[PATCH 4.19 144/234] nios2: use fallback for random_get_entropy() instead of zero

[Greg Kroah-Hartman]

From: "Jason A. Donenfeld" <Jason@xxxxxxxxx>

commit c04e72700f2293013dab40208e809369378f224c upstream.

In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Acked-by: Dinh Nguyen <dinguyen@xxxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/nios2/include/asm/timex.h |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/nios2/include/asm/timex.h
+++ b/arch/nios2/include/asm/timex.h
@@ -20,5 +20,8 @@
 typedef unsigned long cycles_t;
 
 extern cycles_t get_cycles(void);
+#define get_cycles get_cycles
+
+#define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback())
 
 #endif