Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752228AbaBLQsB (ORCPT ); Wed, 12 Feb 2014 11:48:01 -0500 Received: from mail-we0-f179.google.com ([74.125.82.179]:54111 "EHLO mail-we0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751164AbaBLQr6 (ORCPT ); Wed, 12 Feb 2014 11:47:58 -0500 From: Grant Likely Subject: Re: [RFC/PATCH 1/3] of: Add early randomness hooks To: Laura Abbott , Rob Herring , Arnd Bergmann Cc: Laura Abbott , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Kumar Gala , Kees Cook In-Reply-To: <1392168805-14200-2-git-send-email-lauraa@codeaurora.org> References: <1392168805-14200-1-git-send-email-lauraa@codeaurora.org> < 1392168805-14200-2-git-send-email-lauraa@codeaurora.org> Date: Wed, 12 Feb 2014 16:47:51 +0000 Message-Id: <20140212164751.703DFC407C9@trevor.secretlab.ca> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 11 Feb 2014 17:33:23 -0800, Laura Abbott wrote: > Until randomness is added to the kernel's pools, random > numbers returned may not be truly 'random'. Randomness comes > from a variety of sources in the kernel but much of the > randomness comes from device related initialization. This > means that any random numbers that are needed before drivers > are initialized (e.g. stack canary) may not be truely random. > Fix this by build a list of functions that can be used to add > randomness to the kernel's pools very early. The functions are > tied to particular compatible strings of devicetree nodes. The > flattened devicetree is scanned and if the node is present the > function is called. Note that this must happen on the flattened > devicetree to ensure the randomness gets added to the pool > early enough to make a difference. > > Signed-off-by: Laura Abbott Intriguing solution. Looks good to me, but some comments below... > --- > drivers/of/Kconfig | 7 ++++++ > drivers/of/Makefile | 1 + > drivers/of/fdt.c | 7 ++++++ > drivers/of/of_randomness.c | 43 +++++++++++++++++++++++++++++++++++++ > include/asm-generic/vmlinux.lds.h | 5 ++++ > include/linux/of_randomness.h | 42 ++++++++++++++++++++++++++++++++++++ > 6 files changed, 105 insertions(+), 0 deletions(-) > create mode 100644 drivers/of/of_randomness.c > create mode 100644 include/linux/of_randomness.h > > diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig > index c6973f1..6ae4a38 100644 > --- a/drivers/of/Kconfig > +++ b/drivers/of/Kconfig > @@ -75,4 +75,11 @@ config OF_MTD > depends on MTD > def_bool y > > +config OF_RANDOMNESS > + def_bool n There should be the option to turn this off, particularly if it turns out to be expensive in terms of boot time. > + depends on OF_FLATTREE && ARCH_WANT_OF_RANDOMNESS > + help > + OpenFirmware hooks to scan for device randomness > + via flat devicetree Inconsistent whitespace > + > endmenu # OF > diff --git a/drivers/of/Makefile b/drivers/of/Makefile > index efd0510..0ce02d1 100644 > --- a/drivers/of/Makefile > +++ b/drivers/of/Makefile > @@ -9,3 +9,4 @@ obj-$(CONFIG_OF_MDIO) += of_mdio.o > obj-$(CONFIG_OF_PCI) += of_pci.o > obj-$(CONFIG_OF_PCI_IRQ) += of_pci_irq.o > obj-$(CONFIG_OF_MTD) += of_mtd.o > +obj-$(CONFIG_OF_RANDOMNESS) += of_randomness.o > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c > index 758b4f8..c25960e 100644 > --- a/drivers/of/fdt.c > +++ b/drivers/of/fdt.c > @@ -15,6 +15,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -889,6 +890,12 @@ bool __init early_init_dt_scan(void *params) > /* Setup memory, calling early_init_dt_add_memory_arch */ > of_scan_flat_dt(early_init_dt_scan_memory, NULL); > > +#ifdef CONFIG_OF_RANDOMNESS > + /* Add device randomness */ > + of_scan_flat_dt(early_init_dt_scan_early_randomness, NULL); > +#endif Drop the #ifdef in fdt.c and use static inlines in the header file. One that does the of_scan_flat_dt() call, and one empty stub for the !CONFIG_OF_RANDOMNESS case. I would also bypass the of_scan_flat_dt call entirely if the __early_random_funcs list is empty. > + > + > return true; > } > > diff --git a/drivers/of/of_randomness.c b/drivers/of/of_randomness.c > new file mode 100644 > index 0000000..9d23624 > --- /dev/null > +++ b/drivers/of/of_randomness.c > @@ -0,0 +1,43 @@ > +/* Copyright (c) 2013-2014, The Linux Foundation. All rights reserved. > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 and > + * only version 2 as published by the Free Software Foundation. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + */ > + > +#include > +#include > +#include > +#include > +#include > + > +int __init early_init_dt_scan_early_randomness(unsigned long node, > + const char *uname, > + int depth, void *data) > +{ > + struct early_random_func *f; > + void *prop; > + unsigned long len; > + > + prop = of_get_flat_dt_prop(node, "compatible", &len); > + > + if (!prop) > + return 0; > + > + for (f = __early_random_funcs_start; > + f < __early_random_funcs_end; > + f++) { > + pr_debug("Check compat %s addr %p against %s\n", > + f->compat_string, f->add_randomness, (char *)prop); > + if (strcmp(prop, f->compat_string) == 0) > + f->add_randomness(node); > + } > + > + return 0; > +} > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index bc2121f..e5b8be9 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -645,6 +645,11 @@ > *(.security_initcall.init) \ > VMLINUX_SYMBOL(__security_initcall_end) = .; > > +#define EARLY_RANDOM_FUNCS \ > + VMLINUX_SYMBOL(__early_random_funcs_start) = .; \ > + *(.earlyrandom.init) \ > + VMLINUX_SYMBOL(__early_random_funcs_end) = .; > + > #ifdef CONFIG_BLK_DEV_INITRD > #define INIT_RAM_FS \ > . = ALIGN(4); \ > diff --git a/include/linux/of_randomness.h b/include/linux/of_randomness.h > new file mode 100644 > index 0000000..b8b4532 > --- /dev/null > +++ b/include/linux/of_randomness.h > @@ -0,0 +1,42 @@ > +/* Copyright (c) 2013-2014, The Linux Foundation. All rights reserved. > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 and > + * only version 2 as published by the Free Software Foundation. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + */ > +#ifndef LINUX_OF_RANDOMNESS_H > +#define LINUX_OF_RANDOMNESS_H > + > +extern int early_init_dt_scan_early_randomness(unsigned long node, > + const char *uname, > + int depth, void *data); > + > +#ifdef CONFIG_OF_RANDOMNESS > + > +struct early_random_func { > + char *compat_string; > + void (*add_randomness)(unsigned long fdt_node); > +}; > + > +extern struct early_random_func __early_random_funcs_start[]; > +extern struct early_random_func __early_random_funcs_end[]; > + > +#define EARLY_RANDOM_FUNC(c, f) \ > +static struct early_random_func __early_rand##f __used \ > + __attribute((__section__(".earlyrandom.init"))) = { \ > + .compat_string = c, \ > + .add_randomness = f\ > + } \ > + > +#else > + > +#define EARLY_RANDOM_FUNC(f, e) > +#endif > + > +#endif > -- > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > hosted by The Linux Foundation > -- 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/