Index: libexec/rtld-elf/rtld.c
===================================================================
--- libexec/rtld-elf/rtld.c
+++ libexec/rtld-elf/rtld.c
@@ -49,6 +49,7 @@
 #include <sys/uio.h>
 #include <sys/utsname.h>
 #include <sys/ktrace.h>
+#include <sys/jail.h>
 
 #include <dlfcn.h>
 #include <err.h>
@@ -214,6 +215,7 @@
 static Obj_Entry obj_rtld;	/* The dynamic linker shared object */
 static unsigned int obj_count;	/* Number of objects in obj_list */
 static unsigned int obj_loads;	/* Number of loads of objects (gen count) */
+static int jid;			/* JID to attach jail to */
 
 static Objlist list_global =	/* Objects dlopened with RTLD_GLOBAL */
   STAILQ_HEAD_INITIALIZER(list_global);
@@ -421,6 +423,7 @@
     md_abi_variant_hook(aux_info);
 
     fd = -1;
+    jid = -1;
     if (aux_info[AT_EXECFD] != NULL) {
 	fd = aux_info[AT_EXECFD]->a_un.a_val;
     } else {
@@ -779,6 +782,13 @@
     /* Return the exit procedure and the program entry point. */
     *exit_proc = rtld_exit;
     *objp = obj_main;
+
+    /* Attach to a jail */
+    if (jid > 0 && jail_attach(jid) == -1) {
+        _rtld_error("Could not attach to jail");
+        rtld_die();
+    }
+
     return (func_ptr_type) obj_main->entry;
 }
 
@@ -5510,6 +5520,20 @@
 			}
 			*fdp = fd;
 			break;
+			} else if (opt == 'j') {
+				if (j != arglen - 1) {
+					/* -j must be the last option in, e.g., -abcj */
+					_rtld_error("Invalid options: %s", arg);
+					rtld_die();
+				}
+				i++;
+				jid = parse_integer(argv[i]);
+				if (jid == -1) {
+					_rtld_error("Invalid JID: '%s'",
+						argv[i]);
+					rtld_die();
+				}
+				break;
 			} else if (opt == 'p') {
 				*use_pathp = true;
 			} else {
@@ -5554,12 +5578,13 @@
 print_usage(const char *argv0)
 {
 
-	rtld_printf("Usage: %s [-h] [-f <FD>] [--] <binary> [<args>]\n"
+	rtld_printf("Usage: %s [-h] [-f <FD>] [-j <JID>] [--] <binary> [<args>]\n"
 		"\n"
 		"Options:\n"
 		"  -h        Display this help message\n"
 		"  -p        Search in PATH for named binary\n"
 		"  -f <FD>   Execute <FD> instead of searching for <binary>\n"
+		"  -j <JID>  Execute <binary> after attaching to jail with JID <JID>\n"
 		"  --        End of RTLD options\n"
 		"  <binary>  Name of process to execute\n"
 		"  <args>    Arguments to the executed process\n", argv0);