[PATCH] kprobes: fix build with CONFIG_KRETPROBES=n

[Max Filippov <jcmvbkbc@gmail.com>]

When building kernel with CONFIG_KRETPROBES=n kernel/kprobes.c
compilation fails with the following messages:

  kernel/kprobes.c: In function ‘recycle_rp_inst’:
  kernel/kprobes.c:1273:32: error: implicit declaration of function
                                   ‘get_kretprobe’

  kernel/kprobes.c: In function ‘kprobe_flush_task’:
  kernel/kprobes.c:1299:35: error: ‘struct task_struct’ has no member
                                   named ‘kretprobe_instances’

Make references to kretprobe-specific structures and functions
conditional.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 kernel/kprobes.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index dd58c0be9ce2..95ce4d16e63e 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1258,6 +1258,7 @@ void kprobe_busy_end(void)
 }
 
 #if !defined(CONFIG_KRETPROBE_ON_RETHOOK)
+#ifdef CONFIG_KRETPROBES
 static void free_rp_inst_rcu(struct rcu_head *head)
 {
 	struct kretprobe_instance *ri = container_of(head, struct kretprobe_instance, rcu);
@@ -1279,21 +1280,11 @@ static void recycle_rp_inst(struct kretprobe_instance *ri)
 }
 NOKPROBE_SYMBOL(recycle_rp_inst);
 
-/*
- * This function is called from delayed_put_task_struct() when a task is
- * dead and cleaned up to recycle any kretprobe instances associated with
- * this task. These left over instances represent probed functions that
- * have been called but will never return.
- */
-void kprobe_flush_task(struct task_struct *tk)
+static void kretprobe_flush_task(struct task_struct *tk)
 {
 	struct kretprobe_instance *ri;
 	struct llist_node *node;
 
-	/* Early boot, not yet initialized. */
-	if (unlikely(!kprobes_initialized))
-		return;
-
 	kprobe_busy_begin();
 
 	node = __llist_del_all(&tk->kretprobe_instances);
@@ -1306,6 +1297,25 @@ void kprobe_flush_task(struct task_struct *tk)
 
 	kprobe_busy_end();
 }
+NOKPROBE_SYMBOL(kretprobe_flush_task);
+#endif
+
+/*
+ * This function is called from delayed_put_task_struct() when a task is
+ * dead and cleaned up to recycle any kretprobe instances associated with
+ * this task. These left over instances represent probed functions that
+ * have been called but will never return.
+ */
+void kprobe_flush_task(struct task_struct *tk)
+{
+	/* Early boot, not yet initialized. */
+	if (unlikely(!kprobes_initialized))
+		return;
+
+#ifdef CONFIG_KRETPROBES
+	kretprobe_flush_task(tk);
+#endif
+}
 NOKPROBE_SYMBOL(kprobe_flush_task);
 
 static inline void free_rp_inst(struct kretprobe *rp)
-- 
2.30.2