[PATCH 4/6] uprobes/tracing: Introduce is_trace_uprobe_enabled()

[Oleg Nesterov <oleg@redhat.com>]

probe_event_enable/disable() check tu->consumer != NULL to avoid the
wrong uprobe_register/unregister().

We are going to kill this pointer and "struct uprobe_trace_consumer",
so we add the new helper, is_trace_uprobe_enabled(), which can rely
on TP_FLAG_TRACE/TP_FLAG_PROFILE instead.

Note: the current logic doesn't look optimal, it is not clear why
TP_FLAG_TRACE/TP_FLAG_PROFILE are mutually exclusive, we will probably
change this later.

Also kill the unused TP_FLAG_UPROBE.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/trace/trace_probe.h  |    1 -
 kernel/trace/trace_uprobe.c |    9 +++++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 9337086..5c7e09d 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -66,7 +66,6 @@
 #define TP_FLAG_TRACE		1
 #define TP_FLAG_PROFILE		2
 #define TP_FLAG_REGISTERED	4
-#define TP_FLAG_UPROBE		8
 
 
 /* data_rloc: data relative location, compatible with u32 */
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index f02bbec..947379a 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -536,12 +536,17 @@ partial:
 	return TRACE_TYPE_PARTIAL_LINE;
 }
 
+static inline bool is_trace_uprobe_enabled(struct trace_uprobe *tu)
+{
+	return tu->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE);
+}
+
 static int probe_event_enable(struct trace_uprobe *tu, int flag)
 {
 	struct uprobe_trace_consumer *utc;
 	int ret = 0;
 
-	if (tu->consumer)
+	if (is_trace_uprobe_enabled(tu))
 		return -EINTR;
 
 	utc = kzalloc(sizeof(struct uprobe_trace_consumer), GFP_KERNEL);
@@ -565,7 +570,7 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag)
 
 static void probe_event_disable(struct trace_uprobe *tu, int flag)
 {
-	if (!tu->consumer)
+	if (!is_trace_uprobe_enabled(tu))
 		return;
 
 	uprobe_unregister(tu->inode, tu->offset, &tu->consumer->cons);
-- 
1.5.5.1