Commit a0b09f2d authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'random-6.0-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random 

Pull random number generator updates from Jason Donenfeld:
 "Though there's been a decent amount of RNG-related development during
  this last cycle, not all of it is coming through this tree, as this
  cycle saw a shift toward tackling early boot time seeding issues,
  which took place in other trees as well.

  Here's a summary of the various patches:

   - The CONFIG_ARCH_RANDOM .config option and the "nordrand" boot
     option have been removed, as they overlapped with the more widely
     supported and more sensible options, CONFIG_RANDOM_TRUST_CPU and
     "random.trust_cpu". This change allowed simplifying a bit of arch
     code.

   - x86's RDRAND boot time test has been made a bit more robust, with
     RDRAND disabled if it's clearly producing bogus results. This would
     be a tip.git commit, technically, but I took it through random.git
     to avoid a large merge conflict.

   - The RNG has long since mixed in a timestamp very early in boot, on
     the premise that a computer that does the same things, but does so
     starting at different points in wall time, could be made to still
     produce a different RNG state. Unfortunately, the clock isn't set
     early in boot on all systems, so now we mix in that timestamp when
     the time is actually set.

   - User Mode Linux now uses the host OS's getrandom() syscall to
     generate a bootloader RNG seed and later on treats getrandom() as
     the platform's RDRAND-like faculty.

   - The arch_get_random_{seed_,}_long() family of functions is now
     arch_get_random_{seed_,}_longs(), which enables certain platforms,
     such as s390, to exploit considerable performance advantages from
     requesting multiple CPU random numbers at once, while at the same
     time compiling down to the same code as before on platforms like
     x86.

   - A small cleanup changing a cmpxchg() into a try_cmpxchg(), from
     Uros.

   - A comment spelling fix"

More info about other random number changes that come in through various
architecture trees in the full commentary in the pull request:

  https://lore.kernel.org/all/20220731232428.2219258-1-Jason@zx2c4.com/

* tag 'random-6.0-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random:
  random: correct spelling of "overwrites"
  random: handle archrandom with multiple longs
  um: seed rng using host OS rng
  random: use try_cmpxchg in _credit_init_bits
  timekeeping: contribute wall clock to rng on time change
  x86/rdrand: Remove "nordrand" flag in favor of "random.trust_cpu"
  random: remove CONFIG_ARCH_RANDOM
parents 569bede0 7f637be4

Documentation/admin-guide/kernel-parameters.txt

+0 −5
Original line number Diff line number Diff line
@@ -3741,11 +3741,6 @@ 
	noreplace-smp	[X86-32,SMP] Don't replace SMP instructions

			with UP alternatives



	nordrand	[X86] Disable kernel use of the RDRAND and

			RDSEED instructions even if they are supported

			by the processor.  RDRAND and RDSEED are still

			available to user space applications.



	noresume	[SWSUSP] Disables resume and restores original swap

			space.

arch/arm/include/asm/archrandom.h

+2 −0
Original line number Diff line number Diff line
@@ -7,4 +7,6 @@ static inline bool __init smccc_probe_trng(void) 
	return false;

}



#include <asm-generic/archrandom.h>



#endif /* _ASM_ARCHRANDOM_H */

arch/arm64/Kconfig

+0 −8
Original line number Diff line number Diff line
@@ -1895,14 +1895,6 @@ config ARM64_E0PD 


	  This option enables E0PD for TTBR1 where available.



config ARCH_RANDOM

	bool "Enable support for random number generation"

	default y

	help

	  Random number generation (part of the ARMv8.5 Extensions)

	  provides a high bandwidth, cryptographically secure

	  hardware random number generator.



config ARM64_AS_HAS_MTE

	# Initial support for MTE went in binutils 2.32.0, checked with

	# ".arch armv8.5-a+memtag" below. However, this was incomplete

arch/arm64/include/asm/archrandom.h

+47 −65
Original line number Diff line number Diff line
@@ -2,8 +2,6 @@ 
#ifndef _ASM_ARCHRANDOM_H

#define _ASM_ARCHRANDOM_H



#ifdef CONFIG_ARCH_RANDOM



#include <linux/arm-smccc.h>

#include <linux/bug.h>

#include <linux/kernel.h>
@@ -60,7 +58,7 @@ static inline bool __arm64_rndrrs(unsigned long *v) 
	return ok;

}



static inline bool __must_check arch_get_random_long(unsigned long *v)

static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)

{

	/*

	 * Only support the generic interface after we have detected
@@ -68,27 +66,15 @@ static inline bool __must_check arch_get_random_long(unsigned long *v) 
	 * cpufeature code and with potential scheduling between CPUs

	 * with and without the feature.

	 */

	if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v))

		return true;

	return false;

}



static inline bool __must_check arch_get_random_int(unsigned int *v)

{

	if (cpus_have_const_cap(ARM64_HAS_RNG)) {

		unsigned long val;



		if (__arm64_rndr(&val)) {

			*v = val;

			return true;

		}

	}

	return false;

	if (max_longs && cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v))

		return 1;

	return 0;

}



static inline bool __must_check arch_get_random_seed_long(unsigned long *v)

static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)

{

	struct arm_smccc_res res;

	if (!max_longs)

		return 0;



	/*

	 * We prefer the SMCCC call, since its semantics (return actual
@@ -97,10 +83,23 @@ static inline bool __must_check arch_get_random_seed_long(unsigned long *v) 
	 * (the output of a pseudo RNG freshly seeded by a TRNG).

	 */

	if (smccc_trng_available) {

		arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res);

		struct arm_smccc_res res;



		max_longs = min_t(size_t, 3, max_longs);

		arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, max_longs * 64, &res);

		if ((int)res.a0 >= 0) {

			*v = res.a3;

			return true;

			switch (max_longs) {

			case 3:

				*v++ = res.a1;

				fallthrough;

			case 2:

				*v++ = res.a2;

				fallthrough;

			case 1:

				*v++ = res.a3;

				break;

			}

			return max_longs;

		}

	}
@@ -110,32 +109,9 @@ static inline bool __must_check arch_get_random_seed_long(unsigned long *v) 
	 * enough to implement this API if no other entropy source exists.

	 */

	if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndrrs(v))

		return true;

		return 1;



	return false;

}



static inline bool __must_check arch_get_random_seed_int(unsigned int *v)

{

	struct arm_smccc_res res;

	unsigned long val;



	if (smccc_trng_available) {

		arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 32, &res);

		if ((int)res.a0 >= 0) {

			*v = res.a3 & GENMASK(31, 0);

			return true;

		}

	}



	if (cpus_have_const_cap(ARM64_HAS_RNG)) {

		if (__arm64_rndrrs(&val)) {

			*v = val;

			return true;

		}

	}



	return false;

	return 0;

}



static inline bool __init __early_cpu_has_rndr(void)
@@ -145,34 +121,40 @@ static inline bool __init __early_cpu_has_rndr(void) 
	return (ftr >> ID_AA64ISAR0_EL1_RNDR_SHIFT) & 0xf;

}



static inline bool __init __must_check

arch_get_random_seed_long_early(unsigned long *v)

static inline size_t __init __must_check

arch_get_random_seed_longs_early(unsigned long *v, size_t max_longs)

{

	WARN_ON(system_state != SYSTEM_BOOTING);



	if (!max_longs)

		return 0;



	if (smccc_trng_available) {

		struct arm_smccc_res res;



		arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res);

		max_longs = min_t(size_t, 3, max_longs);

		arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, max_longs * 64, &res);

		if ((int)res.a0 >= 0) {

			*v = res.a3;

			return true;

			switch (max_longs) {

			case 3:

				*v++ = res.a1;

				fallthrough;

			case 2:

				*v++ = res.a2;

				fallthrough;

			case 1:

				*v++ = res.a3;

				break;

			}

			return max_longs;

		}



	if (__early_cpu_has_rndr() && __arm64_rndr(v))

		return true;



	return false;

	}

#define arch_get_random_seed_long_early arch_get_random_seed_long_early



#else /* !CONFIG_ARCH_RANDOM */

	if (__early_cpu_has_rndr() && __arm64_rndr(v))

		return 1;



static inline bool __init smccc_probe_trng(void)

{

	return false;

	return 0;

}

#define arch_get_random_seed_longs_early arch_get_random_seed_longs_early



#endif /* CONFIG_ARCH_RANDOM */

#endif /* _ASM_ARCHRANDOM_H */

arch/arm64/kernel/cpufeature.c

+0 −2
Original line number Diff line number Diff line
@@ -2502,7 +2502,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = { 
		.cpu_enable = cpu_enable_e0pd,

	},

#endif

#ifdef CONFIG_ARCH_RANDOM

	{

		.desc = "Random Number Generator",

		.capability = ARM64_HAS_RNG,
@@ -2514,7 +2513,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = { 
		.sign = FTR_UNSIGNED,

		.min_field_value = 1,

	},

#endif

#ifdef CONFIG_ARM64_BTI

	{

		.desc = "Branch Target Identification",