Quoting Oren Laadan (orenl@xxxxxxxxxxx):
> Add checkpoint/restart of controlling terminal: current->signal->tty.
> This is only done for session leaders.
>
> If the session leader belongs to the ancestor pid-ns, then checkpoint
> skips this tty; On restart, it will not be restored, and whatever tty
> is in place from parent pid-ns (at restart) will be inherited.
>
> Signed-off-by: Oren Laadan <orenl@xxxxxxxxxxxxxxx>
Not exactly my area, but looks good
Acked-by: Serge Hallyn <serue@xxxxxxxxxx>
> ---
> checkpoint/signal.c | 78 ++++++++++++++++++++++++++++++++++++++-
> drivers/char/tty_io.c | 33 +++++++++++++----
> include/linux/checkpoint.h | 1 +
> include/linux/checkpoint_hdr.h | 6 +++
> include/linux/tty.h | 5 +++
> 5 files changed, 114 insertions(+), 9 deletions(-)
>
> diff --git a/checkpoint/signal.c b/checkpoint/signal.c
> index ad06783..178a97c 100644
> --- a/checkpoint/signal.c
> +++ b/checkpoint/signal.c
> @@ -315,11 +315,12 @@ static int checkpoint_signal(struct ckpt_ctx *ctx, struct task_struct *t)
> struct ckpt_hdr_signal *h;
> struct signal_struct *signal;
> struct sigpending shared_pending;
> + struct tty_struct *tty = NULL;
> struct rlimit *rlim;
> struct timeval tval;
> cputime_t cputime;
> unsigned long flags;
> - int i, ret;
> + int i, ret = 0;
>
> h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_SIGNAL);
> if (!h)
> @@ -398,9 +399,34 @@ static int checkpoint_signal(struct ckpt_ctx *ctx, struct task_struct *t)
> cputime_to_timeval(signal->it_prof_incr, &tval);
> h->it_prof_incr = timeval_to_ns(&tval);
>
> + /* tty */
> + if (signal->leader) {
> + h->tty_old_pgrp = ckpt_pid_nr(ctx, signal->tty_old_pgrp);
> + tty = tty_kref_get(signal->tty);
> + if (tty) {
> + /* irq is already disabled */
> + spin_lock(&tty->ctrl_lock);
> + h->tty_pgrp = ckpt_pid_nr(ctx, tty->pgrp);
> + spin_unlock(&tty->ctrl_lock);
> + tty_kref_put(tty);
> + }
> + }
> +
> unlock_task_sighand(t, &flags);
>
> - ret = ckpt_write_obj(ctx, &h->h);
> + /*
> + * If the session is in an ancestor namespace, skip this tty
> + * and set tty_objref = 0. It will not be explicitly restored,
> + * but rather inherited from parent pid-ns at restart time.
> + */
> + if (tty && ckpt_pid_nr(ctx, tty->session) > 0) {
> + h->tty_objref = checkpoint_obj(ctx, tty, CKPT_OBJ_TTY);
> + if (h->tty_objref < 0)
> + ret = h->tty_objref;
> + }
> +
> + if (!ret)
> + ret = ckpt_write_obj(ctx, &h->h);
> if (!ret)
> ret = checkpoint_sigpending(ctx, &shared_pending);
>
> @@ -471,8 +497,10 @@ static int restore_signal(struct ckpt_ctx *ctx)
> struct ckpt_hdr_signal *h;
> struct sigpending new_pending;
> struct sigpending *pending;
> + struct tty_struct *tty = NULL;
> struct itimerval itimer;
> struct rlimit rlim;
> + struct pid *pgrp;
> int i, ret;
>
> h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_SIGNAL);
> @@ -492,6 +520,36 @@ static int restore_signal(struct ckpt_ctx *ctx)
> if (ret < 0)
> goto out;
>
> + /* tty - session */
> + if (h->tty_objref) {
> + tty = ckpt_obj_fetch(ctx, h->tty_objref, CKPT_OBJ_TTY);
> + if (IS_ERR(tty)) {
> + ret = PTR_ERR(tty);
> + goto out;
> + }
> + /* this will fail unless we're the session leader */
> + ret = tiocsctty(tty, 0);
> + if (ret < 0)
> + goto out;
> + /* now restore the foreground group (job control) */
> + if (h->tty_pgrp) {
> + ret = do_tiocspgrp(tty, tty_pair_get_tty(tty),
> + h->tty_pgrp);
> + if (ret < 0)
> + goto out;
> + }
> + } else {
> + /*
> + * If tty_objref isn't set, we _keep_ whatever tty we
> + * already have as a ctty. Why does this make sense ?
> + * - If our session is "within" the restart context,
> + * then that session has no controlling terminal.
> + * - If out session is "outside" the restart context,
> + * then we're like to keep whatever we inherit from
> + * the parent pid-ns.
> + */
> + }
> +
> /*
> * Reset real/virt/prof itimer (in case they were set), to
> * prevent unwanted signals after flushing current signals
> @@ -503,7 +561,23 @@ static int restore_signal(struct ckpt_ctx *ctx)
> do_setitimer(ITIMER_VIRTUAL, &itimer, NULL);
> do_setitimer(ITIMER_PROF, &itimer, NULL);
>
> + /* tty - tty_old_pgrp */
> + if (h->tty_old_pgrp) {
> + ret = -EINVAL;
> + if (!current->signal->leader)
> + goto out;
> + rcu_read_lock();
> + pgrp = get_pid(_ckpt_find_pgrp(ctx, h->tty_old_pgrp));
> + rcu_read_unlock();
> + if (!pgrp)
> + goto out;
> + }
> +
> spin_lock_irq(¤t->sighand->siglock);
> + /* tty - tty_old_pgrp */
> + put_pid(current->signal->tty_old_pgrp);
> + current->signal->tty_old_pgrp = pgrp;
> + /* pending signals */
> pending = ¤t->signal->shared_pending;
> flush_sigqueue(pending);
> pending->signal = new_pending.signal;
> diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
> index b8f8d79..0206300 100644
> --- a/drivers/char/tty_io.c
> +++ b/drivers/char/tty_io.c
> @@ -2132,7 +2132,7 @@ static int fionbio(struct file *file, int __user *p)
> * Takes ->siglock() when updating signal->tty
> */
>
> -static int tiocsctty(struct tty_struct *tty, int arg)
> +int tiocsctty(struct tty_struct *tty, int arg)
> {
> int ret = 0;
> if (current->signal->leader && (task_session(current) == tty->session))
> @@ -2221,10 +2221,10 @@ static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
> }
>
> /**
> - * tiocspgrp - attempt to set process group
> + * do_tiocspgrp - attempt to set process group
> * @tty: tty passed by user
> * @real_tty: tty side device matching tty passed by user
> - * @p: pid pointer
> + * @pid: pgrp_nr
> *
> * Set the process group of the tty to the session passed. Only
> * permitted where the tty session is our session.
> @@ -2232,10 +2232,10 @@ static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
> * Locking: RCU, ctrl lock
> */
>
> -static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
> +int do_tiocspgrp(struct tty_struct *tty,
> + struct tty_struct *real_tty, pid_t pgrp_nr)
> {
> struct pid *pgrp;
> - pid_t pgrp_nr;
> int retval = tty_check_change(real_tty);
> unsigned long flags;
>
> @@ -2247,8 +2247,6 @@ static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t
> (current->signal->tty != real_tty) ||
> (real_tty->session != task_session(current)))
> return -ENOTTY;
> - if (get_user(pgrp_nr, p))
> - return -EFAULT;
> if (pgrp_nr < 0)
> return -EINVAL;
> rcu_read_lock();
> @@ -2270,6 +2268,27 @@ out_unlock:
> }
>
> /**
> + * tiocspgrp - attempt to set process group
> + * @tty: tty passed by user
> + * @real_tty: tty side device matching tty passed by user
> + * @p: pid pointer
> + *
> + * Set the process group of the tty to the session passed. Only
> + * permitted where the tty session is our session.
> + *
> + * Locking: RCU, ctrl lock
> + */
> +
> +static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
> +{
> + pid_t pgrp_nr;
> +
> + if (get_user(pgrp_nr, p))
> + return -EFAULT;
> + return do_tiocspgrp(tty, real_tty, pgrp_nr);
> +}
> +
> +/**
> * tiocgsid - get session id
> * @tty: tty passed by user
> * @real_tty: tty side of the tty pased by the user if a pty else the tty
> diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
> index 628d6f6..434c6b1 100644
> --- a/include/linux/checkpoint.h
> +++ b/include/linux/checkpoint.h
> @@ -87,6 +87,7 @@ extern char *ckpt_fill_fname(struct path *path, struct path *root,
>
> /* pids */
> extern pid_t ckpt_pid_nr(struct ckpt_ctx *ctx, struct pid *pid);
> +extern struct pid *_ckpt_find_pgrp(struct ckpt_ctx *ctx, pid_t pgid);
>
> /* socket functions */
> extern int ckpt_sock_getnames(struct ckpt_ctx *ctx,
> diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
> index c9ded68..398d5f7 100644
> --- a/include/linux/checkpoint_hdr.h
> +++ b/include/linux/checkpoint_hdr.h
> @@ -555,13 +555,19 @@ struct ckpt_rlimit {
>
> struct ckpt_hdr_signal {
> struct ckpt_hdr h;
> + /* rlimit */
> struct ckpt_rlimit rlim[CKPT_RLIM_NLIMITS];
> + /* itimer */
> __u64 it_real_value;
> __u64 it_real_incr;
> __u64 it_virt_value;
> __u64 it_virt_incr;
> __u64 it_prof_value;
> __u64 it_prof_incr;
> + /* tty */
> + __s32 tty_objref;
> + __s32 tty_pgrp;
> + __s32 tty_old_pgrp;
> } __attribute__((aligned(8)));
>
> struct ckpt_hdr_signal_task {
> diff --git a/include/linux/tty.h b/include/linux/tty.h
> index fd77894..ee49d97 100644
> --- a/include/linux/tty.h
> +++ b/include/linux/tty.h
> @@ -467,6 +467,11 @@ extern void tty_ldisc_begin(void);
> /* This last one is just for the tty layer internals and shouldn't be used elsewhere */
> extern void tty_ldisc_enable(struct tty_struct *tty);
>
> +/* These are for checkpoint/restart */
> +extern int tiocsctty(struct tty_struct *tty, int arg);
> +extern int do_tiocspgrp(struct tty_struct *tty,
> + struct tty_struct *real_tty, pid_t pgrp_nr);
> +
> #ifdef CONFIG_CHECKPOINT
> struct ckpt_ctx;
> struct ckpt_hdr_file;
> --
> 1.6.0.4
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