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 ktime_read_raw_clock() would be preferable,
because that always needs to return _something_, even falling back to
jiffies eventually. It's not as though ktime_read_raw_clock() 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>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
---
arch/arm/include/asm/timex.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm/include/asm/timex.h b/arch/arm/include/asm/timex.h
index 7c3b3671d6c2..d0b32ce87254 100644
--- a/arch/arm/include/asm/timex.h
+++ b/arch/arm/include/asm/timex.h
@@ -11,5 +11,6 @@
typedef unsigned long cycles_t;
#define get_cycles() ({ cycles_t c; read_current_timer(&c) ? 0 : c; })
+#define random_get_entropy() ((unsigned long)(get_cycles() ?: ktime_read_raw_clock()))
#endif
--
2.35.1
