From: Miroslav Benes <mbenes@suse.cz>

Date: Tue, 15 Jan 2019 17:45:07 +0100

Subject: livepatch: Remove signal sysfs attribute

Git-commit: 0b3d52790e1cfd6b80b826a245d24859e89632f7

Patch-mainline: v5.1-rc1

References: bsc#1071995 fate#323487

The fake signal is send automatically now. We can rely on it completely

and remove the sysfs attribute.

Signed-off-by: Miroslav Benes <mbenes@suse.cz>

Signed-off-by: Jiri Kosina <jkosina@suse.cz>

---

 Documentation/ABI/testing/sysfs-kernel-livepatch | 12 ----

 Documentation/livepatch/livepatch.txt            | 16 ++---

 kernel/livepatch/core.c                          | 32 ---------

 kernel/livepatch/transition.c                    | 82 ++++++++++++------------

 kernel/livepatch/transition.h                    |  1 -

 5 files changed, 48 insertions(+), 95 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-kernel-livepatch b/Documentation/ABI/testing/sysfs-kernel-livepatch

index dac7e1e62a8b..85db352f68f9 100644

--- a/Documentation/ABI/testing/sysfs-kernel-livepatch

+++ b/Documentation/ABI/testing/sysfs-kernel-livepatch

@@ -33,18 +33,6 @@ Contact:	live-patching@vger.kernel.org

 		An attribute which indicates whether the patch is currently in

 		transition.

-What:		/sys/kernel/livepatch/<patch>/signal

-Date:		Nov 2017

-KernelVersion:	4.15.0

-Contact:	live-patching@vger.kernel.org

-Description:

-		A writable attribute that allows administrator to affect the

-		course of an existing transition. Writing 1 sends a fake

-		signal to all remaining blocking tasks. The fake signal

-		means that no proper signal is delivered (there is no data in

-		signal pending structures). Tasks are interrupted or woken up,

-		and forced to change their patched state.

-

 What:		/sys/kernel/livepatch/<patch>/force

 Date:		Nov 2017

 KernelVersion:	4.15.0

diff --git a/Documentation/livepatch/livepatch.txt b/Documentation/livepatch/livepatch.txt

index 407e0f03dc99..4627b41ff02e 100644

--- a/Documentation/livepatch/livepatch.txt

+++ b/Documentation/livepatch/livepatch.txt

@@ -158,13 +158,11 @@ If a patch is in transition, this file shows 0 to indicate the task is

 unpatched and 1 to indicate it's patched.  Otherwise, if no patch is in

 transition, it shows -1.  Any tasks which are blocking the transition

 can be signaled with SIGSTOP and SIGCONT to force them to change their

-patched state. This may be harmful to the system though.

-/sys/kernel/livepatch/<patch>/signal attribute provides a better alternative.

-Writing 1 to the attribute sends a fake signal to all remaining blocking

-tasks. No proper signal is actually delivered (there is no data in signal

-pending structures). Tasks are interrupted or woken up, and forced to change

-their patched state. Despite the sysfs attribute the fake signal is also sent

-every 15 seconds automatically.

+patched state. This may be harmful to the system though. Sending a fake signal

+to all remaining blocking tasks is a better alternative. No proper signal is

+actually delivered (there is no data in signal pending structures). Tasks are

+interrupted or woken up, and forced to change their patched state. The fake

+signal is automatically sent every 15 seconds.

 Administrator can also affect a transition through

 /sys/kernel/livepatch/<patch>/force attribute. Writing 1 there clears

@@ -412,8 +410,8 @@ Information about the registered patches can be found under

 /sys/kernel/livepatch. The patches could be enabled and disabled

 by writing there.

-/sys/kernel/livepatch/<patch>/signal and /sys/kernel/livepatch/<patch>/force

-attributes allow administrator to affect a patching operation.

+/sys/kernel/livepatch/<patch>/force attributes allow administrator to affect a

+patching operation.

 See Documentation/ABI/testing/sysfs-kernel-livepatch for more details.

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c

index adca5cf07f7e..fe1993399823 100644

--- a/kernel/livepatch/core.c

+++ b/kernel/livepatch/core.c

@@ -313,7 +313,6 @@ static int klp_write_object_relocations(struct module *pmod,

  * /sys/kernel/livepatch/<patch>

  * /sys/kernel/livepatch/<patch>/enabled

  * /sys/kernel/livepatch/<patch>/transition

- * /sys/kernel/livepatch/<patch>/signal

  * /sys/kernel/livepatch/<patch>/force

  * /sys/kernel/livepatch/<patch>/<object>

  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>

@@ -382,35 +381,6 @@ static ssize_t transition_show(struct kobject *kobj,

 			patch == klp_transition_patch);

 }

-static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,

-			    const char *buf, size_t count)

-{

-	struct klp_patch *patch;

-	int ret;

-	bool val;

-

-	ret = kstrtobool(buf, &val;;

-	if (ret)

-		return ret;

-

-	if (!val)

-		return count;

-

-	mutex_lock(&klp_mutex);

-

-	patch = container_of(kobj, struct klp_patch, kobj);

-	if (patch != klp_transition_patch) {

-		mutex_unlock(&klp_mutex);

-		return -EINVAL;

-	}

-

-	klp_send_signals();

-

-	mutex_unlock(&klp_mutex);

-

-	return count;

-}

-

 static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,

 			   const char *buf, size_t count)

 {

@@ -442,12 +412,10 @@ static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,

 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);

 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);

-static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal);

 static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);

 static struct attribute *klp_patch_attrs[] = {

 	&enabled_kobj_attr.attr,

 	&transition_kobj_attr.attr,

-	&signal_kobj_attr.attr,

 	&force_kobj_attr.attr,

 	NULL

 };

diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c

index ea7697bb753e..183b2086ba03 100644

--- a/kernel/livepatch/transition.c

+++ b/kernel/livepatch/transition.c

@@ -347,6 +347,47 @@ static bool klp_try_switch_task(struct task_struct *task)

 }

+/*

+ * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set.

+ * Kthreads with TIF_PATCH_PENDING set are woken up.

+ */

+static void klp_send_signals(void)

+{

+	struct task_struct *g, *task;

+

+	if (klp_signals_cnt == SIGNALS_TIMEOUT)

+		pr_notice("signaling remaining tasks\n");

+

+	read_lock(&tasklist_lock);

+	for_each_process_thread(g, task) {

+		if (!klp_patch_pending(task))

+			continue;

+

+		/*

+		 * There is a small race here. We could see TIF_PATCH_PENDING

+		 * set and decide to wake up a kthread or send a fake signal.

+		 * Meanwhile the task could migrate itself and the action

+		 * would be meaningless. It is not serious though.

+		 */

+		if (task->flags & PF_KTHREAD) {

+			/*

+			 * Wake up a kthread which sleeps interruptedly and

+			 * still has not been migrated.

+			 */

+			wake_up_state(task, TASK_INTERRUPTIBLE);

+		} else {

+			/*

+			 * Send fake signal to all non-kthread tasks which are

+			 * still not migrated.

+			 */

+			spin_lock_irq(&task->sighand->siglock);

+			signal_wake_up(task, 0);

+			spin_unlock_irq(&task->sighand->siglock);

+		}

+	}

+	read_unlock(&tasklist_lock);

+}

+

 /*

  * Try to switch all remaining tasks to the target patch state by walking the

  * stacks of sleeping tasks and looking for any to-be-patched or

@@ -586,47 +627,6 @@ void klp_copy_process(struct task_struct *child)

 	/* TIF_PATCH_PENDING gets copied in setup_thread_stack() */

 }

-/*

- * Sends a fake signal to all non-kthread tasks with TIF_PATCH_PENDING set.

- * Kthreads with TIF_PATCH_PENDING set are woken up.

- */

-void klp_send_signals(void)

-{

-	struct task_struct *g, *task;

-

-	if (klp_signals_cnt == SIGNALS_TIMEOUT)

-		pr_notice("signaling remaining tasks\n");

-

-	read_lock(&tasklist_lock);

-	for_each_process_thread(g, task) {

-		if (!klp_patch_pending(task))

-			continue;

-

-		/*

-		 * There is a small race here. We could see TIF_PATCH_PENDING

-		 * set and decide to wake up a kthread or send a fake signal.

-		 * Meanwhile the task could migrate itself and the action

-		 * would be meaningless. It is not serious though.

-		 */

-		if (task->flags & PF_KTHREAD) {

-			/*

-			 * Wake up a kthread which sleeps interruptedly and

-			 * still has not been migrated.

-			 */

-			wake_up_state(task, TASK_INTERRUPTIBLE);

-		} else {

-			/*

-			 * Send fake signal to all non-kthread tasks which are

-			 * still not migrated.

-			 */

-			spin_lock_irq(&task->sighand->siglock);

-			signal_wake_up(task, 0);

-			spin_unlock_irq(&task->sighand->siglock);

-		}

-	}

-	read_unlock(&tasklist_lock);

-}

-

 /*

  * Drop TIF_PATCH_PENDING of all tasks on admin's request. This forces an

  * existing transition to finish.

diff --git a/kernel/livepatch/transition.h b/kernel/livepatch/transition.h

index f9d0bc016067..322db16233de 100644

--- a/kernel/livepatch/transition.h

+++ b/kernel/livepatch/transition.h

@@ -11,7 +11,6 @@ void klp_cancel_transition(void);

 void klp_start_transition(void);

 void klp_try_complete_transition(void);

 void klp_reverse_transition(void);

-void klp_send_signals(void);

 void klp_force_transition(void);

 #endif /* _LIVEPATCH_TRANSITION_H */