lkml.org 
[lkml]   [2022]   [Apr]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH RFC v1 03/10] riscv: use sched_clock() for random_get_entropy() instead of zero
Date
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(-)

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
\
 
 \ /
  Last update: 2022-04-08 20:23    [W:0.152 / U:1.776 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site