[PATCH v4 04/17] context_tracking: Add ct_state and CT_WARN_ON

[Andy Lutomirski <luto@kernel.org>]

This will let us sprinkle sanity checks around the kernel without
making too much of a mess.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 include/linux/context_tracking.h       | 15 +++++++++++++++
 include/linux/context_tracking_state.h |  1 +
 2 files changed, 16 insertions(+)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index b96bd299966f..008fc67d0d96 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -49,13 +49,28 @@ static inline void exception_exit(enum ctx_state prev_ctx)
 	}
 }
 
+
+/**
+ * ct_state() - return the current context tracking state if known
+ *
+ * Returns the current cpu's context tracking state if context tracking
+ * is enabled.  If context tracking is disabled, returns
+ * CONTEXT_DISABLED.  This should be used primarily for debugging.
+ */
+static inline enum ctx_state ct_state(void)
+{
+	return context_tracking_is_enabled() ?
+		this_cpu_read(context_tracking.state) : CONTEXT_DISABLED;
+}
 #else
 static inline void user_enter(void) { }
 static inline void user_exit(void) { }
 static inline enum ctx_state exception_enter(void) { return 0; }
 static inline void exception_exit(enum ctx_state prev_ctx) { }
+static inline enum ctx_state ct_state(void) { return CONTEXT_DISABLED; }
 #endif /* !CONFIG_CONTEXT_TRACKING */
 
+#define CT_WARN_ON(cond) WARN_ON(context_tracking_is_enabled() && (cond))
 
 #ifdef CONFIG_CONTEXT_TRACKING_FORCE
 extern void context_tracking_init(void);
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 678ecdf90cf6..ee956c528fab 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -14,6 +14,7 @@ struct context_tracking {
 	bool active;
 	int recursion;
 	enum ctx_state {
+		CONTEXT_DISABLED = -1,	/* returned by ct_state() if unknown */
 		CONTEXT_KERNEL = 0,
 		CONTEXT_USER,
 		CONTEXT_GUEST,
-- 
2.4.3