From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: "Jason A. Donenfeld" Subject: [PATCH v2 07/11] nios2: use ktime_read_raw_clock() for random_get_entropy() instead of zero Date: Sun, 10 Apr 2022 23:49:47 +0200 Message-Id: <20220410214951.55294-8-Jason@zx2c4.com> In-Reply-To: <20220410214951.55294-1-Jason@zx2c4.com> References: <20220410214951.55294-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, tglx@linutronix.de, arnd@arndb.de Cc: "Jason A. Donenfeld" , Theodore Ts'o , Dominik Brodowski , Russell King , Catalin Marinas , Will Deacon , Geert Uytterhoeven , Thomas Bogendoerfer , Paul Walmsley , Palmer Dabbelt , Albert Ou , "David S . Miller" , Richard Weinberger , Anton Ivanov , Johannes Berg , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Chris Zankel , Max Filippov , John Stultz , Stephen Boyd , Dinh Nguyen , 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 List-ID: 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 Cc: Arnd Bergmann Cc: Dinh Nguyen Signed-off-by: Jason A. Donenfeld --- arch/nios2/include/asm/timex.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/nios2/include/asm/timex.h b/arch/nios2/include/asm/timex.h index a769f871b28d..3c74d3e337a0 100644 --- a/arch/nios2/include/asm/timex.h +++ b/arch/nios2/include/asm/timex.h @@ -9,4 +9,6 @@ typedef unsigned long cycles_t; extern cycles_t get_cycles(void); +#define random_get_entropy() ((unsigned long)(get_cycles() ?: ktime_read_raw_clock())) + #endif -- 2.35.1