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

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Message-Id: <acfc522a-5162-4b33-9d6c-1e25d0c44a71@app.fastmail.com>
Date: Fri, 08 Mar 2024 21:29:51 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Jeremy Linton" <jeremy.linton@....com>,
 "Kees Cook" <keescook@...omium.org>
Cc: linux-arm-kernel@...ts.infradead.org,
 "Catalin Marinas" <catalin.marinas@....com>, "Will Deacon" <will@...nel.org>,
 "Jason A . Donenfeld" <Jason@...c4.com>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 "Mark Rutland" <mark.rutland@....com>,
 "Steven Rostedt" <rostedt@...dmis.org>, "Mark Brown" <broonie@...nel.org>,
 "Guo Hui" <guohui@...ontech.com>, Manoj.Iyer@....com,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
 "James Yang" <james.yang@....com>, "Shiyou Huang" <shiyou.huang@....com>
Subject: Re: [PATCH 1/1] arm64: syscall: Direct PRNG kstack randomization

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