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Subject[PATCH v2 2/2] livepatch: Remove signal sysfs attribute
Date
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>
---
.../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 12a1a65531a0..79876744d8da 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
@@ -587,47 +628,6 @@ 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 */
--
2.20.1
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