linux-kernel - [PATCH 4.19 148/234] xtensa: use fallback for random_get

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Message-Id: <20220623164347.243600867@linuxfoundation.org>
Date:   Thu, 23 Jun 2022 18:43:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>,
        Max Filippov <jcmvbkbc@...il.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH 4.19 148/234] xtensa: use fallback for random_get_entropy() instead of zero

From: "Jason A. Donenfeld" <Jason@...c4.com>

commit e10e2f58030c5c211d49042a8c2a1b93d40b2ffb upstream.

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.

This is accomplished by just including the asm-generic code like on
other architectures, which means we can get rid of the empty stub
function here.

Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Arnd Bergmann <arnd@...db.de>
Acked-by: Max Filippov <jcmvbkbc@...il.com>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/xtensa/include/asm/timex.h |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- a/arch/xtensa/include/asm/timex.h
+++ b/arch/xtensa/include/asm/timex.h
@@ -30,10 +30,6 @@

 extern unsigned long ccount_freq;

-typedef unsigned long long cycles_t;
-
-#define get_cycles()	(0)
-
 void local_timer_setup(unsigned cpu);

 /*
@@ -69,4 +65,6 @@ static inline void set_linux_timer (unsi
 	WSR_CCOMPARE(LINUX_TIMER, ccompare);
 }

+#include <asm-generic/timex.h>
+
 #endif	/* _XTENSA_TIMEX_H */