Subject: Re: [PATCH 1/2] Enable storage keys for radix - user mode execution

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Mon, 22 Aug 2016 11:32:44 +0530

Balbir Singh <[email-masked]> writes:

> ISA 3 defines new encoded access authority that allows instruction
> access prevention in privileged mode and allows normal access
> to problem state. This patch just enables IAMR (Instruction Authority
> Mask Register), enabling AMR would require more work.
>

Don't we need to do them in hypervisor mode. Ie, the hypervisor setup
things such that guest privileged mode cannot execute guest userspace.

> I've tested this with a buggy driver and a simple payload. The payload
> is specific to the build I've tested.
>
> Signed-off-by: Balbir Singh <[email-masked]>
> ---
>  arch/powerpc/mm/pgtable-radix.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
>
> diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
> index af897d9..9e25663 100644
> --- a/arch/powerpc/mm/pgtable-radix.c
> +++ b/arch/powerpc/mm/pgtable-radix.c
> @@ -294,6 +294,27 @@ found:
>  	return;
>  }
>
> +/*
> + * For radix page tables we setup, the IAMR values as follows
> + * IMAR = 0100...00 (key 0 is set to 1)
> + * AMOR = 1100....00 (Mask for key 0 is 11)
> + * AMR, UAMR, UAMOR are not affected
> + */
> +static void __init radix_init_iamr(void)
> +{
> +	unsigned long iamr_mask = 0x4000000000000000;
> +	unsigned long iamr = mfspr(SPRN_IAMR);
> +
> +	unsigned long amor_mask = 0xc000000000000000;
> +	unsigned long amor = mfspr(SPRN_AMOR);

Isn't AMOR hypervisor privileged ?.

> +
> +	iamr |= iamr_mask;
> +	amor |= amor_mask;
> +
> +	mtspr(SPRN_AMOR, amor);
> +	mtspr(SPRN_IAMR, iamr);
> +}
> +
>  void __init radix__early_init_mmu(void)
>  {
>  	unsigned long lpcr;
> @@ -350,6 +371,7 @@ void __init radix__early_init_mmu(void)
>  		radix_init_partition_table();
>  	}
>
> +	radix_init_iamr();
>  	radix_init_pgtable();
>  }
>
> -- 
> 2.5.5