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From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
To:     linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
        tglx@linutronix.de, arnd@arndb.de
Cc:     "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Dinh Nguyen <dinguyen@kernel.org>
Subject: [PATCH v6 12/17] nios2: use fallback for random_get_entropy() instead of zero
Date:   Sat, 23 Apr 2022 23:26:18 +0200
Message-Id: <20220423212623.1957011-13-Jason@zx2c4.com>
In-Reply-To: <20220423212623.1957011-1-Jason@zx2c4.com>
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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 | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/nios2/include/asm/timex.h b/arch/nios2/include/asm/timex.h
index a769f871b28d..40a1adc9bd03 100644
--- a/arch/nios2/include/asm/timex.h
+++ b/arch/nios2/include/asm/timex.h
@@ -8,5 +8,8 @@
 typedef unsigned long cycles_t;
 
 extern cycles_t get_cycles(void);
+#define get_cycles get_cycles
+
+#define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback())
 
 #endif
-- 
2.35.1