Index: tests/sys/vm/mmap_test.c
===================================================================
--- tests/sys/vm/mmap_test.c
+++ tests/sys/vm/mmap_test.c
@@ -110,8 +110,9 @@
 ATF_TC_WITHOUT_HEAD(mmap__bad_arguments);
 ATF_TC_BODY(mmap__bad_arguments, tc)
 {
-	int shmfd, zerofd;
+	int devstatfd, shmfd, zerofd;
 
+	ATF_REQUIRE((devstatfd = open("/dev/devstat", O_RDONLY)) >= 0);
 	ATF_REQUIRE((shmfd = shm_open(SHM_ANON, O_RDWR, 0644)) >= 0);
 	ATF_REQUIRE(ftruncate(shmfd, getpagesize()) == 0);
 	ATF_REQUIRE((zerofd = open("/dev/zero", O_RDONLY)) >= 0);
@@ -127,6 +128,8 @@
 	    "simple /dev/zero shared");
 	checked_mmap(PROT_READ | PROT_WRITE, MAP_PRIVATE, zerofd, 0,
 	    "simple /dev/zero private");
+	checked_mmap(PROT_READ, MAP_SHARED, devstatfd, 0,
+	    "simple /dev/devstat shared");
 
 	/* Extra PROT flags. */
 	checked_mmap(PROT_READ | PROT_WRITE | 0x100000, MAP_ANON, -1, EINVAL,
@@ -161,27 +164,17 @@
 	/* Writable MAP_SHARED should fail on read-only descriptors. */
 	checked_mmap(PROT_READ | PROT_WRITE, MAP_SHARED, zerofd, EACCES,
 	    "MAP_SHARED of read-only /dev/zero");
-}
-
-ATF_TC_WITHOUT_HEAD(mmap__cdev_private);
-ATF_TC_BODY(mmap__cdev_private, tc)
-{
-	int fd;
-
-	fd = open("/dev/mem", O_RDONLY);
-	if (fd == -1)
-		atf_tc_skip("Could not open /dev/mem");
 
 	/*
 	 * Character devices other than /dev/zero do not support private
 	 * mappings.
 	 */
-	checked_mmap(PROT_READ, MAP_PRIVATE, fd, EINVAL,
-	    "MAP_PRIVATE of /dev/mem");
+	checked_mmap(PROT_READ, MAP_PRIVATE, devstatfd, EINVAL,
+	    "MAP_PRIVATE of /dev/devstat");
 }
 
-ATF_TC_WITHOUT_HEAD(mmap__dev_zero);
-ATF_TC_BODY(mmap__dev_zero, tc)
+ATF_TC_WITHOUT_HEAD(mmap__dev_zero_private);
+ATF_TC_BODY(mmap__dev_zero_private, tc)
 {
 	char *p1, *p2, *p3;
 	size_t i;
@@ -217,13 +210,50 @@
 	ATF_REQUIRE(p3[0] == 0);
 }
 
+ATF_TC_WITHOUT_HEAD(mmap__dev_zero_shared);
+ATF_TC_BODY(mmap__dev_zero_shared, tc)
+{
+	char *p1, *p2, *p3;
+	size_t i;
+	int fd;
+
+	ATF_REQUIRE((fd = open("/dev/zero", O_RDWR)) >= 0);
+
+	p1 = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_SHARED, fd,
+	    0);
+	ATF_REQUIRE(p1 != MAP_FAILED);
+
+	p2 = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_SHARED, fd,
+	    0);
+	ATF_REQUIRE(p2 != MAP_FAILED);
+
+	for (i = 0; i < getpagesize(); i++)
+		ATF_REQUIRE_EQ_MSG(0, p1[i], "byte at p1[%zu] is %x", i, p1[i]);
+
+	ATF_REQUIRE(memcmp(p1, p2, getpagesize()) == 0);
+
+	p1[0] = 1;
+
+	ATF_REQUIRE(p2[0] == 0);
+
+	p2[0] = 2;
+
+	ATF_REQUIRE(p1[0] == 1);
+
+	p3 = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_SHARED, fd,
+	    0);
+	ATF_REQUIRE(p3 != MAP_FAILED);
+
+	ATF_REQUIRE(p3[0] == 0);
+}
+
 ATF_TP_ADD_TCS(tp)
 {
 
 	ATF_TP_ADD_TC(tp, mmap__map_at_zero);
 	ATF_TP_ADD_TC(tp, mmap__bad_arguments);
-	ATF_TP_ADD_TC(tp, mmap__cdev_private);
-	ATF_TP_ADD_TC(tp, mmap__dev_zero);
+	ATF_TP_ADD_TC(tp, mmap__dev_zero_private);
+	ATF_TP_ADD_TC(tp, mmap__dev_zero_shared);
 
 	return (atf_no_error());
 }