Index: tests/sys/kern/Makefile
===================================================================
--- tests/sys/kern/Makefile
+++ tests/sys/kern/Makefile
@@ -4,6 +4,7 @@
 .PATH:		${SRCTOP}/sys/kern
 
 TESTSDIR=	${TESTSBASE}/sys/kern
+BINDIR=		${TESTSDIR}
 
 ATF_TESTS_C+=	kern_copyin
 ATF_TESTS_C+=	kern_descrip_test
@@ -13,6 +14,10 @@
 ATF_TESTS_C+=	unix_passfd_test
 TEST_METADATA.unix_seqpacket_test+=	timeout="15"
 
+ATF_TESTS_SH+=	coredump_phnum_test
+
+PROGS+=		coredump_phnum_helper
+
 LIBADD.ptrace_test+=			pthread
 LIBADD.unix_seqpacket_test+=		pthread
 
Index: tests/sys/kern/coredump_phnum_helper.c
===================================================================
--- /dev/null
+++ tests/sys/kern/coredump_phnum_helper.c
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2016, Conrad Meyer
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include <sys/param.h>
+#include <sys/mman.h>
+
+#include <err.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+int
+main(int argc __unused, char **argv __unused)
+{
+	void *v;
+	unsigned i;
+
+	for (i = 0; i < UINT16_MAX + 1000; i++) {
+		v = mmap(NULL, PAGE_SIZE,
+		    (((i % 2) == 0) ? PROT_READ : 0) | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE, -1, 0);
+		if (v == MAP_FAILED)
+			err(1, "mmap");
+	}
+	abort();
+}
Index: tests/sys/kern/coredump_phnum_test.sh
===================================================================
--- /dev/null
+++ tests/sys/kern/coredump_phnum_test.sh
@@ -0,0 +1,57 @@
+atf_test_case coredump_phnum cleanup
+coredump_phnum_head()
+{
+	atf_set "allow_sysctl_side_effects" "1"
+	atf_set "descr" "More than 65534 segments"
+	atf_set "require.progs" "readelf procstat"
+	atf_set "require.user" "root"
+}
+coredump_phnum_body()
+{
+	# Set up core dumping
+	cat > coredump_phnum_restore_state.sh <<-EOF
+	#!/bin/sh
+	ulimit -c '$(ulimit -c)'
+	sysctl kern.coredump=$(sysctl -n kern.coredump)
+	sysctl kern.corefile='$(sysctl -n kern.corefile)'
+EOF
+	chmod +x coredump_phnum_restore_state.sh
+
+	ulimit -c unlimited
+	sysctl kern.coredump=1
+	sysctl kern.corefile="$(pwd)/coredump_phnum_helper.core"
+
+	atf_check -s signal:sigabrt "$(atf_get_srcdir)/coredump_phnum_helper"
+
+	# Check that core looks good
+	if [ ! -f coredump_phnum_helper.core ]; then
+	    atf_fail "Helper program did not dump core"
+	fi
+
+	# These magic numbers don't have any real significance.  They are just
+	# the result of running the helper program and dumping core.  The only
+	# important bit is that they're larger than 65535 (UINT16_MAX).
+	readelf -h coredump_phnum_helper.core | \
+	    atf_check -o "match:65535 \(66169\)" \
+	    grep "Number of program headers:"
+	readelf -l coredump_phnum_helper.core | \
+	    atf_check -o "match:There are 66169 program headers" \
+	    grep -1 "program headers"
+	readelf -S coredump_phnum_helper.core | \
+	    atf_check -o "match: 0000000000000001 .* 66169 " \
+	    grep -A1 "^  \[ 0\] "
+
+	procstat -v coredump_phnum_helper.core | \
+	    atf_check -o "match:66545" wc -l
+}
+coredump_phnum_cleanup()
+{
+	rm -f coredump_phnum_helper.core
+	./coredump_phnum_restore_state.sh
+	rm -f coredump_phnum_restore_state.sh
+}
+
+atf_init_test_cases()
+{
+	atf_add_test_case coredump_phnum
+}