From e9f63df76dcfe798bd47df803d5e9dbdcae0bb0a Mon Sep 17 00:00:00 2001
From: Mark Johnston <markj@FreeBSD.org>
Date: Thu, 23 Nov 2017 14:29:07 +0000
Subject: [PATCH] Duplicate helpers after disabling inherited tracepoints
 during a fork.

We may create probes in the nascent child process, so we first need to
ensure that any inherited tracepoints are first removed. Otherwise the
probe sites will not be in the state expected by fasttrap, and it won't
be able to enable the probes.

MFC after:	2 weeks
---
 .../opensolaris/uts/common/dtrace/fasttrap.c  | 22 +++++++------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c b/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c
index 82353cbb235..9e6bde2eac4 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c
@@ -601,8 +601,8 @@ fasttrap_fork(proc_t *p, proc_t *cp)
 	pid_t ppid = p->p_pid;
 	int i;
 
-#ifdef illumos
 	ASSERT(curproc == p);
+#ifdef illumos
 	ASSERT(p->p_proc_flag & P_PR_LOCK);
 #else
 	PROC_LOCK_ASSERT(p, MA_OWNED);
@@ -610,26 +610,15 @@ fasttrap_fork(proc_t *p, proc_t *cp)
 #ifdef illumos
 	ASSERT(p->p_dtrace_count > 0);
 #else
-	if (p->p_dtrace_helpers) {
-		/*
-		 * dtrace_helpers_duplicate() allocates memory.
-		 */
-		_PHOLD(cp);
-		PROC_UNLOCK(p);
-		PROC_UNLOCK(cp);
-		dtrace_helpers_duplicate(p, cp);
-		PROC_LOCK(cp);
-		PROC_LOCK(p);
-		_PRELE(cp);
-	}
 	/*
 	 * This check is purposely here instead of in kern_fork.c because,
 	 * for legal resons, we cannot include the dtrace_cddl.h header
 	 * inside kern_fork.c and insert if-clause there.
 	 */
-	if (p->p_dtrace_count == 0)
+	if (p->p_dtrace_count == 0 && p->p_dtrace_helpers == NULL)
 		return;
 #endif
+
 	ASSERT(cp->p_dtrace_count == 0);
 
 	/*
@@ -658,6 +647,8 @@ fasttrap_fork(proc_t *p, proc_t *cp)
 	_PHOLD(cp);
 	PROC_UNLOCK(cp);
 	PROC_UNLOCK(p);
+	if (p->p_dtrace_count == 0)
+		goto dup_helpers;
 #endif
 
 	/*
@@ -711,6 +702,9 @@ fasttrap_fork(proc_t *p, proc_t *cp)
 	mutex_enter(&cp->p_lock);
 	sprunlock(cp);
 #else
+dup_helpers:
+	if (p->p_dtrace_helpers != NULL)
+		dtrace_helpers_duplicate(p, cp);
 	PROC_LOCK(p);
 	PROC_LOCK(cp);
 	_PRELE(cp);