Index: linux-user/main.c
===================================================================
--- linux-user/main.c	(revision 5527)
+++ linux-user/main.c	(working copy)
@@ -2186,6 +2186,10 @@
            "-cpu model        select CPU (-cpu ? for list)\n"
            "-drop-ld-preload  drop LD_PRELOAD for target process\n"
            "\n"
+           "Root options:\n"
+           "-chroot dir       chroot to dir\n"
+           "-su uid:gid       set numeric user and group IDs\n"
+           "\n"
            "Debug options:\n"
            "-d options   activate log (logfile=%s)\n"
            "-p pagesize  set the host page size to 'pagesize'\n"
@@ -2301,6 +2305,28 @@
             drop_ld_preload = 1;
         } else if (!strcmp(r, "strace")) {
             do_strace = 1;
+        } else if (!strcmp(r, "chroot")) {
+            if (chdir(argv[optind++]) || chroot(".")) {
+                fprintf(stderr, "Can't chroot to '%s' (are you root?)\n",
+                    argv[--optind]);
+                _exit(1);
+            }
+        } else if (!strcmp(r, "su")) {
+            int temp;
+            char *gid = strchr(argv[optind], ':');
+            if (gid) {
+                temp = atoi(++gid);
+                if (setresgid(temp, temp, temp)) {
+                    fprintf(stderr, "Can't set gid to %d (are you root?)\n",
+                        temp);
+                    _exit(1);
+                }
+           }
+           temp = atoi(argv[optind++]);
+           if (setresuid(temp, temp, temp)) {
+               fprintf(stderr, "Can't set uid to %d (are you root?)\n", temp);
+               _exit(1);
+           }
         } else
         {
             usage();