Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753366AbbGaPCH (ORCPT ); Fri, 31 Jul 2015 11:02:07 -0400 Received: from smtp.nue.novell.com ([195.135.221.5]:50017 "EHLO smtp.nue.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751369AbbGaPCE (ORCPT ); Fri, 31 Jul 2015 11:02:04 -0400 Date: Fri, 31 Jul 2015 23:01:48 +0800 From: joeyli To: Matt Fleming Cc: "Lee, Chun-Yi" , linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, linux-pm@vger.kernel.org, "Rafael J. Wysocki" , Matthew Garrett , Len Brown , Pavel Machek , Josh Boyer , Vojtech Pavlik , Jiri Kosina , "H. Peter Anvin" Subject: Re: [RFC PATCH 05/16] x86/efi: Get entropy through EFI random number generator protocol Message-ID: <20150731150148.GB2067@linux-rxt1.site> References: <1437056730-15247-1-git-send-email-jlee@suse.com> <1437056730-15247-6-git-send-email-jlee@suse.com> <1438272704.11322.13.camel@intel.com> <20150731145256.GA2067@linux-rxt1.site> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150731145256.GA2067@linux-rxt1.site> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4575 Lines: 139 On Fri, Jul 31, 2015 at 10:59:12PM +0800, joeyli wrote: > On Thu, Jul 30, 2015 at 05:11:44PM +0100, Matt Fleming wrote: > > On Thu, 2015-07-16 at 22:25 +0800, 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 > > > --- > > > arch/x86/boot/compressed/efi_random.c | 193 ++++++++++++++++++++++++++++++++++ > > > include/linux/efi.h | 46 ++++++++ > > > 2 files changed, 239 insertions(+) > > > > [...] > > > > > @@ -2,6 +2,191 @@ > > > > > > #include > > > #include > > > +#include > > > + > > > +static efi_status_t efi_locate_rng(efi_system_table_t *sys_table, > > > + void ***rng_handle) > > > +{ > > > + efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID; > > > + unsigned long size = 0; > > > + efi_status_t status; > > > + > > > + status = efi_call_early(locate_handle, > > > + EFI_LOCATE_BY_PROTOCOL, > > > + &rng_proto, NULL, &size, *rng_handle); > > > + > > > + if (status == EFI_BUFFER_TOO_SMALL) { > > > + status = efi_call_early(allocate_pool, > > > + EFI_LOADER_DATA, > > > + size, (void **)rng_handle); > > > + > > > + if (status != EFI_SUCCESS) { > > > + efi_printk(sys_table, " Failed to alloc mem for rng_handle"); > > > + return status; > > > + } > > > + > > > + status = efi_call_early(locate_handle, > > > + EFI_LOCATE_BY_PROTOCOL, &rng_proto, > > > + NULL, &size, *rng_handle); > > > + } > > > + > > > + if (status != EFI_SUCCESS) { > > > + efi_printk(sys_table, " Failed to locate EFI_RNG_PROTOCOL"); > > > + goto free_handle; > > > + } > > > + > > > + return EFI_SUCCESS; > > > + > > > +free_handle: > > > + efi_call_early(free_pool, *rng_handle); > > > + > > > + return status; > > > +} > > > > I would suggest setting *rng_handle = NULL at the beginning of this > > function just because if we ever forget to set it that way in the caller > > this free_pool call might do screwy things. > > > > Thanks for your suggestion, I will set NULL to *rng_handle. > > > > > > +static bool efi_rng_supported(efi_system_table_t *sys_table) > > > +{ > > > + const struct efi_config *efi_early = __efi_early(); > > > + u32 random = 0; > > > + efi_status_t status; > > > + void **rng_handle = NULL; > > > + > > > + status = efi_locate_rng(sys_table, &rng_handle); > > > + if (status != EFI_SUCCESS) > > > + return false; > > > + > > > + if (efi_early->is64) > > > + random = efi_rng_supported64(sys_table, rng_handle); > > > + else > > > + random = efi_rng_supported32(sys_table, rng_handle); > > > + > > > + efi_call_early(free_pool, rng_handle); > > > + > > > + return random; > > > > Oops, 'random' isn't a bool but it should be. > > > > I will change type of random to boot. > > > > @@ -51,6 +236,14 @@ static unsigned long get_random_long(unsigned long entropy, > > > use_i8254 = false; > > > } > > > > > > + if (efi_rng_supported(sys_table)) { > > > + efi_printk(sys_table, " EFI_RNG"); > > > + raw = efi_get_rng(sys_table); > > > + if (raw) > > > + random ^= raw; > > > + use_i8254 = false; > > > + } > > > + > > > if (use_i8254) { > > > efi_printk(sys_table, " i8254"); > > > random ^= i8254(); > > > > Have you looked at the tradeoff in terms of boot time for building a key > > array in 'unsigned long' chunks as opposed to passing the array and size > > directly for the RNG protocol? > > > > I didn't really measure the speed, but directly passing array and size to > RNG protocol should a bit faster than calling the protocol a could of times. > > But, the key generation process only in first time building or trigger by > user raises the rebuild flag. So, it doesn't affect to every booting time. > > Due to I want let the whole key array more random, so each unsigned long > chunk was mixed(xor) by following entropy: > + random long from RDRAND > + RDTSC > + random long from EFI RNG protocol > + last unsigned long chunk > > Another reason is voiding the result of EFI RNG protocol to get weight ^^^^^^^^^ avoiding Sorry for my typo! > higher than other source, in case too trust EFI RNG. Joey Lee -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/