SIGCONT resume whole process */
                if (prop & SA_CONT) {
                        OSBitOrAtomic(P_CONTINUED, &sig_proc->p_flag);
                        sig_proc->p_contproc = current_proc()->p_pid;
                        (void) task_resume_internal(sig_task);
                }
                goto sigout_locked;
        }

        if (action != SIG_DFL) {
                /*
                 *      User wants to catch the signal.
                 *      Wake up the thread, but don't un-suspend it
                 *      (except for SIGCONT).
                 */
                if (prop & SA_CONT) {
                        OSBitOrAtomic(P_CONTINUED, &sig_proc->p_flag);
                        (void) task_resume_internal(sig_task);
                        sig_proc->p_stat = SRUN;
                } else if (sig_proc->p_stat == SSTOP) {
                        goto sigout_locked;
                }
                /*
                 * Fill out siginfo structure information to pass to the
                 * signalled process/thread sigaction handler, when it
                 * wakes up.  si_code is 0 because this is an ordinary
                 * signal, not a SIGCHLD, and so si_status is the signal
                 * number itself, instead of the child process exit status.
                 * We shift this left because it will be shifted right before
                 * it is passed to user space.  kind of ugly to use W_EXITCODE
                 * this way, but it beats defining a new macro.
                 *
                 * Note:        Avoid the SIGCHLD recursion case!
                 */
                if (signum != SIGCHLD) {
                        r_uid = kauth_getruid();

                        sig_proc->si_pid = current_proc()->p_pid;
                        sig_proc->si_status = W_EXITCODE(signum, 0);
                        sig_proc->si_uid = r_uid;
                        sig_proc->si_code = 0;
                }

                goto runlocked;
        } else {
                /*      Default action - varies */
                if (mask & stopsigmask) {
                        assert(signal_reason == NULL);
                        /*
                         * These are the signals which by default
                         * stop a process.
                         *
                         * Don't clog system with children of init
                         * stopped from the keyboard.
                         */
                        if (!(prop & SA_STOP) && sig_proc->p_pptr == initproc) {
                                uth->uu_siglist &= ~mask;
                                proc_unlock(sig_proc);
                                /* siglock still locked, proc_lock not locked */
                                psignal_locked(sig_proc, SIGKILL);
                                goto sigout_unlocked;
                        }

                        /*
                         *      Stop the task
                         *      if task hasn't already been stopped by
                         *      a signal.
                         */
                        uth->uu_siglist &= ~mask;
                        if (sig_proc->p_stat != SSTOP) {
                                sig_proc->p_xstat = signum;
                                sig_proc->p_stat = SSTOP;
                                OSBitAndAtomic(~((uint32_t)P_CONTINUED), &sig_proc->p_flag);
                                sig_proc->p_lflag &= ~P_LWAITED;
                                proc_unlock(sig_proc);

                                pp = proc_parentholdref(sig_proc);
                                stop(sig_proc, pp);
                                if ((pp != PROC_NULL) && ((pp->p_flag & P_NOCLDSTOP) == 0)) {
                                        my_cred = kauth_cred_proc_ref(sig_proc);
                                        r_uid = kauth_cred_getruid(my_cred);
                                        kauth_cred_unref(&my_cred);

                                        proc_lock(sig_proc);
                                        pp->si_pid = sig_proc->p_pid;
                                        /*
                                         * POSIX: sigaction for a stopped child
                                         * when sent to the parent must set the
                                         * child's signal number into si_status.
                                         */
                                        if (signum != SIGSTOP) {
                                                pp->si_status = WEXITSTATUS(sig_proc->p_xstat);
                                        } else {
                                                pp->si_status = W_EXITCODE(signum, signum);
                                        }
                                        pp->si_code = CLD_STOPPED;
                                        pp->si_uid = r_uid;
                                        proc_unlock(sig_proc);

                                        psignal(pp, SIGCHLD);
                                }
                                if (pp != PROC_NULL) {
                                        proc_parentdropref(pp, 0);
                                }

                                goto sigout_unlocked;
                        }

                        goto sigout_locked;
                }

                DTRACE_PROC3(signal__send, thread_t, sig_thread, proc_t, p, int, signum);

                switch (signum) {
                /*
                 * Signals ignored by default have been dealt
                 * with already, since their bits are on in
                 * p_sigignore.
                 */

                case SIGKILL:
                        /*
                         * Kill signal always sets process running and
                         * unsuspends it.
                         */
                        /*
                         *      Process will be running after 'run'
                         */
                        sig_proc->p_stat = SRUN;
                        /*
                         * In scenarios where suspend/resume are racing
                         * the signal we are missing AST_BSD by the time
                         * we get here, set again to avoid races. This
                         * was the scenario with spindump enabled shutdowns.
                         * We would need to cover this approp down the line.
                         */
                        act_set_astbsd(sig_thread);
                        kret = thread_abort(sig_thread);
                        update_thread_policy = (kret == KERN_SUCCESS);

                        if (uth->uu_exit_reason == OS_REASON_NULL) {
                                if (signal_reason == OS_REASON_NULL) {
                                        KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_PROC, BSD_PROC_EXITREASON_CREATE) | DBG_FUNC_NONE,
                                            sig_proc->p_pid, OS_REASON_SIGNAL, signum, 0, 0);

                                        signal_reason = build_signal_reason(signum, NULL);
                                }

                                os_reason_ref(signal_reason);
                                set_thread_exit_reason(sig_thread, signal_reason, TRUE);
                        }

                        goto sigout_locked;

                case SIGCONT:
                        /*
                         * Let the process run.  If it's sleeping on an
                         * event, it remains so.
                         */
                        assert(signal_reason == NULL);
                        OSBitOrAtomic(P_CONTINUED, &sig_proc->p_flag);
                        sig_proc->p_contproc = sig_proc->p_pid;
                        sig_proc->p_xstat = signum;

                        (void) task_resume_internal(sig_task);

                        /*
                         * When processing a SIGCONT, we need to check
                         * to see if there are signals pending that
                         * were not delivered because we had been
                         * previously stopped.  If that's the case,
                         * we need to thread_abort_safely() to trigger
                         * interruption of the current system call to
                         * cause their handlers to fire.  If it's only
                         * the SIGCONT, then don't wake up.
                         */
                        if (((flavor & (PSIG_VFORK | PSIG_THREAD)) == 0) && (((uth->uu_siglist & ~uth->uu_sigmask) & ~sig_proc->p_sigignore) & ~mask)) {
                                uth->uu_siglist &= ~mask;
                                sig_proc->p_stat = SRUN;
                                goto runlocked;
                        }

                        uth->uu_siglist &= ~mask;
                        sig_proc->p_stat = SRUN;
                        goto sigout_locked;

                default:
                        /*
                         * A signal which has a default action of killing
                         * the process, and for which there is no handler,
                         * needs to act like SIGKILL
                         */
                        if (((flavor & (PSIG_VFORK | PSIG_THREAD)) == 0) && (action == SIG_DFL) && (prop & SA_KILL)) {
                                sig_proc->p_stat = SRUN;
                                kret = thread_abort(sig_thread);
                                update_thread_policy = (kret == KERN_SUCCESS);

                                if (uth->uu_exit_reason == OS_REASON_NULL) {
                                        if (signal_reason == OS_REASON_NULL) {
                                                KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_PROC, BSD_PROC_EXITREASON_CREATE) | DBG_FUNC_NONE,
                                                    sig_proc->p_pid, OS_REASON_SIGNAL, signum, 0, 0);

                                                signal_reason = build_signal_reason(signum, NULL);
                                        }

                                        os_reason_ref(signal_reason);
                                        set_thread_exit_reason(sig_thread, signal_reason, TRUE);
                                }

                                goto sigout_locked;
                        }

                        /*
                         * All other signals wake up the process, but don't
                         * resume it.
                         */
                        if (sig_proc->p_stat == SSTOP) {
                                goto sigout_locked;
                        }
                        goto runlocked;
                }
        }
        /*NOTREACHED*/

runlocked:
        /*
         * If we're being traced (possibly because someone attached us
         * while we were stopped), check for a signal from the debugger.
         */
        if (sig_proc->p_stat == SSTOP) {
                if ((sig_proc->p_lflag & P_LTRACED) != 0 && sig_proc->p_xstat != 0) {
                        uth->uu_siglist |= sigmask(sig_proc->p_xstat);
                }

                if ((flavor & PSIG_VFORK) != 0) {
                        sig_proc->p_stat = SRUN;
                }
        } else {
                /*
                 * setrunnable(p) in BSD and
                 * Wake up the thread if it is interruptible.
                 */
                sig_proc->p_stat = SRUN;
                if ((flavor & PSIG_VFORK) == 0) {
                        thread_abort_safely(sig_thread);
                }
        }

sigout_locked:
        if (update_thread_policy) {
                /*
                 * Update the thread policy to heading to terminate, increase priority if
                 * necessary. This needs to be done before we drop the proc lock because the
                 * thread can take the fatal signal once it's dropped.
                 */
                proc_set_thread_policy(sig_thread, TASK_POLICY_ATTRIBUTE, TASK_POLICY_TERMINATED, TASK_POLICY_ENABLE);
        }

        proc_unlock(sig_proc);

sigout_unlocked:
        os_reason_free(signal_reason);
        if ((flavor & PSIG_LOCKED) == 0) {
                proc_signalend(sig_proc, 0);
        }
}

void
psignal(proc_t p, int signum)
{
        psignal_internal(p, NULL, NULL, 0, signum, NULL);
}

void
psignal_with_reason(proc_t p, int signum, struct os_reason *signal_reason)
{
        psignal_internal(p, NULL, NULL, 0, signum, signal_reason);
}

void
psignal_sigkill_with_reason(struct proc *p, struct os_reason *signal_reason)
{
        psignal_internal(p, NULL, NULL, 0, SIGKILL, signal_reason);
}

void
psignal_locked(proc_t p, int signum)
{
        psignal_internal(p, NULL, NULL, PSIG_LOCKED, signum, NULL);
}

void
psignal_vfork_with_reason(proc_t p, task_t new_task, thread_t thread, int signum, struct os_reason *signal_reason)
{
        psignal_internal(p, new_task, thread, PSIG_VFORK, signum, signal_reason);
}


void
psignal_vfork(proc_t p, task_t new_task, thread_t thread, int signum)
{
        psignal_internal(p, new_task, thread, PSIG_VFORK, signum, NULL);
}

void
psignal_uthread(thread_t thread, int signum)
{
        psignal_internal(PROC_NULL, TASK_NULL, thread, PSIG_THREAD, signum, NULL);
}

/* same as psignal(), but prefer delivery to 'thread' if possible */
void
psignal_try_thread(proc_t p, thread_t thread, int signum)
{
        psignal_internal(p, NULL, thread, PSIG_TRY_THREAD, signum, NULL);
}

void
psignal_try_thread_with_reason(proc_t p, thread_t thread, int signum, struct os_reason *signal_reason)
{
        psignal_internal(p, TASK_NULL, thread, PSIG_TRY_THREAD, signum, signal_reason);
}

void
psignal_thread_with_reason(proc_t p, thread_t thread, int signum, struct os_reason *signal_reason)
{
        psignal_internal(p, TASK_NULL, thread, PSIG_THREAD, signum, signal_reason);
}

/*
 * If the current process has received a signal (should be caught or cause
 * termination, should interrupt current syscall), return the signal number.
 * Stop signals with default action are processed immediately, then cleared;
 * they aren't returned.  This is checked after each entry to the system for
 * a syscall or trap (though this can usually be done without calling issignal
 * by checking the pending signal masks in the CURSIG macro.) The normal call
 * sequence is
 *
 *      while (signum = CURSIG(curproc))
 *              postsig(signum);
 */
int
issignal_locked(proc_t p)
{
        int signum, mask, prop, sigbits;
        thread_t cur_act;
        struct uthread * ut;
        proc_t pp;
        kauth_cred_t my_cred;
        int retval = 0;
        uid_t r_uid;

        cur_act = current_thread();

#if SIGNAL_DEBUG
        if (rdebug_proc && (p == rdebug_proc)) {
                ram_printf(3);
        }
#endif /* SIGNAL_DEBUG */

        /*
         * Try to grab the signal lock.
         */
        if (sig_try_locked(p) <= 0) {
                return 0;
        }

        proc_signalstart(p, 1);

        ut = get_bsdthread_info(cur_act);
        for (;;) {
                sigbits = ut->uu_siglist & ~ut->uu_sigmask;

                if (p->p_lflag & P_LPPWAIT) {
                        sigbits &= ~stopsigmask;
                }
                if (sigbits == 0) {             /* no signal to send */
                        retval = 0;
                        goto out;
                }

                signum = ffs((unsigned int)sigbits);
                mask = sigmask(signum);
                prop = sigprop[signum];

                /*
                 * We should see pending but ignored signals
                 * only if P_LTRACED was on when they were posted.
                 */
                if (mask & p->p_sigignore && (p->p_lflag & P_LTRACED) == 0) {
                        ut->uu_siglist &= ~mask;
                        continue;
                }

                if (p->p_lflag & P_LTRACED && (p->p_lflag & P_LPPWAIT) == 0) {
                        /*
                         * If traced, deliver the signal to the debugger, and wait to be
                         * released.
                         */
                        task_t  task;
                        p->p_xstat = signum;

                        if (p->p_lflag & P_LSIGEXC) {
                                p->sigwait = TRUE;
                                p->sigwait_thread = cur_act;
                                p->p_stat = SSTOP;
                                OSBitAndAtomic(~((uint32_t)P_CONTINUED), &p->p_flag);
                                p->p_lflag &= ~P_LWAITED;
                                ut->uu_siglist &= ~mask; /* clear the current signal from the pending list */
                                proc_signalend(p, 1);
                                proc_unlock(p);
                                do_bsdexception(EXC_SOFTWARE, EXC_SOFT_SIGNAL, signum);
                                proc_lock(p);
                                proc_signalstart(p, 1);
                        } else {
                                proc_unlock(p);
                                my_cred = kauth_cred_proc_ref(p);
                                r_uid = kauth_cred_getruid(my_cred);
                                kauth_cred_unref(&my_cred);

                                pp = proc_parentholdref(p);
                                if (pp != PROC_NULL) {
                                        proc_lock(pp);

                                        pp->si_pid = p->p_pid;
                                        pp->p_xhighbits = p->p_xhighbits;
                                        p->p_xhighbits = 0;
                                        pp->si_status = p->p_xstat;
                                        pp->si_code = CLD_TRAPPED;
                                        pp->si_uid = r_uid;

                                        proc_unlock(pp);
                                }

                                /*
                                 *      XXX Have to really stop for debuggers;
                                 *      XXX stop() doesn't do the right thing.
                                 */
                                task = p->task;
                                task_suspend_internal(task);

                                proc_lock(p);
                                p->sigwait = TRUE;
                                p->sigwait_thread = cur_act;
                                p->p_stat = SSTOP;
                                OSBitAndAtomic(~((uint32_t)P_CONTINUED), &p->p_flag);
                                p->p_lflag &= ~P_LWAITED;
                                ut->uu_siglist &= ~mask;

                                proc_signalend(p, 1);
                                proc_unlock(p);

                                if (pp != PROC_NULL) {
                                        psignal(pp, SIGCHLD);
                                        proc_list_lock();
                                        wakeup((caddr_t)pp);
                                        proc_parentdropref(pp, 1);
                                        proc_list_unlock();
                                }

                                assert_wait((caddr_t)&p->sigwait, (THREAD_INTERRUPTIBLE));
                                thread_block(THREAD_CONTINUE_NULL);
                                proc_lock(p);
                                proc_signalstart(p, 1);
                        }

                        p->sigwait = FALSE;
                        p->sigwait_thread = NULL;
                        wakeup((caddr_t)&p->sigwait_thread);

                        if (signum == SIGKILL || ut->uu_siglist & sigmask(SIGKILL)) {
                                /*
                                 * Deliver a pending sigkill even if it's not the current signal.
                                 * Necessary for PT_KILL, which should not be delivered to the
                                 * debugger, but we can't differentiate it from any other KILL.
                                 */
                                signum = SIGKILL;
                                goto deliver_sig;
                        }

                        /* We may have to quit. */
                        if (thread_should_abort(current_thread())) {
                                retval = 0;
                                goto out;
                        }

                        /*
                         * If parent wants us to take the signal,
                         * then it will leave it in p->p_xstat;
                         * otherwise we just look for signals again.
                         */
                        signum = p->p_xstat;
                        if (signum == 0) {
                                continue;
                        }

                        /*
                         * Put the new signal into p_siglist.  If the
                         * signal is being masked, look for other signals.
                         */
                        mask = sigmask(signum);
                        ut->uu_siglist |= mask;
                        if (ut->uu_sigmask & mask) {
                                continue;
                        }
                }

                /*
                 * Decide whether the signal should be returned.
                 * Return the signal's number, or fall through
                 * to clear it from the pending mask.
                 */

                switch ((long)p->p_sigacts->ps_sigact[signum]) {
                case (long)SIG_DFL:
                        /*
                         * If there is a pending stop signal to process
                         * with default action, stop here,
                         * then clear the signal.  However,
                         * if process is member of an orphaned
                         * process group, ignore tty stop signals.
                         */
                        if (prop & SA_STOP) {
                                struct pgrp * pg;

                                proc_unlock(p);
                                pg = proc_pgrp(p);
                                if (p->p_lflag & P_LTRACED ||
                                    (pg->pg_jobc == 0 &&
                                    prop & SA_TTYSTOP)) {
                                        proc_lock(p);
                                        pg_rele(pg);
                                        break; /* ignore signal */
                                }
                                pg_rele(pg);
                                if (p->p_stat != SSTOP) {
                                        proc_lock(p);
                                        p->p_xstat = signum;
                                        p->p_stat = SSTOP;
                                        p->p_lflag &= ~P_LWAITED;
                                        proc_unlock(p);

                                        pp = proc_parentholdref(p);
                                        stop(p, pp);
                                        if ((pp != PROC_NULL) && ((pp->p_flag & P_NOCLDSTOP) == 0)) {
                                                my_cred = kauth_cred_proc_ref(p);
                                                r_uid = kauth_cred_getruid(my_cred);
                                                kauth_cred_unref(&my_cred);

                                                proc_lock(pp);
                                                pp->si_pid = p->p_pid;
                                                pp->si_status = WEXITSTATUS(p->p_xstat);
                                                pp->si_code = CLD_STOPPED;
                                                pp->si_uid = r_uid;
                                                proc_unlock(pp);

                                                psignal(pp, SIGCHLD);
                                        }
                                        if (pp != PROC_NULL) {
                                                proc_parentdropref(pp, 0);
                                        }
                                }
                                proc_lock(p);
                                break;
                        } else if (prop & SA_IGNORE) {
                                /*
                                 * Except for SIGCONT, shouldn't get here.
                                 * Default action is to ignore; drop it.
                                 */
                                break; /* ignore signal */
                        } else {
                                goto deliver_sig;
                        }

                case (long)SIG_IGN:
                        /*
                         * Masking above should prevent us ever trying
                         * to take action on an ignored signal other
                         * than SIGCONT, unless process is traced.
                         */
                        if ((prop & SA_CONT) == 0 &&
                            (p->p_lflag & P_LTRACED) == 0) {
                                printf("issignal\n");
                        }
                        break; /* ignore signal */

                default:
                        /* This signal has an action - deliver it. */
                        goto deliver_sig;
                }

                /* If we dropped through, the signal was ignored - remove it from pending list. */
                ut->uu_siglist &= ~mask;
        } /* for(;;) */

        /* NOTREACHED */

deliver_sig:
        ut->uu_siglist &= ~mask;
        retval = signum;

out:
        proc_signalend(p, 1);
        return retval;
}

/* called from _sleep */
int
CURSIG(proc_t p)
{
        int signum, mask, prop, sigbits;
        thread_t cur_act;
        struct uthread * ut;
        int retnum = 0;


        cur_act = current_thread();

        ut = get_bsdthread_info(cur_act);

        if (ut->uu_siglist == 0) {
                return 0;
        }

        if (((ut->uu_siglist & ~ut->uu_sigmask) == 0) && ((p->p_lflag & P_LTRACED) == 0)) {
                return 0;
        }

        sigbits = ut->uu_siglist & ~ut->uu_sigmask;

        for (;;) {
                if (p->p_lflag & P_LPPWAIT) {
                        sigbits &= ~stopsigmask;
                }
                if (sigbits == 0) {             /* no signal to send */
                        return retnum;
                }

                signum = ffs((unsigned int)sigbits);
                mask = sigmask(signum);
                prop = sigprop[signum];
                sigbits &= ~mask;               /* take the signal out */

                /*
                 * We should see pending but ignored signals
                 * only if P_LTRACED was on when they were posted.
                 */
                if (mask & p->p_sigignore && (p->p_lflag & P_LTRACED) == 0) {
                        continue;
                }

                if (p->p_lflag & P_LTRACED && (p->p_lflag & P_LPPWAIT) == 0) {
                        return signum;
                }

                /*
                 * Decide whether the signal should be returned.
                 * Return the signal's number, or fall through
                 * to clear it from the pending mask.
                 */

                switch ((long)p->p_sigacts->ps_sigact[signum]) {
                case (long)SIG_DFL:
                        /*
                         * If there is a pending stop signal to process
                         * with default action, stop here,
                         * then clear the signal.  However,
                         * if process is member of an orphaned
                         * process group, ignore tty stop signals.
                         */
                        if (prop & SA_STOP) {
                                struct pgrp *pg;

                                pg = proc_pgrp(p);

                                if (p->p_lflag & P_LTRACED ||
                                    (pg->pg_jobc == 0 &&
                                    prop & SA_TTYSTOP)) {
                                        pg_rele(pg);
                                        break;  /* == ignore */
                                }
                                pg_rele(pg);
                                retnum = signum;
                                break;
                        } else if (prop & SA_IGNORE) {
                                /*
                                 * Except for SIGCONT, shouldn't get here.
                                 * Default action is to ignore; drop it.
                                 */
                                break;          /* == ignore */
                        } else {
                                return signum;
                        }
                /*NOTREACHED*/

                case (long)SIG_IGN:
                        /*
                         * Masking above should prevent us ever trying
                         * to take action on an ignored signal other
                         * than SIGCONT, unless process is traced.
                         */
                        if ((prop & SA_CONT) == 0 &&
                            (p->p_lflag & P_LTRACED) == 0) {
                                printf("issignal\n");
                        }
                        break;          /* == ignore */

                default:
                        /*
                         * This signal has an action, let
                         * postsig() process it.
                         */
                        return signum;
                }
        }
        /* NOTREACHED */
}

/*
 * Put the argument process into the stopped state and notify the parent
 * via wakeup.  Signals are handled elsewhere.  The process must not be
 * on the run queue.
 */
static void
stop(proc_t p, proc_t parent)
{
        OSBitAndAtomic(~((uint32_t)P_CONTINUED), &p->p_flag);
        if ((parent != PROC_NULL) && (parent->p_stat != SSTOP)) {
                proc_list_lock();
                wakeup((caddr_t)parent);
                proc_list_unlock();
        }
        (void) task_suspend_internal(p->task);
}

/*
 * Take the action for the specified signal
 * from the current set of pending signals.
 */
void
postsig_locked(int signum)
{
        proc_t p = current_proc();
        struct sigacts *ps = p->p_sigacts;
        user_addr_t catcher;
        uint32_t code;
        int mask, returnmask;
        struct uthread * ut;
        os_reason_t ut_exit_reason = OS_REASON_NULL;

#if DIAGNOSTIC
        if (signum == 0) {
                panic("postsig");
        }
        /*
         *      This must be called on master cpu
         */
        if (cpu_number() != master_cpu) {
                panic("psig not on master");
        }
#endif

        /*
         * Try to grab the signal lock.
         */
        if (sig_try_locked(p) <= 0) {
                return;
        }

        proc_signalstart(p, 1);

        ut = (struct uthread *)get_bsdthread_info(current_thread());
        mask = sigmask(signum);
        ut->uu_siglist &= ~mask;
        catcher = ps->ps_sigact[signum];
        if (catcher == SIG_DFL) {
                /*
                 * Default catcher, where the default is to kill
                 * the process.  (Other cases were ignored above.)
                 */
                sig_lock_to_exit(p);

                /*
                 * exit_with_reason() below will consume a reference to the thread's exit reason, so we take another
                 * reference so the thread still has one even after we call exit_with_reason(). The thread's reference will
                 * ultimately be destroyed in uthread_cleanup().
                 */
                ut_exit_reason = ut->uu_exit_reason;
                os_reason_ref(ut_exit_reason);

                p->p_acflag |= AXSIG;
                if (sigprop[signum] & SA_CORE) {
                        p->p_sigacts->ps_sig = signum;
                        proc_signalend(p, 1);
                        proc_unlock(p);
#if CONFIG_COREDUMP
                        if (coredump(p, 0, 0) == 0) {
                                signum |= WCOREFLAG;
                        }
#endif
                } else {
                        proc_signalend(p, 1);
                        proc_unlock(p);
                }

#if CONFIG_DTRACE
                bzero((caddr_t)&(ut->t_dtrace_siginfo), sizeof(ut->t_dtrace_siginfo));

                ut->t_dtrace_siginfo.si_signo = signum;
                ut->t_dtrace_siginfo.si_pid = p->si_pid;
                ut->t_dtrace_siginfo.si_uid = p->si_uid;
                ut->t_dtrace_siginfo.si_status = WEXITSTATUS(p->si_status);

                /* Fire DTrace proc:::fault probe when signal is generated by hardware. */
                switch (signum) {
                case SIGILL: case SIGBUS: case SIGSEGV: case SIGFPE: case SIGTRAP:
                        DTRACE_PROC2(fault, int, (int)(ut->uu_code), siginfo_t *, &(ut->t_dtrace_siginfo));
                        break;
                default:
                        break;
                }


                DTRACE_PROC3(signal__handle, int, signum, siginfo_t *, &(ut->t_dtrace_siginfo),
                    void (*)(void), SIG_DFL);
#endif

                KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_PROC, BSD_PROC_FRCEXIT) | DBG_FUNC_NONE,
                    p->p_pid, W_EXITCODE(0, signum), 3, 0, 0);

                exit_with_reason(p, W_EXITCODE(0, signum), (int *)NULL, TRUE, TRUE, 0, ut_exit_reason);

                proc_lock(p);
                return;
        } else {
                /*
                 * If we get here, the signal must be caught.
                 */
#if DIAGNOSTIC
                if (catcher == SIG_IGN || (ut->uu_sigmask & mask)) {
                        log(LOG_WARNING,
                            "postsig: processing masked or ignored signal\n");
                }
#endif

                /*
                 * Set the new mask value and also defer further
                 * occurences of this signal.
                 *
                 * Special case: user has done a sigpause.  Here the
                 * current mask is not of interest, but rather the
                 * mask from before the sigpause is what we want
                 * restored after the signal processing is completed.
                 */
                if (ut->uu_flag & UT_SAS_OLDMASK) {
                        returnmask = ut->uu_oldmask;
                        ut->uu_flag &= ~UT_SAS_OLDMASK;
                        ut->uu_oldmask = 0;
                } else {
                        returnmask = ut->uu_sigmask;
                }
                ut->uu_sigmask |= ps->ps_catchmask[signum];
                if ((ps->ps_signodefer & mask) == 0) {
                        ut->uu_sigmask |= mask;
                }
                sigset_t siginfo = ps->ps_siginfo;
                if ((signum != SIGILL) && (signum != SIGTRAP) && (ps->ps_sigreset & mask)) {
                        if ((signum != SIGCONT) && (sigprop[signum] & SA_IGNORE)) {
                                p->p_sigignore |= mask;
                        }
                        ps->ps_sigact[signum] = SIG_DFL;
                        ps->ps_siginfo &= ~mask;
                        ps->ps_signodefer &= ~mask;
                }

                if (ps->ps_sig != signum) {
                        code = 0;
                } else {
                        code = ps->ps_code;
                        ps->ps_code = 0;
                }
                OSIncrementAtomicLong(&p->p_stats->p_ru.ru_nsignals);
                sendsig(p, catcher, signum, returnmask, code, siginfo);
        }
        proc_signalend(p, 1);
}

/*
 * Attach a signal knote to the list of knotes for this process.
 *
 * Signal knotes share the knote list with proc knotes.  This
 * could be avoided by using a signal-specific knote list, but
 * probably isn't worth the trouble.
 */

static int
filt_sigattach(struct knote *kn, __unused struct kevent_qos_s *kev)
{
        proc_t p = current_proc();  /* can attach only to oneself */

        proc_klist_lock();

        kn->kn_proc = p;
        kn->kn_flags |= EV_CLEAR; /* automatically set */
        kn->kn_sdata = 0;         /* incoming data is ignored */

        KNOTE_ATTACH(&p->p_klist, kn);

        proc_klist_unlock();

        /* edge-triggered events can't have fired before we attached */
        return 0;
}

/*
 * remove the knote from the process list, if it hasn't already
 * been removed by exit processing.
 */

static void
filt_sigdetach(struct knote *kn)
{
        proc_t p = kn->kn_proc;

        proc_klist_lock();
        kn->kn_proc = NULL;
        KNOTE_DETACH(&p->p_klist, kn);
        proc_klist_unlock();
}

/*
 * Post an event to the signal filter.  Because we share the same list
 * as process knotes, we have to filter out and handle only signal events.
 *
 * We assume that we process fdfree() before we post the NOTE_EXIT for
 * a process during exit.  Therefore, since signal filters can only be
 * set up "in-process", we should have already torn down the kqueue
 * hosting the EVFILT_SIGNAL knote and should never see NOTE_EXIT.
 */
static int
filt_signal(struct knote *kn, long hint)
{
        if (hint & NOTE_SIGNAL) {
                hint &= ~NOTE_SIGNAL;

                if (kn->kn_id == (unsigned int)hint) {
                        kn->kn_hook32++;
                }
        } else if (hint & NOTE_EXIT) {
                panic("filt_signal: detected NOTE_EXIT event");
        }

        return kn->kn_hook32 != 0;
}

static int
filt_signaltouch(struct knote *kn, struct kevent_qos_s *kev)
{
#pragma unused(kev)

        int res;

        proc_klist_lock();

        /*
         * No data to save - just capture if it is already fired
         */
        res = (kn->kn_hook32 > 0);

        proc_klist_unlock();

        return res;
}

static int
filt_signalprocess(struct knote *kn, struct kevent_qos_s *kev)
{
        int res = 0;

        /*
         * Snapshot the event data.
         */

        proc_klist_lock();
        if (kn->kn_hook32) {
                knote_fill_kevent(kn, kev, kn->kn_hook32);
                kn->kn_hook32 = 0;
                res = 1;
        }
        proc_klist_unlock();
        return res;
}

void
bsd_ast(thread_t thread)
{
        proc_t p = current_proc();
        struct uthread *ut = get_bsdthread_info(thread);
        int     signum;
        static int bsd_init_done = 0;

        if (p == NULL) {
                return;
        }

        /* don't run bsd ast on exec copy or exec'ed tasks */
        if (task_did_exec(current_task()) || task_is_exec_copy(current_task())) {
                return;
        }

        if (timerisset(&p->p_vtimer_user.it_value)) {
                uint32_t        microsecs;

                task_vtimer_update(p->task, TASK_VTIMER_USER, &microsecs);

                if (!itimerdecr(p, &p->p_vtimer_user, microsecs)) {
                        if (timerisset(&p->p_vtimer_user.it_value)) {
                                task_vtimer_set(p->task, TASK_VTIMER_USER);
                        } else {
                                task_vtimer_clear(p->task, TASK_VTIMER_USER);
                        }

                        psignal_try_thread(p, thread, SIGVTALRM);
                }
        }

        if (timerisset(&p->p_vtimer_prof.it_value)) {
                uint32_t        microsecs;

                task_vtimer_update(p->task, TASK_VTIMER_PROF, &microsecs);

                if (!itimerdecr(p, &p->p_vtimer_prof, microsecs)) {
                        if (timerisset(&p->p_vtimer_prof.it_value)) {
                                task_vtimer_set(p->task, TASK_VTIMER_PROF);
                        } else {
                                task_vtimer_clear(p->task, TASK_VTIMER_PROF);
                        }

                        psignal_try_thread(p, thread, SIGPROF);
                }
        }

        if (timerisset(&p->p_rlim_cpu)) {
                struct timeval          tv;

                task_vtimer_update(p->task, TASK_VTIMER_RLIM, (uint32_t *) &tv.tv_usec);

                proc_spinlock(p);
                if (p->p_rlim_cpu.tv_sec > 0 || p->p_rlim_cpu.tv_usec > tv.tv_usec) {
                        tv.tv_sec = 0;
                        timersub(&p->p_rlim_cpu, &tv, &p->p_rlim_cpu);
                        proc_spinunlock(p);
                } else {
                        timerclear(&p->p_rlim_cpu);
                        proc_spinunlock(p);

                        task_vtimer_clear(p->task, TASK_VTIMER_RLIM);

                        psignal_try_thread(p, thread, SIGXCPU);
                }
        }

#if CONFIG_DTRACE
        if (ut->t_dtrace_sig) {
                uint8_t dt_action_sig = ut->t_dtrace_sig;
                ut->t_dtrace_sig = 0;
                psignal(p, dt_action_sig);
        }

        if (ut->t_dtrace_stop) {
                ut->t_dtrace_stop = 0;
                proc_lock(p);
                p->p_dtrace_stop = 1;
                proc_unlock(p);
                (void)task_suspend_internal(p->task);
        }

        if (ut->t_dtrace_resumepid) {
                proc_t resumeproc = proc_find((int)ut->t_dtrace_resumepid);
                ut->t_dtrace_resumepid = 0;
                if (resumeproc != PROC_NULL) {
                        proc_lock(resumeproc);
                        /* We only act on processes stopped by dtrace */
                        if (resumeproc->p_dtrace_stop) {
                                resumeproc->p_dtrace_stop = 0;
                                proc_unlock(resumeproc);
                                task_resume_internal(resumeproc->task);
                        } else {
                                proc_unlock(resumeproc);
                        }
                        proc_rele(resumeproc);
                }
        }

#endif /* CONFIG_DTRACE */

        proc_lock(p);
        if (CHECK_SIGNALS(p, current_thread(), ut)) {
                while ((signum = issignal_locked(p))) {
                        postsig_locked(signum);
                }
        }
        proc_unlock(p);

#ifdef CONFIG_32BIT_TELEMETRY
        if (task_consume_32bit_log_flag(p->task)) {
                proc_log_32bit_telemetry(p);
        }
#endif /* CONFIG_32BIT_TELEMETRY */

        if (!bsd_init_done) {
                bsd_init_done = 1;
                bsdinit_task();
        }
}

/* ptrace set runnable */
void
pt_setrunnable(proc_t p)
{
        task_t task;

        task = p->task;

        if (p->p_lflag & P_LTRACED) {
                proc_lock(p);
                p->p_stat = SRUN;
                proc_unlock(p);
                if (p->sigwait) {
                        wakeup((caddr_t)&(p->sigwait));
                        if ((p->p_lflag & P_LSIGEXC) == 0) {    // 5878479
                                task_release(task);
                        }
                }
        }
}

kern_return_t
do_bsdexception(
        int exc,
        int code,
        int sub)
{
        mach_exception_data_type_t   codes[EXCEPTION_CODE_MAX];

        codes[0] = code;
        codes[1] = sub;
        return bsd_exception(exc, codes, 2);
}

int
proc_pendingsignals(proc_t p, sigset_t mask)
{
        struct uthread * uth;
        thread_t th;
        sigset_t bits = 0;

        proc_lock(p);
        /* If the process is in proc exit return no signal info */
        if (p->p_lflag & P_LPEXIT) {
                goto out;
        }

        if ((p->p_lflag & P_LINVFORK) && p->p_vforkact) {
                th = p->p_vforkact;
                uth = (struct uthread *)get_bsdthread_info(th);
                if (uth) {
                        bits = (((uth->uu_siglist & ~uth->uu_sigmask) & ~p->p_sigignore) & mask);
                }
                goto out;
        }

        bits = 0;
        TAILQ_FOREACH(uth, &p->p_uthlist, uu_list) {
                bits |= (((uth->uu_siglist & ~uth->uu_sigmask) & ~p->p_sigignore) & mask);
        }
out:
        proc_unlock(p);
        return bits;
}

int
thread_issignal(proc_t p, thread_t th, sigset_t mask)
{
        struct uthread * uth;
        sigset_t  bits = 0;

        proc_lock(p);
        uth = (struct uthread *)get_bsdthread_info(th);
        if (uth) {
                bits = (((uth->uu_siglist & ~uth->uu_sigmask) & ~p->p_sigignore) & mask);
        }
        proc_unlock(p);
        return bits;
}

/*
 * Allow external reads of the sigprop array.
 */
int
hassigprop(int sig, int prop)
{
        return sigprop[sig] & prop;
}

void
pgsigio(pid_t pgid, int sig)
{
        proc_t p = PROC_NULL;

        if (pgid < 0) {
                gsignal(-(pgid), sig);
        } else if (pgid > 0 && (p = proc_find(pgid)) != 0) {
                psignal(p, sig);
        }
        if (p != PROC_NULL) {
                proc_rele(p);
        }
}

void
proc_signalstart(proc_t p, int locked)
{
        if (!locked) {
                proc_lock(p);
        }

        if (p->p_signalholder == current_thread()) {
                panic("proc_signalstart: thread attempting to signal a process for which it holds the signal lock");
        }

        p->p_sigwaitcnt++;
        while ((p->p_lflag & P_LINSIGNAL) == P_LINSIGNAL) {
                msleep(&p->p_sigmask, &p->p_mlock, 0, "proc_signstart", NULL);
        }
        p->p_sigwaitcnt--;

        p->p_lflag |= P_LINSIGNAL;
        p->p_signalholder = current_thread();
        if (!locked) {
                proc_unlock(p);
        }
}

void
proc_signalend(proc_t p, int locked)
{
        if (!locked) {
                proc_lock(p);
        }
        p->p_lflag &= ~P_LINSIGNAL;

        if (p->p_sigwaitcnt > 0) {
                wakeup(&p->p_sigmask);
        }

        p->p_signalholder = NULL;
        if (!locked) {
                proc_unlock(p);
        }
}

void
sig_lock_to_exit(proc_t p)
{
        thread_t        self = current_thread();

        p->exit_thread = self;
        proc_unlock(p);

        task_hold(p->task);
        task_wait(p->task, FALSE);

        proc_lock(p);
}

int
sig_try_locked(proc_t p)
{
        thread_t        self = current_thread();

        while (p->sigwait || p->exit_thread) {
                if (p->exit_thread) {
                        return 0;
                }
                msleep((caddr_t)&p->sigwait_thread, &p->p_mlock, PCATCH | PDROP, 0, 0);
                if (thread_should_abort(self)) {
                        /*
                         * Terminate request - clean up.
                         */
                        proc_lock(p);
                        return -1;
                }
                proc_lock(p);
        }
        return 1;
}