| Message ID | 20220408182145.142506-4-Jason@zx2c4.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | archs/random: fallback to using sched_clock() if no cycle counter | expand |
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()
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@arndb.de> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> --- arch/riscv/include/asm/timex.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)