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[v2,05/11] mips: use ktime_read_raw_clock() for random_get_entropy() instead of zero

Message ID 20220410214951.55294-6-Jason@zx2c4.com
State New
Headers show
Series archs/random: fallback to using ktime_read_raw_clock() if no cycle counter | expand

Commit Message

Jason A. Donenfeld April 10, 2022, 9:49 p.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 ktime_read_raw_clock() would be preferable,
because that always needs to return _something_, even falling back to
jiffies eventually. It's not as though ktime_read_raw_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: 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(-)
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Patch

diff --git a/arch/mips/include/asm/timex.h b/arch/mips/include/asm/timex.h
index b05bb70a2e46..fa6a5ca20b46 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 ktime_read_raw_clock();	/* no usable register */
 }
 #define random_get_entropy random_get_entropy