Index: stand/defaults/loader.conf
===================================================================
--- stand/defaults/loader.conf
+++ stand/defaults/loader.conf
@@ -33,6 +33,11 @@
 screensave_load="NO"		# Set to YES to load a screensaver module
 screensave_name="green_saver"	# Set to the name of the screensaver module
 
+###  Early hostid configuration ############################
+hostuuid_load="YES"
+hostuuid_name="/etc/hostid"
+hostuuid_type="hostuuid"
+
 ###  Random number generator configuration  ##################
 # See rc.conf(5). The entropy_boot_file config variable must agree with the
 # settings below.
Index: sys/kern/kern_jail.c
===================================================================
--- sys/kern/kern_jail.c
+++ sys/kern/kern_jail.c
@@ -48,6 +48,7 @@
 #include <sys/taskqueue.h>
 #include <sys/fcntl.h>
 #include <sys/jail.h>
+#include <sys/linker.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/racct.h>
@@ -61,6 +62,7 @@
 #include <sys/socket.h>
 #include <sys/syscallsubr.h>
 #include <sys/sysctl.h>
+#include <sys/uuid.h>
 #include <sys/vnode.h>
 
 #include <net/if.h>
@@ -75,6 +77,7 @@
 #include <security/mac/mac_framework.h>
 
 #define	DEFAULT_HOSTUUID	"00000000-0000-0000-0000-000000000000"
+#define	PRISON0_HOSTUUID_MODULE	"hostuuid"
 
 MALLOC_DEFINE(M_PRISON, "prison", "Prison structures");
 static MALLOC_DEFINE(M_PRISON_RACCT, "prison_racct", "Prison racct structures");
@@ -218,10 +221,38 @@
 void
 prison0_init(void)
 {
+	uint8_t *file, *data;
+	size_t size;
 
 	prison0.pr_cpuset = cpuset_ref(thread0.td_cpuset);
 	prison0.pr_osreldate = osreldate;
 	strlcpy(prison0.pr_osrelease, osrelease, sizeof(prison0.pr_osrelease));
+
+	/* If we have a preloaded hostuuid, use it. */
+	file = preload_search_by_type(PRISON0_HOSTUUID_MODULE);
+	if (file != NULL) {
+		data = preload_fetch_addr(file);
+		size = preload_fetch_size(file);
+		if (data != NULL) {
+			/*
+			 * The preloaded may include trailing whitespace, almost
+			 * certainly a newline; skip over any whitespace or
+			 * non-printable characters to be safe.
+			 */
+			while (size > 0 && data[size - 1] <= 0x20) {
+				data[size--] = '\0';
+			}
+			if (validate_uuid(data, size, NULL) == 0) {
+				(void)strlcpy(prison0.pr_hostuuid, data,
+				    size + 1);
+			} else if (bootverbose) {
+				printf("hostuuid: preload data malformed: '%s'",
+				    data);
+			}
+		}
+	}
+	if (bootverbose)
+		printf("hostuuid: using %s\n", prison0.pr_hostuuid);
 }
 
 /*
Index: sys/kern/kern_uuid.c
===================================================================
--- sys/kern/kern_uuid.c
+++ sys/kern/kern_uuid.c
@@ -382,19 +382,16 @@
 }
 
 int
-parse_uuid(const char *str, struct uuid *uuid)
+validate_uuid(const char *str, size_t size, struct uuid *uuid)
 {
 	u_int c[11];
 	int n;
 
-	/* An empty string represents a nil UUID. */
-	if (*str == '\0') {
-		bzero(uuid, sizeof(*uuid));
-		return (0);
-	}
+	if (size == 0 || *str == '\0')
+		return (EINVAL);
 
 	/* The UUID string representation has a fixed length. */
-	if (strlen(str) != 36)
+	if (size != 36)
 		return (EINVAL);
 
 	/*
@@ -406,25 +403,48 @@
 	if (str[8] != '-')
 		return (EINVAL);
 
+	/* Now check the format. */
 	n = sscanf(str, "%8x-%4x-%4x-%2x%2x-%2x%2x%2x%2x%2x%2x", c + 0, c + 1,
 	    c + 2, c + 3, c + 4, c + 5, c + 6, c + 7, c + 8, c + 9, c + 10);
 	/* Make sure we have all conversions. */
 	if (n != 11)
 		return (EINVAL);
 
-	/* Successful scan. Build the UUID. */
-	uuid->time_low = c[0];
-	uuid->time_mid = c[1];
-	uuid->time_hi_and_version = c[2];
-	uuid->clock_seq_hi_and_reserved = c[3];
-	uuid->clock_seq_low = c[4];
-	for (n = 0; n < 6; n++)
-		uuid->node[n] = c[n + 5];
+	/* Successful scan. Build the UUID if requested. */
+	if (uuid != NULL) {
+		uuid->time_low = c[0];
+		uuid->time_mid = c[1];
+		uuid->time_hi_and_version = c[2];
+		uuid->clock_seq_hi_and_reserved = c[3];
+		uuid->clock_seq_low = c[4];
+		for (n = 0; n < 6; n++)
+			uuid->node[n] = c[n + 5];
+	}
+
+	return (0);
+}
+
+int
+parse_uuid(const char *str, struct uuid *uuid)
+{
+	unsigned int clock_seq;
+	int ret;
+
+	/* An empty string represents a nil UUID. */
+	if (*str == '\0') {
+		bzero(uuid, sizeof(*uuid));
+		return (0);
+	}
+
+	ret = validate_uuid(str, strlen(str), uuid);
+	if (ret != 0)
+		return (ret);
 
 	/* Check semantics... */
-	return (((c[3] & 0x80) != 0x00 &&		/* variant 0? */
-	    (c[3] & 0xc0) != 0x80 &&			/* variant 1? */
-	    (c[3] & 0xe0) != 0xc0) ? EINVAL : 0);	/* variant 2? */
+	clock_seq = uuid->clock_seq_hi_and_reserved;
+	return (((clock_seq & 0x80) != 0x00 &&		/* variant 0? */
+	    (clock_seq & 0xc0) != 0x80 &&		/* variant 1? */
+	    (clock_seq & 0xe0) != 0xc0) ? EINVAL : 0);	/* variant 2? */
 }
 
 int
Index: sys/sys/uuid.h
===================================================================
--- sys/sys/uuid.h
+++ sys/sys/uuid.h
@@ -66,6 +66,21 @@
 int snprintf_uuid(char *, size_t, struct uuid *);
 int printf_uuid(struct uuid *);
 int sbuf_printf_uuid(struct sbuf *, struct uuid *);
+
+/*
+ * There are a few key differences between validate_uuid and parse_uuid:
+ *
+ * - The struct uuid * parameter to validate_uuid is optional, so the caller
+ *    can simply validate UUID format without doing anything with the result.
+ * - validate_uuid will not pass an empty string as a valid UUID, as it doesn't
+ *    strictly meet the formatting requirements.  parse_uuid will accept an
+ *    empty string and zero out the uuid struct accordingly.
+ * - parse_uuid does additional semantic checks on clock_seq_hi_and_reserved
+ *    that validate_uuid will not do.
+ *
+ * validate_uuid is intended to strictly check that it's a well-formed uuid.
+ */
+int validate_uuid(const char *, size_t, struct uuid *);
 int parse_uuid(const char *, struct uuid *);
 int uuidcmp(const struct uuid *, const struct uuid *);