X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/89b3af67bb32e691275bf6fa803d1834b2284115..c3c9b80d004dbbfdf763edeb97968c6997e3b45b:/bsd/kern/kern_sig.c

diff --git a/bsd/kern/kern_sig.c b/bsd/kern/kern_sig.c
index 2333f91fb..74ecaf338 100644
--- a/bsd/kern/kern_sig.c
+++ b/bsd/kern/kern_sig.c
@@ -1,8 +1,8 @@
 /*
- * Copyright (c) 2000-2001 Apple Computer, Inc. All rights reserved.
+ * 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
@@ -11,10 +11,10 @@
  * 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,
@@ -22,10 +22,9 @@
  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  * Please see the License for the specific language governing rights and
  * limitations under the License.
- * 
+ *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
-/* Copyright (c) 1995-1998 Apple Computer, Inc. All Rights Reserved */
 /*
  * Copyright (c) 1982, 1986, 1989, 1991, 1993
  *	The Regents of the University of California.  All rights reserved.
@@ -65,8 +64,14 @@
  *
  *	@(#)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 */
+#define SIGPROP         /* include signal properties table */
 #include <sys/param.h>
 #include <sys/resourcevar.h>
 #include <sys/proc_internal.h>
@@ -79,34 +84,42 @@
 #include <sys/kernel.h>
 #include <sys/wait.h>
 #include <sys/signalvar.h>
-#if KTRACE
-#include <sys/ktrace.h>
-#endif
 #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 <bsm/audit_kernel.h>
-
-#include <machine/spl.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/lock.h>
-#include <kern/task.h>		/* extern void   *get_bsdtask_info(task_t); */
+#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
@@ -114,52 +127,95 @@
  * +++
  */
 extern int thread_enable_fpe(thread_t act, int onoff);
-extern void unix_syscall_return(int error);
-extern thread_t	port_name_to_thread(mach_port_name_t port_name);
-extern kern_return_t check_actforsig(task_t task, thread_t thread, int setast);
-extern kern_return_t get_signalact(task_t , thread_t *, int);
-extern boolean_t thread_should_abort(thread_t);
+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, int code, int sub);
+extern void doexception(int exc, mach_exception_code_t code,
+    mach_exception_subcode_t sub);
 
-void stop(struct proc *p);
-int cansignal(struct proc *, kauth_cred_t, struct proc *, int);
-int killpg1(struct proc *, int, int, int);
-void sigexit_locked(struct proc *, int);
-int setsigvec(struct proc *, int, struct __user_sigaction *);
-void exit1(struct proc *, int, int *);
-void psignal_uthread(thread_t, int);
+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(void *, void *,time_t, int32_t, void (*)(int));
-kern_return_t semaphore_timedwait_trap_internal(void *, time_t, int32_t, void (*)(int));
-kern_return_t semaphore_wait_signal_trap_internal(void *, void *, void (*)(int));
-kern_return_t semaphore_wait_trap_internal(void *, void (*)(int));
+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 *);
 
-static int	filt_sigattach(struct knote *kn);
-static void	filt_sigdetach(struct knote *kn);
-static int	filt_signal(struct knote *kn, long hint);
 
-struct filterops sig_filtops =
-	{ 0, filt_sigattach, filt_sigdetach, filt_signal };
+/* 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_64to32(struct user_sigaltstack *in, struct sigaltstack *out)
+sigaltstack_kern_to_user32(struct kern_sigaltstack *in, struct user32_sigaltstack *out)
 {
-	out->ss_sp	= CAST_DOWN(void *,in->ss_sp);
-	out->ss_size	= in->ss_size;
-	out->ss_flags	= in->ss_flags;
+	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;
 }
 
 /*
@@ -168,402 +224,521 @@ sigaltstack_64to32(struct user_sigaltstack *in, struct sigaltstack *out)
  * the beginning.
  */
 static void
-sigaltstack_32to64(struct sigaltstack *in, struct user_sigaltstack *out)
+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);
+	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_64to32(struct user_sigaction *in, struct sigaction *out)
+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 = CAST_DOWN(sig_t,in->__sigaction_u.__sa_handler);
+	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_32to64(struct __sigaction *in, struct __user_sigaction *out)
+__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;
+int ram_debug = 0;
+unsigned int rdebug_proc = 0;
 void
 ram_printf(int x)
 {
-    printf("x is %d",x);
-
+	printf("x is %d", x);
 }
 #endif /* SIGNAL_DEBUG */
 
-int
-signal_lock(struct proc *p)
-{
-int error = 0;
-#if DIAGNOSTIC
-#if SIGNAL_DEBUG
-#ifdef __ppc__
-        {
-            int register sp, *fp, numsaved; 
- 
-            __asm__ volatile("mr %0,r1" : "=r" (sp));
-
-            fp = (int *)*((int *)sp);
-            for (numsaved = 0; numsaved < 3; numsaved++) {
-                p->lockpc[numsaved] = fp[2];
-                if ((int)fp <= 0)
-                        break;
-                fp = (int *)*fp;
-            }
-        }
-#endif /* __ppc__ */       
-#endif /* SIGNAL_DEBUG */
-#endif /* DIAGNOSTIC */
 
-siglock_retry:
-	error = lockmgr((struct lock__bsd__ *)&p->signal_lock[0], LK_EXCLUSIVE, 0, (struct proc *)0);
-	if (error == EINTR)
-		goto siglock_retry;
-	return(error);
+void
+signal_setast(thread_t sig_actthread)
+{
+	act_set_astbsd(sig_actthread);
 }
 
-int
-signal_unlock(struct proc *p)
+static int
+cansignal_nomac(proc_t src, kauth_cred_t uc_src, proc_t dst, int signum)
 {
-#if DIAGNOSTIC
-#if SIGNAL_DEBUG
-#ifdef __ppc__
-        {
-            int register sp, *fp, numsaved; 
- 
-            __asm__ volatile("mr %0,r1" : "=r" (sp));
-
-            fp = (int *)*((int *)sp);
-            for (numsaved = 0; numsaved < 3; numsaved++) {
-                p->unlockpc[numsaved] = fp[2];
-                if ((int)fp <= 0)
-                        break;
-                fp = (int *)*fp;
-            }
-        }
-#endif /* __ppc__ */       
-#endif /* SIGNAL_DEBUG */
-#endif /* DIAGNOSTIC */
+	/* you can signal yourself */
+	if (src == dst) {
+		return 1;
+	}
 
-	/* TBD:  check p last arg */
-	return(lockmgr((struct lock__bsd__ *)&p->signal_lock[0], LK_RELEASE, (simple_lock_t)0, (struct proc *)0));
-}
+	/* you can't send the init proc SIGKILL, even if root */
+	if (signum == SIGKILL && dst == initproc) {
+		return 0;
+	}
 
-void
-signal_setast(sig_actthread)
-thread_t sig_actthread;
-{
-	act_set_astbsd(sig_actthread);
+	/* 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 p, with ucred uc, send the signal signum to process q?
+ * 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(p, uc, q, signum)
-	struct proc *p;
-	kauth_cred_t uc;
-	struct proc *q;
-	int signum;
+cansignal(proc_t src, kauth_cred_t uc_src, proc_t dst, int signum)
 {
-	/* you can signal yourself */
-	if (p == q)
-		return(1);
+#if CONFIG_MACF
+	if (mac_proc_check_signal(src, dst, signum)) {
+		return 0;
+	}
+#endif
 
-	if (!suser(uc, NULL))
-		return (1);		/* root can always signal */
+	return cansignal_nomac(src, uc_src, dst, signum);
+}
 
-	if (signum == SIGCONT && q->p_session == p->p_session)
-		return (1);		/* SIGCONT in session */
+/*
+ * <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;
 
-	/*
-	 * Using kill(), only certain signals can be sent to setugid
-	 * child processes
-	 */
-	if (q->p_flag & P_SUGID) {
-		switch (signum) {
-		case 0:
-		case SIGKILL:
-		case SIGINT:
-		case SIGTERM:
-		case SIGSTOP:
-		case SIGTTIN:
-		case SIGTTOU:
-		case SIGTSTP:
-		case SIGHUP:
-		case SIGUSR1:
-		case SIGUSR2:
-			if (uc->cr_ruid == q->p_ucred->cr_ruid ||
-			    kauth_cred_getuid(uc) == q->p_ucred->cr_ruid ||
-			    uc->cr_ruid == kauth_cred_getuid(q->p_ucred) ||
-			    kauth_cred_getuid(uc) == kauth_cred_getuid(q->p_ucred))
-				return (1);
-		}
-		return (0);
-	}
-
-	/* XXX
-	 * because the P_SUGID test exists, this has extra tests which
-	 * could be removed.
-	 */
-	if (uc->cr_ruid == q->p_ucred->cr_ruid ||
-	    uc->cr_ruid == q->p_ucred->cr_svuid ||
-	    kauth_cred_getuid(uc) == q->p_ucred->cr_ruid ||
-	    kauth_cred_getuid(uc) == q->p_ucred->cr_svuid ||
-	    uc->cr_ruid == kauth_cred_getuid(q->p_ucred) ||
-	    kauth_cred_getuid(uc) == kauth_cred_getuid(q->p_ucred))
-		return (1);
-	return (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(struct proc *p, register struct sigaction_args *uap, __unused register_t *retval)
+sigaction(proc_t p, struct sigaction_args *uap, __unused int32_t *retval)
 {
-	struct user_sigaction vec;
-	struct __user_sigaction __vec;
+	struct kern_sigaction vec;
+	struct __kern_sigaction __vec;
 
-	struct user_sigaction *sa = &vec;
-	register struct sigacts *ps = p->p_sigacts;
+	struct kern_sigaction *sa = &vec;
+	struct sigacts *ps = p->p_sigacts;
 
-	register int signum;
-	int bit, error=0;
+	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);
+	    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)
+		if ((ps->ps_sigonstack & bit) != 0) {
 			sa->sa_flags |= SA_ONSTACK;
-		if ((ps->ps_sigintr & bit) == 0)
+		}
+		if ((ps->ps_sigintr & bit) == 0) {
 			sa->sa_flags |= SA_RESTART;
-		if (ps->ps_siginfo & bit)
+		}
+		if (ps->ps_siginfo & bit) {
 			sa->sa_flags |= SA_SIGINFO;
-		if (ps->ps_signodefer & bit)
+		}
+		if (ps->ps_signodefer & bit) {
 			sa->sa_flags |= SA_NODEFER;
-		if (ps->ps_64regset & bit)
-			sa->sa_flags |= SA_64REGSET;
-		if ((signum == SIGCHLD) && (p->p_flag & P_NOCLDSTOP))
+		}
+		if ((signum == SIGCHLD) && (p->p_flag & P_NOCLDSTOP)) {
 			sa->sa_flags |= SA_NOCLDSTOP;
-		if ((signum == SIGCHLD) && (p->p_flag & P_NOCLDWAIT))
+		}
+		if ((signum == SIGCHLD) && (p->p_flag & P_NOCLDWAIT)) {
 			sa->sa_flags |= SA_NOCLDWAIT;
+		}
 
 		if (IS_64BIT_PROCESS(p)) {
-			error = copyout(sa, uap->osa, sizeof(struct user_sigaction));
+			struct user64_sigaction vec64 = {};
+			sigaction_kern_to_user64(sa, &vec64);
+			error = copyout(&vec64, uap->osa, sizeof(vec64));
 		} else {
-			struct sigaction vec32;
-			sigaction_64to32(sa, &vec32);
-			error = copyout(&vec32, uap->osa, sizeof(struct sigaction));
+			struct user32_sigaction vec32 = {};
+			sigaction_kern_to_user32(sa, &vec32);
+			error = copyout(&vec32, uap->osa, sizeof(vec32));
+		}
+		if (error) {
+			return error;
 		}
-		if (error)
-			return (error);
 	}
+
 	if (uap->nsa) {
-		if (IS_64BIT_PROCESS(p)) {
-			error = copyin(uap->nsa, &__vec, sizeof(struct __user_sigaction));
-		} else {
-			struct __sigaction __vec32;
-			error = copyin(uap->nsa, &__vec32, sizeof(struct __sigaction));
-			__sigaction_32to64(&__vec32, &__vec);
+		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);
 		}
-		if (error)
-			return (error);
-		error = setsigvec(p, signum, &__vec);
+		error = setsigvec(p, current_thread(), signum, &__vec, FALSE);
 	}
-	return (error);
+
+	return error;
 }
 
 /* Routines to manipulate bits on all threads */
 int
-clear_procsiglist(struct proc *p,  int bit)
+clear_procsiglist(proc_t p, int bit, boolean_t in_signalstart)
 {
 	struct uthread * uth;
 	thread_t thact;
 
-	signal_lock(p);
+	proc_lock(p);
+	if (!in_signalstart) {
+		proc_signalstart(p, 1);
+	}
 
-	if ((p->p_flag & P_INVFORK) && p->p_vforkact) {
-		thact = p->p_vforkact;	
+	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;
 		}
-		p->p_siglist &= ~bit;
-		signal_unlock(p);
-		return(0);
-	} 
+		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;
-	signal_unlock(p);
-	return(0);
+	if (!in_signalstart) {
+		proc_signalend(p, 1);
+	}
+	proc_unlock(p);
+
+	return 0;
 }
 
 
 static int
-unblock_procsigmask(struct proc *p,  int bit)
+unblock_procsigmask(proc_t p, int bit)
 {
 	struct uthread * uth;
 	thread_t thact;
 
-	signal_lock(p);
-	if ((p->p_flag & P_INVFORK) && p->p_vforkact) {
-		thact = p->p_vforkact;	
+	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;
-		signal_unlock(p);
-		return(0);
-	} 
+		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;
-	signal_unlock(p);
-	return(0);
-}
 
+	proc_signalend(p, 1);
+	proc_unlock(p);
+	return 0;
+}
 
 static int
-block_procsigmask(struct proc *p,  int bit)
+block_procsigmask(proc_t p, int bit)
 {
 	struct uthread * uth;
 	thread_t thact;
 
-	signal_lock(p);
-	if ((p->p_flag & P_INVFORK) && p->p_vforkact) {
-		thact = p->p_vforkact;	
+	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;
-		signal_unlock(p);
-		return(0);
-	} 
+		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;
-	signal_unlock(p);
-	return(0);
+
+	proc_signalend(p, 1);
+	proc_unlock(p);
+	return 0;
 }
 
 int
-set_procsigmask(struct proc *p,  int bit)
+set_procsigmask(proc_t p, int bit)
 {
 	struct uthread * uth;
 	thread_t thact;
 
-	signal_lock(p);
-	if ((p->p_flag & P_INVFORK) && p->p_vforkact) {
-		thact = p->p_vforkact;	
+	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;
-		signal_unlock(p);
-		return(0);
-	} 
+		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;
-	signal_unlock(p);
-	return(0);
+	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(struct proc *p, int signum, struct __user_sigaction *sa)
+setsigvec(proc_t p, __unused thread_t thread, int signum, struct __kern_sigaction *sa, boolean_t in_sigstart)
 {
-	register struct sigacts *ps = p->p_sigacts;
-	register int bit;
+	struct sigacts *ps = p->p_sigacts;
+	int bit;
+
+	assert(signum < NSIG);
 
 	if ((signum == SIGKILL || signum == SIGSTOP) &&
-		sa->sa_handler != SIG_DFL)
-		return(EINVAL);
+	    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_catchmask[signum] = sa->sa_mask & ~sigcantmask;
+	if (sa->sa_flags & SA_SIGINFO) {
 		ps->ps_siginfo |= bit;
-	else
+	} else {
 		ps->ps_siginfo &= ~bit;
-	if (sa->sa_flags & SA_64REGSET)
-		ps->ps_64regset |= bit;
-	else
-		ps->ps_64regset &= ~bit;
-	if ((sa->sa_flags & SA_RESTART) == 0)
+	}
+	if ((sa->sa_flags & SA_RESTART) == 0) {
 		ps->ps_sigintr |= bit;
-	else
+	} else {
 		ps->ps_sigintr &= ~bit;
-	if (sa->sa_flags & SA_ONSTACK)
+	}
+	if (sa->sa_flags & SA_ONSTACK) {
 		ps->ps_sigonstack |= bit;
-	else
+	} else {
 		ps->ps_sigonstack &= ~bit;
-	if (sa->sa_flags & SA_USERTRAMP)
-		ps->ps_usertramp |= bit;
-	else
-		ps->ps_usertramp &= ~bit;
-	if (sa->sa_flags & SA_RESETHAND)
+	}
+	if (sa->sa_flags & SA_RESETHAND) {
 		ps->ps_sigreset |= bit;
-	else
+	} else {
 		ps->ps_sigreset &= ~bit;
-	if (sa->sa_flags & SA_NODEFER)
+	}
+	if (sa->sa_flags & SA_NODEFER) {
 		ps->ps_signodefer |= bit;
-	else
+	} else {
 		ps->ps_signodefer &= ~bit;
+	}
 	if (signum == SIGCHLD) {
-		if (sa->sa_flags & SA_NOCLDSTOP)
-			p->p_flag |= P_NOCLDSTOP;
-		else
-			p->p_flag &= ~P_NOCLDSTOP;
-		if ((sa->sa_flags & SA_NOCLDWAIT) || (sa->sa_handler == SIG_IGN))
-			p->p_flag |= P_NOCLDWAIT;
-		else
-			p->p_flag &= ~P_NOCLDWAIT;
-	}
-
-#ifdef __ppc__ 
-	if (signum == SIGFPE) {
-		if (sa->sa_handler == SIG_DFL || sa->sa_handler == SIG_IGN) 
-			thread_enable_fpe(current_thread(), 0);
-		else
-			thread_enable_fpe(current_thread(), 1);
-	}
-#endif  /* __ppc__ */
+		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.
@@ -572,19 +747,20 @@ setsigvec(struct proc *p, int signum, struct __user_sigaction *sa)
 	 */
 	if (sa->sa_handler == SIG_IGN ||
 	    (sigprop[signum] & SA_IGNORE && sa->sa_handler == SIG_DFL)) {
-
-		clear_procsiglist(p, bit);
-		if (signum != SIGCONT)
-			p->p_sigignore |= bit;	/* easier in psignal */
+		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)
+		if (sa->sa_handler == SIG_DFL) {
 			p->p_sigcatch &= ~bit;
-		else
+		} else {
 			p->p_sigcatch |= bit;
+		}
 	}
-	return(0);
+	return 0;
 }
 
 /*
@@ -592,65 +768,74 @@ setsigvec(struct proc *p, int signum, struct __user_sigaction *sa)
  * set to ignore signals that are ignored by default.
  */
 void
-siginit(p)
-	struct proc *p;
+siginit(proc_t p)
 {
-	register int i;
+	int i;
 
-	for (i = 0; i < NSIG; i++)
-		if (sigprop[i] & SA_IGNORE && i != SIGCONT)
+	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(p, thr_act)
-	register struct proc *p;
-	register thread_t thr_act;
+execsigs(proc_t p, thread_t thread)
 {
-	register struct sigacts *ps = p->p_sigacts;
-	register int nc, mask;
-	struct uthread *ut = (struct uthread *)0;
+	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;
 
-	if (thr_act){
-		ut = (struct uthread *)get_bsdthread_info(thr_act);
-	}
 	/*
 	 * 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((long)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)
+			if (nc != SIGCONT) {
 				p->p_sigignore |= mask;
-			if (thr_act){
-				ut->uu_siglist &= ~mask;
-				p->p_siglist &= ~mask;
-			} else
-				clear_procsiglist(p, 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.
 	 */
-	ps->ps_sigstk.ss_flags = SA_DISABLE;
-	ps->ps_sigstk.ss_size = 0;
-	ps->ps_sigstk.ss_sp = USER_ADDR_NULL;
-	ps->ps_flags = 0;
-	if (thr_act) {
-		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;
-	}
+	/* 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;
 }
 
@@ -661,7 +846,7 @@ execsigs(p, thr_act)
  * the library stub does the rest.
  */
 int
-sigprocmask(register struct proc *p, struct sigprocmask_args *uap, __unused register_t *retval)
+sigprocmask(proc_t p, struct sigprocmask_args *uap, __unused int32_t *retval)
 {
 	int error = 0;
 	sigset_t oldmask, nmask;
@@ -676,8 +861,9 @@ sigprocmask(register struct proc *p, struct sigprocmask_args *uap, __unused regi
 		goto out;
 	}
 	error = copyin(uap->mask, &nmask, sizeof(sigset_t));
-	if (error)
+	if (error) {
 		goto out;
+	}
 
 	switch (uap->how) {
 	case SIG_BLOCK:
@@ -694,19 +880,20 @@ sigprocmask(register struct proc *p, struct sigprocmask_args *uap, __unused regi
 		set_procsigmask(p, (nmask & ~sigcantmask));
 		signal_setast(current_thread());
 		break;
-	
+
 	default:
 		error = EINVAL;
 		break;
 	}
 out:
-	if (!error && omask != USER_ADDR_NULL)
+	if (!error && omask != USER_ADDR_NULL) {
 		copyout(&oldmask, omask, sizeof(sigset_t));
-	return (error);
+	}
+	return error;
 }
 
 int
-sigpending(__unused struct proc *p, register struct sigpending_args *uap, __unused register_t *retval)
+sigpending(__unused proc_t p, struct sigpending_args *uap, __unused int32_t *retval)
 {
 	struct uthread *ut;
 	sigset_t pendlist;
@@ -714,12 +901,12 @@ sigpending(__unused struct proc *p, register struct sigpending_args *uap, __unus
 	ut = (struct uthread *)get_bsdthread_info(current_thread());
 	pendlist = ut->uu_siglist;
 
-	if (uap->osv)
+	if (uap->osv) {
 		copyout(&pendlist, uap->osv, sizeof(sigset_t));
-	return(0);
+	}
+	return 0;
 }
 
-
 /*
  * Suspend process until signal, providing mask to be set
  * in the meantime.  Note nonstandard calling convention:
@@ -730,11 +917,18 @@ static int
 sigcontinue(__unused int error)
 {
 //	struct uthread *ut = get_bsdthread_info(current_thread());
-  unix_syscall_return(EINTR);
+	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(register struct proc *p, struct sigsuspend_args *uap, __unused register_t *retval)
+sigsuspend_nocancel(proc_t p, struct sigsuspend_nocancel_args *uap, __unused int32_t *retval)
 {
 	struct uthread *ut;
 
@@ -750,183 +944,334 @@ sigsuspend(register struct proc *p, struct sigsuspend_args *uap, __unused regist
 	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);
+	(void) tsleep0((caddr_t) p, PPAUSE | PCATCH, "pause", 0, sigcontinue);
 	/* always return EINTR rather than ERESTART... */
-	return (EINTR);
+	return EINTR;
 }
 
 
 int
-__disable_threadsignal(struct proc *p, 
-					   __unused register struct __disable_threadsignal_args *uap, 
-					   __unused register_t *retval)
+__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 */
-	signal_lock(p);
-	uth->uu_flag |= UT_NO_SIGMASK;
-	signal_unlock(p);
+	uth->uu_flag |= (UT_NO_SIGMASK | UT_CANCELDISABLE);
+
+	return 0;
+}
+
+void
+__pthread_testcancel(int presyscall)
+{
+	thread_t self = current_thread();
+	struct uthread * uthread;
 
-	return(0);
+	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(p, uap, retval)
-	struct proc *p;
-	register struct __pthread_markcancel_args *uap;
-	register_t *retval;
+__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);
+	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);
+	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 & (P_VFORK | UT_CANCEL | UT_CANCELED )) == 0) {
+	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);
+		if (((uth->uu_flag & UT_NOTCANCELPT) == 0)
+		    && ((uth->uu_flag & UT_CANCELDISABLE) == 0)) {
+			thread_abort_safely(target_act);
+		}
 	}
 
 	thread_deallocate(target_act);
-	return (error);
+	return error;
 }
 
-/* if action =0 ; return the cancellation state , 
+/* 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(p, uap, retval)
-	struct proc *p;
-	register struct __pthread_canceled_args *uap;
-	register_t *retval;
+__pthread_canceled(__unused proc_t p,
+    struct __pthread_canceled_args *uap, __unused int32_t *retval)
 {
-	thread_act_t thr_act;
+	thread_act_t thread;
 	struct uthread *uth;
 	int action = uap->action;
 
-	thr_act = current_act();
-	uth = (struct uthread *)get_bsdthread_info(thr_act);
+	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);
+	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) 
+__posix_sem_syscall_return(kern_return_t kern_result)
 {
 	int error = 0;
 
-	if (kern_result == KERN_SUCCESS)
+	if (kern_result == KERN_SUCCESS) {
 		error = 0;
-	else if (kern_result == KERN_ABORTED)
+	} else if (kern_result == KERN_ABORTED) {
 		error = EINTR;
-	else if (kern_result == KERN_OPERATION_TIMED_OUT) 
+	} else if (kern_result == KERN_OPERATION_TIMED_OUT) {
 		error = ETIMEDOUT;
-	else
+	} 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
-__semwait_signal(p, uap, retval)
-	struct proc *p;
-	register struct __semwait_signal_args *uap;
-	register_t *retval;
+__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(uap->timeout) {
+		if ((ts.tv_sec & 0xFFFFFFFF00000000ULL) != 0) {
+			ts.tv_sec = 0xFFFFFFFF;
+			ts.tv_nsec = 0;
+			truncated_timeout = TRUE;
+		}
 
 		if (uap->relative) {
-			then.tv_sec = uap->tv_sec;
-			then.tv_nsec = uap->tv_nsec;
+			then.tv_sec = (unsigned int)ts.tv_sec;
+			then.tv_nsec = (clock_res_t)ts.tv_nsec;
 		} else {
 			nanotime(&now);
-			then.tv_sec = uap->tv_sec - now.tv_sec;
-			then.tv_nsec = uap->tv_nsec - now.tv_nsec;
-			if (then.tv_nsec < 0) {
-				then.tv_nsec += NSEC_PER_SEC;
-				then.tv_sec--; 
+
+			/* 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 == (void *)NULL)
-			kern_result = semaphore_timedwait_trap_internal(uap->cond_sem, then.tv_sec, then.tv_nsec, __posix_sem_syscall_return);
-		else
+		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 == (void *)NULL)
+		if (uap->mutex_sem == 0) {
 			kern_result = semaphore_wait_trap_internal(uap->cond_sem, __posix_sem_syscall_return);
-		else
-
+		} else {
 			kern_result = semaphore_wait_signal_trap_internal(uap->cond_sem, uap->mutex_sem, __posix_sem_syscall_return);
+		}
 	}
 
-out:
-	if (kern_result == KERN_SUCCESS)
-		return(0);
-	else if (kern_result == KERN_ABORTED)
-		return(EINTR);
-	else if (kern_result == KERN_OPERATION_TIMED_OUT) 
-		return(ETIMEDOUT);
-	else
-		return(EINVAL);
+	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 
-__pthread_kill(__unused struct proc *p, 
-			   register struct __pthread_kill_args *uap, 
-			   __unused register_t *retval) 
+int
+__semwait_signal_nocancel(__unused proc_t p, struct __semwait_signal_nocancel_args *uap,
+    __unused int32_t *retval)
 {
-	thread_t target_act;
-	int error = 0;
-	int signum = uap->sig;
-	struct uthread *uth;
+	kern_return_t kern_result;
+	mach_timespec_t then;
+	struct timespec now;
+	struct user_timespec ts;
+	boolean_t truncated_timeout = FALSE;
 
-	target_act = (thread_t)port_name_to_thread(uap->thread_port);
+	if (uap->timeout) {
+		ts.tv_sec = (user_time_t)uap->tv_sec;
+		ts.tv_nsec = uap->tv_nsec;
 
-	if (target_act == THREAD_NULL)
-		return (ESRCH);
-	if ((u_int)signum >= NSIG) {
+		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;
 	}
@@ -938,18 +1283,23 @@ __pthread_kill(__unused struct proc *p,
 		goto out;
 	}
 
-	if (signum)
+	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);
+	return error;
 }
 
 
-int 
-pthread_sigmask(__unused register struct proc *p, 
-				register struct pthread_sigmask_args *uap, 
-				__unused register_t *retval)
+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;
@@ -967,8 +1317,9 @@ pthread_sigmask(__unused register struct proc *p,
 	}
 
 	error = copyin(set, &nset, sizeof(sigset_t));
-	if (error)
+	if (error) {
 		goto out;
+	}
 
 	switch (uap->how) {
 	case SIG_BLOCK:
@@ -984,56 +1335,73 @@ pthread_sigmask(__unused register struct proc *p,
 		ut->uu_sigmask = (nset & ~sigcantmask);
 		signal_setast(current_thread());
 		break;
-	
+
 	default:
 		error = EINVAL;
-
 	}
 out:
-	if (!error && oset != USER_ADDR_NULL)
+	if (!error && oset != USER_ADDR_NULL) {
 		copyout(&oldset, oset, sizeof(sigset_t));
+	}
 
-	return(error);
+	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(register struct proc *p, register struct sigwait_args *uap, __unused register_t *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;
+	sigset_t sigw = 0;
 	int signum;
 
 	ut = (struct uthread *)get_bsdthread_info(current_thread());
 
-	if (uap->set == USER_ADDR_NULL)
-		return(EINVAL);
+	if (uap->set == USER_ADDR_NULL) {
+		return EINVAL;
+	}
 
 	error = copyin(uap->set, &mask, sizeof(sigset_t));
-	if (error)
-		return(error);
+	if (error) {
+		return error;
+	}
 
 	siglist = (mask & ~sigcantmask);
 
-	if (siglist == 0)
-		return(EINVAL);
+	if (siglist == 0) {
+		return EINVAL;
+	}
 
-	signal_lock(p);
-	if ((p->p_flag & P_INVFORK) && p->p_vforkact) {
-		signal_unlock(p);
-		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) ) {
+			if ((sigw = uth->uu_siglist & siglist)) {
 				break;
 			}
 		}
+		proc_signalend(p, 1);
 	}
-	signal_unlock(p);
+
 	if (sigw) {
 		/* The signal was pending on a thread */
 		goto sigwait1;
@@ -1045,18 +1413,23 @@ sigwait(register struct proc *p, register struct sigwait_args *uap, __unused reg
 	 * 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)
-		return(EINVAL);
+	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; 
+	ut->uu_sigmask = ~(siglist | sigcantmask);
+	ut->uu_sigwait = siglist;
+
 	/* No Continuations for now */
-	error =  tsleep((caddr_t)&ut->uu_sigwait, PPAUSE|PCATCH, "pause", 0);
+	error =  msleep((caddr_t)&ut->uu_sigwait, &p->p_mlock, PPAUSE | PCATCH, "pause", 0);
 
-	if ((error == EINTR) || (error == ERESTART))
+	if (error == ERESTART) {
 		error = 0;
+	}
 
 	sigw = (ut->uu_sigwait & siglist);
 	ut->uu_sigmask = ut->uu_oldmask;
@@ -1066,420 +1439,762 @@ sigwait1:
 	ut->uu_sigwait = 0;
 	if (!error) {
 		signum = ffs((unsigned int)sigw);
-		if (!signum)
+		if (!signum) {
 			panic("sigwait with no signal wakeup");
-		ut->uu_siglist &= ~(sigmask(signum));
-		if (uap->sig != USER_ADDR_NULL)
-				error = copyout(&signum, uap->sig, sizeof(int));
-	}
+		}
+		/* Clear the pending signal in the thread it was delivered */
+		uth->uu_siglist &= ~(sigmask(signum));
 
-	return(error);
+#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(struct proc *p, register struct sigaltstack_args *uap, __unused register_t *retval)
+sigaltstack(__unused proc_t p, struct sigaltstack_args *uap, __unused int32_t *retval)
 {
-	struct sigacts *psp;
-	struct user_sigaltstack *pstk;
-	struct user_sigaltstack ss;
-	struct uthread *uth;
-	int uthsigaltstack = 0;
+	struct kern_sigaltstack ss;
+	struct kern_sigaltstack *pstk;
 	int error;
+	struct uthread *uth;
+	int onstack;
 
 	uth = (struct uthread *)get_bsdthread_info(current_thread());
-	uthsigaltstack = p->p_lflag & P_LTHSIGSTACK;
 
-	psp = p->p_sigacts;
-	if (uthsigaltstack != 0)  {
-		pstk = &uth->uu_sigstk;
-		if ((uth->uu_flag & UT_ALTSTACK) == 0)
-			uth->uu_sigstk.ss_flags |= SA_DISABLE;
-	} else {
-		pstk = &psp->ps_sigstk;
-		if ((psp->ps_flags & SAS_ALTSTACK) == 0)
-			psp->ps_sigstk.ss_flags |= SA_DISABLE;
+	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)) {
-			error = copyout(pstk, uap->oss, sizeof(struct user_sigaltstack));
+			struct user64_sigaltstack ss64 = {};
+			sigaltstack_kern_to_user64(pstk, &ss64);
+			error = copyout(&ss64, uap->oss, sizeof(ss64));
 		} else {
-			struct sigaltstack ss32;
-			sigaltstack_64to32(pstk, &ss32);
-			error = copyout(&ss32, uap->oss, sizeof(struct sigaltstack));
+			struct user32_sigaltstack ss32 = {};
+			sigaltstack_kern_to_user32(pstk, &ss32);
+			error = copyout(&ss32, uap->oss, sizeof(ss32));
+		}
+		if (error) {
+			return error;
 		}
-		if (error)
-			return (error);
 	}
-	if (uap->nss == USER_ADDR_NULL)
-		return (0);
+	if (uap->nss == USER_ADDR_NULL) {
+		return 0;
+	}
 	if (IS_64BIT_PROCESS(p)) {
-		error = copyin(uap->nss, &ss, sizeof(struct user_sigaltstack));
+		struct user64_sigaltstack ss64;
+		error = copyin(uap->nss, &ss64, sizeof(ss64));
+		sigaltstack_user64_to_kern(&ss64, &ss);
 	} else {
-		struct sigaltstack ss32;
-		error = copyin(uap->nss, &ss32, sizeof(struct sigaltstack));
-		sigaltstack_32to64(&ss32,&ss);
+		struct user32_sigaltstack ss32;
+		error = copyin(uap->nss, &ss32, sizeof(ss32));
+		sigaltstack_user32_to_kern(&ss32, &ss);
+	}
+	if (error) {
+		return error;
 	}
-	if (error)
-		return (error);
-	if ((ss.ss_flags & ~SA_DISABLE) != 0)  {
-		return(EINVAL);
+	if ((ss.ss_flags & ~SA_DISABLE) != 0) {
+		return EINVAL;
 	}
 
 	if (ss.ss_flags & SA_DISABLE) {
-		if (uthsigaltstack != 0)  {
-			/* 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;
-		} else {
-			if (psp->ps_sigstk.ss_flags & SA_ONSTACK)
-				return (EINVAL);
-			psp->ps_flags &= ~SAS_ALTSTACK;
-			psp->ps_sigstk.ss_flags = ss.ss_flags;
+		/* 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;
 		}
-		
-		return (0);
+		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);
-	if (uthsigaltstack != 0)  {
-		uth->uu_flag |= UT_ALTSTACK;
-		uth->uu_sigstk= ss;
-	} else {
-		psp->ps_flags |= SAS_ALTSTACK;
-		psp->ps_sigstk= ss;
+	if (ss.ss_size < OLDMINSIGSTKSZ) {
+		return ENOMEM;
 	}
-	return (0);
+	uth->uu_flag |= UT_ALTSTACK;
+	uth->uu_sigstk = ss;
+	return 0;
 }
 
 int
-kill(struct proc *cp, struct kill_args *uap, __unused register_t *retval)
+kill(proc_t cp, struct kill_args *uap, __unused int32_t *retval)
 {
-	register struct proc *p;
+	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);
+	AUDIT_ARG(pid, uap->pid);
+	AUDIT_ARG(signum, uap->signum);
 
-	if ((u_int)uap->signum >= NSIG)
-		return (EINVAL);
+	if ((u_int)uap->signum >= NSIG) {
+		return EINVAL;
+	}
 	if (uap->pid > 0) {
 		/* kill single process */
-		if ((p = proc_findref(uap->pid)) == NULL) {
+		if ((p = proc_find(uap->pid)) == NULL) {
 			if ((p = pzfind(uap->pid)) != NULL) {
 				/*
-				 * IEEE Std 1003.1-2001: return success
-				 * when killing a zombie.
+				 * POSIX 1003.1-2001 requires returning success when killing a
+				 * zombie; see Rationale for kill(2).
 				 */
-				return (0);
+				return 0;
 			}
-			return (ESRCH);
+			return ESRCH;
 		}
 		AUDIT_ARG(process, p);
 		if (!cansignal(cp, uc, p, uap->signum)) {
-			proc_dropref(p);
-			return(EPERM);
+			proc_rele(p);
+			return EPERM;
 		}
-		if (uap->signum)
+		if (uap->signum) {
 			psignal(p, uap->signum);
-		proc_dropref(p);
-		return (0);
+		}
+		proc_rele(p);
+		return 0;
 	}
 	switch (uap->pid) {
-	case -1:		/* broadcast signal */
-		return (killpg1(cp, uap->signum, 0, 1));
-	case 0:			/* signal own process group */
-		return (killpg1(cp, uap->signum, 0, 0));
-	default:		/* negative explicit process group */
-		return (killpg1(cp, uap->signum, -(uap->pid), 0));
+	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.
- * cp is calling process.
  */
 int
-killpg1(cp, signum, pgid, all)
-	register struct proc *cp;
-	int signum, pgid, all;
+killpg1(proc_t curproc, int signum, int pgid, int all, int posix)
 {
-	register struct proc *p;
-	kauth_cred_t uc = cp->p_ucred;
+	kauth_cred_t uc;
 	struct pgrp *pgrp;
-	int nfound = 0;
-	
+	int error = 0;
+
+	uc = kauth_cred_proc_ref(curproc);
+	struct killpg1_iterargs karg = {
+		.curproc = curproc, .uc = uc, .nfound = 0, .signum = signum
+	};
+
 	if (all) {
-		/* 
-		 * broadcast 
+		/*
+		 * Broadcast to all processes that the user can signal (pid was -1).
 		 */
-		for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) {
-			if (p->p_pid <= 1 || p->p_flag & P_SYSTEM || 
-			    p == cp || !cansignal(cp, uc, p, signum))
-				continue;
-			nfound++;
-			if (signum)
-				psignal(p, signum);
-		}
+		struct killpg1_filtargs kfarg = {
+			.posix = posix, .curproc = curproc
+		};
+		proc_iterate(PROC_ALLPROCLIST | PROC_ZOMBPROCLIST, killpg1_callback,
+		    &karg, killpg1_allfilt, &kfarg);
 	} else {
-		if (pgid == 0)		
-			/* 
-			 * zero pgid means send to my process group.
+		if (pgid == 0) {
+			/*
+			 * Send to current the current process' process group.
 			 */
-			pgrp = cp->p_pgrp;
-		else {
+			pgrp = proc_pgrp(curproc);
+		} else {
 			pgrp = pgfind(pgid);
-			if (pgrp == NULL)
-				return (ESRCH);
-		}
-		for (p = pgrp->pg_members.lh_first; p != 0;
-		     p = p->p_pglist.le_next) {
-			if (p->p_pid <= 1 || p->p_flag & P_SYSTEM ||
-			    p->p_stat == SZOMB ||
-			    !cansignal(cp, uc, p, signum))
-				continue;
-			nfound++;
-			if (signum)
-				psignal(p, signum);
+			if (pgrp == NULL) {
+				error = ESRCH;
+				goto out;
+			}
 		}
+
+		/* PGRP_DROPREF drops the pgrp refernce */
+		pgrp_iterate(pgrp, PGRP_DROPREF, killpg1_callback, &karg,
+		    killpg1_pgrpfilt, NULL);
 	}
-	return (nfound ? 0 : ESRCH);
+	error = (karg.nfound > 0 ? 0 : (posix ? EPERM : ESRCH));
+out:
+	kauth_cred_unref(&uc);
+	return error;
 }
 
 /*
  * Send a signal to a process group.
  */
 void
-gsignal(pgid, signum)
-	int pgid, signum;
+gsignal(int pgid, int signum)
 {
 	struct pgrp *pgrp;
 
-	if (pgid && (pgrp = pgfind(pgid)))
+	if (pgid && (pgrp = pgfind(pgid))) {
 		pgsignal(pgrp, signum, 0);
+		pg_rele(pgrp);
+	}
 }
 
 /*
- * Send a signal to a process group.  If checktty is 1,
+ * Send a signal to a process group.  If checkctty is 1,
  * limit to members which have a controlling terminal.
  */
-void
-pgsignal(pgrp, signum, checkctty)
-	struct pgrp *pgrp;
-	int signum, checkctty;
+
+static int
+pgsignal_filt(proc_t p, void * arg)
 {
-	register struct proc *p;
+	int checkctty = *(int*)arg;
 
-	if (pgrp)
-		for (p = pgrp->pg_members.lh_first; p != 0;
-		     p = p->p_pglist.le_next)
-			if (checkctty == 0 || p->p_flag & P_CONTROLT)
-				psignal(p, signum);
+	if ((checkctty == 0) || p->p_flag & P_CONTROLT) {
+		return 1;
+	} else {
+		return 0;
+	}
 }
 
-/*
- * Send signal to a backgrounded process blocked due to tty access
- * In FreeBSD, the backgrounded process wakes up every second and
- * discovers whether it is foregounded or not. In our case, we block 
- * the thread in tsleep as we want to avoid storm of processes as well 
- * as the suspend is only at AST level
- */
-void
-tty_pgsignal(pgrp, signum)
-	struct pgrp *pgrp;
-	int signum;
+
+static int
+pgsignal_callback(proc_t p, void * arg)
 {
-	register struct proc *p;
+	int  signum = *(int*)arg;
+
+	psignal(p, signum);
+	return PROC_RETURNED;
+}
+
 
-	if (pgrp)
-		for (p = pgrp->pg_members.lh_first; p != 0;
-		     p = p->p_pglist.le_next)
-			if ((p->p_flag & P_TTYSLEEP) && (p->p_flag & P_CONTROLT))
-				psignal(p, signum);
+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, u_long code)
+threadsignal(thread_t sig_actthread, int signum, mach_exception_code_t code, boolean_t set_exitreason)
 {
-	register struct uthread *uth;
-	register struct task * sig_task;
-	register struct proc *p ;
+	struct uthread *uth;
+	struct task * sig_task;
+	proc_t p;
 	int mask;
 
-	if ((u_int)signum >= NSIG || signum == 0)
+	if ((u_int)signum >= NSIG || signum == 0) {
 		return;
+	}
 
 	mask = sigmask(signum);
-	if ((mask & threadmask) == 0)
+	if ((mask & threadmask) == 0) {
 		return;
+	}
 	sig_task = get_threadtask(sig_actthread);
-	p = (struct proc *)(get_bsdtask_info(sig_task));
+	p = (proc_t)(get_bsdtask_info(sig_task));
 
 	uth = get_bsdthread_info(sig_actthread);
-	if (uth && (uth->uu_flag & UT_VFORK))
+	if (uth->uu_flag & UT_VFORK) {
 		p = uth->uu_proc;
+	}
 
-	if (!(p->p_flag & P_TRACED) && (p->p_sigignore & mask))
+	proc_lock(p);
+	if (!(p->p_lflag & P_LTRACED) && (p->p_sigignore & mask)) {
+		proc_unlock(p);
 		return;
+	}
 
 	uth->uu_siglist |= mask;
-	p->p_siglist |= mask;	/* just for lame ones looking here */
 	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);
 }
 
- 
-void
-psignal(p, signum)
-	register struct proc *p;
-	register int signum;
+/* Called with proc locked */
+static void
+set_thread_extra_flags(struct uthread *uth, os_reason_t reason)
 {
-	psignal_lock(p, signum, 1);
+	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
-psignal_vfork(struct proc *p, task_t new_task, thread_t thr_act, int signum)
+set_thread_exit_reason(void *th, void *reason, boolean_t proc_locked)
 {
-	register int prop;
-	register sig_t action;
-	int mask;
-	struct uthread *uth;
-
-	if ((u_int)signum >= NSIG || signum == 0)
-		panic("psignal signal number");
-	mask = sigmask(signum);
-	prop = sigprop[signum];
+	struct uthread *targ_uth = get_bsdthread_info(th);
+	struct task *targ_task = NULL;
+	proc_t targ_proc = NULL;
 
-#if SIGNAL_DEBUG
-        if(rdebug_proc && (p == rdebug_proc)) {
-                ram_printf(3);
-        }
-#endif /* SIGNAL_DEBUG */
+	os_reason_t exit_reason = (os_reason_t)reason;
 
-	if ((new_task == TASK_NULL) || (thr_act == (thread_t)NULL)  || is_kerneltask(new_task))
+	if (exit_reason == OS_REASON_NULL) {
 		return;
+	}
 
+	if (!proc_locked) {
+		targ_task = get_threadtask(th);
+		targ_proc = (proc_t)(get_bsdtask_info(targ_task));
 
-	uth = get_bsdthread_info(thr_act);
-	signal_lock(p);
+		proc_lock(targ_proc);
+	}
 
-	/*
-	 * proc is traced, always give parent a chance.
-	 */
-	action = SIG_DFL;
+	set_thread_extra_flags(targ_uth, exit_reason);
 
-	if (p->p_nice > NZERO && action == SIG_DFL && (prop & SA_KILL) &&
-		(p->p_flag & P_TRACED) == 0)
-		p->p_nice = NZERO;
+	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 (prop & SA_CONT) {
-		p->p_siglist &= ~stopsigmask;
-		uth->uu_siglist &= ~stopsigmask;
+	if (!proc_locked) {
+		assert(targ_proc != NULL);
+		proc_unlock(targ_proc);
 	}
+}
 
-	if (prop & SA_STOP) {
-		/*
-		 * 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.
-		 */
-		if (prop & SA_TTYSTOP && p->p_pgrp->pg_jobc == 0 &&
-			action == SIG_DFL)
-			goto psigout;
-		uth->uu_siglist &= ~contsigmask;
-		p->p_siglist &= ~contsigmask;
-	}
-	uth->uu_siglist |= mask;
-	p->p_siglist |= mask;   /* just for lame ones looking here */
-	
-	/* Deliver signal to the activation passed in */
-	act_set_astbsd(thr_act);
+/*
+ * 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;
 
-	/*
-	 *	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.
-	 */
-	if ((signum == SIGKILL) && (p->p_nice > NZERO)) {
-		p->p_nice = NZERO;
-	}
+	*thr = THREAD_NULL;
 
-	/*
-	 *	This 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 (p->p_flag & P_TRACED) {
-		if (p->p_stat != SSTOP)
-			goto run;
-		else
-			goto psigout;
-	}
-run:
-	/*
-	 * If we're being traced (possibly because someone attached us
-	 * while we were stopped), check for a signal from the debugger.
-	 */
-	if (p->p_stat == SSTOP) {
-		if ((p->p_flag & P_TRACED) != 0 && p->p_xstat != 0) {
-			uth->uu_siglist |= sigmask(p->p_xstat); 
-			p->p_siglist |= mask;   /* just for lame ones looking here */
+	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;
 		}
 	}
 
-	/*
-	 * setrunnable(p) in BSD
-	 */
-	p->p_stat = SRUN;
+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;
+	}
 
-psigout:
-	signal_unlock(p);
+	return KERN_FAILURE;
 }
 
-static thread_t
-get_signalthread(struct proc *p, int signum)
+static os_reason_t
+build_signal_reason(int signum, const char *procname)
 {
-	struct uthread *uth;
-	thread_t thr_act;
-	sigset_t mask = sigmask(signum);
-	thread_t sig_thread_act;
-	struct task * sig_task = p->task;
-	kern_return_t kret;
-	
-	if ((p->p_flag & P_INVFORK) && p->p_vforkact) {
-		sig_thread_act = p->p_vforkact;	
-		kret = check_actforsig(sig_task, sig_thread_act, 1);
-		if (kret == KERN_SUCCESS) 
-			return(sig_thread_act);
-		else
-			return(THREAD_NULL);
-	} 
+	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;
 
-	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))) {
-			if (check_actforsig(p->task, uth->uu_act, 1) == KERN_SUCCESS)
-				return(uth->uu_act);
-		}
+	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 (get_signalact(p->task, &thr_act, 1) == KERN_SUCCESS) {
-		return(thr_act);
+
+	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(THREAD_NULL);
+	return signal_reason;
 }
 
 /*
@@ -1487,6 +2202,9 @@ get_signalthread(struct proc *p, int signum)
  * 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.
@@ -1495,456 +2213,228 @@ get_signalthread(struct proc *p, int signum)
  *
  * Other ignored signals are discarded immediately.
  */
-void
-psignal_lock(p, signum, withlock)
-	register struct proc *p;
-	register int signum;
-	register int withlock;
-{
-	register int prop;
-	register sig_t action;
-	thread_t	sig_thread_act;
-	register task_t		sig_task;
-	int mask;
-	struct uthread *uth;
-	boolean_t funnel_state = FALSE;
-	int sw_funnel = 0;
+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);
+	}
 
-	if ((u_int)signum >= NSIG || signum == 0)
-		panic("psignal signal number");
 	mask = sigmask(signum);
 	prop = sigprop[signum];
 
 #if SIGNAL_DEBUG
-        if(rdebug_proc && (p == rdebug_proc)) {
-                ram_printf(3);
-        }
+	if (rdebug_proc && (p != PROC_NULL) && (p == rdebug_proc)) {
+		ram_printf(3);
+	}
 #endif /* SIGNAL_DEBUG */
 
-	if (thread_funnel_get() == (funnel_t *)0) {
-		sw_funnel = 1;
-		funnel_state = thread_funnel_set(kernel_flock, TRUE);
+	/* 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 (((sig_task = p->task) == TASK_NULL)  || is_kerneltask(sig_task)) {
-		if (sw_funnel)
-			thread_funnel_set(kernel_flock, funnel_state);
-		return;
+	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;
 	}
 
-        KNOTE(&p->p_klist, NOTE_SIGNAL | signum);
+	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.
+	 * 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(p->p_flag, P_REBOOT)) {
-		if (sw_funnel)
-			thread_funnel_set(kernel_flock, funnel_state);
+	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 (withlock)
-		signal_lock(p);
+	if ((flavor & (PSIG_VFORK | PSIG_THREAD)) == 0) {
+		proc_knote(sig_proc, NOTE_SIGNAL | signum);
+	}
 
-	/*
-	 *	Deliver the 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.  We have
-	 *	an implicit reference to the current thread, but need
-	 *	an explicit one otherwise.  The thread reference keeps
-	 *	the corresponding task data structures around too.  This
-	 *	reference is released by thread_deallocate.
-	 */
-	
-	if (((p->p_flag & P_TRACED) == 0) && (p->p_sigignore & mask))
-		goto psigout;
-
-	/* If successful return with ast set */
-	sig_thread_act = get_signalthread(p, signum);
-
-	if (sig_thread_act == THREAD_NULL) {
-		/* XXXX FIXME
-		 * if it is sigkill, may be we should
-	 	 * inject a thread to terminate
-	 	 */
-#if SIGNAL_DEBUG
-       		ram_printf(1);
-#endif /* SIGNAL_DEBUG */
-		goto psigout;
+	if ((flavor & PSIG_LOCKED) == 0) {
+		proc_signalstart(sig_proc, 0);
 	}
 
-	uth = get_bsdthread_info(sig_thread_act);
+	/* 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;
+	}
 
 	/*
-	 * If proc is traced, always give parent a chance.
+	 * 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?
 	 */
-	if (p->p_flag & P_TRACED)
-		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 (p->p_sigignore & mask)
-			goto psigout;
-		/* sigwait takes precedence */
-		if (uth->uu_sigwait & mask)
-			action = KERN_SIG_WAIT;
-		else if (uth->uu_sigmask & mask)
-			action = KERN_SIG_HOLD;
-		else if (p->p_sigcatch & mask)
-			action = KERN_SIG_CATCH;
-		else
-			action = SIG_DFL;
-	}
+	proc_lock(sig_proc);
 
-	if (p->p_nice > NZERO && action == SIG_DFL && (prop & SA_KILL) &&
-		(p->p_flag & P_TRACED) == 0)
-		p->p_nice = NZERO;
-
-	if (prop & SA_CONT) {
-		uth->uu_siglist &= ~stopsigmask;
-		p->p_siglist &= ~stopsigmask;
+	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 (prop & SA_STOP) {
-		/*
-		 * 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.
-		 */
-		if (prop & SA_TTYSTOP && p->p_pgrp->pg_jobc == 0 &&
-			action == SIG_DFL)
-			goto psigout;
-		uth->uu_siglist &= ~contsigmask;
-		p->p_siglist &= ~contsigmask;
+	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->uu_siglist |= mask;
-	p->p_siglist |= mask;   /* just for lame ones looking here */
 
-	
-	/*
-	 * Defer further processing for signals which are held,
-	 * except that stopped processes must be continued by SIGCONT.
-	 */
-	if (action == KERN_SIG_HOLD && ((prop & SA_CONT) == 0 || p->p_stat != SSTOP)) {
-		goto psigout;
-	}
-	/*
-	 *	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.
-	 */
-	if ((signum == SIGKILL) && (p->p_nice > NZERO)) {
-		p->p_nice = NZERO;
-	}
+	uth = get_bsdthread_info(sig_thread);
 
 	/*
-	 *	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 proc is traced, always give parent a chance.
 	 */
-	if (p->p_flag & P_TRACED) {
-	   	if (p->p_stat != SSTOP)
-			goto run;
-		else
-			goto psigout;
-	}
-
-	if (action == KERN_SIG_WAIT) {
-		uth->uu_sigwait = mask;
-		uth->uu_siglist &= ~mask;
-		p->p_siglist &= ~mask;
-		wakeup(&uth->uu_sigwait);
-		/* if it is SIGCONT resume whole process */
-		if (prop & SA_CONT) {
-			p->p_flag |= P_CONTINUED;
-			(void) task_resume(sig_task);
-		}
-		goto psigout;
-	}
 
-	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) {
-			if (p->p_flag & P_TTYSLEEP) {
-				p->p_flag &= ~P_TTYSLEEP;
-				wakeup(&p->p_siglist);
-			} else {
-				p->p_flag |= P_CONTINUED;
-				(void) task_resume(sig_task);
-			}
-			p->p_stat = SRUN;
-		} else if (p->p_stat == SSTOP)
-			goto psigout;
-		goto run;
-	} else {
-		/*	Default action - varies */
-		if (mask & stopsigmask) {
-			/*
-			 * 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) && p->p_pptr == initproc) {
-				psignal_lock(p, SIGKILL, 0);
-				uth->uu_siglist &= ~mask;
-				p->p_siglist &= ~mask;
-				goto psigout;
-			}
-                        
+	if ((flavor & PSIG_VFORK) == 0) {
+		if (sig_proc->p_lflag & P_LTRACED) {
+			action = SIG_DFL;
+		} else {
 			/*
-			 *	Stop the task
-			 *	if task hasn't already been stopped by
-			 *	a signal.
+			 * 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.)
 			 */
-			uth->uu_siglist &= ~mask;
-			p->p_siglist &= ~mask;
-			if (p->p_stat != SSTOP) {
-				p->p_xstat = signum;
-				stop(p);
-				if ((p->p_pptr->p_flag & P_NOCLDSTOP) == 0) {
-					struct proc *pp = p->p_pptr;
-
-					pp->si_pid = p->p_pid;
-					pp->si_status = p->p_xstat;
-					pp->si_code = CLD_STOPPED;
-					pp->si_uid = p->p_ucred->cr_ruid;
-					psignal(pp, SIGCHLD);
-				}
+			if (sig_proc->p_sigignore & mask) {
+				goto sigout_locked;
 			}
-			goto psigout;
-		}
 
-		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'
-			 */
-			p->p_stat = SRUN;
-
-			thread_abort(sig_thread_act);
-
-			goto psigout;
-
-		case SIGCONT:
-			/*
-			 * Let the process run.  If it's sleeping on an
-			 * event, it remains so.
-			 */
-			if (p->p_flag & P_TTYSLEEP) {
-				p->p_flag &= ~P_TTYSLEEP;
-				wakeup(&p->p_siglist);
+			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 {
-				p->p_flag |= P_CONTINUED;
-				(void) task_resume(sig_task);
+				action = SIG_DFL;
 			}
-			uth->uu_siglist &= ~mask;
-			p->p_siglist &= ~mask;
-			p->p_stat = SRUN;
-
-			goto psigout;
-
-		default:
-			/*
-			 * All other signals wake up the process, but don't
-			 * resume it.
-			 */
-			if (p->p_stat == SSTOP)
-				goto psigout;
-			goto run;
 		}
 	}
-	/*NOTREACHED*/
-run:
-	/*
-	 * If we're being traced (possibly because someone attached us
-	 * while we were stopped), check for a signal from the debugger.
-	 */
-	if (p->p_stat == SSTOP) {
-		if ((p->p_flag & P_TRACED) != 0 && p->p_xstat != 0)
-			uth->uu_siglist |= sigmask(p->p_xstat); 
-	} else {
-		/*
-	 	 * setrunnable(p) in BSD and
-	 	 * Wake up the thread if it is interruptible.
-	 	 */
-		p->p_stat = SRUN;
-		thread_abort_safely(sig_thread_act);
-	}
-psigout:
-	if (withlock) 
-		signal_unlock(p);
-	if (sw_funnel)
-			thread_funnel_set(kernel_flock, funnel_state);
-}
-
-
-/* psignal_lock(p, signum, withlock ) */
-void
-psignal_uthread(thr_act, signum)
-	thread_t thr_act;
-	int signum;
-{
-	struct proc *p;
-	register int prop;
-	register sig_t action;
-	thread_t	sig_thread_act;
-	register task_t		sig_task;
-	int mask;
-	struct uthread *uth;
-	kern_return_t kret;
-	int error = 0;
-
-	p = (struct proc *)get_bsdtask_info(get_threadtask(thr_act));
-	if ((u_int)signum >= NSIG || signum == 0)
-		panic("Invalid signal number in psignal_uthread"); 
-	mask = sigmask(signum);
-	prop = sigprop[signum];
-
-#if SIGNAL_DEBUG
-        if(rdebug_proc && (p == rdebug_proc)) {
-                ram_printf(3);
-        }
-#endif /* SIGNAL_DEBUG */
-
-	/*
-	 *	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 (((sig_task = p->task) == TASK_NULL)  || is_kerneltask(sig_task)) {
-		return;
-	}
-
-	sig_thread_act = thr_act;
-	/*
-	 * 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.
-	 */
-	if (ISSET(p->p_flag, P_REBOOT)) {
-		return;
-	}
-
-	signal_lock(p);
-
-	/*
-	 *	Deliver the 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.  We have
-	 *	an implicit reference to the current thread, but need
-	 *	an explicit one otherwise.  The thread reference keeps
-	 *	the corresponding task data structures around too.  This
-	 *	reference is released by thread_deallocate.
-	 */
-	
-	if (((p->p_flag & P_TRACED) == 0) && (p->p_sigignore & mask))
-		goto puthout;
-
-	kret = check_actforsig(sig_task, sig_thread_act, 1);
-
-	if (kret != KERN_SUCCESS) {
-		error = EINVAL;
-		goto puthout;
-	}
-
 
-	uth = get_bsdthread_info(sig_thread_act);
-
-	/*
-	 * If proc is traced, always give parent a chance.
-	 */
-	if (p->p_flag & P_TRACED)
-		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 (p->p_sigignore & mask)
-			goto puthout;
-		/* sigwait takes precedence */
-		if (uth->uu_sigwait & mask)
-			action = KERN_SIG_WAIT;
-		else if (uth->uu_sigmask & mask)
-			action = KERN_SIG_HOLD;
-		else if (p->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 (p->p_nice > NZERO && action == SIG_DFL && (prop & SA_KILL) &&
-		(p->p_flag & P_TRACED) == 0)
-		p->p_nice = NZERO;
-
 	if (prop & SA_CONT) {
 		uth->uu_siglist &= ~stopsigmask;
-		p->p_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.
 		 */
-		if (prop & SA_TTYSTOP && p->p_pgrp->pg_jobc == 0 &&
-			action == SIG_DFL)
-			goto puthout;
+		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;
-		p->p_siglist &= ~contsigmask;
 	}
+
 	uth->uu_siglist |= mask;
-	p->p_siglist |= mask;   /* just for lame ones looking here */
 
 	/*
 	 * Defer further processing for signals which are held,
 	 * except that stopped processes must be continued by SIGCONT.
 	 */
-	if (action == KERN_SIG_HOLD && ((prop & SA_CONT) == 0 || p->p_stat != SSTOP))
-		goto puthout;
-		
+	/* 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) && (p->p_nice > NZERO)) {
-		p->p_nice = NZERO;
+	if ((signum == SIGKILL) && (sig_proc->p_nice > NZERO)) {
+		sig_proc->p_nice = NZERO;
 	}
 
 	/*
@@ -1952,24 +2442,43 @@ psignal_uthread(thr_act, signum)
 	 *	stopped) so that it can discover the signal in
 	 *	issig() and stop for the parent.
 	 */
-	if (p->p_flag & P_TRACED) {
-	   	if (p->p_stat != SSTOP)
-			goto psurun;
-		else
-			goto puthout;
+	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;
-		p->p_siglist &= ~mask;
 		wakeup(&uth->uu_sigwait);
 		/* if it is SIGCONT resume whole process */
 		if (prop & SA_CONT) {
-			p->p_flag |= P_CONTINUED;
-			(void) task_resume(sig_task);
+			OSBitOrAtomic(P_CONTINUED, &sig_proc->p_flag);
+			sig_proc->p_contproc = current_proc()->p_pid;
+			(void) task_resume_internal(sig_task);
 		}
-		goto puthout;
+		goto sigout_locked;
 	}
 
 	if (action != SIG_DFL) {
@@ -1979,13 +2488,38 @@ psignal_uthread(thr_act, signum)
 		 *	(except for SIGCONT).
 		 */
 		if (prop & SA_CONT) {
-			p->p_flag |= P_CONTINUED;
-			(void) task_resume(sig_task);
+			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 psurun;
+
+		goto runlocked;
 	} else {
 		/*	Default action - varies */
 		if (mask & stopsigmask) {
+			assert(signal_reason == NULL);
 			/*
 			 * These are the signals which by default
 			 * stop a process.
@@ -1993,42 +2527,70 @@ psignal_uthread(thr_act, signum)
 			 * Don't clog system with children of init
 			 * stopped from the keyboard.
 			 */
-			if (!(prop & SA_STOP) && p->p_pptr == initproc) {
-				psignal_lock(p, SIGKILL, 0);
+			if (!(prop & SA_STOP) && sig_proc->p_pptr == initproc) {
 				uth->uu_siglist &= ~mask;
-				p->p_siglist &= ~mask;
-				goto puthout;
+				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;
-			p->p_siglist &= ~mask;
-			if (p->p_stat != SSTOP) {
-				p->p_xstat = signum;
-				if ((p->p_pptr->p_flag & P_NOCLDSTOP) == 0) {
-					struct proc *pp = p->p_pptr;
-
-					pp->si_pid = p->p_pid;
-					pp->si_status = p->p_xstat;
+			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 = p->p_ucred->cr_ruid;
+					pp->si_uid = r_uid;
+					proc_unlock(sig_proc);
+
 					psignal(pp, SIGCHLD);
 				}
-				stop(p);
+				if (pp != PROC_NULL) {
+					proc_parentdropref(pp, 0);
+				}
+
+				goto sigout_unlocked;
 			}
-			goto puthout;
+
+			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.
-			 */
+		/*
+		 * Signals ignored by default have been dealt
+		 * with already, since their bits are on in
+		 * p_sigignore.
+		 */
 
 		case SIGKILL:
 			/*
@@ -2038,101 +2600,205 @@ psignal_uthread(thr_act, signum)
 			/*
 			 *	Process will be running after 'run'
 			 */
-			p->p_stat = SRUN;
+			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);
+				}
 
-			thread_abort(sig_thread_act);
+				os_reason_ref(signal_reason);
+				set_thread_exit_reason(sig_thread, signal_reason, TRUE);
+			}
 
-			goto puthout;
+			goto sigout_locked;
 
 		case SIGCONT:
 			/*
 			 * Let the process run.  If it's sleeping on an
 			 * event, it remains so.
 			 */
-			if (p->p_flag & P_TTYSLEEP) {
-				p->p_flag &= ~P_TTYSLEEP;
-				wakeup(&p->p_siglist);
-			} else {
-				p->p_flag |= P_CONTINUED;
-				(void) task_resume(sig_task);
+			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;
-			p->p_siglist &= ~mask;
-			p->p_stat = SRUN;
-			goto puthout;
+			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.
 			 */
-			goto psurun;
+			if (sig_proc->p_stat == SSTOP) {
+				goto sigout_locked;
+			}
+			goto runlocked;
 		}
 	}
 	/*NOTREACHED*/
-psurun:
+
+runlocked:
 	/*
 	 * If we're being traced (possibly because someone attached us
 	 * while we were stopped), check for a signal from the debugger.
 	 */
-	if (p->p_stat == SSTOP) {
-		if ((p->p_flag & P_TRACED) != 0 && p->p_xstat != 0) {
-			uth->uu_siglist |= sigmask(p->p_xstat); 
-			p->p_siglist |= sigmask(p->p_xstat); 
+	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.
-	 	 */
-		p->p_stat = SRUN;
-		thread_abort_safely(sig_thread_act);
+		 * 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);
 	}
 
-puthout:
-		signal_unlock(p);
+	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);
+}
 
-__inline__ void
-sig_lock_to_exit(struct proc *p)
+void
+psignal_with_reason(proc_t p, int signum, struct os_reason *signal_reason)
 {
-	thread_t	self = current_thread();
+	psignal_internal(p, NULL, NULL, 0, signum, signal_reason);
+}
 
-	p->exit_thread = self;
-	(void) task_suspend(p->task);
+void
+psignal_sigkill_with_reason(struct proc *p, struct os_reason *signal_reason)
+{
+	psignal_internal(p, NULL, NULL, 0, SIGKILL, signal_reason);
 }
 
-__inline__ int
-sig_try_locked(struct proc *p)
+void
+psignal_locked(proc_t p, int signum)
 {
-	thread_t	self = current_thread();
+	psignal_internal(p, NULL, NULL, PSIG_LOCKED, signum, NULL);
+}
 
-	while (p->sigwait || p->exit_thread) {
-		if (p->exit_thread) {
-			if (p->exit_thread != self) {
-				/*
-				 * Already exiting - no signals.
-				 */
-				thread_abort(self);
-			}
-			return(0);
-		}
-		if(assert_wait_possible()) {
-			assert_wait((caddr_t)&p->sigwait_thread, 
-					(THREAD_INTERRUPTIBLE));
-		}
-		signal_unlock(p);
-		thread_block(THREAD_CONTINUE_NULL);
-		signal_lock(p);
-		if (thread_should_abort(self)) {
-			/*
-			 * Terminate request - clean up.
-			 */
-			return -1;
-		}
-	}
-	return 1;
+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);
 }
 
 /*
@@ -2148,157 +2814,169 @@ sig_try_locked(struct proc *p)
  *		postsig(signum);
  */
 int
-issignal(p)
-	register struct proc *p;
+issignal_locked(proc_t p)
 {
-	register int signum, mask, prop, sigbits;
+	int signum, mask, prop, sigbits;
 	thread_t cur_act;
 	struct uthread * ut;
-	struct proc *pp;
+	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);
-        }
+	if (rdebug_proc && (p == rdebug_proc)) {
+		ram_printf(3);
+	}
 #endif /* SIGNAL_DEBUG */
-	signal_lock(p);
 
 	/*
 	 * Try to grab the signal lock.
 	 */
 	if (sig_try_locked(p) <= 0) {
-		signal_unlock(p);
-		return (0);
+		return 0;
 	}
 
+	proc_signalstart(p, 1);
+
 	ut = get_bsdthread_info(cur_act);
-	for(;;) {
-		sigbits = ut->uu_siglist  & ~ut->uu_sigmask;
+	for (;;) {
+		sigbits = ut->uu_siglist & ~ut->uu_sigmask;
 
-		if (p->p_flag & P_PPWAIT)
+		if (p->p_lflag & P_LPPWAIT) {
 			sigbits &= ~stopsigmask;
-		if (sigbits == 0) {	 	/* no signal to send */
-			signal_unlock(p);
-			return (0);
 		}
-		signum = ffs((long)sigbits);
+		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_TRACED was on when they were posted.
+		 * only if P_LTRACED was on when they were posted.
 		 */
-		if (mask & p->p_sigignore && (p->p_flag & P_TRACED) == 0) {
-			ut->uu_siglist &= ~mask;		/* take the signal! */
-			p->p_siglist &= ~mask;		/* take the signal! */
+		if (mask & p->p_sigignore && (p->p_lflag & P_LTRACED) == 0) {
+			ut->uu_siglist &= ~mask;
 			continue;
 		}
-		if (p->p_flag & P_TRACED && (p->p_flag & P_PPWAIT) == 0)  {
-			register task_t	task;
+
+		if (p->p_lflag & P_LTRACED && (p->p_lflag & P_LPPWAIT) == 0) {
 			/*
-			 * If traced, always stop, and stay
-			 * stopped until released by the debugger.
+			 * If traced, deliver the signal to the debugger, and wait to be
+			 * released.
 			 */
-			/* ptrace debugging */
+			task_t  task;
 			p->p_xstat = signum;
-			pp = p->p_pptr;
-			if (p->p_flag & P_SIGEXC) {
+
+			if (p->p_lflag & P_LSIGEXC) {
 				p->sigwait = TRUE;
 				p->sigwait_thread = cur_act;
 				p->p_stat = SSTOP;
-				p->p_flag &= ~(P_WAITED|P_CONTINUED);
-				ut->uu_siglist &= ~mask;	/* clear the old signal */
-				p->p_siglist &= ~mask;	/* clear the old signal */
-				signal_unlock(p);
+				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);
-				signal_lock(p);
+				proc_lock(p);
+				proc_signalstart(p, 1);
 			} else {
-//				panic("Unsupportef gdb option \n");;
-				pp->si_pid = p->p_pid;
-				pp->si_status = p->p_xstat;
-				pp->si_code = CLD_TRAPPED;
-				pp->si_uid = p->p_ucred->cr_ruid;
-				psignal(pp, SIGCHLD);
+				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.
-			 	*	XXX Inline the task_suspend because we
-			 	*	XXX have to diddle Unix state in the
-			 	*	XXX middle of it.
-			 	*/
+				 *	XXX Have to really stop for debuggers;
+				 *	XXX stop() doesn't do the right thing.
+				 */
 				task = p->task;
-				task_hold(task);
+				task_suspend_internal(task);
+
+				proc_lock(p);
 				p->sigwait = TRUE;
 				p->sigwait_thread = cur_act;
 				p->p_stat = SSTOP;
-				p->p_flag &= ~(P_WAITED|P_CONTINUED);
-				ut->uu_siglist &= ~mask;	/* clear the old signal */
-				p->p_siglist &= ~mask;	/* clear the old signal */
+				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();
+				}
 
-				wakeup((caddr_t)p->p_pptr);
-				signal_unlock(p);
 				assert_wait((caddr_t)&p->sigwait, (THREAD_INTERRUPTIBLE));
 				thread_block(THREAD_CONTINUE_NULL);
-				signal_lock(p);
+				proc_lock(p);
+				proc_signalstart(p, 1);
 			}
 
 			p->sigwait = FALSE;
 			p->sigwait_thread = NULL;
 			wakeup((caddr_t)&p->sigwait_thread);
 
-			/*
-			 * This code is to detect when gdb is killed
-			 * even as the traced program is attached.
-			 * pgsignal would get the SIGKILL to traced program
-			 * That's what we are trying to see (I hope)
-			 */
-			if (ut->uu_siglist & sigmask(SIGKILL)) {
+			if (signum == SIGKILL || ut->uu_siglist & sigmask(SIGKILL)) {
 				/*
-				 * Wait event may still be outstanding;
-				 * clear it, since sig_lock_to_exit will
-				 * wait.
+				 * 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.
 				 */
-				clear_wait(current_thread(), THREAD_INTERRUPTED);
-				sig_lock_to_exit(p);
-				/*
-			 	* Since this thread will be resumed
-			 	* to allow the current syscall to
-			 	* be completed, must save u_qsave
-			 	* before calling exit().  (Since exit()
-			 	* calls closef() which can trash u_qsave.)
-			 	*/
-				signal_unlock(p);
-				exit1(p,signum, (int *)NULL);
-				return(0);
+				signum = SIGKILL;
+				goto deliver_sig;
 			}
 
-			/*
-			 *	We may have to quit
-			 */
+			/* We may have to quit. */
 			if (thread_should_abort(current_thread())) {
-				signal_unlock(p);
-				return(0);
+				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)
+			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;
-			p->p_siglist |= mask;   /* just for lame ones looking here */
-			if (ut->uu_sigmask & mask)
+			if (ut->uu_sigmask & mask) {
 				continue;
+			}
 		}
 
 		/*
@@ -2308,23 +2986,7 @@ issignal(p)
 		 */
 
 		switch ((long)p->p_sigacts->ps_sigact[signum]) {
-		
 		case (long)SIG_DFL:
-			/*
-			 * Don't take default actions on system processes.
-			 */
-			if (p->p_pptr->p_pid == 0) {
-#if DIAGNOSTIC
-				/*
-				 * Are you sure you want to ignore SIGSEGV
-				 * in init? XXX
-				 */
-				printf("Process (pid %d) got signal %d\n",
-					p->p_pid, signum);
-#endif
-				break; 				/* == ignore */
-			}
-			
 			/*
 			 * If there is a pending stop signal to process
 			 * with default action, stop here,
@@ -2333,36 +2995,56 @@ issignal(p)
 			 * process group, ignore tty stop signals.
 			 */
 			if (prop & SA_STOP) {
-				if (p->p_flag & P_TRACED ||
-					(p->p_pgrp->pg_jobc == 0 &&
-					prop & SA_TTYSTOP))
-					break;	/* == ignore */
+				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;
-					stop(p);
-					if ((p->p_pptr->p_flag & P_NOCLDSTOP) == 0) {
-						pp = p->p_pptr;
+					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 = p->p_xstat;
+						pp->si_status = WEXITSTATUS(p->p_xstat);
 						pp->si_code = CLD_STOPPED;
-						pp->si_uid = p->p_ucred->cr_ruid;
+						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 */
+				break; /* ignore signal */
 			} else {
-				ut->uu_siglist &= ~mask;	/* take the signal! */
-				p->p_siglist &= ~mask;	/* take the signal! */
-				signal_unlock(p);
-				return (signum);
+				goto deliver_sig;
 			}
-			/*NOTREACHED*/
 
 		case (long)SIG_IGN:
 			/*
@@ -2371,76 +3053,78 @@ issignal(p)
 			 * than SIGCONT, unless process is traced.
 			 */
 			if ((prop & SA_CONT) == 0 &&
-				(p->p_flag & P_TRACED) == 0)
+			    (p->p_lflag & P_LTRACED) == 0) {
 				printf("issignal\n");
-			break;		/* == ignore */
+			}
+			break; /* ignore signal */
 
 		default:
-			/*
-			 * This signal has an action, let
-			 * postsig() process it.
-			 */
-			ut->uu_siglist &= ~mask;		/* take the signal! */
-			p->p_siglist &= ~mask;		/* take the signal! */
-			signal_unlock(p);
-			return (signum);
-		}
-		ut->uu_siglist &= ~mask;		/* take the signal! */
-		p->p_siglist &= ~mask;		/* take the signal! */
+			/* 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(p)
-    register struct proc *p;
+CURSIG(proc_t p)
 {
-	register int signum, mask, prop, sigbits;
+	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 == 0) {
+		return 0;
+	}
 
-	if (((ut->uu_siglist & ~ut->uu_sigmask) == 0) && ((p->p_flag & P_TRACED) == 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_flag & P_PPWAIT)
+	for (;;) {
+		if (p->p_lflag & P_LPPWAIT) {
 			sigbits &= ~stopsigmask;
-		if (sigbits == 0) {	 	/* no signal to send */
-			return (retnum);
+		}
+		if (sigbits == 0) {             /* no signal to send */
+			return retnum;
 		}
 
-		signum = ffs((long)sigbits);
+		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_TRACED was on when they were posted.
+		 * only if P_LTRACED was on when they were posted.
 		 */
-		if (mask & p->p_sigignore && (p->p_flag & P_TRACED) == 0) {
+		if (mask & p->p_sigignore && (p->p_lflag & P_LTRACED) == 0) {
 			continue;
 		}
-		if (p->p_flag & P_TRACED && (p->p_flag & P_PPWAIT) == 0) {
-			/*
-			 * Put the new signal into p_siglist.  If the
-			 * signal is being masked, look for other signals.
-			 */
-			mask = sigmask(signum);
-			if (ut->uu_sigmask & mask)
-				continue;
-			return(signum);
+
+		if (p->p_lflag & P_LTRACED && (p->p_lflag & P_LPPWAIT) == 0) {
+			return signum;
 		}
 
 		/*
@@ -2450,23 +3134,7 @@ CURSIG(p)
 		 */
 
 		switch ((long)p->p_sigacts->ps_sigact[signum]) {
-		
 		case (long)SIG_DFL:
-			/*
-			 * Don't take default actions on system processes.
-			 */
-			if (p->p_pptr->p_pid == 0) {
-#if DIAGNOSTIC
-				/*
-				 * Are you sure you want to ignore SIGSEGV
-				 * in init? XXX
-				 */
-				printf("Process (pid %d) got signal %d\n",
-					p->p_pid, signum);
-#endif
-				break; 				/* == ignore */
-			}
-			
 			/*
 			 * If there is a pending stop signal to process
 			 * with default action, stop here,
@@ -2475,10 +3143,17 @@ CURSIG(p)
 			 * process group, ignore tty stop signals.
 			 */
 			if (prop & SA_STOP) {
-				if (p->p_flag & P_TRACED ||
-					(p->p_pgrp->pg_jobc == 0 &&
-					prop & SA_TTYSTOP))
-					break;	/* == ignore */
+				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) {
@@ -2486,11 +3161,11 @@ CURSIG(p)
 				 * Except for SIGCONT, shouldn't get here.
 				 * Default action is to ignore; drop it.
 				 */
-				break;		/* == ignore */
+				break;          /* == ignore */
 			} else {
-				return (signum);
+				return signum;
 			}
-			/*NOTREACHED*/
+		/*NOTREACHED*/
 
 		case (long)SIG_IGN:
 			/*
@@ -2499,18 +3174,18 @@ CURSIG(p)
 			 * than SIGCONT, unless process is traced.
 			 */
 			if ((prop & SA_CONT) == 0 &&
-				(p->p_flag & P_TRACED) == 0)
+			    (p->p_lflag & P_LTRACED) == 0) {
 				printf("issignal\n");
-			break;		/* == ignore */
+			}
+			break;          /* == ignore */
 
 		default:
 			/*
 			 * This signal has an action, let
 			 * postsig() process it.
 			 */
-			return (signum);
+			return signum;
 		}
-		sigbits &= ~mask;		/* take the signal! */
 	}
 	/* NOTREACHED */
 }
@@ -2520,15 +3195,16 @@ CURSIG(p)
  * via wakeup.  Signals are handled elsewhere.  The process must not be
  * on the run queue.
  */
-void
-stop(p)
-	register struct proc *p;
+static void
+stop(proc_t p, proc_t parent)
 {
-	p->p_stat = SSTOP;
-	p->p_flag &= ~(P_WAITED|P_CONTINUED);
-	if (p->p_pptr->p_stat != SSTOP)
-		wakeup((caddr_t)p->p_pptr);
-	(void) task_suspend(p->task);	/*XXX*/
+	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);
 }
 
 /*
@@ -2536,64 +3212,110 @@ stop(p)
  * from the current set of pending signals.
  */
 void
-postsig(int signum)
+postsig_locked(int signum)
 {
-	struct proc *p = current_proc();
+	proc_t p = current_proc();
 	struct sigacts *ps = p->p_sigacts;
 	user_addr_t catcher;
-	u_long code;
+	uint32_t code;
 	int mask, returnmask;
 	struct uthread * ut;
+	os_reason_t ut_exit_reason = OS_REASON_NULL;
 
 #if DIAGNOSTIC
-	if (signum == 0)
+	if (signum == 0) {
 		panic("postsig");
+	}
 	/*
 	 *	This must be called on master cpu
 	 */
-	if (cpu_number() != master_cpu)
+	if (cpu_number() != master_cpu) {
 		panic("psig not on master");
+	}
 #endif
 
-	signal_lock(p);
 	/*
 	 * Try to grab the signal lock.
 	 */
 	if (sig_try_locked(p) <= 0) {
-		signal_unlock(p);
 		return;
 	}
 
+	proc_signalstart(p, 1);
+
 	ut = (struct uthread *)get_bsdthread_info(current_thread());
 	mask = sigmask(signum);
 	ut->uu_siglist &= ~mask;
-	p->p_siglist &= ~mask;
 	catcher = ps->ps_sigact[signum];
-#if KTRACE
-	//LP64: catcher argument is a 64 bit user space handler address
-	if (KTRPOINT(p, KTR_PSIG))
-		ktrpsig(p->p_tracep,
-		    signum, CAST_DOWN(void *,catcher), ut->uu_flag & UT_SAS_OLDMASK ?
-		    &ut->uu_oldmask : &ut->uu_sigmask, 0);
-#endif
 	if (catcher == SIG_DFL) {
 		/*
 		 * Default catcher, where the default is to kill
 		 * the process.  (Other cases were ignored above.)
 		 */
-		/* called with signal_lock() held */
-		sigexit_locked(p, signum);
+
+		/*
+		 * 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;
-		/* NOTREACHED */
 	} else {
 		/*
 		 * If we get here, the signal must be caught.
 		 */
 #if DIAGNOSTIC
-		if (catcher == SIG_IGN || (ut->uu_sigmask & mask))
+		if (catcher == SIG_IGN || (ut->uu_sigmask & mask)) {
 			log(LOG_WARNING,
-				"postsig: processing masked or ignored signal\n");
+			    "postsig: processing masked or ignored signal\n");
+		}
 #endif
+
 		/*
 		 * Set the new mask value and also defer further
 		 * occurences of this signal.
@@ -2607,24 +3329,22 @@ postsig(int signum)
 			returnmask = ut->uu_oldmask;
 			ut->uu_flag &= ~UT_SAS_OLDMASK;
 			ut->uu_oldmask = 0;
-		} else
+		} else {
 			returnmask = ut->uu_sigmask;
+		}
 		ut->uu_sigmask |= ps->ps_catchmask[signum];
-		if ((ps->ps_signodefer & mask) == 0)
+		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))
+			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;
 		}
-#ifdef __ppc__
-		/* Needs to disable to run in user mode */
-		if (signum == SIGFPE) {
-			thread_enable_fpe(current_thread(), 0);
-		}
-#endif  /* __ppc__ */
 
 		if (ps->ps_sig != signum) {
 			code = 0;
@@ -2632,245 +3352,419 @@ postsig(int signum)
 			code = ps->ps_code;
 			ps->ps_code = 0;
 		}
-		p->p_stats->p_ru.ru_nsignals++;
-		sendsig(p, catcher, signum, returnmask, code);
+		OSIncrementAtomicLong(&p->p_stats->p_ru.ru_nsignals);
+		sendsig(p, catcher, signum, returnmask, code, siginfo);
 	}
-	signal_unlock(p);
+	proc_signalend(p, 1);
 }
 
 /*
- * Force the current process to exit with the specified signal, dumping core
- * if appropriate.  We bypass the normal tests for masked and caught signals,
- * allowing unrecoverable failures to terminate the process without changing
- * signal state.  Mark the accounting record with the signal termination.
- * If dumping core, save the signal number for the debugger.  Calls exit and
- * does not return.
+ * 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.
  */
- /* called with signal lock */
-void
-sigexit_locked(p, signum)
-	register struct proc *p;
-	int signum;
-{
-
-	sig_lock_to_exit(p);
-	p->p_acflag |= AXSIG;
-	if (sigprop[signum] & SA_CORE) {
-		p->p_sigacts->ps_sig = signum;
-		signal_unlock(p);
-		if (coredump(p) == 0)
-			signum |= WCOREFLAG;
-	} else 
-		signal_unlock(p);
-		
-	exit1(p, W_EXITCODE(0, signum), (int *)NULL);
-	/* NOTREACHED */
-}
-
 
 static int
-filt_sigattach(struct knote *kn)
+filt_sigattach(struct knote *kn, __unused struct kevent_qos_s *kev)
 {
-	struct proc *p = current_proc();
-	boolean_t funnel_state;
+	proc_t p = current_proc();  /* can attach only to oneself */
 
-	kn->kn_ptr.p_proc = p;
-	kn->kn_flags |= EV_CLEAR;		/* automatically set */
+	proc_klist_lock();
+
+	kn->kn_proc = p;
+	kn->kn_flags |= EV_CLEAR; /* automatically set */
+	kn->kn_sdata = 0;         /* incoming data is ignored */
 
-	/* Take the funnel to protect the proc while adding to the list */
-	funnel_state = thread_funnel_set(kernel_flock, TRUE);
 	KNOTE_ATTACH(&p->p_klist, kn);
-	thread_funnel_set(kernel_flock, funnel_state);
 
-	return (0);
+	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)
 {
-	struct proc *p = kn->kn_ptr.p_proc;
-	boolean_t funnel_state;
+	proc_t p = kn->kn_proc;
 
-	funnel_state = thread_funnel_set(kernel_flock, TRUE);
+	proc_klist_lock();
+	kn->kn_proc = NULL;
 	KNOTE_DETACH(&p->p_klist, kn);
-	thread_funnel_set(kernel_flock, funnel_state);
+	proc_klist_unlock();
 }
 
 /*
- * signal knotes are shared with proc knotes, so we apply a mask to 
- * the hint in order to differentiate them from process hints.  This
- * could be avoided by using a signal-specific knote list, but probably
- * isn't worth the trouble.
+ * 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_data++;
+		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_data != 0);
+
+	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 thr_act)
+bsd_ast(thread_t thread)
 {
-	struct proc *p = current_proc();
-	struct uthread *ut = get_bsdthread_info(thr_act);
-	int	signum;
-	user_addr_t pc;
-	boolean_t funnel_state;
+	proc_t p = current_proc();
+	struct uthread *ut = get_bsdthread_info(thread);
+	int     signum;
 	static int bsd_init_done = 0;
 
-	if (p == NULL)
+	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);
 
-	funnel_state = thread_funnel_set(kernel_flock, TRUE);
+		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);
+			}
 
-	if ((p->p_flag & P_OWEUPC) && (p->p_flag & P_PROFIL)) {
-		pc = get_useraddr();
-		addupc_task(p, pc, 1);
-		p->p_flag &= ~P_OWEUPC;
+			psignal_try_thread(p, thread, SIGVTALRM);
+		}
 	}
 
-	if (CHECK_SIGNALS(p, current_thread(), ut)) {
-		while ( (signum = issignal(p)) )
-			postsig(signum);
+	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 (!bsd_init_done) {
-		bsd_init_done = 1;
-		bsdinit_task();
+
+	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);
+		}
 	}
 
-	(void) thread_funnel_set(kernel_flock, FALSE);
-}
+#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);
+	}
 
-/*
- * Follwing routines are called using callout from bsd_hardclock
- * so that psignals are called in a thread context and are funneled
- */
-void
-psignal_vtalarm(struct proc *p)
-{
-	boolean_t funnel_state;
+	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 (p == NULL)
-		return;
-	funnel_state = thread_funnel_set(kernel_flock, TRUE);
-	psignal_lock(p, SIGVTALRM, 1);
-	(void) thread_funnel_set(kernel_flock, FALSE);
-}
+	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);
+		}
+	}
 
-void
-psignal_xcpu(struct proc *p)
-{
-	boolean_t funnel_state;
+#endif /* CONFIG_DTRACE */
 
-	if (p == NULL)
-		return;
-	funnel_state = thread_funnel_set(kernel_flock, TRUE);
-	psignal_lock(p, SIGXCPU, 1);
-	(void) thread_funnel_set(kernel_flock, FALSE);
-}
+	proc_lock(p);
+	if (CHECK_SIGNALS(p, current_thread(), ut)) {
+		while ((signum = issignal_locked(p))) {
+			postsig_locked(signum);
+		}
+	}
+	proc_unlock(p);
 
-void
-psignal_sigprof(struct proc *p)
-{
-	boolean_t funnel_state;
+#ifdef CONFIG_32BIT_TELEMETRY
+	if (task_consume_32bit_log_flag(p->task)) {
+		proc_log_32bit_telemetry(p);
+	}
+#endif /* CONFIG_32BIT_TELEMETRY */
 
-	if (p == NULL)
-		return;
-	funnel_state = thread_funnel_set(kernel_flock, TRUE);
-	psignal_lock(p, SIGPROF, 1);
-	(void) thread_funnel_set(kernel_flock, FALSE);
+	if (!bsd_init_done) {
+		bsd_init_done = 1;
+		bsdinit_task();
+	}
 }
 
-/* ptrace set runnalbe */
+/* ptrace set runnable */
 void
-pt_setrunnable(struct proc *p)
+pt_setrunnable(proc_t p)
 {
-task_t task;
+	task_t task;
 
 	task = p->task;
 
-	if (p->p_flag & P_TRACED) {
+	if (p->p_lflag & P_LTRACED) {
+		proc_lock(p);
 		p->p_stat = SRUN;
+		proc_unlock(p);
 		if (p->sigwait) {
 			wakeup((caddr_t)&(p->sigwait));
-			task_release(task);
+			if ((p->p_lflag & P_LSIGEXC) == 0) {    // 5878479
+				task_release(task);
+			}
 		}
 	}
 }
 
-
 kern_return_t
 do_bsdexception(
-	    int exc,
-	    int code,
-	    int sub)
+	int exc,
+	int code,
+	int sub)
 {
-	exception_data_type_t   codes[EXCEPTION_CODE_MAX];
+	mach_exception_data_type_t   codes[EXCEPTION_CODE_MAX];
 
-	codes[0] = code;	
+	codes[0] = code;
 	codes[1] = sub;
-	return(bsd_exception(exc, codes, 2));
+	return bsd_exception(exc, codes, 2);
 }
 
 int
-proc_pendingsignals(struct proc *p, sigset_t mask)
+proc_pendingsignals(proc_t p, sigset_t mask)
 {
 	struct uthread * uth;
 	thread_t th;
 	sigset_t bits = 0;
-	int error;
 
+	proc_lock(p);
 	/* If the process is in proc exit return no signal info */
-	if (p->p_lflag & P_LPEXIT) 
-		return(0);
-
-	/* duplicate the signal lock code to enable recursion; as exit
-	 * holds the lock too long. All this code is being reworked
-	 * this is just a workaround for regressions till new code
-	 * arrives.
-	 */
-ppend_retry:
-		error = lockmgr((struct lock__bsd__ *)&p->signal_lock[0], (LK_EXCLUSIVE | LK_CANRECURSE), 0, (struct proc *)0);
-		if (error == EINTR)
-			goto ppend_retry;
+	if (p->p_lflag & P_LPEXIT) {
+		goto out;
+	}
 
-	if ((p->p_flag & P_INVFORK) && p->p_vforkact) {
-		th = p->p_vforkact;	
+	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:
-	signal_unlock(p);
-	return(bits);
+	proc_unlock(p);
+	return bits;
 }
 
 int
 thread_issignal(proc_t p, thread_t th, sigset_t mask)
 {
 	struct uthread * uth;
-	sigset_t  bits=0;
+	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;
+}
 
-		uth = (struct uthread *)get_bsdthread_info(th);
-		if (uth) {
-			bits = (((uth->uu_siglist & ~uth->uu_sigmask) & ~p->p_sigignore) & mask);
-		}
-		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;
+}