[PATCH v10 3/3] arm64: Use v8.5-RNG entropy for KASLR seed

Mark Rutland mark.rutland at arm.com
Fri Jan 10 04:35:36 PST 2020


On Fri, Jan 10, 2020 at 12:23:41PM +0000, Mark Brown wrote:
> When seeding KALSR on a system where we have architecture level random
> number generation make use of that entropy, mixing it in with the seed
> passed by the bootloader. Since this is run very early in init before
> feature detection is complete we open code rather than use archrandom.h.
> 
> Signed-off-by: Mark Brown <broonie at kernel.org>

Reviewed-by: Mark Rutland <mark.rutland at arm.com>

Mark.

> ---
>  arch/arm64/kernel/kaslr.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
> index 2a11a962e571..53b8a4ee64ff 100644
> --- a/arch/arm64/kernel/kaslr.c
> +++ b/arch/arm64/kernel/kaslr.c
> @@ -120,6 +120,17 @@ u64 __init kaslr_early_init(u64 dt_phys)
>  		return 0;
>  	}
>  
> +	/*
> +	 * Mix in any entropy obtainable architecturally, open coded
> +	 * since this runs extremely early.
> +	 */
> +	if (__early_cpu_has_rndr()) {
> +		unsigned long raw;
> +
> +		if (__arm64_rndr(&raw))
> +			seed ^= raw;
> +	}
> +
>  	if (!seed) {
>  		kaslr_status = KASLR_DISABLED_NO_SEED;
>  		return 0;
> -- 
> 2.20.1
> 



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