Re: [PATCH 1/1] arm64: syscall: Direct PRNG kstack randomization

From: "Arnd Bergmann" <arnd@arndb.de>
To: "Jeremy Linton" <jeremy.linton@arm.com>,
	"Kees Cook" <keescook@chromium.org>
Cc: linux-arm-kernel@lists.infradead.org,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Will Deacon" <will@kernel.org>,
	"Jason A . Donenfeld" <Jason@zx2c4.com>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Mark Brown" <broonie@kernel.org>,
	"Guo Hui" <guohui@uniontech.com>,
	Manoj.Iyer@arm.com, linux-kernel@vger.kernel.org,
	linux-hardening@vger.kernel.org,
	"James Yang" <james.yang@arm.com>,
	"Shiyou Huang" <shiyou.huang@arm.com>
Subject: Re: [PATCH 1/1] arm64: syscall: Direct PRNG kstack randomization
Date: Fri, 08 Mar 2024 21:29:51 +0100	[thread overview]
Message-ID: <acfc522a-5162-4b33-9d6c-1e25d0c44a71@app.fastmail.com> (raw)
In-Reply-To: <db7dfa2d-c7c6-4b10-981a-a7ecc87c8541@arm.com>

On Fri, Mar 8, 2024, at 17:49, Jeremy Linton wrote:
> On 3/7/24 05:10, Arnd Bergmann wrote:
>>
>> I'm not sure I understand the logic. Do you mean that accessing
>> CNTVCT itself is slow, or that reseeding based on CNTVCT is slow
>> because of the overhead of reseeding?
>
> Slow, as in, its running at a much lower frequency than a cycle counter.

Ok, I see. Would it be possible to use PMEVCNTR0 instead?

      Arnd