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[v4,06/11] nios2: use fallback for random_get_entropy() instead of zero

Message ID 20220413115411.21489-7-Jason@zx2c4.com
State Superseded
Headers show
Series [v4,01/11] timekeeping: add raw clock fallback for random_get_entropy() | expand

Commit Message

Jason A. Donenfeld April 13, 2022, 11:54 a.m. UTC 
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@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 arch/nios2/include/asm/timex.h | 2 ++
 1 file changed, 2 insertions(+)
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Patch

diff --git a/arch/nios2/include/asm/timex.h b/arch/nios2/include/asm/timex.h
index a769f871b28d..d9a3f426cdda 100644
--- a/arch/nios2/include/asm/timex.h
+++ b/arch/nios2/include/asm/timex.h
@@ -9,4 +9,6 @@  typedef unsigned long cycles_t;
 
 extern cycles_t get_cycles(void);
 
+#define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback())
+
 #endif