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 sched_clock() would be preferable, because
that always needs to return _something_, even falling back to jiffies
eventually. It's not as though sched_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: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
---
arch/riscv/include/asm/timex.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h
index 507cae273bc6..5b802755ca3a 100644
--- a/arch/riscv/include/asm/timex.h
+++ b/arch/riscv/include/asm/timex.h
@@ -7,6 +7,7 @@
#define _ASM_RISCV_TIMEX_H
#include <asm/csr.h>
+#include <linux/sched/clock.h>
typedef unsigned long cycles_t;
@@ -41,7 +42,7 @@ static inline u32 get_cycles_hi(void)
static inline unsigned long random_get_entropy(void)
{
if (unlikely(clint_time_val == NULL))
- return 0;
+ return sched_clock();
return get_cycles();
}
#define random_get_entropy() random_get_entropy()
--
2.35.1
