[Devel] [user-cr][PATCH 2/2] Add --mount-pty option to mount new devpts

[Oren Laadan]

Based on Serge Hallyn's patch:

  "Trivial patch, and I'm not sure whether we want this or want to do
  it this way.  But it saves me having to do it during my restart.sh
  wrapper shell-script."

Make sure that the old /dev/pts is un-mounted prior to the mount of
the new one.

Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>
---
 restart.c |   40 ++++++++++++++++++++++++++++++++++++++++
 1 files changed, 40 insertions(+), 0 deletions(-)

diff --git a/restart.c b/restart.c
index f42b456..e3c4a5c 100644
--- a/restart.c
+++ b/restart.c
@@ -53,6 +53,7 @@ static char usage_str[] =
 "     --signal=SIG       send SIG to root task on SIGINT (default: SIGKILL\n"
 "                        to container root, SIGINT otherwise)\n"
 "     --mntns            restart under a private mounts namespace\n"
+"     --mount-pty        start in a new devpts namespace to supprt ptys\n"
 "  -w,--wait             wait for root task to termiate (default)\n"
 "     --show-status      show exit status of root task (implies -w)\n"
 "     --copy-status      imitate exit status of root task (implies -w)\n"
@@ -275,6 +276,7 @@ int global_send_sigint = -1;
 int global_sent_sigint;
 
 static int ckpt_remount_proc(void);
+static int ckpt_remount_devpts(void);
 
 static int ckpt_build_tree(struct ckpt_ctx *ctx);
 static int ckpt_init_tree(struct ckpt_ctx *ctx);
@@ -342,6 +344,7 @@ struct args {
 	char *root;
 	int wait;
 	int mntns;
+	int mnt_pty;
 	int show_status;
 	int copy_status;
 	char *freezer;
@@ -432,6 +435,7 @@ static void parse_args(struct args *args, int argc, char *argv[])
 		{ "debug",	no_argument,		NULL, 'd' },
 		{ "warn-pidzero",	no_argument,	NULL, 9 },
 		{ "fail-pidzero",	no_argument,	NULL, 10 },
+		{ "mount-pty",	no_argument,		NULL, 12 },
 		{ NULL,		0,			NULL, 0 }
 	};
 	static char optc[] = "hdvkpPwWF:r:i:l:";
@@ -538,6 +542,9 @@ static void parse_args(struct args *args, int argc, char *argv[])
 		case 11:
 			args->mntns = 1;
 			break;
+		case 12:
+			args->mnt_pty = 1;
+			break;
 		default:
 			usage(usage_str);
 		}
@@ -591,6 +598,9 @@ static void parse_args(struct args *args, int argc, char *argv[])
 		printf("Invalid used of both -l/--logfile and --logfile-fd\n");
 		exit(1);
 	}
+
+	if (args->mnt_pty)
+		args->mntns = 1;
 }
 
 static void report_exit_status(int status, char *str, int debug)
@@ -785,6 +795,10 @@ int main(int argc, char *argv[])
 		exit(1);
 	}
 
+	/* remount /dev/pts ? */
+	if (args.mnt_pty && ckpt_remount_devpts() < 0)
+		exit(1);
+
 	/* self-restart ends here: */
 	if (args.self) {
 		restart(getpid(), STDIN_FILENO, RESTART_TASKSELF, args.logfd);
@@ -916,6 +930,32 @@ static int ckpt_collect_child(struct ckpt_ctx *ctx)
 	return ckpt_parse_status(status, mimic, verbose);
 }
 
+static int ckpt_remount_devpts(void)
+{
+	struct stat ptystat;
+
+	/* make sure /dev/ptmx is a link else we'll just break */
+	if (lstat("/dev/ptmx", &ptystat) < 0) {
+		perror("stat /dev/ptmx");
+		return -1;
+	}
+	if ((ptystat.st_mode & S_IFMT) != S_IFLNK) {
+		ckpt_err("Error: /dev/ptmx must be a link to /dev/pts/ptmx\n");
+		return -1;
+	}
+
+	if (umount2("/dev/pts", MNT_DETACH) < 0) {
+		perror("umount -l /dev/pts");
+		return -1;
+	}
+	if (mount("pts", "/dev/pts", "devpts", 0, "newinstance") < 0) {
+		perror("mount -t devpts -o newinstance");
+		return -1;
+	}
+
+	return 0;
+}
+
 static int ckpt_close_files(void)
 {
 	char fdpath[64], *endp;
-- 
1.6.3.3

_______________________________________________
Containers mailing list
Containers at lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/containers