From: James Morse <james.morse@arm.com>
To: Andre Przywara <andre.przywara@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Richard Henderson <richard.henderson@linaro.org>,
linux-kernel@vger.kernel.org, Mark Brown <broonie@kernel.org>,
Sudeep Holla <sudeep.holla@arm.com>,
Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/2] arm64: Add support for SMCCC TRNG firmware interface
Date: Wed, 7 Oct 2020 15:16:07 +0100 [thread overview]
Message-ID: <65057faa-d06b-6baf-4f12-9587cacbe3a9@arm.com> (raw)
In-Reply-To: <20201006201808.37665-3-andre.przywara@arm.com>
Hi Andre,
On 06/10/2020 21:18, Andre Przywara wrote:
> The ARM architected TRNG firmware interface, described in ARM spec
> DEN0098[1], defines an ARM SMCCC based interface to a true random number
> generator, provided by firmware.
> This can be discovered via the SMCCC >=v1.1 interface, and provides
> up to 192 bits of entropy per call.
>
> Hook this SMC call into arm64's arch_get_random_*() implementation,
> coming to the rescue when the CPU does not implement the ARM v8.5 RNG
> system registers.
>
> For the detection, we piggy back on the PSCI/SMCCC discovery (which gives
> us the conduit to use: hvc or smc), then try to call the
> ARM_SMCCC_TRNG_VERSION function, which returns -1 if this interface is
> not implemented.
> arch/arm64/include/asm/archrandom.h | 83 +++++++++++++++++++++++++----
> 1 file changed, 73 insertions(+), 10 deletions(-)
> diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h
> index ffb1a40d5475..b6c291c42a48 100644
> --- a/arch/arm64/include/asm/archrandom.h
> +++ b/arch/arm64/include/asm/archrandom.h
> @@ -7,6 +7,13 @@
> #include <linux/bug.h>
> #include <linux/kernel.h>
> #include <asm/cpufeature.h>
> +#include <linux/arm-smccc.h>
> +
> +static enum smc_trng_status {
> + SMC_TRNG_UNKNOWN,
> + SMC_TRNG_NOT_SUPPORTED,
> + SMC_TRNG_SUPPORTED
> +} smc_trng_status = SMC_TRNG_UNKNOWN;
Doesn't this static variable in a header file mean each file that includes this has its
own copy? Is that intentional?
Thanks,
James
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next prev parent reply other threads:[~2020-10-07 14:17 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-06 20:18 [PATCH 0/2] arm64: Add support for SMCCC TRNG interface Andre Przywara
2020-10-06 20:18 ` [PATCH 1/2] firmware: smccc: Add SMCCC TRNG function call IDs Andre Przywara
2020-10-06 20:18 ` [PATCH 2/2] arm64: Add support for SMCCC TRNG firmware interface Andre Przywara
2020-10-07 10:48 ` Mark Brown
2020-10-07 14:16 ` James Morse [this message]
2020-10-07 14:43 ` André Przywara
2020-10-12 6:35 ` Ard Biesheuvel
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