Messages in this thread | | | Date | Fri, 06 Nov 2020 15:29:58 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH v2 3/5] ARM: implement support for SMCCC TRNG entropy source |
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On 2020-11-05 12:56, Andre Przywara wrote: > From: Ard Biesheuvel <ardb@kernel.org> > > Implement arch_get_random_seed_*() for ARM based on the firmware > or hypervisor provided entropy source described in ARM DEN0098. > > This will make the kernel's random number generator consume entropy > provided by this interface, at early boot, and periodically at > runtime when reseeding. > > Cc: Linus Walleij <linus.walleij@linaro.org> > Cc: Russell King <linux@armlinux.org.uk> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > [Andre: rework to be initialised by the SMCCC firmware driver] > Signed-off-by: Andre Przywara <andre.przywara@arm.com> > --- > arch/arm/Kconfig | 4 ++ > arch/arm/include/asm/archrandom.h | 64 +++++++++++++++++++++++++++++++ > 2 files changed, 68 insertions(+) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index fe2f17eb2b50..06fda4f954fd 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -1667,6 +1667,10 @@ config STACKPROTECTOR_PER_TASK > Enable this option to switch to a different method that uses a > different canary value for each task. > > +config ARCH_RANDOM > + def_bool y > + depends on HAVE_ARM_SMCCC > + > endmenu > > menu "Boot options" > diff --git a/arch/arm/include/asm/archrandom.h > b/arch/arm/include/asm/archrandom.h > index a8e84ca5c2ee..f3e96a5b65f8 100644 > --- a/arch/arm/include/asm/archrandom.h > +++ b/arch/arm/include/asm/archrandom.h > @@ -2,9 +2,73 @@ > #ifndef _ASM_ARCHRANDOM_H > #define _ASM_ARCHRANDOM_H > > +#ifdef CONFIG_ARCH_RANDOM > + > +#include <linux/arm-smccc.h> > +#include <linux/kernel.h> > + > +#define ARM_SMCCC_TRNG_MIN_VERSION 0x10000UL > + > +extern bool smccc_trng_available; > + > +static inline bool __init smccc_probe_trng(void) > +{ > + struct arm_smccc_res res; > + > + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_VERSION, &res); > + if ((s32)res.a0 < 0) > + return false; > + if (res.a0 >= ARM_SMCCC_TRNG_MIN_VERSION) { > + /* double check that the 32-bit flavor is available */ > + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_FEATURES, > + ARM_SMCCC_TRNG_RND32, > + &res); > + if ((s32)res.a0 >= 0) > + return true; > + } > + > + return false; > +} > + > +static inline bool __must_check arch_get_random_long(unsigned long *v) > +{ > + return false; > +} > + > +static inline bool __must_check arch_get_random_int(unsigned int *v) > +{ > + return false; > +} > + > +static inline bool __must_check arch_get_random_seed_long(unsigned > long *v) > +{ > + struct arm_smccc_res res; > + > + if (smccc_trng_available) { > + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND32, 8 * sizeof(*v), &res); > + > + if (res.a0 != 0) > + return false; > + > + *v = res.a3; > + return true; > + } > + > + return false; > +} > + > +static inline bool __must_check arch_get_random_seed_int(unsigned int > *v) > +{ > + return arch_get_random_seed_long((unsigned long *)v);
I don't think this cast is safe. At least not on 64bit.
M. -- Who you jivin' with that Cosmik Debris?
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