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From: Andrea Righi <andrea.righi@canonical.com>
To: Mark Brown <broonie@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: head: rely on CONFIG_RANDOM_TRUST_CPU
Date: Wed, 17 Aug 2022 16:17:21 +0200	[thread overview]
Message-ID: <Yvz4ccSO+BhICmyE@arighi-desktop> (raw)
In-Reply-To: <YvzqLFDuXtDRxilZ@sirena.org.uk>

On Wed, Aug 17, 2022 at 02:16:28PM +0100, Mark Brown wrote:
> On Wed, Aug 17, 2022 at 11:46:18AM +0200, Andrea Righi wrote:
> > The CONFIG_ARCH_RANDOM .config option has been removed by
> > commit 9592eef7c16e ("random: remove CONFIG_ARCH_RANDOM").
> > 
> > Depend on CONFIG_RANDOM_TRUST_CPU to determine whether we can rely on
> > __arm64_rndr() to initialize the seed for kaslr.
> > 
> > Fixes: 9592eef7c16e ("random: remove CONFIG_ARCH_RANDOM")
> 
> > -#ifdef CONFIG_ARCH_RANDOM
> > +#ifdef CONFIG_RANDOM_TRUST_CPU
> >  		 if (!__early_cpu_has_rndr() ||
> >  		     !__arm64_rndr((unsigned long *)&seed))
> >  #endif
> 
> I think the sense here would be more that we should just unconditionally
> use RNDR if it's present - previously we'd use the result even if we
> didn't have strong trust in the CPU implementation and I don't see why
> we'd want to change that.

Makes sense, in that case it'd be better to just remove the guard
completely, as mentioned by Will.

Thanks,
-Andrea

  reply	other threads:[~2022-08-17 14:17 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-17  9:46 Andrea Righi
2022-08-17 13:16 ` Mark Brown
2022-08-17 14:17   ` Andrea Righi [this message]
2022-08-17 13:51 ` Will Deacon

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