Index: libexec/rtld-elf/rtld.c
===================================================================
--- libexec/rtld-elf/rtld.c
+++ libexec/rtld-elf/rtld.c
@@ -421,6 +421,7 @@
     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 +780,11 @@
     /* 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);
+
     return (func_ptr_type) obj_main->entry;
 }
 
@@ -1820,6 +1826,7 @@
 	struct stat hint_stat;
 	unsigned int SLPndx, hintndx, fndx, fcount;
 	int fd;
+	int jid;
 	size_t flen;
 	uint32_t dl;
 	bool skip;
@@ -5510,6 +5517,20 @@
 			}
 			*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 (fd == -1) {
+					_rtld_error("Invalid JID: '%s'",
+						argv[i]);
+					rtld_die();
+				}
+				break;
 			} else if (opt == 'p') {
 				*use_pathp = true;
 			} else {
@@ -5554,12 +5575,13 @@
 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);