resume_user_mode: Move to resume_user_mode.h

Move set_notify_resume and tracehook_notify_resume into resume_user_mode.h.
While doing that rename tracehook_notify_resume to resume_user_mode_work.

Update all of the places that included tracehook.h for these functions to
include resume_user_mode.h instead.

Update all of the callers of tracehook_notify_resume to call
resume_user_mode_work.

Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-12-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 64 insertions, 0 deletions

diff --git a/include/linux/resume_user_mode.h b/include/linux/resume_user_mode.h
new file mode 100644
index 000000000000..285189454449
--- /dev/null
+++ b/include/linux/resume_user_mode.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef LINUX_RESUME_USER_MODE_H
+#define LINUX_RESUME_USER_MODE_H
+
+#include <linux/sched.h>
+#include <linux/task_work.h>
+#include <linux/memcontrol.h>
+#include <linux/blk-cgroup.h>
+
+/**
+ * set_notify_resume - cause resume_user_mode_work() to be called
+ * @task:		task that will call resume_user_mode_work()
+ *
+ * Calling this arranges that @task will call resume_user_mode_work()
+ * before returning to user mode.  If it's already running in user mode,
+ * it will enter the kernel and call resume_user_mode_work() soon.
+ * If it's blocked, it will not be woken.
+ */
+static inline void set_notify_resume(struct task_struct *task)
+{
+	if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME))
+		kick_process(task);
+}
+
+
+/**
+ * resume_user_mode_work - Perform work before returning to user mode
+ * @regs:		user-mode registers of @current task
+ *
+ * This is called when %TIF_NOTIFY_RESUME has been set.  Now we are
+ * about to return to user mode, and the user state in @regs can be
+ * inspected or adjusted.  The caller in arch code has cleared
+ * %TIF_NOTIFY_RESUME before the call.  If the flag gets set again
+ * asynchronously, this will be called again before we return to
+ * user mode.
+ *
+ * Called without locks.
+ */
+static inline void resume_user_mode_work(struct pt_regs *regs)
+{
+	clear_thread_flag(TIF_NOTIFY_RESUME);
+	/*
+	 * This barrier pairs with task_work_add()->set_notify_resume() after
+	 * hlist_add_head(task->task_works);
+	 */
+	smp_mb__after_atomic();
+	if (unlikely(task_work_pending(current)))
+		task_work_run();
+
+#ifdef CONFIG_KEYS_REQUEST_CACHE
+	if (unlikely(current->cached_requested_key)) {
+		key_put(current->cached_requested_key);
+		current->cached_requested_key = NULL;
+	}
+#endif
+
+	mem_cgroup_handle_over_high();
+	blkcg_maybe_throttle_current();
+
+	rseq_handle_notify_resume(NULL, regs);
+}
+
+#endif /* LINUX_RESUME_USER_MODE_H */