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From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
	arnd@arndb.de
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>,
	Theodore Ts'o <tytso@mit.edu>,
	Dominik Brodowski <linux@dominikbrodowski.net>,
	Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	"David S . Miller" <davem@davemloft.net>,
	Richard Weinberger <richard@nod.at>,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Chris Zankel <chris@zankel.net>,
	Max Filippov <jcmvbkbc@gmail.com>,
	John Stultz <john.stultz@linaro.org>,
	Stephen Boyd <sboyd@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
	linux-riscv@lists.infradead.org, sparclinux@vger.kernel.org,
	linux-um@lists.infradead.org, x86@kernel.org,
	linux-xtensa@linux-xtensa.org
Subject: [PATCH RFC v1 08/10] um: use sched_clock() for random_get_entropy() instead of zero
Date: Fri,  8 Apr 2022 20:21:43 +0200	[thread overview]
Message-ID: <20220408182145.142506-9-Jason@zx2c4.com> (raw)
In-Reply-To: <20220408182145.142506-1-Jason@zx2c4.com>

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 sched_clock() would be preferable, because
that always needs to return _something_, even falling back to jiffies
eventually. It's not as though sched_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.

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: Arnd Bergmann <arnd@arndb.de>
Cc: Richard Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 arch/um/include/asm/timex.h | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/arch/um/include/asm/timex.h b/arch/um/include/asm/timex.h
index e392a9a5bc9b..9f27176adb26 100644
--- a/arch/um/include/asm/timex.h
+++ b/arch/um/include/asm/timex.h
@@ -2,13 +2,8 @@
 #ifndef __UM_TIMEX_H
 #define __UM_TIMEX_H
 
-typedef unsigned long cycles_t;
-
-static inline cycles_t get_cycles (void)
-{
-	return 0;
-}
-
 #define CLOCK_TICK_RATE (HZ)
 
+#include <asm-generic/timex.h>
+
 #endif
-- 
2.35.1


  parent reply	other threads:[~2022-04-08 18:23 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-08 18:21 [PATCH RFC v1 00/10] archs/random: fallback to using sched_clock() if no cycle counter Jason A. Donenfeld
2022-04-08 18:21 ` [PATCH RFC v1 01/10] random: use sched_clock() for random_get_entropy() if no get_cycles() Jason A. Donenfeld
2022-04-08 18:21 ` [PATCH RFC v1 02/10] m68k: use sched_clock() for random_get_entropy() instead of zero Jason A. Donenfeld
2022-04-08 18:21 ` [PATCH RFC v1 03/10] riscv: " Jason A. Donenfeld
2022-04-08 18:21 ` [PATCH RFC v1 04/10] mips: " Jason A. Donenfeld
2022-04-08 18:21 ` [PATCH RFC v1 05/10] arm: " Jason A. Donenfeld
2022-04-08 18:21 ` [PATCH RFC v1 06/10] x86: " Jason A. Donenfeld
2022-04-08 18:21 ` [PATCH RFC v1 07/10] arm64: " Jason A. Donenfeld
2022-04-08 18:33   ` Mark Rutland
2022-04-08 18:40     ` Jason A. Donenfeld
2022-04-08 18:21 ` Jason A. Donenfeld [this message]
2022-04-08 18:21 ` [PATCH RFC v1 09/10] sparc: " Jason A. Donenfeld
2022-04-08 18:21 ` [PATCH RFC v1 10/10] xtensa: " Jason A. Donenfeld
2022-04-09 23:29 ` [PATCH RFC v1 00/10] archs/random: fallback to using sched_clock() if no cycle counter Thomas Gleixner
2022-04-10 14:25   ` Jason A. Donenfeld
2022-04-10 20:57     ` Thomas Gleixner
2022-04-10 21:38       ` Jason A. Donenfeld
2022-04-10 23:03 ` Eric Biggers
2022-04-10 23:29   ` Jason A. Donenfeld

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