From b5e87c0581319481399b6d8e8d6972b5523c18e6 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
Date: Tue, 29 Sep 2015 18:13:33 -0400
Subject: tracing: Add build bug if we have more trace_flags than bits

Add a enum that denotes the last bit of the trace_flags and have a
BUILD_BUG_ON(last_bit > 32).

If we add more bits than we have in trace_flags, the kernel wont build.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7446d42..991bab9 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -7046,6 +7046,12 @@ __init static int tracer_alloc_buffers(void)
 	int ring_buf_size;
 	int ret = -ENOMEM;
 
+	/*
+	 * Make sure we don't accidently add more trace options
+	 * than we have bits for.
+	 */
+	BUILD_BUG_ON(TRACE_ITER_LAST_BIT > 32);
+
 	if (!alloc_cpumask_var(&tracing_buffer_mask, GFP_KERNEL))
 		goto out;
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 8ed9787..0715565 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -966,7 +966,11 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
 #undef C
 #define C(a, b) TRACE_ITER_##a##_BIT
 
-enum trace_iterator_bits { TRACE_FLAGS };
+enum trace_iterator_bits {
+	TRACE_FLAGS
+	/* Make sure we don't go more than we have bits for */
+	TRACE_ITER_LAST_BIT
+};
 
 /*
  * By redefining C, we can make TRACE_FLAGS a list of masks that
-- 
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