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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
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Subject: [PATCH v4 04/11] mips: use fallback for random_get_entropy() instead of zero
Date:   Wed, 13 Apr 2022 13:54:04 +0200
Message-Id: <20220413115411.21489-5-Jason@zx2c4.com>
In-Reply-To: <20220413115411.21489-1-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: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 arch/mips/include/asm/timex.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/include/asm/timex.h b/arch/mips/include/asm/timex.h
index b05bb70a2e46..abc60a6395e3 100644
--- a/arch/mips/include/asm/timex.h
+++ b/arch/mips/include/asm/timex.h
@@ -94,7 +94,7 @@ static inline unsigned long random_get_entropy(void)
 	else if (likely(imp != PRID_IMP_R6000 && imp != PRID_IMP_R6000A))
 		return read_c0_random();
 	else
-		return 0;	/* no usable register */
+		return random_get_entropy_fallback();	/* no usable register */
 }
 #define random_get_entropy random_get_entropy
 
-- 
2.35.1