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>,
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>,
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>,
Dinh Nguyen <dinguyen@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 v4 03/11] riscv: use fallback for random_get_entropy() instead of zero
Date: Wed, 13 Apr 2022 13:54:03 +0200 [thread overview]
Message-ID: <20220413115411.21489-4-Jason@zx2c4.com> (raw)
In-Reply-To: <20220413115411.21489-1-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 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: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
arch/riscv/include/asm/timex.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h
index 507cae273bc6..d6a7428f6248 100644
--- a/arch/riscv/include/asm/timex.h
+++ b/arch/riscv/include/asm/timex.h
@@ -41,7 +41,7 @@ static inline u32 get_cycles_hi(void)
static inline unsigned long random_get_entropy(void)
{
if (unlikely(clint_time_val == NULL))
- return 0;
+ return random_get_entropy_fallback();
return get_cycles();
}
#define random_get_entropy() random_get_entropy()
--
2.35.1
next prev parent reply other threads:[~2022-04-13 11:55 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-13 11:54 [PATCH v4 00/11] archs/random: fallback to best raw ktime when no cycle counter Jason A. Donenfeld
2022-04-13 11:54 ` [PATCH v4 01/11] timekeeping: add raw clock fallback for random_get_entropy() Jason A. Donenfeld
2022-04-13 14:32 ` Rob Herring
2022-04-13 22:38 ` Jason A. Donenfeld
2022-04-14 20:41 ` Rob Herring
2022-04-14 21:49 ` H. Peter Anvin
2022-04-14 10:12 ` Russell King (Oracle)
2022-04-14 11:56 ` Jason A. Donenfeld
2022-04-13 11:54 ` [PATCH v4 02/11] m68k: use fallback for random_get_entropy() instead of zero Jason A. Donenfeld
2022-04-13 11:54 ` Jason A. Donenfeld [this message]
2022-04-13 14:40 ` [PATCH v4 03/11] riscv: " Rob Herring
2022-04-13 22:40 ` Jason A. Donenfeld
2022-04-13 11:54 ` [PATCH v4 04/11] mips: " Jason A. Donenfeld
2022-04-13 12:25 ` Thomas Bogendoerfer
2022-04-13 12:46 ` Maciej W. Rozycki
2022-04-13 22:35 ` Jason A. Donenfeld
2022-04-14 1:16 ` Maciej W. Rozycki
2022-04-14 9:27 ` Jason A. Donenfeld
2022-04-15 12:26 ` Maciej W. Rozycki
2022-04-16 11:09 ` Jason A. Donenfeld
2022-04-16 14:44 ` Maciej W. Rozycki
2022-04-16 22:54 ` Jason A. Donenfeld
2022-04-18 7:10 ` Thomas Bogendoerfer
2022-04-23 23:33 ` Maciej W. Rozycki
2022-04-24 8:15 ` Jason A. Donenfeld
2022-04-24 10:51 ` Maciej W. Rozycki
2022-04-13 11:54 ` [PATCH v4 05/11] arm: " Jason A. Donenfeld
2022-04-13 11:54 ` [PATCH v4 06/11] nios2: " Jason A. Donenfeld
2022-05-23 13:58 ` Dinh Nguyen
2022-04-13 11:54 ` [PATCH v4 07/11] x86: " Jason A. Donenfeld
2022-04-13 11:54 ` [PATCH v4 08/11] um: " Jason A. Donenfeld
2022-04-13 11:54 ` [PATCH v4 09/11] sparc: " Jason A. Donenfeld
2022-04-13 11:54 ` [PATCH v4 10/11] xtensa: " Jason A. Donenfeld
2022-04-13 11:54 ` [PATCH v4 11/11] random: insist on random_get_entropy() existing in order to simplify Jason A. Donenfeld
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