linux-kernel - Re: [PATCH v2 05/16] x86/efi: Get entropy through EFI random number generator protocol

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Message-ID: <20150820144706.GD2567@codeblueprint.co.uk>
Date:	Thu, 20 Aug 2015 15:47:06 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	"Lee, Chun-Yi" <joeyli.kernel@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Josh Boyer <jwboyer@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Matt Fleming <matt.fleming@...el.com>,
	Jiri Kosina <jkosina@...e.cz>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	"Lee, Chun-Yi" <jlee@...e.com>
Subject: Re: [PATCH v2 05/16] x86/efi: Get entropy through EFI random number
 generator protocol

On Tue, 11 Aug, at 02:16:25PM, Lee, Chun-Yi wrote:
> To grab random numbers through EFI protocol as one of the entropies
> source of swsusp key, this patch adds the logic for accessing EFI RNG
> (random number generator) protocol that's introduced since UEFI 2.4.
> 
> Signed-off-by: Lee, Chun-Yi <jlee@...e.com>
> ---
>  arch/x86/boot/compressed/efi_random.c | 209 ++++++++++++++++++++++++++++++++++
>  include/linux/efi.h                   |  13 +++
>  2 files changed, 222 insertions(+)

[...]

Most of this looks good.

> +static unsigned long efi_get_rng(efi_system_table_t *sys_table)
> +{
> +	const struct efi_config *efi_early = __efi_early();
> +	unsigned long random = 0;
> +	efi_status_t status;
> +	void **rng_handle = NULL;
> +
> +	status = efi_locate_rng(sys_table, &rng_handle);
> +	if (status != EFI_SUCCESS)
> +		return 0;
> +
> +	if (efi_early->is64)
> +		random = efi_get_rng64(sys_table, rng_handle);
> +	else
> +		random = efi_get_rng32(sys_table, rng_handle);
> +
> +	efi_call_early(free_pool, rng_handle);
> +
> +	return random;
> +}
  
I think this function is named particularly poorly in the UEFI spec
(GetRNG), can we maybe make this efi_get_rng_number(),
efi_get_rng_value() or efi_get_rng_long() to match the existing
naming?

> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index 85ef051..8914d60 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -427,6 +427,16 @@ typedef struct {
>  #define EFI_PCI_IO_ATTRIBUTE_VGA_PALETTE_IO_16 0x20000
>  #define EFI_PCI_IO_ATTRIBUTE_VGA_IO_16 0x40000
>  
> +typedef struct {
> +	u32 get_info;
> +	u32 get_rng;
> +} efi_rng_protocol_32;
> +
> +typedef struct {
> +	u64 get_info;
> +	u64 get_rng;
> +} efi_rng_protocol_64;
> +

We've been kinda slack with the naming conventions in efi.h but these
should really both be 'efi_rng_protocol_*_t'.

-- 
Matt Fleming, Intel Open Source Technology Center
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