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-rw-r--r--kernel/Makefile1
-rw-r--r--kernel/fork.c2
-rw-r--r--kernel/user-return-notifier.c46
3 files changed, 49 insertions, 0 deletions
diff --git a/kernel/Makefile b/kernel/Makefile
index d7c13d2..6c51128 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -96,6 +96,7 @@ obj-$(CONFIG_SMP) += sched_cpupri.o
obj-$(CONFIG_SLOW_WORK) += slow-work.o
obj-$(CONFIG_SLOW_WORK_DEBUG) += slow-work-debugfs.o
obj-$(CONFIG_PERF_EVENTS) += perf_event.o
+obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
# According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff --git a/kernel/fork.c b/kernel/fork.c
index 166b8c4..7d4a348e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -64,6 +64,7 @@
#include <linux/magic.h>
#include <linux/perf_event.h>
#include <linux/posix-timers.h>
+#include <linux/user-return-notifier.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -249,6 +250,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
goto out;
setup_thread_stack(tsk, orig);
+ clear_user_return_notifier(tsk);
stackend = end_of_stack(tsk);
*stackend = STACK_END_MAGIC; /* for overflow detection */
diff --git a/kernel/user-return-notifier.c b/kernel/user-return-notifier.c
new file mode 100644
index 0000000..03e2d6f
--- /dev/null
+++ b/kernel/user-return-notifier.c
@@ -0,0 +1,46 @@
+
+#include <linux/user-return-notifier.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+
+static DEFINE_PER_CPU(struct hlist_head, return_notifier_list);
+
+#define URN_LIST_HEAD per_cpu(return_notifier_list, raw_smp_processor_id())
+
+/*
+ * Request a notification when the current cpu returns to userspace. Must be
+ * called in atomic context. The notifier will also be called in atomic
+ * context.
+ */
+void user_return_notifier_register(struct user_return_notifier *urn)
+{
+ set_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
+ hlist_add_head(&urn->link, &URN_LIST_HEAD);
+}
+EXPORT_SYMBOL_GPL(user_return_notifier_register);
+
+/*
+ * Removes a registered user return notifier. Must be called from atomic
+ * context, and from the same cpu registration occured in.
+ */
+void user_return_notifier_unregister(struct user_return_notifier *urn)
+{
+ hlist_del(&urn->link);
+ if (hlist_empty(&URN_LIST_HEAD))
+ clear_tsk_thread_flag(current, TIF_USER_RETURN_NOTIFY);
+}
+EXPORT_SYMBOL_GPL(user_return_notifier_unregister);
+
+/* Calls registered user return notifiers */
+void fire_user_return_notifiers(void)
+{
+ struct user_return_notifier *urn;
+ struct hlist_node *tmp1, *tmp2;
+ struct hlist_head *head;
+
+ head = &get_cpu_var(return_notifier_list);
+ hlist_for_each_entry_safe(urn, tmp1, tmp2, head, link)
+ urn->on_user_return(urn);
+ put_cpu_var(return_notifier_list);
+}
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